Loyal Déborah

Anne-Laure Sutter

Rascle Nicole

Intensive Mothering Ideology in France: A Pilot Study [Idéologie du Maternage Intensif en France : Une Etude Pilote]

Keywords: Motherhood, Factor analysis, Validation, semi structured interview, Role

Résumé

Objectif : Le but de cette étude pilote est d'explorer en population Française le concept d'idéologie du maternage intensif et d'obtenir une échelle d'évaluation de ce construit.

Méthode : Les 25 items de l'Intensive Parenting Attitudes Questionnaire (IPAQ), une échelle Américaine, ont été traduits et soumis par internet à des mères et de futures mères (n = 250).

La validité structurelle de cette échelle a été évaluée avec une analyse factorielle confirmatoire.

Par la suite, pour créer de nouveaux items et ainsi améliorer la validité de l'échelle, une analyse de contenu a été réalisée sur la base d'entretiens semi directifs. Des jeunes mères et de futures mères (n = 22) ont été questionnées sur leurs opinions concernant la maternité et les soins à l'enfant. Une analyse de contenu a été effectuée avec des accords inter-juges satisfaisants (.53-.86), et 27 items ont ainsi été créés. Pour finir, l'ensemble des 52 items a été soumis par internet à de jeunes mères et de futures mères (n = 474). La structure de l'échelle a été testée via une analyse factorielle exploratoire.

Résultats : Une nouvelle échelle, la Mesure de l'Idéologie du Maternage Intensif (MIMI) a été obtenue. Cette échelle comprend 21 items et 6 dimensions (Essentialisme, Epanouissement, Puerocentrisme, Défi, Sacrifice et Stimulation) expliquant 59.75% de la variance. La consistance interne des différentes dimensions est satisfaisante (.61-.83). La plupart des dimensions sont faiblement à modérément corrélées (.17-.38).

Conclusions : La MIMI est le premier outil français permettant d'évaluer l'idéologie du maternage intensif. Elle offre d'intéressantes perspectives de recherche en termes de santé psychologique périnatale notamment. Mots Clefs : Maternité ; Analyse Factorielle ; Validation ; entretien semi directif ; Rôle

Introduction

Mothering has been widely described as a role [START_REF] Arendell | Conceiving and investigating motherhood: The decade's scholarship[END_REF] subjected to normative expectations rooted in social contexts [START_REF] Biddle | Role Theory: Expectations, Identities, and Behaviors[END_REF]. Thus ideas about motherhood and childhood are socially determined [START_REF] Arendell | Conceiving and investigating motherhood: The decade's scholarship[END_REF][START_REF] Hays | The cultural contradictions of motherhood[END_REF]. According to Hays [START_REF] Hays | The cultural contradictions of motherhood[END_REF] the U.S. contemporary dominant discourse about motherhood should be seen as an ideology, i.e. a system of interrelated beliefs, she named "Intensive Mothering Ideology" (IMI). According to Hays, most parents assume that mothers are inherently the best caregivers for children. Childrearing is described as a consuming expert-guided activity that must be child-centered. Authoritarian education is scorned whereas benevolent methods are preferred. Parenting is seen as the hardest job in the world but also as the most important and rewarding one. Finally, children are revered owing to their innocence and genuineness.

Few studies have been conducted regarding the consequences of IMI. According to the attachment theory [START_REF] Bowlby | Maternal care and mental health[END_REF], women involvement in mothering seems benefic for the child development and mothers satisfaction and efficacy, but normative aspects of motherhood are also recognized as important contributors to distress in mothers [START_REF] Tummala-Narra | Contemporary impingements on mothering[END_REF]. Difficulties to meet IMI requirements might be a source of emotional disturbance for mothers [START_REF] Flykt | What explains violated expectations of parent-child relationship in transition to parenthood?[END_REF], particularly for working ones confronted to contradictory demands [START_REF] Johnston | Cognitive acrobatics in the construction of worker-mother identity[END_REF][START_REF] Kroska | Exploring the consequences of gender ideology -work discrepancies[END_REF]. Moreover, IMI might be a threat to gender equality [START_REF] Arendell | Conceiving and investigating motherhood: The decade's scholarship[END_REF][START_REF] Macdonald | What's Culture Got to Do with It? Mothering Ideologies as Barriers to Gender Equity[END_REF], notably through essentialism (believing that mother is the natural and best caregiver) which places an undue burden on mothers [START_REF] Brugeilles | Partage des activités parentales: les inégalités perdurent[END_REF]. Thus IMI might be of interest regarding research on maternal mental health [START_REF] Flykt | What explains violated expectations of parent-child relationship in transition to parenthood?[END_REF][START_REF] Rizzo | Insight into the parenthood paradox: Mental health outcomes of intensive mothering[END_REF], gender equality [START_REF] Arendell | Conceiving and investigating motherhood: The decade's scholarship[END_REF][START_REF] Macdonald | What's Culture Got to Do with It? Mothering Ideologies as Barriers to Gender Equity[END_REF][START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF] and work-family balance [START_REF] Johnston | Cognitive acrobatics in the construction of worker-mother identity[END_REF][START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF].

According to Liss et al [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF] the biggest barrier to truly understand IMI consequences for women's mental health is the lack of quantitative measure of the IMI construct. Thus they have developed the Intensive Parenting Attitudes Questionnaire (IPAQ) in United States. Items were derived from previous interviews with mothers and non-mothers about motherhood [START_REF] Hays | The cultural contradictions of motherhood[END_REF][START_REF] Wall | Mothers' Experiences With Intensive Parenting and Brain Development Discourse[END_REF]. Data were then collected online with 595 mothers and, in a second time, 209 childless women.

Exploratory and confirmatory factor analyses were carried out. The first factor Essentialism (8 items) expresses the idea that mothers are better at parenting than fathers. The second factor Fulfillment (4 items) expresses the idea that being a parent is rewarding. The third factor Challenge (6 items) conveys the idea that child-rearing is difficult. The fourth factor Stimulation (4 items) expresses the idea that children must be intellectually stimulated. The last factor Child-Centrism (3 items) conveys the idea that child-rearing should be focused on the child's needs and rhythm. As predicted by Hays [START_REF] Biddle | Role Theory: Expectations, Identities, and Behaviors[END_REF], factors were moderately but significantly correlated with each other, constituting a set of beliefs, i.e. an ideology. The IPAQ showed good construct validity, i.e. factors were positively linked to either the mothers' anxiety about leaving their child, their perception of maternal work as being detrimental to children, or to their participation in household duties and childcare. Of note, IMI was found to be endorsed more by mothers and stay-at-home mothers than by childless women and working mothers. Finally, Rizzo et al [START_REF] Rizzo | Insight into the parenthood paradox: Mental health outcomes of intensive mothering[END_REF] found that in mothers of pre-schoolers, controlling for social support, essentialism was linked to less life satisfaction and challenge was linked to greater depressive symptoms and stress.

Whereas pioneering IMI work was drawn in U.S. context [START_REF] Hays | The cultural contradictions of motherhood[END_REF] it might be suitable in others developed countries such as France. Indeed, Bornstein [START_REF] Bornstein | Ideas about parenting in Argentina, France, and the United States[END_REF] have found that French and U.S. women shared similar views about responsiveness, sensitivity, warmth and stimulation in childcare and hold higher expectations for themselves than for their partners. Moreover, numerous scholars have raised concerns regarding motherhood requirement intensification in France through popular books [START_REF] Badinter | Le conflit : la femme et la mère[END_REF][START_REF] Garcia | Mères sous influence : de la cause des femmes à la cause des enfants[END_REF][START_REF] Missir | Mères, libérez-vous ![END_REF][START_REF] Vaillant | Etre mère : mission impossible[END_REF], as in United States [START_REF] Hays | The cultural contradictions of motherhood[END_REF][START_REF] Douglas | The Mommy Myth: The Idealization of Motherhood and How It Has Undermined All Women[END_REF][START_REF] Warner | Perfect Madness: Motherhood in the Age of Anxiety[END_REF]. Nevertheless, according to numerous scholars, ideas about parenting and childhood depends on social factors [START_REF] Arendell | Conceiving and investigating motherhood: The decade's scholarship[END_REF][START_REF] Hays | The cultural contradictions of motherhood[END_REF]. For instance, United States and France have very different child and family policies. French parent benefit from childcare provision, parental leave and family allowance [START_REF] Thevenon | Family Policies: France[END_REF] whereas U.S "has no explicit family policy, nor does it have a coherent package of social policies that are targeted on children and their families" [START_REF] Kamerman | Child and Family Policies in the United States at the Opening of the Twenty-first Century[END_REF]. Moreover, French women have been found to place less value on bonding, breastfeeding, sacrificing their own needs and responding quickly to baby's ones, and more value on equal task-sharing between parents and child autonomy than U.S. mothers [START_REF] Suizzo | French and American Mothers' Childrearing Beliefs: Stimulating, Responding, and Long-Term Goals[END_REF]. Thus, it remains unclear if IMI might be a relevant concept in France.

Thus, this pilot study was designed to test the validity of the IMI concept in France and to get a valid assessment tool.

General Method

Samples in Steps 1 and 3 (Table 1) were obtained online. The questionnaire was administrated with LimeSurvey [START_REF]LimeSurvey[END_REF] on French forums and Facebook groups (generalist, pregnancy, motherhood, childcare…) using snowball sampling method. This pilot study was approved by a national informatics right committee (https://www.cnil.fr/) and a regional ethic committee (http://www.cpp-soom3.u-bordeaux2.fr/). Statistical analyses were carried out with SPSS 20 and SPSS Amos 20.

Step 2 method and sample are described apart hereafter.

INSERT TABLE 1 ABOUT HERE

Step 1: IPAQ Confirmatory Factor Analysis

Aim

As advised by the International Test Commission [START_REF]International Test Commission Guidelines for Translating and Adapting Tests[END_REF] the aim of Step 1 was to translate the IPAQ and to test its equivalence in a French-speaking sample.

Method

As recommended [START_REF] Byrne | Adaptation of assessment scales in cross-national research: Issues, guidelines, and caveats[END_REF][START_REF] Vallerand | Vers une méthodologie de validation trans-culturelle de questionnaires psychologiques: Implications pour la recherche en langue française[END_REF][START_REF] Van De Vijver | Bias and equivalence in cross-cultural assessment: an overview[END_REF], a translation of the IPAQ items was done by the author and a back-translation was done by a bilingual person. The translation was judged appropriate regarding linguistic and meaning. The set of 25 items was administered online to mothers/mothers-to-be (n = 250, Table 1). A confirmatory factor analysis (unweighted least squares) was performed in order to evaluate the fit of the model [START_REF] Henson | Use of Exploratory Factor Analysis in Published Research Common Errors and Some Comment on Improved Practice[END_REF].

Results

In view of the current recommendations [START_REF] Hooper | Structural Equation Modelling: Guidelines for Determining Model Fit[END_REF][START_REF] Worthington | Scale Development Research: A Content Analysis and Recommendations for Best Practices[END_REF], the fit of the model was considered rather unsatisfactory (Χ 2 /df = 4.20, GFI = .942, AGFI = .929, RMR = .117, NFI = .878). The NFI, GFI and AGFI must be larger than .95 and the RMR must be low. The smaller the Χ 2 /df , the better the fit of the model with a good value smaller than 5.0, if not 2.0. Most factor loadings were satisfactory (.36 to .82) but three of them were problematic with factor loadings under .20. As expected, factors were correlated (r = .12-.63, p<.01). Lastly, internal consistency (Cronbach alpha) was high for Essentialism (.83) and Child-Centrism (.64), but was weaker for Fulfillment (.49), Challenge (.55) and Stimulation (.50).

Discussion

As a result, the IPAQ might be regarded as not suited for French mothers/mothers-to-be.

Lack of measurement equivalence might be due to different biases [START_REF] Byrne | Adaptation of assessment scales in cross-national research: Issues, guidelines, and caveats[END_REF][START_REF] Van De Vijver | Bias and equivalence in cross-cultural assessment: an overview[END_REF]. Construct biases occurs when "there is only partial overlap in the definitions of the construct across cultures" [START_REF] Van De Vijver | Bias and equivalence in cross-cultural assessment: an overview[END_REF].

Indeed, as motherhood is socially determined [START_REF] Arendell | Conceiving and investigating motherhood: The decade's scholarship[END_REF][START_REF] Glenn | Mothering: Ideology, experience, and agency[END_REF][START_REF] Harkness | Culture and Parenting[END_REF][START_REF] Phoenix | Motherhood: meanings, practices, and ideologies[END_REF], IMI might be different in French and U.S. contexts [START_REF] Suizzo | French and American Mothers' Childrearing Beliefs: Stimulating, Responding, and Long-Term Goals[END_REF]. Method biases affect sample, administration and instrument. Regarding samples, Liss et al [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF] population was composed of mothers aged from 20 to 73 years (M = 34.78 ; SD = 8.07) and no information were provided regarding their children's age and their pregnancy status, whereas our population was composed of 18 to 51 years old women (M = 29.67 ; SD = 5.05) who had at least one child under 3 years and were pregnant (14%) or not (79%). Some were expecting their first baby (7%) (Table 1). Regarding administration, both studies were conducted online with snowball sampling but U.S. and French women might display different behaviors online (e.g. willingness to self-disclose…). Finally items biases are due to item ambiguities and connotations that might invoke nuisance traits or abilities.

According to Byrne [START_REF] Byrne | Adaptation of assessment scales in cross-national research: Issues, guidelines, and caveats[END_REF], 3 kind of procedure are used when developing an instrument for a transcultural use. One can translate the instrument (adoption), translate it and check its psychometric properties (adaptation) or build "a new linguistically and culturally appropriate scale" (assembly). This last option should be done when an adaptation process fails. Thus, owing to poor results obtained in this first adaptation step, the next parts of this pilot study were designed to build a new scale.

Step 2: Item Development

Aim

Owing to the poor results of Step 1, Step 2 was designed to enhance the ecological and content validity of a new tool with items derived from French participants' speech.

Method

A semi-structured interview guide was constructed to explore IMI according to themes previously delineated [START_REF] Hays | The cultural contradictions of motherhood[END_REF][START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF]: essentialism, fulfillment, challenge, stimulation and child-centrism (Appendix A). Participants (n = 22) were mothers/mothers-to-be. Pregnant participants were recruited during childbirth information in a local university hospital. Non-pregnant participants, who had a baby in the last year, were contacted by phone thanks to the hospital listing. The average age of participants was 29.54 years (SD = 4.56), ranging from 21 to 36. They were all married or living as couples. Among the 22 participants, 11 were primiparous pregnant women and 11 were mothers (6 non-pregnant and 5 pregnant). Non-pregnant mothers (n = 6) had one or two children and at least one child aged less than 2 years. Pregnant mothers (n = 5) had one child aged less than 5 years, except one mother who had a 10-year-old child. All interviews were conducted in a quiet office. Participants were informed about the duration and anonymity of their participation and signed an informed consent form. Interviews were recorded using an audio device. A thematic content analysis was performed with the Nvivo10 software [START_REF]NVivo Qualitative Data Analysis Software[END_REF].

Results

The coding order was randomly selected. Inter-rater agreement was obtained for 30% of the interviews selected at random and coded by the author and one trained student. Kappa coefficients were satisfactory [START_REF]Nvivo 10 for Windows Help n[END_REF] (> 0.40) ranging from .54 to .86. Agreement was excellent for essentialism (0.87) and challenge (0.76) and good for stimulation (0.69), fulfillment (0.61) and child-centrism (0.54).

These categories seem to be adapted to our participants' speech. Examples of participant's speech can be found in Appendix A. Statement that does not already appear in the IPAQ led to the creation of an item formulated as closely as possible to the participant speech. Twenty-seven new items were thus generated regarding Essentialism (5 new items), Challenge (5 items), Fulfilment (4 items), Child-centrism (5 items) and Stimulation and child needs (8 items).

Step 3: Factor Structure of a New Tool

Aim

Step 3 was designed so as to create a new tool, build on the IPAQ items, translated in Step 1, and the new items created in Step 2.

Method

The 52 items (25 IPAQ items and 27 items created in Step 2) were administered online to mothers/mothers-to-be (n = 474, Table 1). An exploratory factor analysis (principal factor analysis, Oblimin rotation) was performed [START_REF] Henson | Use of Exploratory Factor Analysis in Published Research Common Errors and Some Comment on Improved Practice[END_REF][START_REF] Costello | Best Practices in Exploratory Factor Analysis: Four Recommendations for Getting the Most From Your Analysis[END_REF].

Results

We removed every item with insufficient loadings (<. 30) [START_REF] Worthington | Scale Development Research: A Content Analysis and Recommendations for Best Practices[END_REF][START_REF] Hair | Multivariate data analysis[END_REF] or cross loadings (difference between loadings < .20) [START_REF] Worthington | Scale Development Research: A Content Analysis and Recommendations for Best Practices[END_REF] and re-ran the analysis until we obtained a satisfactory factorial structure. After considering the eigenvalues and the screeplot diagram, a six-factor structure explaining 59.75% of the variance was retained. The Bartlett Test (Χ 2 (210) = 2267.22; p<.00) and the Kaiser-Meyer-Olkin value (.84) [START_REF] Broc | Stats faciles avec R[END_REF] suggested that the data was suitable for analysis. The final structure consisted of 21 items (Table 2). Since some data was missing, the sample was reduced to 411 participants. The new tool was called the Measure of Intensive Mothering Ideology (MIMI) (Appendix B).

INSERT TABLE 2 ABOUT HERE

The first factor, Essentialism (7 items) expresses the idea that mothers are the natural and best caregiver. It contains 3 items from the IPAQ and 4 items derived from the French women's speech. Interestingly, items from the IPAQ that were directed at fathers' incompetence (e.g. Men are unable to care for children unless they are given specific instructions about what to do) were dropped. New items derived from French participant speech stressed the fathers discomfort (e.g.

Fathers sometimes take time to seize their father's role) and the singularity of the mother-baby relation (e.g. There is a more natural, strong and direct link between mother and child than between father and child). The second factor, originally named Fulfilment was renamed Consuming Fulfilment (5 items). It contains 4 items from the IPAQ (one of which was designed to evaluate Challenge) and 1 item derived from the French women's speech (designed to evaluate Challenge. This factor is composed of items about how childrearing is fulfilling (e.g. Holding his or her baby should provide a parent with the deepest level of satisfaction) and consuming (e.g.

Parents never get a mental break from their children, even when they are physically apart).

The third factor, Child-Centrism (2 items), remains unchanged, i.e. children's rhythm and needs must be a priority. It contains 2 items from the IPAQ. One can guess that the dropped IPAQ item (Children should be the center of attention) was not suited for French women because it might be evocative of a spoiled or badly reared child (not bien élevé) [START_REF] Suizzo | French and American Mothers' Childrearing Beliefs: Stimulating, Responding, and Long-Term Goals[END_REF]. Regarding the fourth factor, Challenge (2 items), the primary idea remained the same, i.e. parenting is the hardest job in the world. It contains 2 items from the IPAQ. The fifth factor was new and was labelled "Sacrifice" (3 items). It may seem similar to the Challenge factor, but places emphasis on the sacrifices that being a parent implies (e.g. When becoming a parent, one must be prepared to put on hold one's personal life) more than on the difficulty of the task itself. It contains 2 items from the French women's speech and 1 item from the IPAQ. All items were originally designed to assess Challenge. The sixth factor labelled Stimulation (2 items) encompasses the idea that children need to be stimulated. It contains 1 item from the IPAQ and 1 from the French women's speech.

Interestingly IPAQ items that were dropped were directed at heavy and early intellectual stimulation (e.g. Finding the best educational opportunities for children is important as early as preschool). The Stimulation factor is now directed at one-to-one interactions (e.g. One must stimulate children, play with them, talk to them, sing songs to them, read stories to them). Items derived from French women's speech and directed at other child needs were not kept (e.g. It is important for children to be praised and to develop self-confidence and autonomy…).

Overall, the MIMI is composed of 38% of items derived from the French participants' speech (8/21 items). Moreover, 52% of the IPAQ items (13/25 items) and 29% of the items derived from the French women's speech (8/27 items) were kept. Means and standard deviations were obtained for each dimension (Table 3). Internal consistency (Cronbach alpha) was satisfactory for Essentialism (.83), Consuming Fulfilment (.74), Child-Centrism (.75) and lower for Challenge (.61), Sacrifice (.61) and Stimulation (.64). However, usually recommended cut-off (.70) has been regarded as arbitrary by some authors [START_REF] Lance | The Sources of Four Commonly Reported Cutoff Criteria: What Did They Really Say?[END_REF][START_REF] Rammstedt | Can't We Make It Any Shorter?: The Limits of Personality Assessment and Ways to Overcome Them[END_REF][START_REF] Streiner | Starting at the Beginning: an Introduction to Coefficient Alpha and Internal Consistency[END_REF][START_REF] Ziegler | Short Scales -Five Misunderstandings and Ways to Overcome Them[END_REF] mainly because it's very sensitive to the number of items (more items give higher alpha). Since Challenge, Sacrifice and Stimulation have few items (2 or 3), getting value above .60 might be seen as satisfactory. Nevertheless, twoitem factors are usually considered less reliable [START_REF] Worthington | Scale Development Research: A Content Analysis and Recommendations for Best Practices[END_REF] but some authors raise questions about this misgiving [START_REF] Rammstedt | Can't We Make It Any Shorter?: The Limits of Personality Assessment and Ways to Overcome Them[END_REF][START_REF] Ziegler | Short Scales -Five Misunderstandings and Ways to Overcome Them[END_REF]. Finally, as expected [START_REF] Hays | The cultural contradictions of motherhood[END_REF][START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF] most factors were moderately correlated (Table 4).

INSERT TABLE 3 AND 4 ABOUT HERE

General Discussion

The IPAQ seems to be unsuited for direct use whereas the adapted version, the MIMI presents an additional value in French context. Thus IMI in France might present some special features which might be related to history or child and family policies [START_REF] Thevenon | Family Policies: France[END_REF].

First, Essentialism dimension was no longer about fathers' inabilities per se but about their discomfort with children matters and the idea that they don't have the same kind of relation with children as mothers. Presumably, French women might exhibit a more nuanced form of essentialism more compatible with gender equality ideals, as French mothers have been found to attach greater importance to equal task-sharing [START_REF] Suizzo | French and American Mothers' Childrearing Beliefs: Stimulating, Responding, and Long-Term Goals[END_REF]. Whereas the IPAQ Fulfillment dimension was about how gratifying being a parent is, the MIMI Consuming Fulfilment dimension was also about how parents' minds are always occupied by children. This continuous preoccupation might be linked with increased mental load and interferences [START_REF] Geurts | Work-home interaction from a work psychological perspective: development and validation of a new questionnaire, the SWING[END_REF]. The Challenge dimension remains rather unchanged but, unexpectedly, a new dimension named Sacrifice was found. Interestingly, the notion of sacrifice has been described previously [START_REF] Hays | The cultural contradictions of motherhood[END_REF][START_REF] Badinter | L'amour en plus : histoire de l'amour maternel[END_REF]. As stated by Hays [START_REF] Bowlby | Maternal care and mental health[END_REF] "the very definition of good mothering includes the willingness to give up things so that your children can have things". The MIMI Stimulation dimension was more about one-to-one interactions rather than about providing intensive cognitive stimulation. Presumably, French women might be concerned about overstimulation, as noted previously about U.S. mothers [START_REF] Hays | The cultural contradictions of motherhood[END_REF][START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF]. Mothers are caught in the crossfire of "not enough" and "too much" and "the only way to determine precisely the correct amount of stimulation is to watch the baby at every moment, interpret his behavior and analyze its requirements at that particular time" [START_REF] Hays | The cultural contradictions of motherhood[END_REF]. Finally, as expected, most MIMI factors were correlated confirming the idea that IMI is an ideology or a set of interrelated beliefs [START_REF] Hays | The cultural contradictions of motherhood[END_REF][START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF]. This pilot study has some limitations. First, like the work of Liss et al [START_REF] Warner | Perfect Madness: Motherhood in the Age of Anxiety[END_REF], our study was mainly conducted through internet (Step 1 and 3), a method which is cost-effective but does not allow the sampled population to be controlled (i.e. participants could take the questionnaire in group). However, this remains a marginal consideration [START_REF] Birnbaum | Psychological Experiments on the Internet[END_REF]. Furthermore, our participants were rather privileged women, mainly well-educated, young and married or living as a couple. In addition, including primiparous pregnant women might have added heterogeneity. However, they represented 7 % of Sample 1 and 5% of Sample 2, so this recruitment bias might be considered as marginal. Like the IPAQ, the MIMI does not contain items regarding child sacredness and the need for expert guidance in childrearing. Therefore, these aspects of IMI described by Hays [START_REF] Bowlby | Maternal care and mental health[END_REF] remain unevaluated. Presumably, they might be less essential to IMI, less consensual or less verbalized. For instance, women might fear to be deemed as needy and incompetent if they rely on expert advice. Of note, child sacredness and the need for expert guidance were not assessed per se by semi-structured interview (Appendix A) but questions about one component could have elicited another one (e.g. What must guide a parent when making decisions concerning the child? could have elicited ideas about expert guidance such as I rely on my family doctor or I read books about child development). Finally, it would have been interesting to explore quantitative differences between French and U.S. samples [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF] regarding endorsement of IMI. Nevertheless, as the IPAQ was found to be unsuitable for use in French mothers/mothers-to-be (Step 1), such comparisons were not computed.

Further research is needed to test the construct validity of the MIMI in French population as it was done for the IPAQ in the U.S. population [START_REF] Rizzo | Insight into the parenthood paradox: Mental health outcomes of intensive mothering[END_REF][START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF]. In subsequent studies, for instance, the MIMI could be linked to professional status, being a mother or being childless [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF][START_REF] Katz-Wise | Gender-role attitudes and behavior across the transition to parenthood[END_REF], level of education [START_REF] Davis | Gender ideology: components, predictors, and consequences[END_REF] and to concepts such as beliefs about the consequences of maternal employment on children [START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF][START_REF] Hyde | Beliefs about the consequences of maternal employment for children: Psychometric analyses[END_REF], work centrality, shared household and parental duties [START_REF] Macdonald | What's Culture Got to Do with It? Mothering Ideologies as Barriers to Gender Equity[END_REF][START_REF] Liss | Development and validation of a quantitative measure of intensive parenting attitudes[END_REF]. Attitude toward highly normative childcare practices such as breastfeeding [START_REF] Lee | Breastfeeding advocacy, risk society and health moralism: A decade's scholarship[END_REF] might be of particular interest.

Overall, the MIMI is a promising tool and could be used in France and possibly European countries. Postpartum mental health might be better understood if normative aspects were considered: high expectations about motherhood may be difficult to meet and to reconcile with other life requirements, particularly in mothers with low resources.

In conclusion, IMI, which was drawn in the U.S. context, seems to be suitable in France with some special features. IMI can be evaluated in France with the MIMI in mothers/mothers-tobe. Further research is needed to establish the validity of this measure and to explore how IMI might be related to mental health, gender equality and family issues. 12* Even if they take care of children a great deal, fathers don't have the same relationship with babies as mothers.

13

Holding his or her baby should provide a parent with the deepest level of satisfaction.

14

Children's needs should come before their parents.

15

A parent should feel complete when he or she looks in the eyes of his or her infant.

16* Mothers are often more comfortable with babies than fathers. 17

It is important to interact regularly with children on their level (e.g. getting down on the floor and playing with them).

18* A parent always fears that something might happen to his children.

19

It is harder to be a good parent than to be a corporate executive.

GENQ:

  In your opinion, what does it mean to be a "good mother"? Do you wish to be a certain kind of mother? ESS = Essentialism, FUL = Fulfillment, CHAL = Challenge, STI/CHI = Stimulation and Childcentrism, GEN = General Q: Questions; Participant's speech examples in italic The child's schedule should take priority over the needs of the parent's.

20

  Although fathers are important, ultimately children need mothers more.21Being a parent brings a person the greatest joy he or she can possibly experience. Note. Essentialism = (02+04+08+09+12+16+20)/7; Consuming Fulfilment = (01+13+15+18+21)/5; Child-centrism = (11+14)/2; Challenge = (07+19)/2; Sacrifice = (03+06+10)/3; Stimulation = (05+17)/2. 1 = Strongly disagree; 2 = Disagree; 3 = Somewhat disagree; 4 = Somewhat Agree; 5 = Agree; 6 = Strongly agree. * Items generated from French participants speech

Table I .

 I Characteristics of Online Samples for Step 1 (N = 250) and Step 3 (N = 474)

		Step 1	Step 3
	Age (years)
	Range	18-51	18-51
	Mean (SD)	29.67 (5.05) 29.82 (4.92)
	Marital status (%)
	Married or PACS a	48%	50%
	Cohabiting couple	47%	45%
	Single	3%	4%
	Educational level (%)
	≥ 2 years post-secondary	61%	58%
	High school diploma	22%	23%
	Work status (%)
	Full-time	33%	34%
	Part-time	22%	24%
	Stay-at-home	28%	26%
	Student	2%	2%
	Pregnant (%)	21%	19%
	Among non-pregnant women
	Number of child (%)
	1	44%	40%
	2	32%	33%
	3 and more	24%	27%
	Youngest child's age (months)
	Range	1-55	0-60
	Mean (SD)	15.10 (12.29) 16.12 (13.74)
	Among pregnant women
	Number of children (%)
	0	34%	29%
	1	32%	39%
	2	21%	21%
	3 and more	13%	11%
	Youngest child's age (months)
	Range	4-104	4-122
	Mean (SD)	31.69 (23.04) 32.48 (23.95)

a : PACS : Civil Solidarity Pact in France

Table II .

 II Exploratory Factor Analysis (Principal Factor Analysis, Oblimin Rotation) for the MIMI in Mothers/Mothers-to-be (N = 411, Step 3)

	Item n°	Abbreviated Content a	1 b	2 b	3 b	4 b	5 b	6 b
	02 c	natural link	.71	.01	.04	.01	.01	.06
	04	do not recognize	.43	.13	.01	.11	.23	.12
	08	do not naturally knows	.63	.03	.01	.11	.12	.12
	09 c	take time to seize	.61	.11	.02	.18	.08	.06
	12 c	don't have the same relationship	.73	.03	.02	.06	.05	.15
	16 c	more comfortable	.58	.16	.02	.09	.01	.01
	20	children need mothers more	.55	.04	.03	.05	.14	.02
	01	never get a mental break	.06	.66	.02	.01	.02	.00
	13	deepest level of satisfaction	.06	.49	.06	.08	.06	.08
	15	feel complete	.12	.57	.18	.01	.05	.07
	18 c	always fears	.06	.51	.02	.02	.12	.05
	21	greatest joy	.08	.55	.07	.02	.05	.15
	11	child's schedule	.04	.02	.85	.04	.06	.01
	14	children's needs	.01	.08	.64	.04	.04	.02
	07	demanding job	.02	.15	.11	.67	.11	.02
	19	corporate executive	.05	.05	.14	.62	.02	.06
	03	time for oneself	.01	.09	.03	.10	.63	.02
	06 c	personal life	.08	.01	.08	.20	.53	.01
	10 c	not allowed to be tired	.05	.05	.04	.12	.51	.02
	05 c	must stimulate	.04	.12	.08	.03	.03	.65
	17	on their level	.01	.02	.09	.01	.02	.65
		Eigenvalues	4.91	2.59	1.48	1.31	1.17	1.08
		% of variance	23.40 12.32 7.04	6.23	5.59	5.18
		Cronbach Alpha	.83	.74	.75	.61	.61	.64
	Note. Factor loadings over .30 appear in bold.
	a All items are available in Appendix B. b 1 = Essentialism, 2 = Consuming Fulfilment, 3 = Child-
	Centrism, 4 = Challenge, 5 = Sacrifice, 6 = Stimulation.

c

Items generated from thematic content analysis in French sample.

Table III .

 III Means and Standard deviations for MIMI Dimensions (N = 434, Step 3) Is being a parent an important matter? Is parenting a pleasant or rewarding activity? "Having a child is one of the most beautiful things one can experience" CHALL Q: Is parenting an easy-going task? How does becoming a parent change one's life? "It's exhausting and even when you're sick you have to go on, you just can't stop"

	APPENDIX A. Semi-Structured Interviews Main Guidelines (Step 2)
	M (SD) Q: Who should take care of the child? Who does the child need the most?
	Essentialism ESS "I think the baby knows his mother's smell and I think that he is naturally attracted more to 3.71 (1.13)
	Consuming Fulfilment 5.25 (0.72) his mother than to his dad"
	Child-Centrism FULF Q:	4.91 (1.10)
	Challenge	5.07 (1.03)
	Sacrifice	3.39 (1.18)
	Stimulation	5.68 (0.54)

STI

/ CHI Q: What needs to be done in order to ensure that the child develops properly? What must guide a parent when making decisions concerning the child? "You must offer him activities to develop his motor skills", "There are activities to do, taking him to the library, reading stories, singing songs, going out…", "Nutrition is important, you have to supervise his growth…"

Conflicts of Interest

We have no conflicts of interest APPENDIX B. The Measure of Intensive Mothering Ideology (MIMI) 10* When becoming a parent, one is not allowed to be tired.


Reinventing Indianness in the wake of Indian removal (1815-1848): Southeastern Indians as participants in the development of a "vast Southern Empire"?

Reinventing Indianness in the wake of Indian removal (1815-1848): Southeastern Indians as participants in the development of a "vast Southern Empire"?

Augustin HABRAN -University of Orléans, France

As they underwent deportation beyond the limits of politically organized territories of the Union, to the outskirts of the American republic1 , in the regions of the Great Plains where the Comanche Empire identified by Hämäläinen had long developed 2 , the acculturated nations of the South-East faced, through dispossession, forced exile and the Trail of Tears, the complete annihilation of their social and cultural environment. While the loss of land implied the end of Indian sovereignty in the East, along with the Supreme Court decision to make Indian nations "domestic and dependent" in 1831, uprooting questioned the very identity -or Indianness -of the relocated nations. They were not only confronted to massive death rates but also to the need to artificially provide the deported people with a new form of unity, away from the land of their ancestors, that had allowed for the organic structure and cohesion of the nations until then. Yet, I contend that removal to Indian Territory could also be analyzed as a challenge to which relocated nations rose. The resilience of the southeastern nations was indeed characterized by a certain ability of reinvent the very notion of Indianness, in finding the means to guarantee new forms of sovereignty on allocated lands, while preserving a certain national cohesion that Indian leaders such as Cherokee chief John Ross had tried so hard to maintain as they resisted federal and local oppression in the 1820s. As they adapted to these new conditions, the Cherokees, Choctaws, Creeks and Chickasaws became the champions of a modern state in the West since they carried out the strategy of resistance through acculturation they had developed in the South-East. In doing so, they transposed in the West the state-making apparatus they had created east of the Mississippi to legally resist land-greedy settlers of the then developing Deep

South. Therefore, one may argue that the position relocated Indian were forced to occupy -on lands that originally belonged to the Plains Indians -and the strategies they developed in situ to survive, made them agents of the territorial and political construction of what Stephen H.

Long had described as the "Great American Desert", and, somehow, by proxy, of imperial expansion on the Great Plains. This, I contend, has to be connected with the pursuance by relocated nations of what I defined in the dissertation I defended in 2017 as "strategic mimesis"3 .

The outstanding process of acculturation of the so-called five "civilized" tribes has been extensively studied by historiography. Ethnohistorians have focused on the cultural changes at stake within the southeastern nations, from the end of the 18 th century to the 1820s, and highlighted the dynamics at work within the nations that explained such transformations of Indian identity, pointing out the emergence of mixed-blood elites that imposed a certain Americanization of Native cultures and led to tensions between what has been alternatively referred to as "traditional" and "progressive" branches, full-bloods and mixed-blood, lower and upper towns, etc. With the increasing scarcity of game caused by the ever-growing pressure of colonial invasion in the South-East, the development of a capitalistic mode of agriculture, fueled by that of Black slavery, that was the cause and consequence of the emergence of a mixed-blood economic and political elite in the nations, came to constitute a means to resist colonization. It granted Indian nations a form of legitimacy to occupy their land as a response to the Euro-American ideology that associated extensive exploitation of land, individual property and sovereignty. "Strategic mimesis", that was instilled through the vertical form of power developed by emerging central governments within the nations, that superseded the traditional clan-based lose confederations of locally influential towns, and mixed-blood figures that gained legitimacy for the role they were able to play as diplomatic and ideological interlocutors with the colonial sphere, aimed, on the surface, at satisfying the Federal will to see the Indians assimilate and "disappear" in showing evidence of a cultural and moral ability to "adapt" while responding, in depth, to tribal and national objectives to preserve territorial sovereignty 4 . The state-like entities developed by the nations in the South-East, framed by laws and constitutions (especially in the case of the Cherokees with the Constitution of 1827) that defined Indian territory in the law, allowed Indian nations to resist expansion using Euro-American legal language and tools that could have left no choice to the Federal and local states but to acknowledge Indian legitimacy. Still, as President Andrew Jackson relied on pseudoscientific racist arguments of Indian "degradation" developed at the time to fulfill the role he was elected for in 1828 -that of a republican representative of the "vast southern empire" 5 , accompanying the momentum of nationalist popular expansion that characterized the 1820s -, he strategically denied the fact that these "few savage hunters", as he called southeastern Indians in his address to Congress, had, as the Cherokee Phoenix affirmed in 1829, "unexpectedly become civilized" 6 .

Following the principle of colonization, developed since the creation of the American Colonization Society in 1816, the forced relocation of southeastern Indians modified dramatically the geopolitical landscape of the Prairie and the Plains. The relocated nations constituted an acculturated population that, according to the terms of the Removal treaties, was allowed to occupy and exploit territories that traditionally belonged to local Indian populations.

Roughly half of the allocated lands corresponded in fact to the important hunting grounds of the Comanches, Kiowas, Katakas, Wichitas and Osages. While the Federal government insisted on the legitimacy of relocated nations to appropriate these lands that were part of the national domain of the United States ever since the Louisiana Purchase of 1803, the treaties imposed on the southeastern nations, including the Treaty of New Echota made with the Cherokees in 1835, guaranteed Federal protection to the deported populations, notably against the Plains Indians.

Besides, the "civilization" they had been denied east of the Mississippi, was now used by the Federal authorities as an argument to legitimize the appropriation of allocated lands by the relocated nations: they were able to produce agricultural work in the manner of Euro-Americans, which was not the case of local populations considered as "savage", as federal agent among the Comanches, A. P. Chouteau, affirmed in 1837:

It has been further stated, that the Comanches are dissatisfied because the Creeks and Choctaws have extended their occupation and improvements to the country heretofore used by themselves as a hunting ground. This matter should be explained to them, so that they may understand that the United States, having purchased these lands from the tribes possessing the occupant title, has guaranteed the exclusive right in it to the emigrated Indians. They cannot, therefore, be permitted to hunt upon it after the latter are prepared to settle upon and cultivate it 7 .

Whereas deportation could have implied a return to a more traditional Indian identity, the rupture imposed by the removal was paradoxically characterized by an acceleration of "strategic mimesis", as Indian leaders tried to adapt and exploit this "domestic dependent" situation in order to reaffirm Indian sovereignty on allocated lands. As they transposed the statemaking apparatus developed in the East, and reinforced it in each nation with the drafting of national constitutions modeled after state constitutions of the Union, that not only reaffirmed the legal legitimacy to occupy geographically delineated territories but also intensified the process of acculturation that culturally positioned Indian Territory in a certain continuity of the American republic, migrating nations managed to use the tools of so-called "civilization" to bring new forms of national cohesion outside ancestral lands8 . In the meantime, the At present they are doing very well. They have erected several buildings for public worship, made large appropriations for schools, and raised 40,000 bushels of corn this year over and above what will be required for consumption. To say nothing of the wealthier half-breeds, who own large cotton plantations, very many of the uneducated full-blood Indians have valuable improvements on the routes travelled by the Texas emigrants. They find a ready market for their produce and are learning to acquire and take care of property9 .

This territorial, economic and cultural development of Indian Territory conferred a certain power of influence upon the relocated nations. As they appropriated the lands they were granted to legitimize their sovereignty despite their dependence on Federal authorities, and as they secured their geographical integrity facing the resistance of Plains Indians, Indian Territory somehow became an outpost of American westward expansion.

The (John Ross's brother), one of the most influent planters of the nation, sent for a boat with 500 slaves from Georgia. And as some Indian planters went to Arkansas and Louisiana regularly to buy slaves, they also benefited from the sale of slaves captured by the Plains Indians in the Republic of Texas. In the 1840s, the Federal government still perceived the development of slavery among Indian nations as a sign of "progress" and "civilization". The annual report of the Commissioner of Indian Affairs in 1842 mentioned that "the Choctaws may be considered as an agricultural and stock-raising people; farms on the Red River will compare with many in the States […]. The richer class in addition to stock own, many of them, a number of slaves, these are engaged, generally, in cultivating cotton" 10 . Therefore, it seems that the possession of slaves and the ongoing subjugation of the latter were considered as evidence of the success of colonization in West by the Federal government and as a means for relocated Indians to legitimize their reinvented forms of sovereignty in Indian Territory. In maintaining not only economic but also ideological ties with the Deep South -in the cultural context of which they had developed "strategic mimesis" -the southeastern nations participated in the development of the Slave South west of the Mississippi. From a "facing West" perspective, one may contend that the reinventing process imposed by deportation made relocated Indians participants in the development of a "vast Southern Empire", which provided them with a certain extent of influence in the South at a time when the debate regarding the establishment of slavery in western territories raged in the United States. What is more, in the process, and from a "facing East" perspective, the geopolitical and cultural position southeastern nations came to occupy in Indian Territory seems to have turned relocated Indians into diplomats and pacifiers vis a vis Plains Indians.

In 1834, Lewis Cass, then Secretary of War, sent an expedition in the westernmost parts of Indian Territory to negotiate peace between relocated nations and Plains Indians, among whom the Comanches, that had been multiplying raids and attacks on relocated nations to resist the loss of their hunting grounds. Led by Colonel Henry Dodge and General Leavenworth, accompanied with George Catlin but also Cherokee, Delaware, Osage and Seneca guides, the expedition reached the Cross Timbers region, at the western limit of Indian Territory, and, after months of negotiations with the Comanches, a treaty was eventually signed at Camp Holmes on August 24, 1835. Although Comanche leaders may not have totally understood that the treaty actually implied they had to relinquish their hunting grounds, the active part taken by relocated Indians in this first stage of the long-term negotiation with the Plains Indians that would go on in the 1840s and 1850s not only illustrates the agency they developed in the securing of their new environment, but also the role they came to occupy in the process as diplomats of the Plains. It seems that the "civilized" character of the deported populations put them in an ambivalent position, at the same time victims of American expansionism and de facto colonizers of the Plains Indians. The creation of Indian Territory led to the emergence of a middle ground between Indian communities, characterized by cultural differences and incomprehension. In his journal, Ethan Allen Hitchcock, an agent in Indian Territory, described a peculiar scene that occurred on December 8, 1841, when some Osages came to visit the Cherokees in traditional attire:

Some half a dozen Osage Indians made their appearance last evening at the Council ground. Their heads were shaved and ornamented with feathers and they wore blankets in primitive style. The Cherokees gathered around them and gazed at them with as much curiosity as if they had never seen an Indian. The Osages would hardly have attracted more curiosity in the city of New York11 .

Two entwined types of interactions developed between the two cultural spheres on this new "Indian Frontier": trade and diplomacy. Merchants of the southeastern nations, along with the white merchants that were allowed to reside in Indian Territory got involved in the economic network of the region, that used to be operated by the French and the Spanish. Manufactured goods -mostly cotton goods -were exchanged for horses, mules, buffalo pelts and fur, but also Black slaves that the Plains Indians stole in the Republic of Texas. The mixed-blood Cherokee, Jesse Chisholm, embodies this growing commercial activity. He was responsible for the creation a trail between Fort Gibson and Fort Towson as early as 1830 and owned several trading posts on Little River and the Canadian River, east of Oklahoma City today. But, most of all, the figure of Jesse Chisholm is a good illustration of the ambivalence of this commercial activity. Indeed, while trading with the Plains Indians, the southeastern nations aimed at imposing their influence on them and securing this artificially created backcountry, with the help of the federal government which, in line with the terms of the Removal treaties that guaranteed the protection of relocated Indians, participated in the building of forts on the western border of Indian Territory (Fort Gibson (1824), Fort Towson (1824), Fort Coffee (1834), Fort Washita (1842), Fort Arbuckle (1850)). With the support of the government, the southeastern nations organized diplomatic relations with the Plains Indians, and somehow became both peacemakers and "civilizers" of the region. In September 1839, the first intertribal council was organized in the Cherokee capital, Tahlequah, where not less than 11 Indian nations convened, which had American authorities fear the nations might organize in a rebellious

  intensification of local agriculture -with the development of plantations and the reinforcement of slavery propelled by wealthy mixed-blood economic and political leaders -, and of transregional trade and exportation of cotton, made migrated Indians central participants in the construction of the western regions of the Union. The annual report of the Commissioner of Indian Affairs for the year 1846 regarding the Chickasaw nation in particularly eloquent in that respect:

  reinforcement of the Peculiar Institution by relocated Indians west of the Mississippi made Indian territory an extension of the Deep South. Deported Indians took their slaves with them along the Trail of Tears. But the striking increase in the number of slaves in Indian Territory seems to indicate that relocated nations participated in a transnational slave trade in the antebellum period. Figures regarding the Cherokee Nation for instance show that the number of slaves went from 1277 in 1820 to 2511 in 1860. As early as 1839, Lewis Ross

Nicolas Guyatt, Bind Us Apart: How Enlightened Americans invented Segregation, Oxford: Oxford University Press,

2 Pekka Hämäläinen, The Comanche Empire, New Haven: Yale University, 2008.

Augustin Habran, "The Southeastern Nations (1815-1861): Identity, Sovereignty and Strategic Mimesis through the Ordeal of Removal", Ph.D. dissertation defended in 2017, University of Paris.

I do not elaborate here on the tensions that occurred within the nations regarding the development of "strategic mimesis", whether they be linked to nativist rebellions against acculturation or to the dissenting vision of the "treaty parties" that threatened the national objective of the strategy for instance. This may be discussed in the debate.

This implied for instance the Cherokee Nation Act of Union of 1839, that followed the assassination of the Treaty Party leaders including Elias Boudinot, Major Ridge and John Ridge, then considered as "traitors".

Annual Report of the Commissioner of IndianAffairs, 1846, p.55.

Grant Foreman, Dir., A Traveler in Indian Territory: The Journal of Ethan Allen Hitchcock, Norman: University of OklahomaPress, 1996Press, [1930], pp.55-56. ], pp.55-56.

confederation against the republic 12 . Interestingly enough, no pan-Indian coalition emerged in the West. Instead, the southeastern nations developed a "civilizing" attitude towards the Plains Indians. The speech made by Creek Chief Rolley McIntosh to the Comanches when the first treaty was signed at Camp Holmes in 1835, that strategically blended incitement to adopt "civilization" and elements of traditional diplomacy, including gift giving and pipe smoking, illustrates this phenomenon: Brothers, we once lived in a country East of this. We broke the bushes out of the way, cleared the road, and we now live in this Country. When we reached our new homes we heard of you in the West. We heard of your way of living. Our forefathers used to live the same way. We now live differently. We live in peace and our children grow up to live in peace. This is the way we should all live. When I first came to the West I heard of your way of living. I heard of your killing each other, and I was sorry, all my people were sorry. …. Here is our little father, the white man, he has raised us, he is the cause of our making peace. … He has done us much good. We, the Muscogees, give you these white beads. They are the emblem of peace. … I wish the treaty we have made may be faithfully observed and that our children may sleep in their cradles in safety. …. I give you this tobacco. When you go home, I want all your warriors to smoke of it, and when the white smoke ascends, altho I shall be at home and not see it, it will be the same as if I was present 13 .

In the Fall of 1845, as the Mexican American war loomed, the federal government sent yet another expedition among the Plains Pah u cah answered these several speeches by stating that he came along way to See his white brothers the Cherokees & Creeks, and he assured them that he was pleased to hear all their talks and he must say were good 14 .

As it is Hicks's journal, it is difficult to determine whether the Comanche chief really considered the Cherokee emissaries as "white". And even if we consider the fact there may be a missing comma between "white brothers" and "Cherokees" in the quote, it is still striking to notice that the whites, the Cherokees and the Creeks are considered as a whole that is culturally sidelined by the Comanche chief. This concluding remark allows for a change of perspective 12 Foreman, A Traveler in Indian Territory, op. cit., pp.69-70. 13 Speech delivered to the Comanches and Osages, August 25, 1835, Western History Collections, Rolley McIntosh collection, Folder 1, University of Oklahoma, Norman, OK. 14 "The Journal of Elijah Hicks", in Chronicles of Oklahoma, vol.13, n°1, 1939, pp.68-99. regarding the multi-faceted post-Removal position of the southeastern Indian nations as they developed strategies to survive and maintain self-determination within the limited frame of the Federal treaties. Facing East from the Great Plains, the strategies emigrated nations developed to affirm their fragile sovereignty in this new environment -that included active participation in treaty-making processes targeting Plains Indians that resembled the colonial attitude adopted towards indigenous populations -seemed to coincide with the momentum of imperial expansionism Plains Indians had to face as a whole. It appears the study of the initiatives taken by post-Removal southeastern nations leads us to reconsider the development of the American nation-state in the West as it imposes a reflection on the complexity of Native American resistance and resilience in the process.


Bruno Baudoin

Stéphanie Satre

Schol- Arly Digital Methods

Editing

S Satre -B

Baudoin

J Salvayre

An epigraphic dataset to share and publish

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The online corpus of inscriptions of Caesarea Mauretaniae


Fayc ¸al

Ben Boualle

MD ` Gue

PhD Laurent Maı ¨moun

PhD Florentin Kucharczak

Pierre Le Fur

D Pharm

MD Fabien Vauchot

MD Boramy Hay

PhD Eric Rondet

MD, PhD Denis Mariano-Goulart

MD Ben Boualle ´gue

Left ventricle function assessment using gated first-pass 18 F-FDG PET: Validation against equilibrium radionuclide angiography

Purpose. We appraised the feasibility of left ventricle (LV) function assessment using gated first-pass 18 F-FDG PET, and assessed the concordance of the produced measurements with equilibrium radionuclide angiography (ERNA).

Materials and Methods. Twenty-four oncologic patients benefited from 99m Tc-labeled redblood-cell ERNA, in planar mode (all patients) and using SPECT (22 patients). All patients underwent gated first-pass 18 F-FDG cardiac PET. Gated dynamic PET images were reconstructed over 1 minute during tracer first-pass inside the LV and post-processed using in-house software (TomPool). After re-orientation into cardiac canonical axes and adjustment of the valves plane using a phase image, pseudo-planar PET images obtained by re-projection were automatically segmented using thresholded region growing and gradient-based delineation to produce an LV ejection fraction (EF) estimate. PET images were also post-processed in fullytomographic mode to produce LV end diastole volume (EDV), end systole volume (ESV), and EF estimates. Concordance was assessed using Lin's concordance (ccc) and Bland-Altman analysis. Reproducibility was assessed using the coefficient of variation (CoV) and intra-class correlation (ICC).

Results. Pseudo-planar PET EF estimates were concordant with planar ERNA (ccc = 0.81, P < .001) with a bias of 0% (95% CI [2 2%; 3%], limits of agreement [2 11%; 12%]). Reproducibility was excellent and similar for both methods (CoV = 2 ± 1% and 3 ± 2%, P = NS; ICC = 0.97 and 0.92, for PET and ERNA, respectively). Measurements obtained in fully-tomographic mode were concordant with SPECT ERNA: ccc = 0.83 and bias = 2 3 mL for LV EDV, ccc = 0.92 and bias = 0 mL for LV ESV, ccc = 0.89 and bias = 2 1% for LV EF (all P values < .001 for ccc, all biases not significant).

Conclusions. Gated first-pass 18 F-FDG PET might stand as a relevant alternative to ERNA for LV function assessment, enabling a joint evaluation of both therapeutic response and cardiac toxicity in oncologic patients receiving cardiotoxic chemotherapy. (

INTRODUCTION

Left ventricle (LV) function assessment plays a critical role in baseline and follow-up assessment of patients with LV systolic [START_REF] Wang | Natural history of asymptomatic left ventricular systolic dysfunction in the community[END_REF] or diastolic [START_REF] Flachskampf | Cardiac imaging to evaluate left ventricular diastolic function[END_REF] dysfunction, or receiving cardiotoxic chemotherapy. [START_REF] Murbraech | Heart failure and asymptomatic left ventricular systolic dysfunction in lymphoma survivors treated with autologous stemcell transplantation: A national cross-sectional study[END_REF] Standard LV function assessment based on the estimation of end diastole volume (EDV), end systole volume (ESV), and ejection fraction (EF) can be achieved using various non-invasive imaging techniques including echocardiography, cardiac magnetic resonance (CMR), and isotopic techniques. Gated equilibrium radionuclide angiography (ERNA), using either planar techniques or single photon emission computerized tomography (SPECT) and 99m Tc-labeled red blood cells, has long proven to be a valuable and reproducible technique for cardiac function evaluation. [START_REF] Van Royen | Comparison and reproducibility of visual echocardiographic and quantitative radionuclide left ventricular ejection fractions[END_REF][START_REF] Sibille | Comparative values of gated blood-pool SPECT and CMR for ejection fraction and volume estimation[END_REF][START_REF] Nichols | Validation of gated blood-pool SPECT regional left ventricular function measurements[END_REF][START_REF] Ioannidis | Electrocardiogram-gated single-photon emission computed tomography versus cardiac magnetic resonance imaging for the assessment of left ventricular volumes and ejection fraction: A meta-analysis[END_REF] Owing to its cost-effectiveness, simplicity, and high reproducibility, planar ERNA stands as the gold-standard for iterative LV EF assessment in adults. 8 SPECT ERNA allows both LV volume and EF estimation and has been thoroughly validated against CMR. [START_REF] Sibille | Comparative values of gated blood-pool SPECT and CMR for ejection fraction and volume estimation[END_REF][START_REF] Nichols | Validation of gated blood-pool SPECT regional left ventricular function measurements[END_REF][START_REF] Ioannidis | Electrocardiogram-gated single-photon emission computed tomography versus cardiac magnetic resonance imaging for the assessment of left ventricular volumes and ejection fraction: A meta-analysis[END_REF] First-pass radionuclide angiography using 99m Tclabeled agents has been extensively employed for LV and right ventricle (RV) function analysis. [START_REF] Friedman | First-pass radionuclide angiography[END_REF] The steadily increasing use of PET in clinical routine reinforces the motivation to develop first-pass PET methods for cardiac function evaluation. [START_REF] Chen | Measurement of cardiac output with first-pass determination during rubidium-82 PET myocardial perfusion imaging[END_REF][START_REF] Kreissl | Noninvasive measurement of cardiovascular function in mice with high-temporal-resolution small-animal PET[END_REF][START_REF] Knaapen | Stroke volume measurements with first-pass dynamic positron emission tomography: Comparison with cardiovascular magnetic resonance[END_REF] Recent studies have highlighted the feasibility of LV function assessment using [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] O-water PET and demonstrated the concordance of the produced estimates with those obtained using either CMR [START_REF] Driessen | Measurement of LV volumes and function using oxygen-15 water-gated PET and comparison with CMR imaging[END_REF][START_REF] Nordstro ¨m | Calculation of left ventricular volumes and ejection fraction from dynamic cardiac-gated 15O-water PET/CT: 5D-PET[END_REF] or myocardial perfusion SPECT. [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] As a rule of thumb, the proposed methods are readily transposable to first-pass PET using any tracer, since the firstpass of the tracer through cardiac cavities provides -at least over a given time range-a set of vascular images that indirectly reflects cardiac function. Nowadays, the most employed PET tracer in clinical routine is [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG, owing to its numerous indications in oncology and cardiology. The development of LV function assessment using first-pass [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET would substantially expand the diagnostic information provided by routine [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET explorations. By obviating the need for ERNA, it would also allow for higher patient comfort and lower received dose. Todica et al described LV volume and function measurements in healthy rats using gated first-pass [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET without significant difference compared to CMR in terms of ejection fraction. [START_REF] Todica | Positron emission tomography in the assessment of left ventricular function in healthy rats: A comparison of four imaging methods[END_REF] To our knowledge, no such measurements have been performed in humans to date.

TomPool is a free software developed in Montpellier University Hospital designed for semi-automated post-processing of equilibrium blood-pool SPECT images. It relies on a watershed immersion algorithm for ventricle segmentation and a deformable reference model for time-activity curve fitting. [START_REF] Collet | Semi-automatic segmentation of gated blood-pool emission tomographic images by watersheds. Application to the determination of right and left ejection fractions[END_REF][START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF][START_REF] De Kerleau | Automatic generation of noise-free time-activity curve with gated blood-pool emission tomography using deformation of a reference curve[END_REF] It has previously been validated against CMR for LV and RV function assessment. [START_REF] Sibille | Comparative values of gated blood-pool SPECT and CMR for ejection fraction and volume estimation[END_REF] In a recent study, it was adapted to first-pass PET data post-processing and allowed to produce LV volume and function estimates using firstpass [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] O-water PET that were in close agreement with those provided by gated myocardial perfusion SPECT. [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] The present work aimed to investigate the feasibility of LV volume and function measurements using gated first-pass [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET, in both pseudo-planar and fully-tomographic post-processing settings, and to compare the produced volume and function estimates with those obtained using gated ERNA in both planar and SPECT modes.

MATERIALS AND METHODS

Patients

Twenty four patients aged 55 ± 13 years (range 23-74 years, 13 men and 11 women) were prospectively recruited from the outpatients of the Nuclear Medicine Department at Montpelier University Hospital from December 2017 to November 2018. Included patients were referred for both [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET and ERNA in routine condition. [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET was performed for baseline or follow-up assessment of their cancer (18 malignant lymphomas, 4 breast cancer, 1 ovarian malignancy, and 1 cystic adenoid carcinoma). ERNA was performed for baseline or follow-up assessment of LV EF during cardiotoxic chemotherapy. The mean delay between [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET and ERNA was 6 ± 6 days (range 1-21 days). None of the recruited patients had documented cardiac disease. The study was approved by the Local Ethics Committee and all patients gave written informed consent. carried out using a dual-head Siemens Intevo camera equipped with low-energy high-resolution parallel-hole collimators. ECG gating used 16 time samples and a 10% R-R interval acceptance window.

Planar acquisitions were performed over 7 minutes in the standard 35°left-anterior-oblique direction. Planar images were sampled on a 64 9 64 matrix with a pixel size of 3.6 mm, and post-processed using the manufacturer's dedicated software. The LV was automatically segmented using gradient-based delineation. Background noise subtraction was applied using a region of interest positioned bottom-left to the LV. Manual adjustment of the automated segmentation mask and background region position was performed whenever necessary.

SPECT acquisitions were performed using 32 projections per head and 20 second per projection. SPECT images were reconstructed using the manufacturer's specifications (3D OSEM, 4 subsets, 6 iterations, 9 mm Gaussian post-filtering), without attenuation and scatter correction. Images were sampled using 6.6 mm isotropic voxels. SPECT data were postprocessed using in-house software TomPool [START_REF] Collet | Semi-automatic segmentation of gated blood-pool emission tomographic images by watersheds. Application to the determination of right and left ejection fractions[END_REF][START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF][START_REF] De Kerleau | Automatic generation of noise-free time-activity curve with gated blood-pool emission tomography using deformation of a reference curve[END_REF] to produce estimates of LV EDV, ESV, and EF.

Gated First Pass 18 F-FDG PET Acquisition and Analysis

Cardiac PET acquisitions were performed using a Siemens Biograph mCT Flow scanner in time-of-flight mode, following IV injection of 3.5 MBqÁkg -1 of 18 F-FDG (246 ± 58 MBq, range 152-350 MBq). A transmission CT scan was obtained prior to PET for attenuation correction purpose (CT-AC). Emission list-mode data were acquired over 5 minutes starting from the IV injection of the tracer to the arm. After correction for random coincidences, scatter, and dead time, PET data were reconstructed twice. First, a dynamic sequence (30 frames of 10 seconds each) was obtained that allowed to identify the starting point for gated reconstructions. That starting point was set as the time at which a significant activity was seen inside the LV. A second image reconstruction was then performed over the first-pass time range using CT-AC 3D OSEM (21 subsets, 3 iterations) with 8-interval gating. The first-pass time range was either set to 1 or 3 minutes. Final image matrices were sampled on a 128 9 128 9 74 grid with 3 mm cubic voxels. 3D Gaussian post-filtering was applied using an 8 mm kernel for pseudo-planar image extraction, and a 15 mm kernel for fullytomographic post-processing. A representative example of gated first-pass PET-CT images is shown in Figure 1. Gated first-pass blood-pool images were then post-processed using in-house software (TomPool) that was originally designed for ERNA and adapted for first-pass data analysis. A complete description of the algorithm can be found in. [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF][START_REF] Collet | Semi-automatic segmentation of gated blood-pool emission tomographic images by watersheds. Application to the determination of right and left ejection fractions[END_REF][START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF][START_REF] De Kerleau | Automatic generation of noise-free time-activity curve with gated blood-pool emission tomography using deformation of a reference curve[END_REF] Regarding pseudo-planar image extraction, the workflow was as follows (see Figure 2). PET images were re-oriented into cardiac canonical axes using horizontal long axis then vertical long axis (VLA) views. VLA images were then summed along the left-right direction in order to compute a VLA phase image, which is a parametric map of the time of end-systole (pixel color codes the gating interval for which the pixel activity is the lowest). Since the volume changes of the ventricles occur in phase opposition compared to those of the atria, the valve plane (i.e., the separation between ventricular and atrial activity) could be easily located and manually positioned using the VLA phase image. Next, the activity located in front of the valve plane was summed along the antero-posterior direction to produce pseudo-planar images that reflect only ventricular activity. Last, automated segmentation of the LV on pseudo-planar images using thresholded region growing (with gradient-based LV/RV delineation) allowed to build an LV time-activity curve from which LV EF was inferred. Manual refinement of the produced contours was performed whenever necessary. Background noise subtraction was applied using a square region of interest of 5 pixels automatically positioned at a 24 mm distance left to the LV. Thresholds ranging from 40% to 70% were tested in order to determine the optimal threshold value with respect to planar and SPECT ERNA.

Regarding fully-tomographic post-processing, a four-dimensional immersion algorithm was run that produced a partition of the gated images into 4D regions centered on local intensity maxima. Each region was then assigned either to the LV, RV, or extra-ventricular structures depending on the relative position of its barycentre with respect to the reference planes (septum and valve planes). The LV segmentation mask was obtained using a thresholding method at a fixed percentage of the 4D maximal intensity value inside the regions belonging to LV. Thresholds ranging from 50% to 70% were tested in order to determine the optimal threshold value. LV volumes were computed using a count-based method in which the volume of each voxel was normalized by the ratio of its intensity to the LV maximal intensity. Ventricular ejection curves were fitted to the 8 time samples using a deformable curve model that allowed to estimate LV EDV, ESV, and EF. [START_REF] De Kerleau | Automatic generation of noise-free time-activity curve with gated blood-pool emission tomography using deformation of a reference curve[END_REF]

Statistical Analysis

Continuous variables are expressed as mean ± standard deviation (min-max range). Parameters obtained using pseudoplanar PET were compared to those given by planar and SPECT ERNA. Parameters obtained using fully-tomographic PET were compared to those given by SPECT ERNA. Concordance and correlation between LV volume and function given by gated first-pass PET and those given by ERNA were assessed using Pearson's correlation coefficient (R), Lin's concordance correlation coefficient (ccc), and Bland-Altman analysis. Difference between homologous variables was characterized using a paired Student's t-test after checking data sample normalcy using the Kolmogorov-Smirnov test. Planar ERNA and pseudo-planar PET data were post-processed in a blinded fashion by 3 independent nuclear medicine specialists in order to assess the reproducibility of the LV EF measurements using the intra-class correlation (ICC) coefficient and the coefficient of variation (CoV).

RESULTS

Dosimetry

Effective dose was 5.7 ± 0.2 (range 5.3-6.4) mSv for ERNA. Regarding PET-CT acquisition, total effective dose for the standard acquisition was 11.0 ± 3.2 (range 6.5-17.2) mSv (mean dose 4.7 mSv for [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG and 6.3 mSv for chest-abdomen-pelvis CT). Additional effective dose due to cardiac CT was 3.8 ± 1.0 (range 1.7-5.4) mSv.

Pseudo-planar PET

The optimal first-pass time range (either 1-minute or 3-minutes) was first assessed against planar ERNA as the reference. Visually, pseudo-planar images obtained using a first-pass time range of 1-minute had higher LVto-background contrast than 3-minutes images (see Online Figure 1) due to substantial myocardial and hepatic uptake on 3-minutes images. Quantitatively, 1minute LV EF estimates showed higher concordance with planar ERNA estimates than 3-minutes estimates (optimal Lin's concordance 0.82 and 0.63 respectively, see Online Table 1 and Online Figure 2 for details). Manual adjustment of the LV automatic segmentation was necessary in 2/24 cases for planar ERNA, in 1/24 case for 1-minute pseudo-planar PET, and in 7/24 cases for 3-minutes pseudo-planar PET As such, 1-minute was considered as the optimal first-pass time range and all the results presented in the sequel are related to 1-minute PET images.

The best concordance and lowest bias of pseudoplanar PET with planar ERNA and SPECT ERNA was achieved using 50% and 65% segmentation thresholds respectively. Figure 3 shows the scatter plots and Bland-Altman diagrams assessing the concordance between LV EF obtained using pseudo-planar PET and planar (top) and SPECT (bottom) ERNA. With respect to planar ERNA, using a 50% threshold, Lin's concordance was 0.81 (P \ .001) and bias was 0% (not significant, 95% CI [-2%; 3%], limits of agreement [-11%; 12%]). As demonstrated by the Bland-Altman diagram, there was a moderate albeit significant trend towards an underestimation of low EFs and overestimation of high EFs using pseudo-planar PET. With respect to SPECT ERNA, using a 65% threshold, Pearson's correlation and Lin's concordance were both 0.75 (P \ .001) and bias was 0% (not significant, 95% CI [-4%; 4%], limits of agreement [-17%; 18%]).

Planar ERNA LV EF reproducibility was characterized by a CoV of 3 ± 2% (range [0; 10%]) and an ICC coefficient of 0.92. Pseudo-planar PET (50% threshold) LV EF reproducibility was characterized by a CoV of 2 ± 1% [0; 6%]) and an ICC coefficient of 0.97. No statistical difference was found between the CoV obtained in planar ERNA and those obtained in pseudo-planar PET.

Fully-tomographic Post-processing

LV delineation using a 60% segmentation threshold yielded the highest concordance and lowest bias of firstpass PET with SPECT ERNA in terms of LV EDV, ESV, and EF (see Online Table 2 for details). Figure 4 shows the scatter plots and Bland-Altman diagrams assessing the concordance between LV EDV, ESV, and EF (from left to right) obtained using fully-tomographic PET and SPECT ERNA. Lin's concordance was 0.83 for LV EDV, 0.92 for LV ESV, and 0.89 for LV EF (all P values \ .001). Bias was -3 mL (not significant, 95% CI [-7; 1] mL, limits of agreement [-20; 14] mL) for LV EDV, 0 mL (not significant, 95% CI [-2; 2] mL, limits of agreement [-9; 9] mL) for LV ESV, and -1% (not significant, 95% CI [-4%; 1%], limits of agreement [-12%; 10%]) for LV EF.

Figure 5 shows a representative example of SPECT ERNA (left) and first-pass PET (right). From top to bottom are displayed the 3D segmentations (raw volumes and parametric surface rendering) at end diastole and end systole, and the LV time-activity curves. Cine gated images are provided as supplemental material (see Online Figure 3). In the present study, we assessed feasibility and relevance of LV EF and volume measurements from gated first-pass [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET. First-pass PET images were post-processed in both pseudo-planar and fullytomographic modes. The motivation to develop a pseudo-planar approach was based on the fact that, owing to its high reproducibility, planar ERNA stands as the gold-standard isotopic method for iterative LV EF evaluation and detection of drug-induced cardiac toxicity. [START_REF] Hesse | EANM/ESC guidelines for radionuclide imaging of cardiac function[END_REF][START_REF] Ganz | Review of tests for monitoring doxorubicin-induced cardiomyopathy[END_REF] Besides, pseudo-planar post-processing is much more practical in terms of post-processing time (less than one minute compared to several minutes for the fully-tomographic approach), making it readily implementable in clinical routine. As such, pseudoplanar techniques based on re-projection of SPECT data have already been developed using standard and dedicated cameras. [START_REF] Bartlett | Left ventricular ejection fraction: Comparison of results from planar and SPECT gated blood-pool studies[END_REF][START_REF] Wells | Planar radionuclide angiography with a dedicated cardiac SPECT camera[END_REF][START_REF] Hofman | Measurement of left ventricular volumes and function with O-15-labeled carbon monoxide gated positron emission tomography: Comparison with magnetic resonance imaging[END_REF] To our knowledge, this is the proof of concept for LV function assessment using first-pass [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET in humans along with a post-processing workflow compatible with patient throughput in nuclear medicine labs. In this context, the use of the routine tracer [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG appears crucial since previous attempts to asses LV function using first-pass PET methods relied on [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] Owater or [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] O-labeled carbon monoxide which are restricted to institutions equipped with an on-site cyclotron. [START_REF] Driessen | Measurement of LV volumes and function using oxygen-15 water-gated PET and comparison with CMR imaging[END_REF][START_REF] Nordstro ¨m | Calculation of left ventricular volumes and ejection fraction from dynamic cardiac-gated 15O-water PET/CT: 5D-PET[END_REF][START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF][START_REF] Hofman | Measurement of left ventricular volumes and function with O-15-labeled carbon monoxide gated positron emission tomography: Comparison with magnetic resonance imaging[END_REF] In a patient viewpoint, there are mainly two expected benefits from [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET-based LV function assessment. First, it allows to evaluate both disease extension (or therapeutic response) and LV function in a single examination. Second, it enables a moderate albeit significant reduction in terms of effective dose (3.8 mSv for cardiac CT vs 5.7 mSv for ERNA). At our institution, a large proportion of patients addressed for concomitant [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET and ERNA are affected by hematologic malignancies. In these often young patients for whom a long follow-up including repeated isotopic explorations is required, dosimetric considerations are of critical importance. [START_REF] Nievelstein | Radiation exposure and mortality risk from CT and PET imaging of patients with malignant lymphoma[END_REF] Dynamic PET acquisitions were performed over 5 minutes in order to estimate the optimal time range for first-pass image extraction. Due to substantial myocardial uptake (with respect to vascular activity) from the first minutes following tracer injection, [START_REF] Bøtker | Myocardial glucose uptake measured with fluorodeoxyglucose: A proposed method to account for variable lumped constants[END_REF] the PET images with the higher LV-to-background contrast were those obtained using a short first-pass time range of 1 minute. Although the kinetics of 18 F-FDG myocardial uptake is known to be highly variable and dependent upon fasting state and plasma glucose and insulin levels, [START_REF] Choi | Factors affecting myocardial 2-[F-18]fluoro-2-deoxy-Dglucose uptake in positron emission tomography studies of normal humans[END_REF] myocardial uptake was negligible on 1-minute images in all of our patients. Owing to that high contrast, the absence of splenic uptake interfering with background correction, and the cancelation of atrial activity on the short-axis images obtained by re-projection, the LV EF estimates produced by the pseudo-planar method favorable inter-operator reproducibility (mean CoV 2%). The variability of planar ERNA LV EF measurements was slightly higher (mean CoV 3%) and similar to that reported in the literature. [START_REF] Okada | Observer variance in the qualitative evaluation of left ventricular wall motion and the quantitation of left ventricular ejection fraction using rest and exercise multigated blood pool imaging[END_REF][START_REF] Heidendal | Reproducibility of ejection fraction measurements by gated equilibrium blood pool scintigraphy[END_REF] Using an adapted segmentation threshold at 50% of the global maximal LV activity on pseudo-planar images, there was an excellent agreement between the two methods (no significant bias, limits of agreement around ± 10%). Importantly, considering the reference cutoff at 50% to detect LV dysfunction in patient receiving cardiotoxic therapies, 8 all patients were identically classified using planar ERNA and pseudo-planar PET (22 normal and 2 altered LV EF). It has however to be noted that a trend towards a proportional bias is observed on the Bland-Altman diagram. The mean bias was not significant because the optimal segmentation threshold was set so as to maximize the concordance between planar ERNA and pseudo-planar PET EF estimates. The proportional bias may be explained by the fact that pseudo-planar PET post-processing allows to exclude atrial activity by re-projecting only ventricular activity. Using planar atrial activity may overlap ventricular activity, leading to relative EF under-estimation especially at high EF values.

Concordance of pseudo-planar LV EF estimates with those provided by SPECT ERNA was moderate, especially for high EF values (limits of agreement around ± 20%). Nevertheless, Pearson's correlation (R = 0.75) was similar to that reported in the literature between planar ERNA and SPECT ERNA processed using standard commercial software. [START_REF] Harel | SPECT versus planar gated blood pool imaging for left ventricular evaluation[END_REF] Although 16-interval gating is recommended for planar ERNA and sometimes preferred for SPECT ERNA, [START_REF] Wells | Planar radionuclide angiography with a dedicated cardiac SPECT camera[END_REF][START_REF] Hofman | Measurement of left ventricular volumes and function with O-15-labeled carbon monoxide gated positron emission tomography: Comparison with magnetic resonance imaging[END_REF] it has been shown that LV EF estimates obtained using 8-frame gated SPECT ERNA do not significantly differ from those obtained using 16-frame gating [START_REF] Kim | Gated blood pool SPECT for measurement of left ventricular volumes and left ventricular ejection fraction: Comparison of 8 and 16 frame gated blood pool SPECT[END_REF] and are concordant with CMR measurements. [START_REF] Sibille | Comparative values of gated blood-pool SPECT and CMR for ejection fraction and volume estimation[END_REF] In our study, gated PET data were sampled using 8 frames/cycle. This was primarily motivated by the inherent low-count nature of short duration first-pass data, and in line with previous studies exploring the feasibility of first-pass PET LV EF assessment. [START_REF] Driessen | Measurement of LV volumes and function using oxygen-15 water-gated PET and comparison with CMR imaging[END_REF][START_REF] Nordstro ¨m | Calculation of left ventricular volumes and ejection fraction from dynamic cardiac-gated 15O-water PET/CT: 5D-PET[END_REF][START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF][START_REF] Todica | Positron emission tomography in the assessment of left ventricular function in healthy rats: A comparison of four imaging methods[END_REF] The fully-tomographic post-processing of first-pass PET data provided LV assessment that was highly concordant with SPECT ERNA measurements in terms of LV EDV, ESV, and EF. Volume measurements relied on a count-based approach assuming a uniform activity distribution inside the LV. This method is supposed to account for signal blurring at the ventricle edges due to partial volume effect and motion artifacts. When passing from equilibrium to first-pass imaging, the uniformity assumption was reasonably maintained for what concerns the LV since tracer dilution in blood flow was sufficient downstream the pulmonary circulation. [START_REF] Dokoumetzidis | A model for transport and dispersion in the circulatory system based on the vascular fractal tree[END_REF] The optimal threshold value for LV segmentation was found to be 60%, which is higher than the optimal threshold previously reported using first-pass [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] O-water PET. [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] The discrepancy between the two threshold values was likely due to a better resolution and contrast in [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG images compared to [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] O-water images (smaller positron range, slower tracer diffusion to the myocardium) and to the different gold-standards employed (ERNA vs myocardial perfusion SPECT). Although feasible using first-pass PET methods, [START_REF] Boualle | Feasibility of biventricular volume and function assessment using first-pass gated 15 O-water PET[END_REF] right ventricle (RV) analysis was not performed because it was beyond the scope of the present study and because gold-standard assessment of RV function was not available in our cohort.

Last, the technique presented in the present study should be feasible and relevant in the frame of cardiac PET for which a hypoglycemic regime and/or a euglycemic hyperinsulinemic clamp is usually performed. Indeed, in either case myocardial uptake is expected to be negligible during the first minutes post-injection that are exploited for first-pass blood-pool analysis. [START_REF] Knuuti | Euglycemic hyperinsulinemic clamp and oral glucose load in stimulating myocardial glucose utilization during positron emission tomography[END_REF]

NEW KNOWLEDGE GAINED

This study demonstrates that LV function assessment is feasible using gated first-pass [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET-CT, yielding higher patient comfort and lower total dosimetry. First-pass PET images are mineable using either pseudo-planar or fully-tomographic approaches. The latter provides a complete characterization of LV functional parameters (including volumes and EF) that is in good agreement with SPECT ERNA assessment. The pseudo-planar workflow yields reproducible LV EF estimates that are highly concordant with planar ERNA measurements. Its implementation should easily fit within a clinical routine framework.

CONCLUSION

Gated first-pass [START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] F-FDG PET might stand as a relevant alternative to ERNA for LV function assessment, enabling a joint evaluation of both therapeutic response and cardiac toxicity in oncologic patients receiving cardiotoxic chemotherapy.

Figure 1 .

 1 Figure 1. Representative gated first-pass 18 F-FDG PET-CT images. Images were reconstructed from gated list-mode data over 1 min during the first-pass of the tracer inside the LV (8-interval gating, 15 mm Gaussian post-filtering). Images are shown in horizontal long axis, vertical long axis, and short axis. Time frames are swept from top to bottom then left to right.

Figure 2 .

 2 Figure2. Workflow for LV EF estimation using pseudo-planar PET images. PET images are reoriented into canonical axes using horizontal long axis (A) then vertical long axis (B) views. VLA images are then summed along the left-right direction in order to compute a VLA phase image (C) that allows to manually position the valve plane (highlighted vertical line). Next, the activity located in front of the valve plane is summed along the anterior-posterior direction to produce pseudo-planar images of ventricular activity (D). Last, automated segmentation of the LV on pseudo-planar images using thresholded region growing and gradient-based delineation allows to build an LV time-activity curve (E).

Figure 3 .

 3 Figure 3. Comparison between LV EF estimates obtained using pseudo-planar gated first-pass PET images and (left) planar and (right) SPECT ERNA. Top: scatter plots. The dotted lines indicate the perfect identity. The dashed lines stand for the linear regression. Bottom: Bland-Altman diagrams. The dotted lines indicate the mean difference (grayed is the 95% confidence interval) and the plain lines the 95% limits of agreement. The dashed line stands for the linear regression (not shown if not significant). R Pearson's correlation; ccc Lin's concordance correlation coefficient.

Figure 4 .

 4 Figure 4. Comparison between LV EDV, ESV, and EF estimations obtained using gated first-pass PET and SPECT ERNA. Top: scatter plots. The dotted lines indicate the perfect identity. The dashed lines stand for the linear regression. Bottom: Bland-Altman diagrams. The dotted lines indicate the mean difference (grayed is the 95% confidence interval) and the plain lines the 95% limits of agreement. R Pearson's correlation, ccc Lin's concordance correlation coefficient.

Figure 5 .

 5 Figure 5. Representative example of SPECT ERNA (left) and first-pass PET (right) in patient #11 (male, 72 years, baseline assessment in a follicular lymphoma). From top to bottom are shown the 3D segmentations (raw volumes and parametric surface rendering: left ventricle in red, right ventricle in blue, extra-ventricular structures in green) at end diastole and end systole, and the LV time-activity curves.

Ben Boualle `gue et al LV function assessment by first-pass[START_REF] Piot | Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: A preliminary study[END_REF] FDG PET

Disclosure

The authors have no conflict of interest to disclose.

Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.'


est destinée au dépôt

Real-time shear wave ultrasound elastography: a new tool for the evaluation of diaphragm and limb muscle stiffness in critically ill patients

Aurelien Flattres, Yassir Aarab, Stéphanie Nougaret, Fanny Garnier, R.

Larcher, Mathieu Amalric, Kada Klouche, Pascal Etienne, Gilles Subra, Samir Jaber, et al.

To cite this version:

Aurelien Flattres, Yassir Aarab, Stéphanie Nougaret, Fanny Garnier, R. Larcher, et al.. Real-time shear wave ultrasound elastography: a new tool for the evaluation of diaphragm and limb muscle stiffness in critically ill patients. Critical Care, 2020, 24, pp.34. 10.1186/s13054-020-2745-6. hal-