domain: sdv.ib sdv spi

text:
Hugo Dorez

Raphaël Sablong

Laurence Canaple

Hervé Saint-Jalmes

Sophie Gaillard

Driffa Moussata

PhD Olivier Beuf

Endoluminal high-resolution MR imaging protocol for colon walls analysis in mouse model of colitis

ABSTRACT:

Object: An endoluminal MR imaging protocol including the design of an endoluminal coil (EC) was defined for high spatial resolution MR imaging of mice gastrointestinal walls at 4.7T.

Materials and Methods: A receive-only radiofrequency single-loop coil was developed for mice colon wall imaging. Combined with a specific protocol, the prototype was first characterized in vitro on phantoms and on vegetables. Signal-to-noise ratio (SNR) profiles were compared with a quadrature volume birdcage coil (QVBC). Endoluminal MR imaging protocol combined with the EC was assessed in vivo on mice.

Results: SNR measured close to the coil is significantly higher (10 times and up to 3 mm of the EC center) than the SNR measured with the QVBC. The gain in SNR can be used to reduce the in-plane pixel size up to 39x39µm² (234 µm slice thickness) without time penalty.

The different colon wall layers can only be distinguished on images acquired with the EC. Conclusion: Dedicated EC provides suitable images for the assessment of mice colon wall layers. This proof of concept provides gain in spatial resolution and leads to adequate protocols, for the assessment of human colorectal cancer that can now be used as a new imaging tool for a better understanding of the pathology.

KEYWORDS: Colorectal Neoplasms, Magnetic Resonance Imaging, Colitis, Instrumentation INTRODUCTION:

Every year, on the overall cases of cancer diagnosed in the world, 13% are colorectal cancer (CRC) [START_REF] Bray | Global cancer transitions according to the Human Development Index (2008-2030): a population-based study[END_REF][START_REF] Jemal | Global cancer statistics[END_REF][START_REF] Siegel | Colorectal cancer statistics, 2014[END_REF]. It is the second deadliest cancer in Western countriesjust behind lung cancer.

The 5-years survival rate is higher than 80% when the cancer is diagnosed and treated at an early stage [START_REF] O'connell | Colon Cancer Survival Rates With the New American Joint Committee on Cancer Sixth Edition Staging[END_REF].The cancerogenesis of CRC has not been yet precisely established but two major pathways have been identified [START_REF] Takayama | Colorectal cancer: genetics of development and metastasis[END_REF]:the chromosomal instability pathway (adenomacarcinoma sequence) and the microsatellite instability. Those pathways induce changes in the cellular proliferation with abnormal cells growing and infiltration into the gastrointestinal walls. The different stages of CRC infiltration are well known [START_REF] Bisognin | An integrative framework identifies alternative splicing events in colorectal cancer development[END_REF][START_REF] Fearon | Molecular Genetics of Colorectal Cancer[END_REF].It is first characterized by an inflammation stage affecting the superficial layer of the colon wall. Then, the abnormal cells proliferation infiltrates the wall to deeper structures and, eventually, reaches the lymphatic system. Because the survival of patientsstrongly depends on the diagnosis stage, anearly and accurate diagnosisto improve thetherapeutic response efficacy is highly beneficial to the patient. Magnetic Resonance Imaging (MRI), computed tomography (CT), positron emission tomography (PET) andsome optical modalitiesprovide different kind of information when imaging gastrointestinal walls.However, it is still difficult (using those modalities and associated protocols) to assess fine structures from the abnormal cells proliferation.Today, endoscopic ultrasound (EUS) is widely used in clinical routine for the staging of colorectal cancer lesions [START_REF] Vanagunas | Accuracy of Endoscopic Ultrasound for Restaging Rectal Cancer Following Neoadjuvant Chemoradiation Therapy[END_REF][START_REF] Puli | Accuracy of Endoscopic Ultrasound to Diagnose Nodal Invasion by Rectal Cancers: A Meta-Analysis and Systematic Review[END_REF][START_REF] Puli | Can Endoscopic Ultrasound Predict Early Rectal Cancers That Can Be Resected Endoscopically? A Meta-Analysis and Systematic Review[END_REF]. It is an available and low costreal-time (motion free) imaging modality.

Moreover, the sensitivity of EUS for rectal tumors invasion is approximately 88-95% while specificity is nearly 100% (for stage 2 and more) [START_REF] Puli | How Good is Endoscopic Ultrasound in Differentiating Various T Stages of Rectal Cancer? Meta-Analysis and Systematic Review[END_REF]. However, EUS is especially used on rectal carcinomas and fewer studies have shown the potential of this modality on colon cancer [START_REF] Vander Noot | Diagnosis of gastrointestinal tract lesions by endoscopic ultrasound-guided fine-needle aspiration biopsy[END_REF][START_REF] Hurlstone | Endoscopic Ultrasound Miniprobe Staging of Colorectal Cancer: Can Management Be Modified?[END_REF][START_REF] Hurlstone | High magnification chromoscopic colonoscopy or high frequency 20 MHz mini probe endoscopic ultrasound staging for early colorectal neoplasia: a comparative prospective analysis[END_REF]. EUS is also strongly dependent on operator and patient and thus require practice to perform anaccurate diagnosis.This is especially the case when examination is performed at early stages of CRC. Some studies describe the use of endoscopic MRI comparedto EUS [START_REF] Pilleul | In vitro rat colonic wall imaging with MR endoluminal coil: Feasibility study and histologic correlations1[END_REF][START_REF] Beuf | In vivo colon wall imaging using endoluminal coils: Feasibility study on rabbits[END_REF][START_REF] Maldjian | Endorectal surface coil MR imaging as a staging technique for rectal carcinoma: a comparison study to rectal endosonography[END_REF][START_REF] Syms | Magnetic Resonance Imaging Duodenoscope[END_REF][START_REF] Pilleul | High-resolution MR imaging appearance of colonic tissue in rabbits using an endoluminal coil[END_REF] to assess colorectal region.MRI is well suited to investigate human soft tissues and provides a good spatial resolution for the characterization and staging of gastrointestinal lesions [START_REF] Klessen | Local staging of rectal cancer: the current role of MRI[END_REF]. The modality provides ways of performing high-resolution quantitative maps, various contrast imaging and three-dimensional acquisitions but also performing magnetic resonance spectroscopy.However, colon and rectal walls assessment requires an even higher spatial resolution for visualizing different wall layers in detail [START_REF] Beaumont | MR Evaluation of Rectal Cancer: Current Concepts[END_REF]. It has been shown that spatial resolution in MRI could be used to depict more precisely, using EC, the gut wall than EUS,for N-staging [START_REF] Maldjian | Endorectal surface coil MR imaging as a staging technique for rectal carcinoma: a comparison study to rectal endosonography[END_REF] for example or for the staging of inflammation degrees and cancer lesions. Despite the fact that endoscopic MRI has demonstrated to be superior to MRI using external array coils, by providingexquisiteinformation of wall structures [START_REF] Beuf | In vivo colon wall imaging using endoluminal coils: Feasibility study on rabbits[END_REF][START_REF] Pilleul | High-resolution MR imaging appearance of colonic tissue in rabbits using an endoluminal coil[END_REF][START_REF] Armenean | Endoluminal loop radiofrequency coils for gastrointestinal wall imaging[END_REF][START_REF] Armenean | Optimization of endoluminal loop radiofrequency coils for gastrointestinal wall MR imaging[END_REF], the use of endoscopic coils in human can induce strong local temperature increase at coil tip and along the coaxial cable [START_REF] Ladd | Reduction of resonant RF heating in intravascular catheters using coaxial chokes[END_REF][START_REF] Nitz | On the heating of linear conductive structures as guide wires and catheters in interventional MRI[END_REF][START_REF] Shellock | Radiofrequency Energy-Induced Heating During MR Procedures: A Review[END_REF]. While heating can be strongly reduced adding for example radiofrequency traps [START_REF] Ladd | Reduction of resonant RF heating in intravascular catheters using coaxial chokes[END_REF][START_REF] Gauss | RF traps for radio frequency coils used in MRI[END_REF], the use of inner coils on humans was currently limited to prostate or rectumand endoscopic MRI of colon based on the use of endoluminal coil is not performed on patient.Especially due to the Human colon anatomy (angle at the rectosigmoid junction) and theinvasive procedure (requires anesthesia and insertion of the coil into the patient's rectum).

Today, a better understanding of the CRC genesis to adapt therapeutics responses and increase the survival of patients is needed. This goes through the following of the adenomacarcinoma sequence(inflammation to cancer) on a model of CRC.The follow-up of this sequence on Human longitudinal studies based on endoscopic MRI is not yet possible due to current safety issues. Moreover, the development of CRC on Human is a long process that can last over decades to understand the growth mechanisms (inflammation evolving into cancer).

Nevertheless, this can be doneon a mouse model of colitis [START_REF] Tanaka | A novel inflammation-related mouse colon carcinogenesis model induced by azoxymethane and dextran sodium sulfate[END_REF], chemically induced by the combination of dextran sulfate sodium (DSS 2% in drinking water) and azoxymethan (AOM, 10mg/kg).Trying to understand the growth mechanisms of CRC and to assess the potential of MRI in a mouse model of colitis present several advantages: first, the pathology induced by the method introduced by Tanaka et al in 2003 is a reliable model with strong correlations between Human and mice CRC; then, it is possible to follow mice on a much shorter time period (typically six months); and, finally, the examination can be performed for each stages. This paper is describing an endoluminal MRI protocol dedicated to the examination of a mouse cancer model as a preliminary and mandatory step before to move to clinical Human CRC examinations.

While MRI is well suited to investigate abdominal-anatomical structures [START_REF] Klessen | Local staging of rectal cancer: the current role of MRI[END_REF],colon and rectal walls assessment requires an even higher spatial resolution for visualizing different wall layersin detail [START_REF] Beaumont | MR Evaluation of Rectal Cancer: Current Concepts[END_REF], even more on mice (colon wall thickness 0.3-0.7 mm [START_REF] Aychek | Quantitative analysis of intravenously administered contrast media reveals changes in vascular barrier functions in a murine colitis model[END_REF]), still within a limited acquisition time suitable for in vivo examination.

Endoluminal Coil (EC) is drastically increasing the signal-to-noise ratio (SNR) close to the coil compared to external array coil [START_REF] Beuf | In vivo colon wall imaging using endoluminal coils: Feasibility study on rabbits[END_REF][START_REF] Pilleul | High-resolution MR imaging appearance of colonic tissue in rabbits using an endoluminal coil[END_REF][START_REF] Armenean | Endoluminal loop radiofrequency coils for gastrointestinal wall imaging[END_REF][START_REF] Armenean | Optimization of endoluminal loop radiofrequency coils for gastrointestinal wall MR imaging[END_REF]. This kind of elongated loop, based on two coplanar copper traces, was already used for intravascular MRI and MRS in the midnineties [START_REF] Atalar | High resolution intravascular MRI and MRS by using a catheter receiver coil[END_REF]. The temperature around the EC was measured during in vitroacquisition [START_REF] Verret | RF heating reduction associated to an MR endoluminal coil at 3T. ESMRMB[END_REF].

No abnormal and critical temperature increasing was observed. EC can provide ahigher spatial and/or temporal resolution and image quality to improve the characterization and staging of colorectal lesions. The aim of this study was to develop, build and characterize an EC for mice rectal wall investigation together with the adapted protocol. The proof of concept of the whole protocol was demonstrated on a limited number of examinations at different stages of a mouse model of CRC.

MATERIALS AND METHODS:

Endoluminal Coil description:

The EC was designed for mice colon investigation on a 4.7 T Bruker Biospec system (Bruker, Ettlingen, Germany). It is a single loop with dimensions sized to the colon mouse anatomy [START_REF] Komárek | Chapter 2.2 -Gross Anatomy[END_REF]which leads to a 30 mm length and a 1.6 mmouter diameter(heat shrink coating included).The copper tracksare 0.8 mm width and 0.8 mm thick with a copperthickness of 35 µm. Following these characteristics, the inductance and resistance of the copper tracks were calculated using the analytical expression of two-distanttraces equation.The coil loop and tuning and matching circuit (including a ground plane on the back side of the circuit)were mechanically carved (Circuit Board Plotters S63, LPKF Laser and Electronics®, Germany) on both sides of a FR4 epoxy substrate of 0.8 mm thickness (C.I.F®, Buc, France).Nonmagnetic electronic circuit components were soldered on a single face. The two longest conductors of the loop have been placedon each side of the substrate.A copper tape was used at the distal end of the coil to close the loop between the two faces (Fig1).One for connecting the loop to the upper face (straight arrows) and, the second one, to connect the direct current (DC) ground and radiofrequency (RF) signal ground together (dashed arrows)to the ground plane.This is done to avoid current loops between two different grounds. The RF signal was carried out by a coaxial cable (RG-58, Radiall®, France) and the DC current travels through a 8-wires cable (Alpha Wire®, New Jersey, USA) connected on a nonmagnetic Fisher connector (Plugs 4032, Fisher Connectors®, Suisse) to the coil. This latter decoupling cable is connected to the 14 pinsconnector of the Bruker decoupling box cable through a homemade Fisher-Bruker conversion cable.A heat shrink coating (PF3-135) houses the loop coil to isolate the tracks from colon and rectum tissues.The end of the coil was sealed with glue (Araldite PRECISION, Araldite®, Bâle, Switzerland). When the EC is used,the electrical circuitis isolated with polytetrafluoroethylene (PTFE or Teflon, DuPont®, Wilmington, USA) to avoid contacts with tissues or liquids.

Endoluminal Coil characterization:

The resonant circuit is based on a RLC resonator circuit made of fixed nonmagnetic components (ATC, Huntington Station, New York, USA) and trimmer components (AT 57290, Temex Ceramics®, Bordeaux, France) -Fig 1 .Considering only the intrinsic parameters of the coil, which are the coil geometry, the materials used and the coupling effects (mutual inductance for example); the loop inductance and resistance wereestimated to 33.2 nH and 0.1 Ohm respectively.The values were calculated and corrected using measurements on a Vector Network Analyzer (E5070B -ENA Series, Agilent Technologies®, California, USA) -VNA.Intrinsic characteristics of electronic components (series resistances, self-inductances, parallel capacitances, self-frequency resonance) were modeled to simulate the precise electronic behavior of the coil. Modeling was done usinga Simulation Program with Integrated Circuit Emphasis(LTspiceIV, Linear Technology®, Milpitas, USA) feed with electronic components characteristics based on their individual datasheets. The value and manufacturers of the electronic components are summarized in table 1.

In thecoil design,there are basically four functionsto achieve.Briefly, the capacitor 𝐶 𝑡 insures the tuning function, changing this value adjust the resonance frequency of the coil (on the S11 magnitude chart). Capacitors𝐶 𝑚 ,1 and 𝐶 𝑚 ,2 are used for matching the coil to the 50 Ohms impedance of receiver circuit in order to maximize the signal power transmission. The𝐶 𝐵,1 and 𝐶 𝐵,2 capacitors areused for blocking the DC current into theloop coil to improve the decoupling efficiency. It could alsocreate a local static magnetic field interfering with the static magnetic field B 0 . This ensures the correct decoupling of the loop coil. Mounted in series with 𝐶 𝑡 , capacitors can also contributemarginally for tuning the coil. Trimmer capacitors can be tuned mechanically with a nonmagnetic screwdriver to adjust the coil to match to 50 Ohms at the working frequency of 200 MHz (proton resonance frequency at 4.7 T). Finally, the decoupling circuit is represented by two Choke inductors and one PIN diode. The Choke inductors 𝐿 𝐵,1 and 𝐿 𝐵,2 protect the receiver amplifier from the induced RF current during the RF transmit pulses.

The PIN diode was mounted in parallel to the loop coil to minimize the series resistance and so maximizes the Quality factor (Q-factor) and thus the SNR [START_REF] Doty | Radio frequency coil technology for small-animal MRI[END_REF][START_REF] Hoult | The signal-to-noise ratio of the nuclear magnetic resonance experiment[END_REF].The quality factor of the coil was measured using a Vector Network Analyzer (VNA). The loaded Q-factor Q L was measured with the EC inserted into a phantom containing a solution of saline solution and the unloaded Q-factor Q 0 was measured without the phantom.

SNR assessment:

All the experiments were performed on a 4.7 T Bruker Biospec System (Bruker, Ettlingen, Germany). In order to characterize the EC, each acquisition done with the EC was also compared to a 1 H 32 mm inner diameter quadrature volume birdcage coil (Rapid Biomedical®, Rimpar, Germany) -QVBC dedicated to mouse body. However, the QVBC used does not include any decoupling circuit. As a consequence, the EC should not be inserted within the sample during QVBC operation. That is the reason why, when using the QVBC, an optical fiber (HCG 600, OFS®, Atlanta, USA) surrounded by a heat shrink coating was inserted into the mouse rectum instead of the EC. The outer diameter of the optical fiber and the heat shrink coating is 1.6 mm. Then, when using the EC, the QVBC was replaced by a 1 H 72 mm inner diameter transmit linear volume coil (Rapid Biomedical®, Rimpar, Germany) -VCincluding an active decoupling circuit. A protocol was developed and optimized for the purpose of EC assessment on phantom and small animals. Three axial 3D fast low-angle-shot (FLASH) sequences were used for anatomical and structure imaging but also for computing parametric T1 maps [START_REF] Cheng | Rapid high-resolution T1 mapping by variable flip angles: Accurate and precise measurements in the presence of radiofrequency field inhomogeneity[END_REF]. Then, one coronal FLASH 3D Slab sequence is performed to assess the colon along the EC. Finally, for computing parametric T2 maps, a 2D multiple spin-echo sequence was carried out. Table 2summarizes the sequences parameters used in the in vivoprotocol.

For SNR gain assessment, the coil was inserted into a12 mm outer diameter tube filled with a solution of 1.25 g/L of 4 NiSO and 5 g/L of NaCl to mimic approximately the loading conditions found in livingtissues and have convenient relaxation times (T1-valueof 218 ms and T2-value of 140 ms). First, the receiver EC was placed at the center of the VC used in transmit mode. The EC was driven by the active decoupling circuit during transmission. For SNR comparisons, axial images were acquired using FLASH 3D Slab sequences (table 3).

Then, VC and EC were replaced by the QVBC and the optical fiber, respectively.With the same protocol, MR images were acquired using the QVBC(emission/reception mode). Slab was positioned manually to scan the same region in order to allow co-localization. The SNR were compared after correcting for difference in voxel size including the antialiasing steps, receive bandwidth and number of excitations between the EC and VCs [START_REF] Hashemi | MRI: The Basics[END_REF].SNR profiles were normalized using thismethod and plotted in the same graph.

Spatial resolution and contrast enhancement using an EC:

The improvement of SNR provided by the EC can be used to decrease the voxel size without acquisition time penalties. To assess the spatial resolution achievable in the region of interest (ROI) with the EC within a reasonable acquisition time, a phantom containing the same 4 NiSO solution was filled with optical fibers of standard diameters (ranging from 150 µm to 1000 µm). Using the transmit VC and the EC in reception mode, two sequences were acquired. First, an axial FLASH 3D Slab with a pixel size of 83x83 µm²(slice of 234 µm thick) was carried out(sequence 1 in table 3). Then, the sequence was adjusted to reduce the voxel size up to 39x39 µm²keeping a slice thickness of 234 µm(sequence 2 in table 3). The structures observed were measured using the software ImageJ [39]and compared to the optical fiber diameters measured with a digital caliper.

After having characterized the ECs on inorganic phantoms, experiments were carried out on organic phantoms such as onions in order to evaluate thesensitivity of such coils.Onions offer fine lamellar structures divided in several bulbs inside. The thickness of the different layers is, in average, the same as the one expected in mouse colon wall. Images performed on vegetables provide good markers to evaluate the sensitivity of the coil by analyzing the finest structure observable (for a given SNR).Experiments were performed using 3D Slab FLASH sequences (

In vivomouse colon examination:

In vivo experiments wereperformed to evaluate the feasibility and interest of using an EC in a mouse model of colitis.The study was carried out on mice chemically treated during two months to induce colitis using a combination of azoxymethan (AOM, intraperitoneal injection, 10 mg/kg body weight) and dextran sulfate sodium (DSS, in drinking water, concentration of 2%) and four mice without treatment used as control.The experiments were in accordance with the rules and regulations of the UCBL Ethics Committee on animal experimentation. Prior to the examination, mice were kept on a 12 hours day/night rhythm in a 300 cm² plastic cages with straw bedding, pellet food and tap water. Mice were anesthetized using an isoflurane tabletop station (TEM Sega®, Lormont, France). Animals respiratory index was monitored during the experimentation by using a pressure sensor placed on the mouse chest. During the induction phase, mice were anesthetized with 3% of isoflurane and aspiration flow set up on 0.4 L/min. During imaging,the anesthesia was maintained with 1.4 to 1.7% isoflurane vaporization and aspiration flow set up on 0.4 L/min.Images of colon wall were first acquired by using thetransmit/receive QVBC. In that case, to mimic the presence of the EC, an optical fiber was carefully introduced into the mouse rectum using sterilized lubricant KY gel (K-Y®, Johnson & Johnson, USA) and held in position with adhesive tape (strap on the MRI bed).Then, to assess colon wall layers with the EC, the QVBC was replaced by the linear VC. MR images were acquired to assess colon wall layers using described protocol in table 2.

For each animals, T1-and T2-maps were computed using a linear fit from sequences acquired at different flip angle (15°, 20°, 25°) [START_REF] Cheng | Rapid high-resolution T1 mapping by variable flip angles: Accurate and precise measurements in the presence of radiofrequency field inhomogeneity[END_REF] and an exponential fit [START_REF] Gibbs | Comparison of quantitative T2 mapping and diffusion-weighted imaging in the normal and pathologic prostate[END_REF] at six different echo times (12.8 ms, 25.21 ms, 37.81 ms, 50.42 ms, 63.03 ms and 75.63 ms), respectively.Before the computation, images were threshold with an automatic method. The threshold level was set to three times the standard deviation measured in aROI with no signal (located in the top left corner of the image far from the EC).Two additional maps, representing the T1 linear fit quality and the T2 exponential fit quality, were also computed. To ensure reliable values of T1 and T2 relaxation times, fits having a coefficient of determination (R²) inferior to 0.98were systematically excluded from the representation.

For each in vitro and in vivo experiment, the coil was held in position with adhesive tape and not tilted during acquisitions. The EC was oriented in such a way to keep the B 1 of the EC perpendicular to both static B 0 and transmit RF B 1 magnetic fields. Hence maximum sensitivity and geometric decoupling are ensured respectively. As the colon natural behavior is to fold, the EC is always encompassed by colon structures ensuring almost uniform radial signal intensity.

RESULTS:

An endoluminal MR coil, fitting the constraints for in vivo experimentation on mice (colon and rectum walls assessment) was designed and built. The prototypes are waterproof, reusable, biocompatible (with the investigated environment) and can be tuned/matched to the appropriate resonance frequency. The measured loaded Q-factor ( L Q ) of the coil was 32 and the coupling coefficient was found equal to 1.25. This leads to a value of 72 for the unloaded Q-factor. The adaptation, at the 200. [START_REF] Hurlstone | Endoscopic Ultrasound Miniprobe Staging of Colorectal Cancer: Can Management Be Modified?[END_REF] MHzworking frequency in loading conditions was 50.03 Ohms.The decoupling efficiency of the EC was tested using a VNA. When the pin diode is activated, the resonance frequency is shifted to 150 MHz and the isolation at the resonance frequency reach -43 dB.

The EC provide a higher SNR in the close vicinity of the coil than the one obtained with quadrature volume birdcage coil. The EC geometry and dimensions fit with the use of the volume birdcage coil (72 mm inner diameter), without causing interferences and/or impacting the image quality. The absence of signal highlights in the close vicinity of the EC was confirmed when acquiring images with the body coil.Indeed, the continuously decoupled EC, not impacting the image around loop coil,was attested the correct functioning and efficacy of the decoupling circuit. The results of the SNR obtained with the EC compared with the QVBC acquired on phantom solutions are shown in figure 2.In receive mode, the SNR profile of the EC wasmuch higher than the one achieved with the QVBC up to 3 mmapart from the coil center. SNR profiles plotted in figure 2 werecorrected regarding the voxel size, bandwidth and number of excitations for a straightforward comparison.The EC SNRgain is 10 times greater at the close proximity and reaches the SNR of the QVBC at approximately 3 mm from the center.

A precise measurement of the structures observable in the loop-coil field of view was achieved on the phantomconstituted with calibrated optical fibers (figure 3).Optical fibersdiameters were measured with a standard deviation of ±6.3 µmusing the ImageJ software and then compared with a digital caliper (nominal precision ±10 µm).

Experiments led on vegetables have shown the feasibility to obtain high spatial resolution images and depict structural details. It is possible to distinguish the lamellar structures of the onion to approximately 3 mmof the coil center (figure 4).White arrows on figure 4localizethe same thin slice of the onion obtained with the VC (figure 4a) and with the EC (figure 4b and4c) at two different spatial resolutions (different SNR).

In vivo Experiments

The EC geometry fits the mouse anatomy and is adapted to in vivo experiments. Once the mouse is anesthetized, the insertion of the EC performed by an experimented gastroenterologist is simple and harmless for the animal. The animal's recovery time is short and no signs of prostration and/or pain were observed during the following few hours in accordance with the French legislation. Images acquired in vivo show a very good quality (figure 5),in term ofcontrast and high spatial resolution. The use of the QVBC does not allow a correct visualization of colon walls due to limited achievable spatial resolution.Whereas the SNR gain provided by the EC is used to increase spatial resolution and to depict nicely the mouse rectum wall layers and surrounding structures.On figure 5b, the map ratio of SNR EC /SNR QVBC is overlaid on MR images and undoubtedly illustrates the improved SNR area given by the EC. The white arrow on figure 5a1 and 5c locates a blood vessel used for co-localization. The examination with the EC gives a better visualization of colorectal wall layers and surrounding structures (figure 5d and5e). White arrows locate also the mucosasubmucosa complex. Using such a coil allows to increase spatial resolution up to 39 µm inplane resolution (with 234 µm slice thickness, see figure 6a and6b). It is then possible to well distinguish the mucosa complex in details.  is the mucosa,  the submucosa and  the muscularis externa. On figure 6b, locates a thin muscle layer.

The T1-and T2-values of structures around the EC can be seen on figure 7.The maps have been calculated and plotted with an estimation of the fit quality to ensure reliable values.It is worth noting that this parametric procedure removes the strong signal intensity decay that could lead to misinterpretation on the magnitude images. T1-and T2-maps plotted from two different slices illustrate different structures; identifies a muscle structure and  the colon wall. The averaged T1 relaxation times were measured at 800 ms ± 100 ms and 1200 ms ± 200 ms respectively.Then, looking at the T2 maps, mucosa layer and musclaris externa are clearly differentiable ( and on figure 7).The T2 relaxation times are nearly identical, 80ms ± 10ms for both structures. Finally, ✱ locates the submucosa which tends to have lower T2 values (50 ms ± 10ms). The fit quality maps show a reproducible method for T1-and T2-values with only a few points excluded in the field-of-view considered.

DISCUSSION:

EC have been used since the late eighties [START_REF] Schnall | Prostate: MR imaging with an endorectal surface coil[END_REF] but essentially for visualizing human prostate and rectum regions [START_REF] Stoker | Endoluminal MR imaging of diseases of the anus and rectum[END_REF][START_REF] Sathyanarayana | MRI endoscopy using intrinsically localized probes[END_REF][START_REF] Zagoria | Assessment of rectal tumor infiltration utilizing endorectal MR imaging and comparison with endoscopic rectal sonography[END_REF][START_REF] D'amico | Endorectal coil magnetic resonance imaging identifies locally advanced prostate cancer in select patients with clinically localized disease[END_REF].Currently, the major problem lies in the heat induce by the RF current into conductors. Several studies have shown the potential of using RF traps to reduce this increase in temperature [START_REF] Ladd | Reduction of resonant RF heating in intravascular catheters using coaxial chokes[END_REF][START_REF] Shellock | Radiofrequency Energy-Induced Heating During MR Procedures: A Review[END_REF][START_REF] Verret | Réalisation de capteurs endoluminaux en Imagerie de Résonance Magnétique à 3T: performances et sécurité[END_REF]. Optical transmission and optical decoupling system have also been proposed in order to replace conventional coaxial cable [START_REF] Ayde | Potentialities of an Electro-Optic Crystal Fed by Nuclear Magnetic Resonant Coil for Remote and Low-Invasive Magnetic Field Characterization[END_REF][START_REF] Fandrey | Development of an Active Intravascular MR Device With an Optical Transmission System[END_REF]. More recently, the exploration of metamaterials have open new perspectives for alternative ways of RF signal transmission [START_REF] Syms | Periodic Analysis of MR-Safe Transmission Lines[END_REF]. These metamaterials could overcome several coaxial cable disadvantages such as high propagation loss or heating along the conductor in the presence of electrical fields. But also, reaching the Human colon is difficult due to the 90° angle and assessing higher structures in the colon may require flexible endorectal MR probes. Other studies have shown the high potential of using ECson preclinical models such as pigs [START_REF] Thörmer | Novel technique for MR elastography of the prostate using a modified standard endorectal coil as actuator[END_REF], rabbits [START_REF] Beuf | In vivo colon wall imaging using endoluminal coils: Feasibility study on rabbits[END_REF][START_REF] Pilleul | High-resolution MR imaging appearance of colonic tissue in rabbits using an endoluminal coil[END_REF] and rats [START_REF] Pilleul | In vitro rat colonic wall imaging with MR endoluminal coil: Feasibility study and histologic correlations1[END_REF]. But, it is the first reported study assessing colon and rectum walls using dedicated endorectal coils on a mouse model of colitis (inflammation evolving into cancer).

In this study, the feasibility to design an EC for small animal colon wall imaging such as mice was demonstrated. It has been shown that EC can provide typical 40 µm in-plane pixel images with a slice thickness of 234 µm along digestive tract.External volume coils provide less detailed images in similar conditions (same sequence parameters and position). It enables the visualization of colon wall layers and deeper structures with a spatial resolution and SNR not achievable with quadrature volume birdcage coil dedicated to mice gastrointestinal imaging.

For decoupling the EC during the emission of radiofrequencies RF pulses, a parallel decoupling circuit was used. This choice was made to decrease the total resistance of the coil. Indeed,regarding the coil's dimensions and components, one third to one half of the total circuit resistance is due to the PIN diode characteristics alone.Placing the PIN diode in series leads in higher decoupling efficiency but decreases the quality factor and the SNR as well.

When the PIN diode is placed in parallel of the tuning capacitor, the resistance is lowered.

The quality factor of the coil is improvedbut the decoupling efficiency is reduced. The PIN diode is not entirely shutting down the loop coil and a weak fraction of the radiofrequency signal can still go through into the loop.In principle a coil having one or two parallel PIN diodes mounted in series with the loop would benefit from a better decoupling performance.

Even if this solution is feasible for in vitro experiments it is not compatible with in vivo experiments.PIN diode used here are bigger components than case A ATC capacitors. Several PIN diodes on the coil will result in blocking the access to trimmer capacitors.

Using those trimmer capacitors help for tuning/matching the coil at the desired frequency but this kind of component has a poor life time, due to their mechanism working with a screwdriver, and had to be changed regularly. Usually, trimmer capacitors are linked to insulating sticks for tuning and matching. In the case of small coils it is difficult to have such a configuration.

A heat shrink coating covers the EC duringin vivo or in vitro experiments to prevent the sensor from immediate short-circuit risk. Consequently,the copper tracks are isolated from the surrounding mediumbut this protection layer weakens the maximum SNR achievable in the close vicinity of the coil. Using a thinner protection could improve the SNR close to the coil.Besides, the EC is wrapped with PTFE to protect the electronic circuit during in vivo experiments:as the coil is used in wet environment, long-term oxidation of the copper tracks can appear if the PTFE is not removed after each use and the EC not properly dried.

Oxidation could lead to short-circuits, deterioration of the copper tracks and/or components and degradation of transmission line properties.A protective plastic cover will be designed and printed to improve protection. SNR comparisons could not be achieved using the QVBC at the exact same position due to the absence of decoupling circuit on this coil. The comparison was then done sequentially slice by slice and correlated with images acquired with the EC. Mouse's body examinationwould hardly be done with the available 70 mm inner diameter birdcage coil. However, the use of a 40 mm inner diameter linear birdcage coil with active decoupling system would easily allow switching between EC and volume coil. Beside the easier and straightforward comparison in SNR, this setup would allow to acquire very local images of the colon as well as more regional images of the mouse. This setup would be a considerable way of improvement.

The phantom containing optical fibers was useful to assess the size of structures that could be observed (from 150 µm to 1 mm) in the EC FOV. On the figure 3, optical fibers seem to be equally distributed around the EC.Asoptical fibersfell downto the bottom of the container the upper part of the phantom was not containing enough fibers. More of them will have to be added to distribute correctly optical fibers around the sensor.Despite the fact that the sequences choose for imaging the phantom had a slice thickness of 234 µm, no partial volume effect was observe when measuring outer diameter of the optical fibers.

For the experimentations done on vegetables, onions have been chosen for their structure.

Despite the fact that onions present very thin lamellar patterns, it can be assimilated to a semirigid material. Themolecules of water are constrained by their environment. So, when looking closely to the lamellar structure of this vegetable, it appears that air gaps are located between each slice. This causes some susceptibility artefacts. Moreover, the slice position chosen for the comparison wasnot exactly the same than the one obtain with the VC.To be able to localize the same structures between body coil images and EC images, the VC was used instead of the QVBC. The SNR of the VC allows the overall visualization of several layers of the vegetable. But to depict lamellar structure, the VC is inappropriate due to insufficient SNR. The use of the EC increases drastically the local SNR and fine structures can be visualized. But it also causes a highlight on the image, in the close vicinity of the coil. To obtain the same details with the QVBC, the same sequence was done using six averages; the acquisition time was increase to 1h15min.

In vivo acquisitions show a huge improvement in the differentiation of colon wall layerscomparedto the QVBC. The designed EC fits with the straight configuration of the mouse colon. Indeed, human colon presents curves which cannot be passed using such a rigid coil. For one of the healthy mouse, the colon was sampled for further analyzes.During the dissection, the length, average diameter and thickness of the colon were approximately measured, using a digital caliper, to optimize the coil loop.

The protocol duration developed for the need of the study wasshort enough (~38 min) to ensure the safe examination and recovery of the animal. It provides anatomical and parametric images (T1 and T2 values). Three scout sequences with orthogonal plane orientationswere first done with the VC in emission/reception mode. Acquisitions were compared between images acquired with and without a trigger deviceusing a respiratory sensor place on the lower part of the abdomen. Though respiratory movement is ample and cardiac beats are rapid, those movements are far from the colon and no significant differences were observed. So, no sequence triggering was performed in order to reduce the acquisition time.

Nevertheless, colon can be affected by peristaltic movements.These movements have been evaluated using an optical system developed for this purpose. Movements of colon walls are slow, not regular and limited in amplitude.The degradation induced by this motion on image quality is thus difficult to evaluate.A further analysis will be done to quantify this movement and see the influence on MR images.

The EC provides a high SNR in its close vicinity but the SNR drops down heavily. Up to 3 mmfrom the center, the SNR is higher than the one with the QVBC, further the sensitivity of the EC begins very poor. The colon wall thickness was measuresin the range of 0.2to0.5 mm (0.3 -1mm in the literature [START_REF] Tanaka | A novel inflammation-related mouse colon carcinogenesis model induced by azoxymethane and dextran sodium sulfate[END_REF][START_REF] Larsson | Magnetic resonance imaging of experimental mouse colitis and association with inflammatory activity[END_REF]). Regions of interest, such as colon walls, are closely located to the loop coil where the EC provides a very high SNR.Looking further the two first millimeters is not required for the purpose of this study.On figure 6, thein-plane pixel size was reduced (~39 µm pixel width with a slice thickness of 234 µm). As the SNR is decreasing with the improvement of spatial resolution, the gain in SNR provided by EC is used to define the best compromise between pixel size and signal intensity. As the QVBC does not possess a decoupling circuit, the colocalization was done using anatomical markers.

Blood vessels are convenient to localize the slice position. The mouse bladder and vertebrae can also be used as convenient landmarks.

Even if an optical endoscopic control exam is realized before inserting the coil into the mouse rectum, sometimes the lumen is still filled with feces and other natural substances. Those feces tend to drastically decrease the signal leading in an important loss of contrast around the feces. The systematic endoscopic control combined with a medication controlling the peristaltic movement (loperamide for example) could help to reduce the presence of feces in the lumen.During the evolution of the pathology, bleeding can also appear. When the EC is pulled out from the colon the presence of blood is sometimes noticed. This also induces distortion into the image quality and has to be taken into account for image processing.

Computed parametric T1-and T2-maps remove the strong SNR decay associated with the use of the EC. It is a fact that these strong intensity variations reduce the way the image is ridden compare to uniform signal intensity (provided by a QVBC for example).The T1 and T2 relaxation times obtained on the colon walls present an important standard deviation from the mean value. This is due to heterogeneity and size of the in vivo structures but also depends on the fit quality. Theoretically, in each pixel it is possible to obtain a value of the T1 and T2.

Practically, some fits present a coefficient of determination to low to be taken into account. A part of the problem is due to the high and rapid variation of structures observed in vivo.

Moreover, structures are very thin and can be essentially made of fat (for deeper structures for example). The non-significant values are removed from the results and can cause holes in the maps. A further study will beto evaluate the influence of the number and values of flip angles on fit quality. The 0.98 threshold here is chosen following what anatomical structures need to be seen in the EC FOV. It corresponds to a setting neither too general nor drastic. Information furnish by a fit quality of 0.98 are corresponding to the colon wall and surrounding structures.

When designing the coil, there were no considerations of heating and/or specific absorption rate (SAR) taken into account.Indeed, during MR procedures, the radiofrequency power transmitted (from the emission coil) for imaging is turned into heat through resistive losses.

Furthermore, when a conductor is placed within the imaging volume (as with the use of ECs) the RF electrical field accompanying the RF magnetic field pulses induces currents that can causelocal concentration of the SAR [START_REF] Nitz | On the heating of linear conductive structures as guide wires and catheters in interventional MRI[END_REF][START_REF] Shellock | Radiofrequency Energy-Induced Heating During MR Procedures: A Review[END_REF][START_REF] Yeung | RF safety of wires in interventional MRI: using a safety index[END_REF][START_REF] Konings | Heating Around Intravascular Guidewires by Resonating RF Waves[END_REF].In our case, the loop can be considered as a wire but the quarter wavelength (at 200 MHz) is much higher than the length of the loop.

It has been assumed that wire lengths less than a quarter wavelengths are generally safe.

Thepresence of an active decoupling circuit is also mandatory toreduce SAR concentration [START_REF] Ladd | Reduction of resonant RF heating in intravascular catheters using coaxial chokes[END_REF].Further work will be to combine the EC with magnetic resonance spectroscopy (MRS) in the colon wall. MRS could provide information on the biochemical composition of deep tissue layers. Quantitative analysis of the biochemical contents could also bring new markers to improve the measurements. But several challenges still lie ahead, such as strong B 0 inhomogeneities and phase shift due to the difference of magnetic susceptibility between air in the lumen and wall tissues.

In order to exploit the described work, a longitudinal follow up over six months involving 24 mice will be performed to explore in vivo the gastrointestinal wall in its entire depth. MR ECs open new perspectives as a minimally invasive technique to characterize colorectal cancer lesions and inflammatory bowel disease and then, offer a new technique to better understand the development of the colon wall pathologies.

CONCLUSION:

In conclusion, an endoluminal coil was developed for imaging the colon and rectum walls on a mouse model of colitis. The strong local SNR increase provided by the use of such coils allows imaging the gastrointestinal tract at very high spatial resolution (up to approximately 40 µm in plane resolution with a slice thickness of 234 µm). Associated to a dedicated protocol, it provides details in deep still thin structures of colon wall.

COMPLIANCE WITH ETHICAL STANDARDS:

Disclosure of potential conflicts of interest: the authors declare that they have no conflict of interest.

Research involving animals: all applicable international, national, and/or institutional guidelines for the care and use of animals were followed.

All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted.

LIST OF FIGURES

Legend of Fig1:

  20 mm FOV, 25 mm slab thickness, TR/TE = 25/4.31 ms with 25°flip angle, 256x192x96 matrix, 36 764 Hz bandwidth and 11'31'' acquisition time). The VC was turned in emission mode and the EC switched on reception mode.Finally, the spatial resolution was increased by reducing the pixel size down to 39x39 µm² (10 mm FOV, 15 mm slab thickness, TR/TE = 20/6.1 ms with 20° flip angle, 256x256x64 matrix, 25 kHz bandwidth and 10'55'' acquisition time) with a slice thickness equals to 234 µm.

Fig 1

 1 Fig 1 (a) Electric scheme of the coil. The corresponding part between the scheme and the pictures are

Fig 3

 3 Fig 3 Images of the phantom created for the purpose of the experiments. (a) and (b) represent a

Fig 5 Fig 6

 56 Fig 5 in vivo experiments were performed on a mouse model of colitis. MR images acquired with the

Table 2

 2 Sequence and parameters used for the in vivo protocol. The scout sequences are not mentioned.

Table 3Sequences

 3Sequences used for the characterization of the EC and the assessment of the EC during in vitro experiments.

This work was supported by the LABEX PRIMES (ANR-11-LABX-0063) of "Université de Lyon", within the program "Investissements d'Avenir" (ANR-11-IDEX-0007) operated by the French National Research Agency (ANR).


Nanette S Levinson

Meryem Marzouki
email: meryem.marzouki@lip6.fr

Straddling Hegemony and Resistance in Internet Governance: The Soft Power of International Organizations

the context of complex, cross--national and cross--sector Internet governance issues. This paper reports on the strategies developed by several IOs to channel their main issues, positions and visions related to Internet governance using primarily the Internet Governance Forum (IGF). It then focuses on one case study, that of UNESCO and its roles in Internet governance, especially in the context of the post World Summit on the Information Society review activities. The case study research stems from the authors' larger three--year project on international organizations and Internet governance (Levinson and Marzouki, 2015a; 2015b).

This research uses multiple methods. Interviews with those individuals charged with

Internet related policy functions at the international organizations we studied constitute a major data gathering function. Additionally, content analysis of documents and archival analysis amplifies and provides a foundation for interview findings. Finally, observation and participant observation at key meetings adds to data gathering and data analysis. For the specific analysis of the participation of IOs in the IGF proceedings since 2006, quantitative analysis of IGF sessions was also used.

Introduction

As the United Nations General Assembly prepares to review the WSIS+10 in December 2015, including the outputs of the CSTD working groups concerned with improving the IGF (Internet Governance Forum) and with enhancing cooperation related to international Internet public policy issues, it is particularly fitting to examine the roles of international organizations in the Internet governance ecosystem. Much attention has been paid to the private sector and to civil society in the context of multistakeholder discussions of Internet policy issues [START_REF] Almeida | The Origin and Evolution of Multistakeholder Models[END_REF][START_REF] Brousseau | Old Issues, New Framings, Uncertain Implications[END_REF][START_REF] Cammaerts | Power Dynamics in Multi--stakeholder Policy Processes and Intra-civil Society Networking[END_REF][START_REF] Carr | Power Plays in Global Internet Governance[END_REF][START_REF] Denardis | Thinking Clearly About Multistakeholder Internet Governance[END_REF][START_REF] Epstein | The Making of Information Governance Institutions[END_REF][START_REF] Franklin | Digital Dilemmas: Power, Resistance, and the Internet[END_REF][START_REF] Gasser | Multistakeholder as Governance Groups: Observations from Case Studies[END_REF][START_REF] Malcolm | Multistakeholder Governance and the Internet Governance Forum[END_REF][START_REF] Mueller | Networks and States: The Global Politics of Internet Governance[END_REF][START_REF] Pavan | Frames and Communication in the Governance of Global Communication: A Network Study of the Internet Governance Forum[END_REF]. There is also important scholarship related to the technical infrastructure of the Internet and its implications for Internet governance and related policy issues [START_REF] Denardis | Protocol Politics: The Globalization of Internet Governance[END_REF][START_REF] Denardis | The Global War For Internet Governance[END_REF][START_REF] Mueller | Ruling the Root: Internet Governance and the Taming of Cyberspace[END_REF][START_REF] Musiani | Practice, Plurality, Performativity, and Plumbing: Internet Governance Research Meets Science and Technology Studies[END_REF][START_REF] Musiani | Practice, Plurality, Performativity, and Plumbing: Internet Governance Research Meets Science and Technology Studies[END_REF]Radu et al., 2014).

Traditionally, international organizations including the United Nations system work at the behest of their member nations and play key coordinating roles. They are neither bottom-up type organizations nor do they necessarily have private sector or civil society organization type characteristics. In the last decade or so, research has extended beyond portraying their more hegemonic type government--down roles. Rather there is work [START_REF] Schemeil | Bringing International Organization In: Global Institutions as Adaptive Hybrids[END_REF] that portrays a more nuanced vision of post--2000 international organizations. But there is almost no research that examines international organizations in

International Organizations As Actors in Internet Governance

In previous work, we have shown how IOs have managed to establish themselves as actors in Internet governance processes (Levinson and Marzouki, 2015a;2015b). In summary, they worked hard over time to move away from a traditional view of their "facilitating role in the coordination of Internet related public policy issues" where paragraph 35 of the WSIS Tunis Agenda1 confined them, in the shadow and at the service of their member states.

Studying the UNESCO, the OECD, the Council of Europe, and the ITU (the latter only through its participation at IGF proceedings), our findings so far have shown the following main IOs actions to achieve this objective:

--In terms of intra--IOs developments and agenda setting: an evolution from coordinating mechanisms for nation--states (issues, preferences, participations, politics) to stakeholders in their own right (agenda and opportunities) in IG arenas; 3 --In terms of partnerships: from serving and interacting with member states to subtly broader focus on interactions with civil society, the private sector, and other contemporary stakeholders (such as the technical community) to help institutionalize IG processes; --In terms of positioning themselves from periphery to core of IG: they heightened the link at each IO between IG policy issues/spaces and the IO's policy purviews and mandates as they change over time; they increased the number of people within the IO working on topics related to IG; they linked IG--related topics to more central/powerful elements/sections/divisions of the IO; --In terms of issue/policy entrepreneurship efforts: From secretariat members role as "civil servants" ("We are the member states", as interviewed key leaders from different IOs repeatedly told us) to the crafting of their own ideas to link IG to their core missions and mandates, with help of allies/partners, mainly from civil society Building on these preliminary results, this paper develops the analysis of IOs' strategies in the course of their participation in the IGF proceedings over time. While many IOs with different mandates participate each year in the IGF, we have identified four that demonstrate a more regular and important participation; these four IOs are: the OECD, the UNESCO, the CoE and the ITU. Furthermore, it focuses on the UNESCO as a more in depth case study.

IOs and the Internet Governance Agenda Setting

In (Levinson and Marzouki, 2015a) we concentrated our analysis on how IOs crafted their role at IGF mainly on the level of their involvement through the relative amount of IGF workshops (co--)organization and participation. We worked on the skeletal structure of IGF events, composed of the following types of sessions:

--Main sessions: 4--5 sessions, each focusing on one of the substantive themes chosen the given year (e.g. 'Security, Openness and Privacy' or 'Critical Internet Resources' have become established themes), plus generally one session dedicated to 'Emerging Issues' and one to 'Taking Stock and the way forward'.

--Workshops (WS): a series or sessions related to each Main session, to feed its discussions and further develop the related substantive theme.

--Open Forum (OF): as described by the IGF, "All major organizations dealing with Internet governance related issues are to be given a workshop slot, at their request, to hold an open forum in order to present and discuss their activities." --Best Practice Forum (BPF): again as described by the IGF, their objective is "to demonstrate, in a multistakeholder environment, some of the good practices that have been adapted with regard to the key IGF themes in general and to the development and deployment of the Internet in particular. The sessions can have either a thematic or a country focus." --Dynamic Coalition Meetings (DC): loose structures described as "informal, issue-specific groups comprising members of various stakeholder groups." It has to establish itself with an action plan and minimal coordination means, and show that its membership comes from at least three different stakeholder categories.

It is subject to registration with and approval by the IGF Secretariat. At each yearly IGF meeting, dynamic coalitions are given a specific time slot for a public meeting, and must provide a public report of this activity.

Going further with the analysis of this data, we consider in this paper all kind of sessions, not only the workshops. Each year, the IGF publishes a report book where all workshops are documented. This was the basis of our previous data collection. In order to consider all kinds of sessions, as described above, we turned to a living archive of the IGF meetings since Athens in 2006. "Friends of the IGF2 " is a community--based project set up by a small consultancy company based in New Zealand A first metric that we considered is the level of involvement of the four identified IOs (OECD, UNESCO, CoE, ITU) in IGF sessions, either as organizer, co--organizer or participant in a given session of any kind. We also wanted to evaluate the evolution of this involvement over meetings, from Rio in 2007 to Istanbul in 2014. To this end, we evaluated for each IO the number of sessions in participated, and calculated the percentage of the total number of sessions this participation represents, as shown in With the exception of the Bali meeting, where all four IOs drastically reduced their attendance, and thus their participation to IGF sessions, due to budget issues, we can identify a rather strong participation of IOs to all sessions (as a reminder, we mean by participation either taking part in the organization of a session or at least speaking as panelist). Figure 1 also singularly highlights the role of the CoE among other IOs, with a major involvement in IGFs. As we already have qualitatively analyzed in a comprehensive manner in [Levinson and Marzouki, 2015b], the CoE managed to become an inescapable actor of the IGF -and, more generally speaking, of the whole Internet governance ecosystem -by succeeding in putting the main issue of its mandate, human rights, at the center of any Internet governance process. The Vilnius meeting was the first to show the effectiveness of this strategy. Further, Figure 1 shows the Vilnius meeting as the peak of participation for all IOs besides the OECD (for which the peak is rather at the Nairobi meeting). This can be explained by the fact that the Vilnius meeting, in addition to being held in Europe -where all IOs have their headquarters thus involving relatively limited costs to attend --was held in 2010. That year, the renewal of the first 5--years mandate of the IGF was at stake, with some controversies surrounding the expected decision from the United Nations General Assembly, as reported by the press4 . IOs for which the IGF continuation was of outmost importance showed thus a strong presence at the 2010 meeting. An additional explication of the massive CoE presence in Vilnius is that this meeting was held only two years after the inception of the European regional implementation of the IGF, the EuroDIG series of annual meetings, which started in 2008 in Strasbourg5 . Note that the CoE being the main organizer of EuroDIG, thus the Vilnius meeting was also an opportunity to publicize more in this part of the continent this regional achievement. Substantive topics correspond to the main topics organizing the IGF over time, with some new topics emerging at some points, either because they have matured and can be one of the focus of a given IGF session or because, eventually, their political acceptance has been granted after some years of controversies: the "human rights" topic typically corresponds to the latter category. Also, over time, some topics have been grouped to form an overarching one: one example is the merging of the "Access" and "Diversity" topic into a single one, combining a variety of issues to realize Internet access to the greatest number of people, including through an increased linguistic diversity of content. In the same way, "Privacy" and "Security" topics have sometimes been combined, although "Security" extends in some discussion cases to issues such as child protection and the fight against harmful content on the Internet. "Openness" groups into a single IGF topic issues such as freedom of expression, freedom of information, open access, commons, Free/Libre and open source software and, more recently, network neutrality. "Critical Internet Resources" concerns the management of Internet names and numbers, as well as protocols, in one word, the main topics substantive topics dealt with by ICANN, as well as, for some of them, by the ITU. Finally, "Internet Governance for Development" speaks for itself.

As for procedural topics, "Enhanced cooperation" is a code word stemming from the WSIS Tunis Agenda 6 (paragraphs 69--71) that has been a source of controversies since then, mostly between those with a multilateral view of Internet governance and those with a multistakeholder view of this process. To express it as a caricature, it relates to the old "ITU model vs. ICANN model" of the Internet governance controversy. The "Internet Governance

Principles" topic is a more generic way of identifying the discussions relating to Internet governance processes institutionalization, and "Multistakeholderism" addresses process issues as well, while focusing on the participation of all stakeholders and their interactions.

With regards to the last two categories, "Regional and National Initiatives" is mainly used for sessions reporting on regional and national implementations of the IGF; and "Other" categorizes such sessions as opening and ceremonies, etc.

Considering this understanding of topics used as labels by the "Friends of the IGF" website, and considering the fact that there has been an evolution of sessions labeling over time by the successive IGF meetings, we have decided, from a methodological point of view, to regroup some of the topics and to discard some others in our further analysis, since this paper is concerned with the role of the four identified IOs in shaping the IG discussions agenda through channeling their own issues and mandates in these global debates. In other words we are interested in their participation by topic in different kinds of IGF sessions.

We thus discarded all sessions labeled "Regional and National Initiatives" as well as those labeled "Other". Unfortunately, the 160 sessions of the Istanbul meeting in 2014 have not yet been labeled on the "Friends of the IGF" website (as for now, they all are labeled "other"). We have thus discarded the 160 Istanbul sessions as well from our analysis. In total, this analysis is consequently based on 656 sessions (from IGF Athens in 2006 to IGF Bali in 2013) instead of the 1035 available. 6 See footnote 1 supra 10 Following some label grouping, we used the following labels:

--Process/GoodGov: this new label regroups "Enhanced Cooperation", "Internet Governance Principles" and Multistakeholderism". In other words, it concerns sessions discussing Internet governance processes and good governance principles;

--IG4D: "Internet Governance for Development" kept as is;

--CIR: "Critical Internet Resources" kept as is;

--Acc/Div: this new label regroups "Access" and "Diversity";

--Openness: kept as is;

--Sec/Priv: this new label regroups "Security" and "Privacy";

--HR: "Human Rights" kept as is.

On this labeling basis, Table 3

Table 3. Repartition of IOs sessions topics

Two kinds of information can be derived from Table 3 data. First is the distribution by topic of a given IO's involvement in IGF sessions. This information, depicted in Figure 2, informs on the importance given to each topic by the considered IOs. The second information is the distribution of the respective weights of all four considered IOs in the discussions on each topic. This information is depicted in Figure 3. setting than its own formal meetings; as one of our interviewee form this IO acknowledged:

"The role of the Secretariat is to be forward--looking: we are a bit provocative"; "We can engage people who are not on our table - or don't even know about us - and identify who is important in the field". This interviewee also appreciates the diverse views that can be heard only at IGF: speaking specifically on the post--Snowden's revelations Bali meeting in The latter remark also explains, on Figure 3, the dominant weight of the Council of Europe on the "Privacy and Security" topic. The same applies to "Human Rights" topic, while it appears from Figure 2 that this topic is far less important with regards to others, for all IOs including the CoE. The explanation is here that, while CoE has been the most active IOs on human rights in terms of involvement in IGF, the topic itself emerged rather late in the IGF proceedings as a topic on its own, due to strong reluctance of the IGF MAG (Multistakeholder Advisory Group), especially its government members, to highlight this sensitive issue as an IGF topic during many years.

Figure 3. Respective weights of IOs in each topic's discussions (%)

Figure 3 also highlights that the ITU is the most important IO dealing with "IG4D" (Internet Governance for Development), in line with the core mandate of this IO. ITU also shows the same interest as, rather surprisingly, the CoE regarding the "CIR" (Critical Internet resources) topic. On this issue, the ITU obviously had to maintain a strong involvement, especially with regards to the ITU vs. ICANN "battle" mainly during the early IGF meetings.

Regarding the CoE, one explanation could be its strong involvement in IGF discussions as a whole, much more than other IOs (as shown in Figure 1), being "beaten" only by one IO or another on the core topic of this IO's mandate (such as ITU and UNESCO for "Access and Diversity" or ITU for "IG4D". Regarding the "Openness" topic (which is larger than solely Finally, the most interesting finding shown in Figure 3 is certainly the respective weights of the four considered IOs with regards to the "Process/Good Governance" topic that, as a reminder, regroups discussions on "Enhanced Cooperation", "Internet Governance Principles" and Multistakeholderism", in other words, mostly each stakeholder's role in Internet governance processes and their interactions. Figure 3 shows that ITU was the most involved in such discussions (again, beyond the sole "ITU vs. ICANN battle", the "multilateral vs. multistakeholder battle" model), immediately followed by the CoE, and then, far beyond, the OECD and the UNESCO.

This analysis of IGF meetings over time, both in terms of numerical involvement of IOs in IGF sessions and in terms of the specific interests of the four identified OIs in IGF topics, especially with respect to their respective mandates, demonstrates how these IOs have developed strategies to channel, and sometimes even impose, issues at the core of their mandates in IGF discussions; and how they forged their own paths in such a multistakeholder arena. Such pathways include coalescing with other stakeholders around some issues of common interest (as demonstrated in [Levinson and Marzouki, 2015a],

crafting research agendas, and allowing their Secretariats to smoothly circumvent some of their Member States positions and, as a result, producing positions and non--binding international instruments related to the most contentious IG issues. These outcomes have managed to overcome sometimes very conflicting positions among different stakeholders, through the processes and means IOs use to straddle hegemonic and resisting positions from other stakeholders, in particular by shaping dialogues and influencing best practices.

The specific case of UNESCO provides an in--depth analysis of these patterns.

An In Depth Case Study: The UNESCO

UNESCO presents a particularly interesting case because of its long history as a UN agency working directly with civil society. This dates to its creation in 1945-long before the Internet became a global communication medium. Indeed one can think of UNESCO as a 'learning lab' for other international organizations, in terms of its work with civil society.

(See [START_REF] Levinson | Advances in Virtual Learning: From Cross--cultural Teams to Regional/Global MOOCS[END_REF], for further analysis of complex organizations as learning laboratories in an inter--organizational setting.) For example, UNESCO, unlike the ITU, actually has and has had structural affordances (now called the Division of National Commissions and Civil Society) for working directly with civil society organizations. These predate by far those in the OECD or the newer nonstructural attempts to incorporate civil society into some ITU activities.

These connections with civil society and with organizations in other sectors have revolved around UNESCO's priorities [START_REF] Pohle | UNESCO and INFOethics: Seeking global ethical values in the Information Society[END_REF]. enhancing the free flow of information and ideas throughout the world" are "essential for UNESCO to fulfill its mandate and mission entrusted by the Member States".

It is also useful to note that UNESCO implemented its Internet Study as a result of UNESCO's proposed by international organizations only occur in five of the thematic clusters, with the largest number also falling in the category of human rights. This compares with those proposed by the private sector, where the largest number is in the area of security. In this regard, it is interesting to report a comment from a UNESCO interviewee, reflecting on the "Connecting the Dots" Conference where the interviewee observes: "We should be speaking more to corporations". The UNESCO website lists the Disney Corporation as a participant;

Disney did provide a long submission and was an active participant at the Conference. Note that the interviewee approached corporations to invite them to the Conference. Some were interested and others not.

Focusing on nongovernmental organizations, UNESCO does participate in relevant NGO sponsored conferences. In fact, UNESCO promoted its ideas of 'Internet universality" and its survey at twenty different conferences around the world. It also speaks "from time to time" with the EU and would like to work more with them.

  and technical community organizations (examples: The OECD made a strong link at the Seoul Ministerial meeting in 2008 between IG issues and the Internet economy; The CoE made human rights in IG a priority in its internal strategy; The UNESCO crafted the concept of 'Internet Universality' to channel almost all issues within its mandate in IG discussions, as detailed later in this paper); --In terms of using the IGF as a main vehicle: IOs bringing back home and institutionalizing collective IGF work (example: the CoE Council of Ministers adopted a Recommendation on a Guide to Human Rights for Internet Users in 2014, that stemmed from the IGF's Internet Rights and Principles Dynamic Coalition (IRPDC) Charter of Human Rights and Principles for the Internet developed in 2010 as a basis. This Recommendation was drafted by a multistakeholder CoE committee of experts which included members of this dynamic coalition); IOs as Backbone of IGF (Example: IOs involvement in IGF main discursive activity accounts for 31% of all IGF Workshops in the period from 2006--2012).

Figure 1 .

 1 Figure 1. Representation of IOs participation rate in IGF sessions

Figure 2 .

 2 Figure 2. Distribution of each IO's involvement over all topics (%)

Freedom

  of expression to also encompass issues such as open content, open data and open software), unsurprisingly the UNESCO played a major role, together with the CoE.

  37 th General Conference Resolution 52 in 2013. It did this as a springboard for action at the 38 th General Conference of UNESCO scheduled for November 2015. UNESCO implemented a yearlong consultative process prior to the study; and a global multistakeholder conference to review the study, resulting in the earlier discussed outcomes document. UNESCO's Executive Board (196 th Session) recommended the Outcome Document for member state deliberation at the November 2015 General Conference. At the same time the Board forwarded the outcome Document as a "non--binding input to the post--2015 Development Agenda" as well as to both the UN General Assembly overall WSIS review and the high level meeting of the General Assembly per resolution 68/302. The UN Secretariat--prepared 10--11 June 2015 Informal Summary of the "Initial Stocktaking Meeting On the Process of the Intergovernmental Negotiations On the Review Of The Implementation of the Outcomes of the World Summit on the Information Society (WSIS)"provides data that helps track the role of UNESCO as it relates to Internet governance in the context of the UN system. The Summary notes that UNESCO as well as the ITU and UNCTAD provided reports to assist the General Assembly in reviewing WSIS. Indrajit Banerjee presented the UNESCO report, highlighting UNESCO's "coordination of international activities" and linked this to the organization's "long standing goal of inclusive Knowledge Societies". He then went on to talk about the Outcomes Documents from UNESCO's February 2013 conference co--organized with the ITU, UNCTAD and UNDP, and its March 2015 conference outcome document on the future of the Internet (discussed earlier in this paper.)In terms of documenting the role of international organizations as 'idea generators', the Geneva Internet Platform Initiative 12 newsletter, Digital Watch (Issue 1, 2015), offers a chart on "IG At A Glance --What is the Focus of IGF 2015 13 " that diagrams the general themes of workshops proposed for the IGF 2015. It uses the following categories and provides data that are not available yet from the "Friends of the IGF" database: Civil Society, Governments, Technical Community, International Organizations, and Private Sector. The largest number of proposals stem from civil society, and fall across the eight--identified thematic clusters, with the largest number falling in the Human Rights category. Those

Table 1 . Number of available IGF sessions in corpus, by meeting and by type

 1 3 . It provides a searchable and browsable repository of transcripts and video of all IGF sessions. Currently, there are all in all 1035 sessions archived, from IGF Athens 2006 to IGF Istanbul 2014. It is, to our knowledge, the most complete IGF sessions archive and could constitute a good basis for empirical research on the IGF discussions. Available sessions on the "Friends of the IGF" website are summarized in Table1.Considering that only the 10 main sessions are available for the Athens 2006 edition of the IGF, we will discard this meeting from our analysis.

		Main	WS	BPF	OF	DC	Other	Total
	Athens	10	0	0	0	0	0	10
	Rio	14	39	28	9	10	10	110
	Hyderabad 14	62	9	7	9	2	103
	Sharm	14	69	16	9	7	1	116
	Vilnius	12	69	1	6	12	14	114
	Nairobi	13	79	1	5	9	10	117
	Baku	8	97	0	7	8	26	146
	Bali	13	92	1	20	9	25	159
	Istanbul	10	91	5	11	11	22	160
	Total	108	598	61	74	75	119	1035

Table 2

 2 Table 2 and represented in Figure 1.

		OECD	UNESCO	CoE	ITU
	Rio	8.18	10.00	16.36	18.18
	Hyderabad 12.62	17.48	13.59	14.56
	Sharm	11.21	15.52	21.55	21.55
	Vilnius	14.04	25.44	57.89	34.21
	Nairobi	23.93	13.68	42.74	29.06
	Baku	11.64	15.07	28.08	23.29
	Bali	3.77	4.40	4.40	7.55
	Istanbul	8.13	9.38	14.38	11.25

. Rate of IOs participation in IGF sessions, per meeting (%)

  2013, s/he added: "What we heard, we couldn't hear elsewhere than at IGF. It helps understand the context. Of course, I read blogs and stuff, but all are Anglo--Saxons. At IGF, you can hear other voices". With regards to UNESCO, "Access and Diversity" is the topic at the heart of its mandate, and through which UNESCO tried to "regain its place" in the post--WSIS game after having been marginalized, as one of our interviewee from this organization told us. With regards to the Council of Europe, although Privacy is one of the main human rights issues on which the organization has been focusing in Internet governance discussions, it could appear surprising at first glance that the "Privacy and Security" topic is given so much

importance with regards to e.g. "Openness" or "Human rights"; however, a careful analysis of the CoE involvement in IGF meetings show that, like the OECD, the CoE took advantage of the IGF to channel its own instruments as well, a main one in this context being the Council of Europe Convention on Cybercrime 9 : two different divisions of the CoE's "Information Society and Action Against Cybercrime" Directorate 10 joined force to achieve this strong involvement.

  In another section of its website, UNESCO discusses its contribution to the 2014 IGF held in Istanbul. It provides a listing of IGF sessions to which UNESCO contributed or where UNESCO served as a co--organizer. There is a webpage devoted exclusively to "UNESCO in the Internet Governance Forum". It also emphasizes UNESCO's response to the IGF MAG's call for input on its impacts (or, in other words), "concrete actions and decisions that have been taken by different stakeholders as a result of the engagement and discussions of Internet related issues". In sum, the UNESCO website points out in regard to UNESCO and Internet governance that "all of these elements (with regard to the Internet's role in "fostering sustainable human development and building more democratic societies" and for"

	statement and vision texts, by the plenary by consensus".
	Our interview and documentary research
	indicates that while Internet governance was not initially or traditionally seen as a UNESCO
	priority, today Internet governance issues (and concomitant collaborations) are linked
	directly to UNESCO's mission and its priorities.
	UNESCO began to lay the groundwork for a concept it coined 'Internet universality' in
	approximately 2012 and to link it directly to the core work of UNESCO. This idea seeding
	included designing and implementing a survey resulting in a UNESCO consultative
	multistakeholder study "within the framework of UNESCO's work on the World Summit on
	the Information Society" (see Connecting the Dots: Options For Future Action Outcome
	Document, 2015 11 ). The draft study then served as the foundation for the 3--4 March 2015
	culminating conference at UNESCO headquarters entitled "Connecting The Dots: Options
	For Future Action".
	The Outcomes Document from this conference provides important evidence regarding our
	general argument concerning the roles of international organizations. First, it supplies key
	'contexting' as we call it, inextricably linking Internet governance issues to core UNESCO
	functions and priorities. In 1.6 of the document, it lists as an "overarching option(s) for
	UNESCO", the "strengthen(ing) the cross--cutting role of the Internet in all of UNESCO
	programmatic activities, including Priority Africa, Priority Gender Equality, support to
	Small Islands Developing States and least Developed Countries, as well as in UNESCO's
	leadership of the International Decade for the Rapprochement of Cultures". The following
	sections (2--5) focus specifically on UNESCO priorities and highlight options for UNESCO
	related to a specific priority. These are: Section 2, Access to Information and Knowledge;
	Section 3, Freedom of Expression; Section 4. Privacy; and Section 5. Ethical Dimensions of
	11 See
	<http://www.unesco.org/new/fileadmin/MULTIMEDIA/HQ/CI/CI/pdf/outcome_documen
	t.pdf>

All WSIS-related documents can be found at <http://www.itu.int/wsis>

Available at <friendsoftheigf.org>

Chalmers and Associates. See the project description at <http://chalmers.associates/pdf/FoIGF--info_sheet.pdf>

See e.g. "Controversy Over New IGF Mandate, UN Role In Internet Governance" at: <http://www.ip--watch.org/2010/11/04/controversy--over--new--igf--mandate--un--role--in--internet-governance/>

5 See <http://www.eurodig.org>

See <http://conventions.coe.int/Treaty/FR/Treaties/Html/185.htm>

See <http://www.coe.int/en/web/human--rights--rule--of--law/information--society--and-action--against--crime--directorate>

See <http://www.giplatform.org>

See <http://www.giplatform.org/sites/default/files/DigitalWatchNewsletter1.pdf>, page 3

the Information Society.

The final two sections of the Outcomes Document are central to illustrating this 'contexting' feature of international organizations in 2015, especially with regard to Internet governance. Section 6 lists options related to crosscutting issues, highlighting the integrative nature of Internet governance issues across priority areas. The final Section 7 lists options related to UNESCO's role. Here the document makes three vibrant points. The first is to 'reinforce UNESCO's contributions and leadership within the UN system, including continued implementation of the WSIS outcomes, the WSIS+10 review, the IGF and the post--2015 development agenda". The second calls for "engage (ing) as relevant with partners outside of the UN system"; it lists 5 ways to do this plus a range of partners across the sectors. The 5 ways are:

• "Providing expert advice

The third and final point in this section and for the document as a whole is to "support Member States in ensuring that Internet policy and regulation involves the participation of all stakeholders, and integrates international human rights and gender equality."

Second this Outcomes Document also seeks to establish the primacy of UNESCO's role in the UN system with regard to Internet governance policy issues -through its historic missions and current priorities [START_REF] Mansell | Renewing the Knowledge Societies Vision: Towards Knowledge Societies for Peace and Sustainable Development[END_REF][START_REF] Souter | Towards Inclusive Knowledge Societies. A review of UNESCO's action in implementing the WSIS outcomes[END_REF].

Beyond the survey and the Outcomes Document, UNESCO also highlights elsewhere on its website its key roles in both the first and second WSIS+10 Review events. UNESCO actually hosted the first review meeting in Paris and served as a co--organizer for the second event in Geneva, hosted by the ITU. With regard to the first event, UNESCO underlines the outcomes of the event which it organized and hosted; with regard to the second event, it notes that UNESCO provided participants at that high level event a "compromise text on the Media Action Line" and notes that "after long negotiations, the UNESCO proposed text was finally accepted without amendment and therefore all Action line texts could be adopted with the

Conclusions

This case study of UNESCO as an international organization working in the Internet governance ecosystem space highlights the themes we identified at the beginning of this paper. It shows how UNESCO staff (and ultimately its General Conference) re--envisioned and, indeed, reshaped the communication of its mission in a post--internet initiation era.

Through linking the concept of 'internet universality' to its long--standing missions, and obtaining backing from its General conference, it has strengthened both its relevancy and organizational position/power since 2012.

The UNESCO case also illustrates in a more detailed way the patterns that emerge from our study in the first part of this paper on the IGF data provided by the "Fiends of the IGF" database. Similar to its sister international organizations, UNESCO is continuing to play a reinforced and amplified role in a relatively new but key global governance arena.