Audrey Duran

Gaspard Dussert

Carole Lartizien
email: carole.lartizien@creatis.insa-lyon.fr

Learning to segment prostate cancer by aggressiveness from scribbles in bi-parametric MRI

Keywords: Prostate cancer, Weakly-supervised learning, Semantic segmentation, Multiparametric MRI, Deep Learning, Gleason Score, CNN constraints

In this work, we propose a deep U-Net based model to tackle the challenging task of prostate cancer segmentation by aggressiveness in MRI based on weak scribble annotations. This model extends the size constraint loss proposed by Kervadec et al. 1 in the context of multiclass detection and segmentation task. This model is of high clinical interest as it allows training on prostate biopsy samples and avoids time-consuming full annotation process. Performance is assessed on a private dataset (219 patients) where the full ground truth is available as well as on the ProstateX-2 challenge database, where only biopsy results at different localisations serve as reference. We show that we can approach the fully-supervised baseline in grading the lesions by using only 6.35% of voxels for training. We report a lesion-wise Cohen's kappa score of 0.29 ± 0.07 for the weak model versus 0.32 ± 0.05 for the baseline. We also report a kappa score (0.276 ± 0.037) on the ProstateX-2 challenge dataset with our weak U-Net trained on a combination of ProstateX-2 and our dataset, which is the highest reported value on this challenge dataset for a segmentation task to our knowledge.

INTRODUCTION

Deep learning has become the state-of-the-art approach for the processing and analysis of many medical imaging problems, including detection and segmentation tasks. [START_REF] Tajbakhsh | Embracing imperfect datasets: A review of deep learning solutions for medical image segmentation[END_REF] However, the vast majority of the proposed models are fully supervised, meaning that they require a large amount of annotated data to perform well, which is hard to acquire due to the high expertise and time needed for the annotation. To alleviate the need for full annotation, weakly-supervised approaches have been widely studied over the past few years. [START_REF] Chan | A Comprehensive Analysis of Weakly-Supervised Semantic Segmentation in Different Image Domains[END_REF] They consist in learning from partial labels, such as image tags, bounding boxes or scribbles.

In this paper, we address the challenging task of segmentation and characterisation of prostate cancer (PCa) aggressiveness in bi-parametric MRI (bp-MRI) based on scribbles. This task has only been barely addressed and only in a fully supervised manner, for PCa detection [START_REF] Cao | Joint Prostate Cancer Detection and Gleason Score Prediction in mp-MRI via FocalNet[END_REF] or segmentation by aggressiveness. [START_REF] De Vente | Deep Learning Regression for Prostate Cancer Detection and Grading in Bi-parametric MRI[END_REF][START_REF] Duran | ProstAttention-Net: A deep attention model for prostate cancer segmentation by aggressiveness in MRI scans[END_REF] We recently tackled this issue based on a U-Net backbone architecture combining multi-task learning and an attention model. [START_REF] Duran | ProstAttention-Net: A deep attention model for prostate cancer segmentation by aggressiveness in MRI scans[END_REF] Besides the time gain with weak labels, this problem is of high clinical interest as cancer aggressiveness, graded by Gleason score (GS), is mostly determined based on biopsy samples, that characterize the lesion at a specific location but do not allow to know the extent of the lesion. This kind of approach could also allow the inclusion of the ProstateX-2 dataset, which is the only public database, so far, containing PCa patient MRI exams, each associated to the centroid coordinates and the aggressiveness of its reported lesions. Lesions distribution according to the GS group is detailed in Table 1 for both datasets, where GS 3+3 and GS ≥ 8 represent the less and most aggressive cancers, respectively. Input MRI exams are series of axial T2 weighted (T2w) and apparent diffusion coefficient (ADC), stacked in two channels.

Multichannel 3D input T2w and ADC images of both datasets were resampled to a 1 × 1 mm 2 pixel size and automatically cropped to a 96 × 96 pixels region on the image's center. The slice thickness was preserved and is around 3 for our private dataset as well as for most of ProstateX-2 patients. Most of our dataset acquisitions contain 24 slices while it is variable but around 20 slices for ProstateX-2 challenge dataset. Intensity was linearly normalized into [0, 1] by patient and channel. Circular scribble annotations were automatically generated on both our private and ProstateX-2 datasets, as follows:

• Our dataset : circular scribbles with radius ≤ 4 pixels (i.e. 4 mm) were drawn by randomly sampling, on each transverse slice of the the training dataset, one location in the prostate zone as well as one location in each reported lesion. If no scribble with a 4 pixels radius could fit in the lesion, radius was reduced until the scribble could meet the overlapping criterion.

• ProstateX-2 : circular scribbles with radius of 4 pixels (i.e. 4 mm) were drawn on each slice of the training dataset. Lesion scribbles were centered at the reported ground truth lesion center. As prostate annotations are not available, scribbles in the prostate gland were inferred from the lesion localisation as follows : the x coordinate of the prostate scribble was chosen at 11 mm from the lesion's center in direction to the center of the image. For the y position, it was defined at 11 mm in direction of the center of the image if the lesion was in the transition zone (TZ) and kept unchanged if the lesion was in the peripheral zone (PZ). Scribbles drawn in the slice of the lesion coordinates were reported to the 2 adjacent slices, and only annotated slices were used for training. Consistency of the obtained scribbles was checked visually. Table 2 reports the ratio between the number of annotated voxels in the scribbles and in the full segmentation masks for each class, corresponding to 6.35% in total. Note that even if the ratio seems high for some classes (32.77% for GS6 for example), it still constitutes a huge time saving as the radiologist only needs to pick one point for each lesion and the circle scribble would be generated automatically around this center with the chosen radius.

A weak multi-class segmentation model of

H(S) + λC(V S ) (1)
where λ is a positive constant weighting the two terms, V S = p∈Ω S p with S p the softmax probability at pixel p in the image domain Ω, and the functions H, C are given by:

H(S) = - 1 |Ω A | p∈Ω A log (S p ) (2) C(V S ) =    (V S -a) 2 , if V S < a (V S -b) 2 , if V S > b 0, otherwise (3)
with Ω A the domain of annotated pixels, a and b the lower and upper bounds of the region of interest respectively. In this study, we address a multi-class problem with class labels c ranging from 1 to c=6 for the background, the overall prostate area, GS 6, GS 3+4, GS 4+3 and GS ≥ 8 lesions, respectively. To adapt to a multi-class output with C classes and account for class imbalance, the global loss term is obtained by a weighted sum of the loss terms (1) applied independently on each class c ̸ = 1 as follows :

c∈{2,...,6} w c (H(S c ) + λC(V Sc )), (4)
with w c the weight for class c.

We used this constraint at the image level with image-tag priors, following the definition in Kervadec et al., 1 that is enforcing the presence of the target class by setting a = 1 and b = |Ω| (the image domain) or the absence of the target with parameters a = b = 0. When the target is present in the image, the predicted object will always be smaller than the upper bound b but the lower bound a remains crucial. In addition, both bounds are used when the target is absent of the image, making this constraint non-trivial.

Backbone architecture

The model used in this work is based on a standard four blocks U-Net, 8 with batch normalization layers to reduce over-fitting and leaky ReLU activations. It produces a 6-channels segmentation maps, corresponding class labels c ranging from 1 to 6 for the background, the overall prostate area, GS 6, GS 3+4, GS 4+3 and GS ≥ 8 lesions. This standard U-Net architecture was shown efficient for the detection and grading of PCa with bp-MRI. [START_REF] Duran | ProstAttention-Net: A deep attention model for prostate cancer segmentation by aggressiveness in MRI scans[END_REF]

Experiments

In this study, we perform different experiments:

• we first evaluate performance of our proposed scribble based weak U-Net based on the image tags bounds constrained loss by comparing it to the fully supervised approach based on our private fully annotated dataset ;

• we then include the weakly annotated data from ProstateX-2 challenge and train the weak segmentation model on both ProstateX-2 and our datasets.

Implementation details Each model was trained and validated using a 5-fold cross-validation, with 4 replicates for each cross-validation experiment. Patients were distributed in the folds so as to balance as much as possible the number of lesions per class, and the number of patients from each database (ProstateX-2 and ours) for the hybrid training of the weakly supervised architecture. Training and evaluation were conducted on the whole patient 3D volumes. Data augmentation was applied during the training phase to reduce overfitting. Final lesion maps were estimated from the labeled maps outputted from the U-Net decoder branch using a 3-connectivity rule to identify the connected components. Lesions smaller than 26 voxels (ie. 78 mm 3 ) were removed. All networks were trained using Adam and a L2 weight regularization with γ = 10 -4 . The initial learning rate was set to 10 -3 with a 0.5 decay after 25 epochs without validation loss improvement. Batch size was set to 32. Hyperparameters were tuned with random grid search. We set λ value for the constraint in Eq.

(1) to 10 -5 , w c = 0.22 for the cancer classes, w c = 0.12 for the prostate (c = 2) (these values were found to be the optimal to account for class imbalance in our dataset). The fully supervised baseline was trained with the sum of the crossentropy and Dice weighted losses. The pipeline was implemented in python with the Keras-Tensorflow 2.4 library.

Performance evaluation

Performance evaluation was conducted from the final lesion maps generated by each model using quadratic weighted Cohen's kappa coefficient (as proposed in the ProstateX-2 challenge) for both datasets and free-response receiver operating characteristics (FROC) curve for our private dataset. Evaluation on our dataset was performed as follows : if a predicted lesion intersected a ground truth lesion with at least 10% of its volume, it was counted as a true positive. Then, to compute the FROC, we measured the percentage of detected lesion (sensitivity) as a function of the mean number of false positive lesion detections per patient at different probability thresholds. The Cohen kappa score was computed based on the 4-classes confusion matrix encompassing GS 6, GS 3+4, GS 4+3 and GS ≥ 8 lesion categories.

For ProstateX-2 dataset, as lesion contours are not available, we followed the evaluation method proposed by De Vente et al. [START_REF] De Vente | Deep Learning Regression for Prostate Cancer Detection and Grading in Bi-parametric MRI[END_REF] : for each reference lesion center (whose coordinates and GS are provided by the ProstateX-2 challenge organizers), the lesion was assigned the Gleason score corresponding to the cluster containing it, if any. If the reference lesion center did not intersect any detected lesion, it was reported as a GS 6 lesion.

RESULTS

Table 3 reports segmentation performance of all considered models, namely the fully supervised U-Net model (referred to as 'fully supervised') trained with a weighted cross-entropy + Dice loss, a weakly supervised U-Net trained with partial cross-entropy only (referred to as 'Partial CE') and the proposed weakly supervised U-Net trained with a loss term combining partial cross-entropy and image tags priors (referred to as 'Partial CE + Tags').

Performance achieved for these three models trained and tested on our private dataset indicate, as expected, that the highest values of kappa coefficient of 0.324 ± 0.053 and sensitivity at 2FP of 0.649 ±0.033 are obtained with the fully supervised U-Net. However, performance of the proposed weak U-Net model with partial CE + Tags is close to the fully supervised model with kappa coefficient of 0.289 ± 0.072 and sensitivity at 2FP of 0.587 ±0.053. According to a Wilcoxon signed-rank test, the difference is not significant with a p-value of 0. the kappa metric and 0.409 for the sensitivity. The poor performance achieved with the weak model trained on partial CE only (kappa coefficient of -0.054 ± 0.193 and sensitivity at 2FP of 0.016 ±0.008) confirms the positive impact of the image-tags constraint.

The highest reported performance on the ProstateX-2 dataset is achieved with the proposed weak model trained on both datasets with the combined partial CE and image tags priors. Note that the reported kappa score of 0.276 ± 0.037 is, as far as we know, the highest value reported in the literature so far. The proposed constraint loss term, however, is not sufficient to enable correct training on the ProstateX-2 data only, as revealed by the very low kappa metric of -0.002 ± 0.003. This can be explained by the small size of the ProstateX-2 train dataset (99 patients), for which only slices with a lesion were included. In addition, prostate scribbles in the normal prostate tissue for this dataset were generated from the known lesion's positions, as described above, thus inducing less variability than among our private dataset which contains prostate scribbles annotations in lesion-free prostate slices.

Concerning visual results (see Figure 1), we can see that even with weak annotations, segmentation maps are of good quality. Segmentation of the prostate is slightly less precise on our dataset with the weak model than with the supervised one, when trained on our dataset only, but segmentation accuracy improves when trained on both ProstateX-2 and our datasets. One interesting result concerns generalization on ProstateX-2 dataset : visually, the worst performing model is the supervised one. We can see that even the prostate tissue is not well segmented. It seems that the fully-supervised model is more prone to overfitting and is likely not to consider the prostate shape but independent pixels unlike the weakly supervised models.

CONCLUSIONS

Results reveal that we can approach fully-supervised performance by training a U-Net model with only 6.35% of pixels annotation thanks to a loss term combining partial cross-entropy and a size constraint loss derived from that of Kervadec et al. [START_REF] Kervadec | Constrained-CNN losses for weakly supervised segmentation[END_REF] These results are particularly interesting considering the time gain when using scribbles instead of pixel-level annotation. In addition, scribble ground truth is very relevant for PCa screening as most of the databases rely on biopsy results. Such scribble-based segmentation models are likely to ease the inclusion of data from different sources (e.g. different centers or scanners) to tackle the recurrent domain shift problem in medical image segmentation.

In Kervadec et al., 1 the authors also proposed a higher supervision with adapted bounds for the size constraints, defined from the dataset statistics. This approach seemed very interesting for the lesion segmentation task as the higher the Gleason score, the bigger the lesion. However, preliminary results did not show any improvement when using more precise size constraints based on the observed lesion size distribution in comparison to the rough image tag. The size constraints are difficult to define for this problem, as some small elements of a lesion might be present on a slice but not representing the global 3D lesion size and more than one object can be present on the same slice, on the contrary to segmentation tasks considered in Kervadec et al.

Perspectives would be to investigate hybrid training on both fully and weakly annotated datasets and lesion shape constraints tailored to our application.

Figure 1 .

 1 Figure 1. Prediction for several images from validation sets. The images from the first three rows come from our dataset while images from the two last rows come from the ProstateX-2 challenge dataset. Second column: fully supervised U-Net trained with our dataset. Third and fourth columns: weakly supervised U-Net trained on scribble annotations of our dataset and of both ProstateX-2 and our datasets, respectively.

Table 1 .

 1 Lesions distribution by Gleason score (GS) in both datasets.Two datasets are used in this study, both containing lesion's aggressiveness information (by Gleason score):• Our private dataset. The main dataset used in this study consists of a series of axial T2 weighted (T2w) and apparent diffusion coefficient (ADC) MR images from 219 patients, acquired in clinical practice at our partner clinical center. All patients underwent a radical prostatectomy and their exams were fully annotated (including lesions with their associated Gleason score and prostate contours) at pixel-level based on prostatectomy gold standard ground truth. Imaging was performed on three different scanners from different constructors and magnetic field strength : 67 exams on a 1.5T Symphony scanner (Siemens Medical Systems), 126 on a 3T scanner Discovery scanner (General Electric) and 26 on a 3T Ingenia scanner (Philips Healthcare).• ProstateX-2 train set. ProstateX-2 challenge dataset 7 is composed of a training set of 99 patients with 112 lesions. These data were acquired on 3T MAGNETOM Trio and Skyra (Siemens Medical Systems) scanners with different imaging parameters. The ground truth consists of the coordinates of each lesion's center based on biopsy results, with its associated Gleason score. Note that the ProstateX-2 test set was not used since no ground truth is available and the challenge webpage is closed.

		GS 3+3 GS 3+4	GS 4+3 GS ≥ 8 Total
	Our dataset	104	126	56	52	338
	ProstateX-2	36	41	20	15	112
		2. MATERIALS AND METHODS
	2.1 Data description

Table 2 .

 2 Ratio between the number of annotated voxels in the scribbles and in the full segmentation masks for each class in our private dataset.

	Class	Prostate GS 6	GS 3+4 GS 4+3 GS ≥ 8 Total
	Ratio (%)	4.92	32.77	29.36	25.85	18.36	6.35

  PCa in bp-MRI 2.2.1 Constrained loss function for weak supervision based on Kervadec et al. 1 Kervadec et al. recently proposed a new loss function for partially annotated data. It combines a partial crossentropy (CE) term H estimated on the annotated voxels and a constraint term C, that penalizes predicted segmentation whose size is outside a defined interval [a, b] :

Table 3 .

 3 Segmentation performance. The results correspond to the average metrics obtained on 4 replicates of 5-fold cross-validation. CE : cross-entropy. Tags : Image tags bounds constraint.

	165 for

ACKNOWLEDGMENTS

This work was supported by the RHU PERFUSE (ANR-17-RHUS-0006) of Université Claude Bernard Lyon 1 (UCBL), within the program "Investissements d'Avenir" operated by the French National Research Agency (ANR). It was performed within the framework of the LABEX PRIMES (ANR-11-LABX-0063) of Université de Lyon operated by the French National Research Agency (ANR).


Audrey Duran

Gaspard Dussert

Carole Lartizien

PERFUSION IMAGING IN DEEP PROSTATE CANCER DETECTION FROM MP-MRI: CAN WE TAKE ADVANTAGE OF IT?

Keywords: prostate cancer, mp-MRI, dynamic MRI, segmentation, CNN

To our knowledge, all deep computer-aided detection and diagnosis (CAD) systems for prostate cancer (PCa) detection consider bi-parametric magnetic resonance imaging (bp-MRI) only, including T2w and ADC sequences while excluding the 4D perfusion sequence,which is however part of standard clinical protocols for this diagnostic task. In this paper, we question strategies to integrate information from perfusion imaging in deep neural architectures. To do so, we evaluate several ways to encode the perfusion information in a U-Net like architecture, also considering early versus mid fusion strategies. We compare performance of multiparametric MRI (mp-MRI) models with the baseline bp-MRI model based on a private dataset of 219 mp-MRI exams. Perfusion maps derived from dynamic contrast enhanced MR exams are shown to positively impact segmentation and grading performance of PCa lesions, especially the 3D MR volume corresponding to the maximum slope of the wash-in curve as well as Tmax perfusion maps. The latter mp-MRI models indeed outperform the bp-MRI one whatever the fusion strategy, with Cohen's kappa score of 0.318±0.019 for the bp-MRI model and 0.378 ± 0.033 for the model including the maximum slope with a mid fusion strategy, also achieving competitive Cohen's kappa score compared to state of the art.

INTRODUCTION

Deep learning has become the state-of-the-art approach for the processing and analysis of many medical imaging problems, including detection and segmentation tasks. Many CAD systems for prostate cancer (PCa) detection and segmentation from MRI are based on convolutional neural networks (CNN) [START_REF] Rogier | Artificial intelligence in multiparametric prostate cancer imaging with focus on deep-learning methods[END_REF]. However, deep models render difficult the inclusion of high dimensional input data, such as 4-dimensional (4D) perfusion MR.In addition, the impact of this MR dynamic contrast enhanced (DCE) modality in PCa detection is controversial [START_REF] Verma | Overview of Dynamic Contrast-Enhanced MRI in Prostate Cancer Diagnosis and Management[END_REF][START_REF] Visschere | Dynamic contrast-enhanced imaging has limited added value over T2-weighted imaging and diffusion-weighted imaging when using PI-RADSv2 for diagnosis of clinically significant prostate cancer in patients with elevated PSA[END_REF][START_REF] Woo | Head-to-Head Comparison Between Biparametric and Multiparametric MRI for the Diagnosis of Prostate Cancer: A Systematic Review and Meta-Analysis[END_REF][START_REF] Brancato | Assessment of DCE Utility for PCa Diagnosis Using PI-RADS v2.1: Effects on Diagnostic Accuracy and Reproducibility[END_REF]. As a consequence, as far as we know, all deep PCa segmentation models using original MR images as input (thus excluding the radiomics-based approaches) only include T2 weighted (T2w) and diffusion weighted imaging (DWI) sequences, leading to bi-parametric (bp) models. In this paper, we question the contribution of the dynamic sequence in the context of the challenging task of segmentation and grading of PCa in mp-MRI, addressed in few studies [START_REF] Cao | Joint Prostate Cancer Detection and Gleason Score Prediction in mp-MRI via FocalNet[END_REF][START_REF] Duran | Prostate Cancer Semantic Segmentation by Gleason Score Group in bi-parametric MRI with Self Attention Model on the Peripheral Zone[END_REF][START_REF] De Vente | Deep Learning Regression for Prostate Cancer Detection and Grading in Bi-parametric MRI[END_REF][START_REF] Duran | ProstAttention-Net: a deep attention model for prostate cancer segmentation by aggressiveness in MRI scans[END_REF]. We evaluate several ways to encode the perfusion information in 3D and compare performance of mp-MRI models with the baseline bp-MRI model. Several types of perfusion maps were derived from the time series of 3D dynamic contrast enhanced (DCE) image stacks acquired for each patient after the bolus injection of gadolinium contrast agent. These maps consist either in specific 3D MR volumes extracted at specific time points from the time series or from semi-quantitative parametric maps extracted from the processing of kinetic curves at voxel level, as illustrated in Figure 1.

MATERIALS AND METHODS

Perfusion maps

Tmax Tmax maps are parametric maps, where each voxel value corresponds to the time where the maximum value of the time intensity curve was observed. The unit is arbitrary since dynamic MR shows variable temporal resolution.

Wash-in The wash-in period corresponds to the period of the time intensity curve ranging from the onset to the time of peak intensity, where the onset is defined as the time corresponding to the maximum acceleration on the time-intensity curve. The wash-in maps are derived by computing the slope observed in the time-intensity curve during the wash-in period at voxel level. The higher the wash-in slope, the faster the wash-in speed, that is a suspicious sign of cancer tissue.

Wash-out Similarly to the wash-in map, the wash-out map contains the voxel-based slope values observed in the timeintensity curve during the wash-out time period ranging from Tmax until the end of the acquisition.

Maximum slope time volume This 3D map is the 3D MR volume of the DCE times series corresponding to the volume where the maximum slope (or signal enhancement) was observed in the signal intensity curve.

Maximum percentage of enhancement maps This 3D map reflects the percentage enhancement from the signal intensity changes between the first image and the images obtained during the wash-in period, regardless of the time when the maximal enhancement appears. Those maps were described in [START_REF] Yoon | Dynamic Contrast-Enhanced MRI of the Prostate: Can Auto-Generated Wash-in Color Map Be Useful in Detecting Focal Lesion Enhancement?[END_REF].

Quantitative pharmacokinetic maps derived from compartmental modeling such as K trans , K ep , V e and V p were not considered because of their high dependence to the arterial input function and variability depending on the MR scanner acquisition parameters [START_REF] Brunelle | Variability induced by the MR imager in dynamic contrast-enhanced imaging of the prostate[END_REF].

Data description

The private dataset used in this study consists of a series of axial T2w, apparent diffusion coefficient (ADC) and DCE MR images from 219 patients, acquired in clinical practice at our partner clinical center. Imaging was performed on three different scanners from different constructors and magnetic field strengths: 67 exams on a 1.5T Symphony scanner (Siemens Medical Systems), 126 on a 3T scanner Discovery scanner (General Electric) and 26 on a 3T Ingenia scanner (Philips Healthcare). For DCE imaging, an intravenous injection of 0.2ml/kg of gadoterate meglumine was performed at 3 ml/s. Temporal resolution was adapted to the field strength and depends on the scanner. All patients underwent a radical prostatectomy. After correlation with the whole-mount specimens, the uroradiologists outlined reported 338 prostate lesions as 1, where GS 3+3 and GS ≥ 8 represent the less and most aggressive cancers, respectively. The detailed protocol and acquisition parameters can be found in [START_REF] Bratan | Influence of imaging and histological factors on prostate cancer detection and localisation on multiparametric MRI: a prospective study[END_REF].

Multiclass deep segmentation of PCa

The model used in this work is based on a standard four blocks U-Net [START_REF] Ronneberger | U-Net: Convolutional Networks for Biomedical Image Segmentation[END_REF], with batch normalization layers to reduce over-fitting and leaky ReLu activations. It produces a 6-channels segmentation maps, corresponding to 6 class labels for the background, the overall prostate area, GS 6, GS 3+4, GS 4+3 and GS ≥ 8 lesions. This standard U-Net architecture was shown efficient for the detection and grading of PCa with bp-MRI [START_REF] Duran | Prostate Cancer Semantic Segmentation by Gleason Score Group in bi-parametric MRI with Self Attention Model on the Peripheral Zone[END_REF][START_REF] Duran | ProstAttention-Net: a deep attention model for prostate cancer segmentation by aggressiveness in MRI scans[END_REF]. Two different fusion strategies of the different modalities were considered in this work as depicted on Figure 2 : • early fusion, where all considered modalities are stacked in a multichannel input; • mid fusion, where each modality is encoded independently into distinct convolutional branches of the U-Net, sharing the same decoding branch. Feature maps from each encoding branch are concatenated in the latent space after the encoders (after the 10th convolutional layer).

For each fusion strategy, we considered one baseline biparametric model including T2w and ADC maps as well as different multiparametric models accounting for one of the perfusion maps listed above in addition to the T2w and ADC maps.

Experiments

Each model was trained and validated using a 5-fold crossvalidation, with 4 replicates for each cross-validation experiment for more representative results. Multichannel input MR images were resampled to a 1 × 1 × 3 mm 3 voxel size and automatically cropped to a 96 × 96 pixels region on the image's center. Intensity was linearly normalized into [0, 1] by volume. Data augmentation was applied during the training phase to reduce overfitting and batch size was set to 32. All models were trained using a combination of the dice loss and cross entropy, with Adam optimizer and a L2 weight regularization with γ = 10 -4 . The initial learning rate was set to 10 -3 with a 0.5 decay after 25 epochs without validation loss improvement. The pipeline was implemented with the Keras-Tensorflow 2.4 library. Lesion detection performance was evaluated through freeresponse receiver operating characteristics (FROC) analysis, first considering the performance of each model to discriminate clinically significant (CS) lesions (GS > 6), then its ability to discriminate lesions of each GS group. Cohen's quadratic weighted kappa coefficient was also computed at the lesion level as described in [START_REF] Duran | ProstAttention-Net: a deep attention model for prostate cancer segmentation by aggressiveness in MRI scans[END_REF].

RESULTS

Table 2 shows detection and segmentation performance of CS (GS > 6) lesions for each perfusion map and each fusion strategy in comparison with the baseline bp-MRI model. Considering the early fusion strategy, the addition of the max slope volume, Tmax or wash-out map to the T2 and ADC maps is shown to boost the model performance compared to the baseline. For the max slope and the Tmax maps, we observe a sensitivity gain of 5.4% and 4.1% respectively at 1 false positive (FP), 2.6% and 3.3% at 2FP and the maximum sensitivity increased by 5.8% and 5.9%. For those 2 models, the maximal number of FP is also reduced by 0.152 for the max slope and 0.172 for the Tmax. % enhancement and wash-in maps are not shown to bring discriminant information for this task. Considering the Cohen's kappa coefficient, the best value of 0.343 ± 0.050 is obtained with the wash-out model, that outperforms the baseline (0.318 ± 0.019).

Performance achieved with the two best performing parametric maps (Tmax and max slope volume) of the early fusion scenario were compared to that achieved with the same perfusion maps in the mid-fusion strategy. This approach does not show a clear impact : at 1FP, sensitivities of these 3 models (second part of Table 2) are lower than with the early fusion strategy, but at 2FP, the max slope and Tmax sensitivies are higher than with the early fusion strategy.

Table 3 allows a finer analysis of the sensitivity for each Gleason Score (GS) group. It reflects the model ability to both localize lesions and assign their correct GS. Regarding the early fusion strategy, here again, models trained with Tmax perfusion map or max slope volume outperform the baseline, except for the GS 3+4 (class with the highest number of lesions in the dataset, see Table 1) where sensitivities of all models are very close and for the GS 3+3 for Tmax. The wash-out is also shown to perform well and outperform the baseline for each GS but the GS 3+4 at 1.5FP. The mid fusion strategy seems to outperform the early fusion, in particular when accounting for Tmax perfusion map.

CONCLUSIONS

This study demonstrates that perfusion maps derived from DCE MR exams positively impact the performance of deep multiclass segmentation models of PCa. Reported performance are in par with the state of the art and outperform the reported kappa of 0.172 ± 0.169 [START_REF] De Vente | Deep Learning Regression for Prostate Cancer Detection and Grading in Bi-parametric MRI[END_REF] with a bp-MRI ordinal regression model on the ProstateX-2 challenge dataset. Performance gain was shown to depend on the considered perfusion maps and fusion strategy. Although no strict guidelines could be driven from this study, we showed that, globally, the Tmax, and max slope volume improved detection sensitivity of CS and GS PCa lesions. This is concordant with other studies where the Tmax was found to have a significant impact on the detection of PCa lesions [START_REF] Zhao | Dynamic Contrast-Enhanced MRI of Prostate Lesions of Simultaneous [68Ga]Ga-PSMA-11 PET/MRI: Comparison between Intraprostatic Lesions and Correlation between Perfusion Parameters[END_REF]. The mid fusion strategy seems to be beneficial both in terms of detection sensitivity and prostate segmentation. The concatenation of each sequence data at a higher representation level is likely to allow extracting more discriminant features from each MR sequence. This fusion strategy might also be less sensitive to small misalignment between sequences.

Our study does not demonstrate the positive impact of wash-in maps unlike some other standard radiomic studies [START_REF] Sub | Prostate Cancer Detection on Dynamic Contrast-Enhanced MRI: Computer-Aided Diagnosis Versus Single Perfusion Parameter Maps[END_REF][START_REF] Hoang Dinh | Quantitative Analysis of Prostate Multiparametric MR Images for Detection of Aggressive Prostate Cancer in the Peripheral Zone: A Multiple Imager Study[END_REF]. This might be explained by the way we extracted wash-in maps : the end of the wash-in period was indeed defined at the time where the brightest intensity was observed in the voxel, that might be reached at the end of the acquisition. In addition, the intensity normalisation was performed after the volume slices were cropped to a 96 × 96 size, so it doesn't consider the external iliac vein and artery, where a high signal is observed at the arrival time. This might induce high intervariability of the wash-in maps impairing the impact of this perfusion map.

Perspectives would be to further evaluate the impact of the perfusion map normalisation as well as include together the three perfusion maps (Tmax, max slope, wash-out) in addition to the T2w and ADC maps in the U-Net based PCa segmentation model, in a early or mid fusion strategy.

COMPLIANCE WITH ETHICAL STANDARDS

This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the appropriate national administrative authorities (Comité de Protection des Personnes, reference L 09-04 and Commission Nationale de l'Informatique et des Libertés, treatment n • 08-06) and patients gave written informed consent for researchers to use their MR imaging and pathologic data.

Fig. 1 :

 1 Fig. 1: Example perfusion maps considered in this study. Higher values of the parametric maps ((b) to (e)) are shown in red while lower values are in blue. This example shows a GS 3+4 lesion drawn on the T2w sequence. GT: ground truth.

Fig. 2 :

 2 Fig. 2: Simplified architecture of the U-Net (a) early and (b) mid fusion models. For the sake of simplicity, skip connections are not shown for the mid fusion but the feature maps of each branch are concatenated before integration in the decoder branch.

Table 3 :

 3 ± 0.02 bp-MRI + max slope 0.58 ± 0.05 0.56 ± 0.03 0.37 ± 0.03 0.37 ± 0.03 0.47 ± 0.02 0.39 ± 0.02 0.17 ± 0.03 0.16 ± 0.04 bp-MRI + Tmax 0.58 ± 0.05 0.54 ± 0.03 0.51 ± 0.03 0.49 ± 0.04 0.50 ± 0.03 0.43 ± 0.06 0.11 ± 0.02 0.10 ± 0.02 Mean detection sensitivity for each GS group. Results correspond to the average metrics obtained on 4 replicates of 5-fold cross-validation. The best results for each metric and fusion strategy are in bold.

Fig. 3 :

 3 Fig. 3: Example predictions for the same slice for several models. The two outlined regions in the ground truth image correspond to GS 3+4 (green) and GS 4+3 (blue) PCa lesions, respectively.

Table 1 :

 1 Lesions distribution by Gleason Score (GS) our dataset.

	GS 3+3 GS 3+4 GS 4+3 GS ≥ 8 Total
	104	126	56	52	338
	well as all prostate contours. Their distribution according to
	the Gleason score (GS) group is detailed in Table

Table 2 :

 2 Segmentation performance. Results correspond to the average metrics obtained on 4 replicates of 5-fold crossvalidation. The best results for each metric and fusion strategy are in bold.

	Model			Kappa	Sensi at 1FP	Sensi at 2FP	Sensi max		Max FP	Dice prostate
					Early fusion
	baseline : bp-MRI		0.318 ± 0.019	0.544 ± 0.029	0.660 ± 0.030	0.674 ± 0.031	2.134 ± 0.139	0.789 ± 0.002
	bp-MRI + max slope		0.303 ± 0.054 0.598 ± 0.026 0.686 ± 0.036	0.705 ± 0.039	1.982 ± 0.304	0.769 ± 0.007
	bp-MRI + % enhancement	0.312 ± 0.035	0.525 ± 0.019	0.649 ± 0.025	0.693 ± 0.030	2.525 ± 0.185	0.771 ± 0.002
	bp-MRI + Tmax		0.328 ± 0.026	0.585 ± 0.020	0.693 ± 0.024 0.706 ± 0.019 1.962 ± 0.165	0.770 ± 0.008
	bp-MRI + wash-in		0.281 ± 0.020	0.541 ± 0.041	0.659 ± 0.030	0.687 ± 0.024	2.308 ± 0.388	0.784 ± 0.013
	bp-MRI + wash-out		0.343 ± 0.050 0.553 ± 0.021	0.665 ± 0.015	0.680 ± 0.015	2.302 ± 0.104	0.778 ± 0.003
						Mid fusion
	baseline : bp-MRI		0.333 ± 0.060	0.529 ± 0.017	0.656 ± 0.010	0.687 ± 0.010	2.440 ± 0.341	0.792 ± 0.004
	bp-MRI + max slope		0.378 ± 0.033 0.569 ± 0.029	0.693 ± 0.022	0.708 ± 0.017	1.929 ± 0.111 0.798 ± 0.004
	bp-MRI + Tmax		0.315 ± 0.064 0.582 ± 0.041 0.712 ± 0.009 0.732 ± 0.007 2.331 ± 0.399	0.778 ± 0.008
			GS ≥ 8	GS 4+3	GS 3+4			GS 3+3
	Model	1.5 FP	1 FP	1.5 FP	1 FP	1.5 FP	1 FP	1.5 FP	1 FP
						Early fusion
	baseline : bp-MRI	0.57 ± 0.06	0.56 ± 0.05	0.42 ± 0.07

0.41 ± 0.06 0.45 ± 0.02 0.37 ± 0.01 0.14 ± 0.05 0.12 ± 0.04 bp-MRI + max slope 0.64 ± 0.03 0.62 ± 0.02 0.46 ± 0.03 0.45 ± 0.04 0.43 ± 0.05 0.37 ± 0.02 0.17 ± 0.04 0.15 ± 0.03 bp-MRI + % enhan. 0.62 ± 0.03 0.61 ± 0.02 0.42 ± 0.08 0.40 ± 0.06 0.43 ± 0.02 0.36 ± 0.04 0.06 ± 0.04 0.06 ± 0.03 bp-MRI + Tmax 0.61 ± 0.03 0.61 ± 0.03 0.47 ± 0.02 0.46 ± 0.01 0.44 ± 0.03 0.36 ± 0.01 0.09 ± 0.03 0.08 ± 0.03 bp-MRI + wash-in 0.54 ± 0.09 0.52 ± 0.05 0.45 ± 0.02 0.45 ± 0.02 0.44 ± 0.05 0.37 ± 0.05 0.10 ± 0.02 0.09 ± 0.02 bp-MRI + wash-out 0.60 ± 0.05 0.59 ± 0.05 0.46 ± 0.02 0.45 ± 0.03 0.44 ± 0.02 0.37 ± 0.03 0.16 ± 0.02 0.14 ± 0.02 Mid fusion baseline : bp-MRI 0.56 ± 0.04 0.55 ± 0.03 0.45 ± 0.10 0.44 ± 0.09 0.46 ± 0.02 0.38 ± 0.04 0.20 ± 0.02 0.17

ACKNOWLEDGMENTS

This work was supported by the RHU PERFUSE (ANR-17-RHUS-0006) of Université Claude Bernard Lyon 1 (UCBL), within the program "Investissements d'Avenir" operated by the French National Research Agency (ANR).


Gunnar Kudrjavets
email: g.kudrjavets@rug.nl

Ayushi Rastogi
email: a.rastogi@rug.nl

Jeff Thomas
email: jeffdthomas@fb.com

Nachiappan Nagappan

On Quantifying the Benefits of Dead Code Removal

Abstract-Engineers consider the presence of dead code as an undesirable attribute of the code base. The industry lacks methods to quantify the benefits of deleting dead code efficiently. The current approach utilizes a simplistic metric that uses the lines of code (LOC) deleted as a proxy to estimate the benefit gained. However, not all LOC are equal. The research community can support the industry and propose methods and metrics that can help to (a) determine the priority order for dead code removal, and (b) quantify the benefits of dead code removal. Improved metrics can result in a more objective ranking of dead code deletion efforts when compared to other competing tasks.

Introduction. Dead code is code that is either needlessly executed or code that a system contains but never runs. Unnecessary code is a subcategory of technical debt and a "bad code smell" [START_REF] Romano | A multistudy investigation into dead code[END_REF]. It is also a cause for maintenancerelated issues [START_REF] Eder | How much does unused code matter for maintenance?[END_REF]. The presence of dead code is one of the categories in the Common Weakness Enumeration system [START_REF]Dead Code (4.6)[END_REF]. In programmer folklore, dead code is an undesirable trait [START_REF] Neville-Neil | Removing Kode[END_REF].

The first automated attempt to remove dead code happens during the compilation. Compilers use techniques such as interprocedural optimization [START_REF] Debray | Compiler techniques for code compaction[END_REF] to remove dead code. Approaches like static analysis can supplement compiler optimizations [START_REF] Haas | Is static analysis able to identify unnecessary source code?[END_REF]. Tools can efficiently determine if code is not called and optimize it away. However, automation cannot identify code that becomes unnecessary because of either changing requirements or obsolete features. These decisions require human intervention.

Organizations use various human-centric approaches to remove dead code systemically. For example, they establish virtual teams consisting of "janitors" [START_REF] Morgenthaler | Searching for build debt: Experiences managing technical debt at Google[END_REF] or designate a set of engineers as the "Code Cleanup Crew." Organizations may also implement dedicated global engineering efforts that are either scheduled or continuous. Online services companies A and B resort to a mix of material and social rewards. In our experience at company A, engineers who delete at least N LOC acquire a dedicated badge on an internal employee profile page, get a limited-edition t-shirt, and become members of the selective "Dead Code Society."

Problem. Each organization or project has several competing priorities. Organizations can invest engineering effort into activities such as developing new features, fixing existing defects, or improving a product's performance. Intuitively engineers know the tax dead code imposes on the development process. In commercial software development, organizations decide where to invest engineering resources by calculating the estimated return on the investment. There are no straightforward approaches to estimating the value gained from deleting dead code. Compared to other engineering activities, the ben-efits of which are well-known, calculating the estimated return on investment for dead code deletion presents a challenge.

The existing framework of "the bigger the number of deleted LOC, the better" is overly simplistic. This valuation scheme does not correctly quantify the benefits gained from deleting dead code. Not all lines of code are equal. The benefit from dead code deletion depends on a variety of contextual factors such as (a) abstraction level (e.g., kernel mode versus user mode), (b) performance cost (e.g., variable initialization versus creating a thread), and (c) exposure and intended usage (e.g., primary attack surface versus a rarely used feature).

Challenges to the research community. The research community can help practitioners by (a) conducting studies on systems that use a systematic approach to delete dead code (e.g., an effort to "prune" code in OpenBSD [START_REF] Unangst | Pruning and Polishing: Keeping OpenBSD Modern[END_REF]) to investigate if other system characteristics such as performance, quality, or the perceived cleanliness of code base change as a result, (b) providing means to compose guidance about the order in which to focus on different system components (e.g., based on abstraction level, code coverage, or attack surface), and (c) defining methods to quantify the benefits of deleting dead code that are more precise than the number of LOC deleted.


ART HISTORY WITHIN ANATOLIAN STUDIES

An approach to Lycian images Fabienne Colas-Rannou Abstract: Lycia is an area of Southern Anatolia famous for its stone monuments and sculpture, dating to between the 6 th and the 4 th centuries BC, under Achaemenid rule of Anatolia. The geographical and historical context of Lycia, and a cultural history with signs of an outward-looking attitude to Greek culture, has meant that many academic treatises have focused either on the Greek elements in Lycian art or on the Persian ones (see for example [START_REF] Jacobs | Griechische und persische Elemente in der Grabkunst Lykiens zur Zeit der Achämenidenherrschaft[END_REF]. Lycian art is thus often seen as a "peripheral" phenomenon to Greek and/or Persian art. The history of Lycian studies, more specifically the field of Lycian sculpture, is heavily dominated by traditional academic fields. Accordingly, Lycian studies have long been promoted by Hellenists, and sometimes Orientalists, but much less by Anatolia specialists. This paper will focus on historiography and methodology.

It will develop a methodological and conceptual approach that can be used to study images in specific Lycian and Anatolian contexts, allowing us to reassess the concepts of "Hellenization" and "Iranization". "Images" are understood as figurative representations. From an art historical vantage point, this paper aims to illustrate how iconography and iconology can improve our knowledge of Lycian culture and history during the 1 st millennium BC, and highlight the fact that Lycian culture is an original Anatolian culture.

Keywords: Lycia, art history, historiography, Pierre Demargne, iconography, iconology, mixity, fluidity Art history within Anatolian studies 1 DISCOVERING LYCIAN ART DURING THE 18 TH AND 19 TH CENTURIES AD: The difficulty of defining Lycian art and a possible origin of the traditional view "between Greece and Persia"

During the 1770s, Choiseul-Gouffier noticed the specificity of some sarcophagi from ancient Telmessos, describing one of them as follows:

"Ce tombeau est le plus grand de tous ceux que nous avons rencontrés en cet endroit; il est d'un dessin très singulier, et je n'en connais aucun du même genre. Il semble qu'on ait voulu imiter un édifice construit en bois; c'est au moins ce que paraissent indiquer ces dés de pierre ou ces mutules que l'on a conservées, ainsi que ces panneaux correctement dessinés, et qui sont pris dans la pièce même." 1

He appreciated the monumental rock-cut tombs at Telmessos, making connections between them and Persian and Greek architecture: As they were gradually "discovered" by Europeans during the 19 th century AD, the Lycian stone monuments were noted for the singularity of their architecture (rock-cut tombs, pillar tombs, sarcophagi). In his "In my former rambles in Asia Minor I observed that each district had a peculiarity in the architecture of its tombs, and that none was more distinctly marked than that of the ancient Lycia." 4

He highlighted "four" kinds of tombs peculiar to Lycia, which relate to the categories currently known as Lycian pillar tombs, sarcophagi and rock-cut tombs, and included a drawing on a plate attached to the text (Fig. 2). In trying to characterize these original architectural forms, Fellows borrowed terms from other cultural contexts and periods, and called them "the Obelisk, the Gothic, and the Elizabethan forms". Previously, in the same journal, Charles Texier was able to use the vocabulary of Greek architecture to describe the front of some tombs at Telmessos which imitate Greek architecture (Texier 1849: 188; the same tombs were observed by Choiseul-Gouffier; see, above, the last ones mentioned by this author). Now, instead, we see the "difficulty" he has in describing the architecture of these Lycian rock-cut tombs at Phellos (Fig. 3). The reference to tombs in Persepolis is also present in Texier's book, in the passage relating to Lycian rock-cut tombs at Telmessos. 7 Nevertheless, even if some original elements could be noted in Lycian architecture, the style of the reliefs that adorned Lycian stone monuments could be seen as Greek. Writing about Xanthos, for example, Charles Fellows noted: "The whole of the sculpture is Greek, fine, bold, and simple, bespeaking an early age of that people. At this point, we see the emergence of one of the most striking aspects of Lycian studies until the 20 th century -an approach which interpreted Lycian sculpture and iconography closely (in some instances, strictly) on the basis of its relationship to Greek art and culture. This approach was mainly developed by European scholars during the 20 th century. We can consider this historiographic phenomenon through the interesting case of one of the scholars who strongly promoted the study of ancient Lycia: Pierre Demargne (1903Demargne ( -2000)), excavation leader at Xanthos.

2 A HELLENIST'S VIEW AND THE NOTION OF "PERIPHERY":

The example of Pierre Demargne

The French scholar Pierre Demargne led the archaeological team at Xanthos from 1950 onwards. He published important works about Xanthos and its monuments (four volumes in the "Fouilles de Xanthos" collection and numerous journal articles 9 ). He was a Hellenist, he had been a member of the French Archaeological School at Athens, and taught ancient Greek literature and Greek archaeology at a university in France. 10 Before excavating in Lycia, he had worked in Crete and had shown a special interest in the 7 th century BC -the so-called "Orientalizing period" of Greece. Demargne developed his ideas about cultural contacts within the framework of the notion of "periphery". This notion was highlighted during the 8 th International Congress of Classical Archaeology which he co-organized in Paris in 1963. The proceedings were published in Paris in 1965 under the main title: "Le rayonnement des civilisations grecque et romaine sur les cultures périphériques". It was a new perspective in the sense that it opened up the view to areas other than "traditional" Greece and Italy (Demargne 1965a: 1-3) 11 . However, this approach to cultural contacts between Greece and non-Greek areas mostly tended to emphasize a kind of Greek cultural superiority and "Greek influence" on other ancient cultures or civilizations, in an unequal relationship. P. Demargne employed this approach to Lycian sculpture, and defined Lycia as an "intermediary zone" within this "periphery" -Greece (Continental Greece and Asia Minor) remaining the "centre" from which cultural diffusion spread (Demargne 1965b;Demargne 1978: 753). This way of understanding cultural contacts can still be detected in Demargne's works during the 1970s, with the idea of "hellénisme conquérant", although the author did note that new notions were emerging among scholars: On the one hand, he showed genuine curiosity and great erudition, and promoted the monuments from Xanthos among ancient art; on the other hand, we notice a lack of focus on Lycian sculpture as autonomous and original, Anatolian phenomenon. His recurrent use of the adjectives "Archaic" and "Classical", borrowed from Greek studies for Lycian sculpture, is noteworthy (Demargne 1965b: 500;Demargne 1978). Demargne was connected with the network of scholars excavating in Turkey, and he knew items from other parts of Anatolia (see, for example, Demargne 1965b: 500; Demargne 1981b: 586). Nonetheless, his studies of Lycian sculpture, especially his analyses of the style of carving, repeatedly referred to Greek models (e.g. Demargne 1978). Of course, this was justified: Greek sculpture had an impact on Lycian sculpture; and Demargne rightly raised the question of the identity of craftsmen (for example Demargne 1965b: 500; Childs/Demargne 1989), which remains important. In some papers, however, Demargne could be said to describe the style of Lycian sculpture in a depreciative way (his choice of French vocabulary may be significant). This was the case in his paper for the Paris congress, for example, when he mentions the reliefs belonging to the buildings "H" and "G" from the Lycian acropolis at Xanthos: Art history within Anatolian studies "[…] les personnages drapés nous paraissent très particulièrement maladroits parce qu'ils prétendent sans doute imiter les formes plus évoluées de modèles grecs." 13 We find the same tone in his remarks on the East pediment of the socalled "Nereid Monument" and the seated male figure:

"le trois-quarts est passablement maladroit et manque tout à fait d'élégance." 14 Elsewhere, we find a similar approach to another "peripheral area", in the context of a comparison with sculpture from Cyprus dating to the 5 th century BC:

"Chypre, […], nous fournirait des exemples d'un archaïsme prolongé, à l'affligeante médiocrité : une vraie rechute après l'éclat des années 500." 15 Furthermore, his position was ambiguous, as he used both the idea of an efficient and prevailing Hellenism and that of local "cultural, religious and political ideologies" 16 , which could have interfered with this Greek "influence".

"Toutes proches de la côte les zones que nous appelons intermédiaires demeurent indigènes, tout en subissant depuis longtemps l'influence grecque…" 17 "Là où prévalent la vieille iconographie et l'idéologie dynastique, réapparaissent les formes et les procédés de l'archaïsme qui sont aussi ceux de l'Orient." 18 Pierre Demargne's proposal to define three periods in the history of the "hellenization" of Lycia was mainly based on the carving style, and consisted of two high periods and between them a time of weaker influence (Demargne 1974a: 587-590). This enabled him to postulate a certain refusal or resistance, sometimes seen as an "unfitness" and as an expression of "conservatism" (Demargne 1965b: 500;Demargne 1974a: 589). The notion of "archaism" could be associated with the notion of "provincialism" (another term suggesting periphery) when applied to sculpture dating to the 4 th century BC (Demargne 1981b 19 ).

In the 8 th volume of the "Fouilles de Xanthos" on the decorative sculpture of the Nereid Monument, written in collaboration with William Childs and published in 1989 (Childs/Demargne 1989), the propensity towards a depreciative approach had weakened, and the more moderate point of view employed in this volume better appreciated the balance between a Greek "influence" and the local context.

Thus, in his works we find both the recurrent idea of a Greek art employed to express an Oriental ideology (for example Demargne 1976: 82;Demargne 1981a) and the idea of an Achaemenid reference in the treatment of certain figurative scenes or human figures (Demargne 1974b: 70, 79, 81;Demargne 1976: 84, 87), and thus of Lycian art positioned between the Greek world and Persia. Furthermore, he proposed the reading of some patterns in a Greek way, within the frame of a progression of Hellenism in Lycia. 20Pierre Demargne was very interested in iconography and tried to identify patterns and understand them. Despite the fact that he was able to write that "a stylistic likeness doesn't necessarily lead to a same interpretation" (about the Payava sarcophagus, Demargne 1974b: 75), guided by a "Greek-looking" style of carving, Demargne sometimes went too far in interpreting Lycian images in a Greek manner (just as other scholars did), without questioning iconographic gaps and the fact that they could express a Lycian meaning (whatever the style was, i.e. independently of a "Greek-looking" style). In my opinion, the most obvious example is the interpretation given to the free-standing female figures distributed among the intercolumniations of the Arbinas tomb at Xanthos as "Nereids" (known as the Nereid Monument) 21 ; and to the Art history within Anatolian studies akroteria (fragmentary human figures) of the same monument as "Thetis and Peleus" (Demargne 1987).

Thus, he never really highlighted in a positive way the idea of active Lycian choices from both Greek and Achaemenid art. Pierre Demargne was a man of his times, and his approach to ancient intercultural contacts can well be understood in the context of a contemporary history of colonialism, notably in France (decolonization and Colonization Wars during the 1950s and 1960s). The fact of associating the adjective "indigène"/indigenous with Lycian culture is also significant; this adjective is present in a lot of papers, and was still used in the volume published in 1989 on the Nereid Monument (Demargne 1965b: 501-502;Demargne 1974a: 586;Demargne 1974b: 68, 70, 91;Demargne 1976: 82, 95;Demargne 1981a: 85-86;Demargne 1981b: 592;Childs/Demargne 1989: 353, 369, 370; see above the citation of Demargne 1978: 753).

Since Pierre Demargne was naturally not alone in his attitude, further examples by other scholars could be added (and will be, elsewhere, for comparison). 22 More generally, the concept of "Hellenization" was used to enhance a kind of Greek cultural superiority, a diffusion of Greek culture among non-Greek people, Lycians notably, who had to welcome it, in a passive way. 23It is important to note that Pierre Demargne's approach was "ambivalent", due to the difficulty of defining Lycian art in the complicated context of an Anatolian background, which was impacted by both Greek and Oriental art (revived by Achaemenid royal art).

USEFUL CONCEPTS AND NOTIONS:

A reassessment

New concepts and notions have to be explored, because they are useful: firstly, the concept of "cultural transfer", as initiated in France for example, in the field of Contemporary History [START_REF] Espagne | Les transferts culturels franco-allemands[END_REF]). This concept has been used in the field of Ancient History, and more precisely in Greek History (Couvenhes/Legras 2006; Dan/Queyrel 2014). Its "neutrality" can prove useful in the study of intercultural contacts, because it includes the ideas of interaction and reciprocity, human mobility, circulation of ideas and artefacts, with a focus on process (its media and stakes), selection phenomena, and "semantic change". Secondly, concepts or theories about ethnicity and ethnic identity, such as first developed by anthropologists and ethnologists like Jean-Loup Amselle and Fredrick Barth [START_REF] Amselle | Logiques métisses[END_REF][START_REF] Barth | Introduction[END_REF]), may also be useful. We can retain three main theoretical concepts: contact between group members generates group consciousness; within a specific socio-historical context, cultural exchange allows human groups to define constantly evolving ethnic boundaries (Poutignat/Streiff-Fenart 1995: 134-188); ethnic identity goes beyond cultural identity, as it implies "identity stakes".

Whilst researching the notions of ethnicity or ethnic identity within Greek antiquity, historians, archaeologists, and art historians have found a number of further developments. They pointed out that cultural features were relevant criteria in the process of defining ethnic identity. Further, they showed that ethnic messages were not only contained in written sources, but also in material culture, artefacts and styles (e.g. in sculpture), which could thus also be used as distinctive markers by and among human groups (see e.g. Müller/Prost 2002; Croissant 2007; Müller/Veïsse 2014). 24In Lycian studies, these concepts can help to explain some results of cultural interaction, some aspects of the creative process, and choices made in specific historical contexts.

ICONOGRAPHY AND ICONOLOGY

For a long time, Lycian art has predominantly been explored through stylistic studies or in the context of specific archaeological sites (e.g. Xanthos and Limyra) or specific monuments (notably the Nereid Monument, the Heroon at Limyra, the Heroon at Trysa). A broader approach to Lycian art, encompassing all Lycian sites and monuments, and using Art history within Anatolian studies iconography and iconology, constitutes an important development in Lycian studies.

The fields of iconography and iconology were significantly developed by Erwin Panofsky, e.g. in his book on the Renaissance [START_REF] Panofsky | Essais d'iconologie. Les thèmes humanistes dans l'art de la Renaissance[END_REF], as well as by François Lissarrague in his works on ancient Greek images. In particular, we would point to the definitions and methodological explanations given by both scholars (Panofsky 1967: 13-31;Lissarrague 1990: 1-12). Lissarrague's useful and clear definitions may be retained: from a general point of view, iconography is the study of figurative representations; more precisely, iconography leads to the recognition and decipherment of images, while iconology attempts to highlight the links between images and human behaviours, or human beliefs, within the frame of a specific society. 25 François Lissarrague is one of French scholars from the "Centre Louis Gernet -centre de recherches comparées sur les sociétés anciennes" in Paris. 26 These scholars led research on ancient Greece, particularly Greek images, using ideas inspired by Social and Cultural Anthropology, Semiology and Linguistics, as well as, from a methodological point of view, by Structuralism. According to this perspective, images are considered as a kind of language. This has been expressed and explained very well by Jean-Pierre Vernant in the preface of the book entitled "La cité des images" [START_REF] Vernant | Préface. In: La cité des images[END_REF]. This approach offers an interesting guideline for organizing the analysis of Lycian images and understanding their complex creative process. In contrast to the Greek context, the Lycian one is more complicated, as there is no local literary tradition to assist in interpreting figurative representations within the local culture.

APPLICATION IN THE FIELD OF LYCIAN STUDIES

From a Lycian studies perspective, the aim is to "decipher", i.e. to decode, to understand Lycian images in a Lycian context. From a methodological point of view, important points are: the identification of iconographic themes; the analysis of iconographic patterns, styles (figurative conventions) and compositions; the research into series, variable and stable components; and the study of the iconographic programme (association and juxtaposition of patterns and themes) and its insertion in the architecture. A comparative approach of art within the Lycian corpus, and beyond, with other Anatolian, East Mediterranean, Greek, Persian and Oriental art, is another important stage.

Employing this method, the main conclusions are as follows: Lycian images were created by mixing a style of sculpture which might imitate a Greek style with iconographic patterns borrowed from Greek and Persian art, as well as iconographic patterns which recalled Anatolian and East Mediterranean traditions, and others that seem to have been "purely" Lycian. The images thus created were therefore typically Lycian and had a Lycian meaning. Lycians selected the images or icons available to them. This creative process applies to both style and iconography, and also includes the notion of "fluidity", as new images were constantly being selected and the way in which the images were manipulated also changed. Such a method of studying Lycian images allows us to appreciate the traditional Anatolian cultural background in Lycia during the 6 th , 5 th and 4 th centuries BC, and to understand the interaction of different scales (local, micro-regional, regional, extra-regional) which had an impact on the creative process in Lycia (see Colas-Rannou 2020). I will discuss in detail some aspects of this "fluidity" (with synchronic and diachronic approaches), using the following four significant Lycian examples. 27 Firstly, let us compare two examples of a mixed style and iconography, one dated to the 5 th century and another dated to the 4 th century BC: reliefs from what is called "Building G" of the "Lycian Acropolis" at Xanthos (c. 470-460 BC) and reliefs from the Heroon at Trysa (c. 380-370 BC for Childs 1976: 315-316; see also Marksteiner 2002: 187;earlier, c. 410-400 BC for Landskron 2015: 347-349). Different juxtapositions of patterns borrowed from Greek and Persian art can be noticed. Attributed to the same "Building G" are two slabs depicting satyrs and belonging to what is known as the "satyrs and wild beasts frieze", and other slabs which depict a procession or parade of riders and charioteers course of the terrace or platform on which the building was situated, while the "parade" frieze (British Museum 311-312-313, Antalya Museum 3532) is attributed to the external walls of the chamber (Metzger 1963: 49-61, Pl. 33.1, 37.1, 38, 39.1;[START_REF] Coupel | Reliefs inédits de l'acropole de Xanthos[END_REF]Metzger 1974;Bruns-Özgan 1987: cat. M 4;Draycott 2015: 129-133). These satyrs from Xanthos (Fig. 4) have the same appearance as Greek satyrs. They are naked, with the same main characteristics (snub nose, ears and tail of a horse, beard), but are not shown doing exactly the same that Greek satyrs generally do in Greek imagery. The association/composition with wild beasts is original, too. This depiction of a "hunting satyr" holding a tree branch is a unique occurrence in the Lycian corpus. Within the "parade" frieze, the image of a male figure (groom) walking behind a horse, with his forearm resting on the horse's back (B 312; Fig. 5) recalls a motif which adorned the Apadana at Persepolis. The reliefs of this frieze depict horses with the knotted tails and forelocks of Persian horses [START_REF] Bernard | Remarques sur le décor sculpté d'un édifice de Xanthos[END_REF]. At the beginning of the 4 th century (or a little earlier), reliefs belonging to the Heroon at Trysa in Central Lycia convey a different combination. The monument was a wall encircling an area, the Heroon temenos, which contained a house-tomb. The walls were [START_REF] Landskron | Das Heroon von Trysa. Ein Denkmal in Lykien zwischen Ost und West. Untersuchungen zu Bildschmuck[END_REF]. Here, I focus on the decoration of the gate and on the original juxtaposition (Landskron 2015: 57-70, Pl. 23-26). On each side of this gate, we notice a mixture of iconographic elements borrowed from Greek and Persian repertoire, as well as Lycian motifs. These patterns, with their different origins, are juxtaposed. On the internal side (Fig. 6), on each side post of the door, the Greek pattern of the Kalathiskos dancers is present, while on the lintel there are eight figures of the Oriental/East Mediterranean god Bes, dancing or playing musical instruments. The main features of the god Bes are recognizable: with the frontal position of the dancing figures, and their seemingly grotesque attitudes and ugly faces. On the other side of the lintel, the exterior side of the gate, three types of patterns are juxtaposed (Fig. 7). Four forequarters of winged bulls are spread horizontally across the lintel. These forequarters of winged bulls recall Persian capitals with double forequarters of bulls (without wings), which can be found on Persian royal rock-cut tombs (Naqsh-i Rustam and Persepolis) and in Persian palaces (Susa and Persepolis;Schmidt 1953: 80, 100, Fig. 44 C-E, 104, 48 B-E, Pl. 54 A;[START_REF] Schmidt | Persepolis. III. The royal tombs and other monuments[END_REF]. A gorgoneion is carved in the middle of the lintel, between the two central winged bulls. The gorgoneion, or Gorgon's head, was a Greek apotropaic motif, which may have preserved its original meaning here, as it was placed just above the gate and in the middle of the lintel. It is interesting to point out that the gorgoneion was not used anymore in Greek funerary art after the Archaic period [START_REF] Floren | Studien zur Typologie des Gorgoneion. Ghirshman, Roman 1963: Perse. Proto-Iraniens[END_REF]Woysch-Méautis 1982: 81-83, 134;LIMC 1988, s.v. Gorgo, Gorgones). A Lycian motif, frequently found on Lycian tombs from the 4 th century BC (sarcophagi or rock-tombs), is carved under the winged animals (Rodenwaldt 1940: 45-46). It shows a man and a woman seated, facing each other, accompanied by relatives and pets. The scene is presented twice. The first couple is seated on the left side, each person under one winged bull: on the left, the man is in right profile, and on the right, the woman is in left profile. The second couple is seated on the right side of the lintel in a symmetrical position. This pattern evokes the image of a dynastic couple, found notably on the East pediment of the Nereid Monument from Xanthos (Childs/Demargne 1989: 216-220, 256, Pl. 140, Pl. LXVII). Thus, nearly a century apart, two iconographic combinations ("Building G" at Xanthos / Heroon at Trysa) can be identified, which mix Greek and Persian elements, albeit not the same ones, and in different ways. 28 Next, I would like to focus on a special phenomenon: a traditional theme depicted with a new iconographic pattern and a new style. The lid of a Lycian sarcophagus from Limyra (called the "Centaurs's Sarcophagus") in Eastern Lycia, dated to around 350-330 BC, bears a relief with two male figures wearing oriental clothes, fighting an eagle-headed griffin (Bruns-Özgan 1987: cat. S 12, Pl. 36.1;Borchhardt/ Pekridou-Gorecki 2012: cat. 3, Pl. 16.3). On the right, the griffin is using its beak to attack a male figure who has fallen to the ground; its paws grasp the human body, its raised wings are outspread. The male figure is leaning on his left arm, with his left bent knee, his head raised towards the griffin; he wears a tunic which reaches above his knee, girt at the waist (over trousers?), and a conic cap or headdress. On the left, behind the griffin, a prancing horse fights with the griffin; the rider, who wears the same tunic as the other protagonist, is holding up a spear in 165 Art history within Anatolian studies his right hand to throw at the griffin. The details are significant, notably: the Oriental clothing of both male figures, the crest behind the eagle's head, the attitude of the rider and horse with raised forelegs, the griffin above the male figure on the ground. The same details and composition (with these three elements: rider and horse/griffin/fallen male figure) can be found on Attic red-figure vases belonging to the Kertch style dated to the 4 th century BC, e.g. on the neck of the Attic krater kept in the Louvre Museum inv. G 530 (mid-4 th century BC; Boardman 2001: Fig. 261;LIMC 1997: suppl. s.v. Arimaspoi, Pl. 343, n° 39). 29 On Greek vases, the scene recalls the Arimaspoi of Greek mythology. In my opinion, in a Lycian context it does not have the same meaning, and a Greek literary or mythological tradition is not required to elucidate the Lycian interpretation of the scene. The depiction is used by the Lycian sarcophagus owner to promote himself, in a kind of heroization, with assimilation into a victorious hero beating a hybrid creature. The Greek iconographic pattern allows the renewal of an older Anatolian and East Mediterranean theme of hero or royal hero combatting a griffin. The theme is known from East Mediterranean, Mesopotamian, and Neo-Hittite images. For the motif showing a standing hero holding a sword and combatting an eagle-headed griffin, see, for example: a silver bowl from Kourion in Cyprus dated to the end of the 8 th century or the beginning of the 7 th century BC (Markoe 1985: 177-178, Cy8, 256);30 a Neo-Hittite orthostat from Tell Halaf (9 th -8 th century BC ;Orthmann 1971: 331, Tell Halaf A3/55, Pl. 9f); and ivory plaques from Nimrud (8 th century BC; Mallowan 1966: 537, Fig. 456, ND 10696, 587, Fig. 559). In the Lycian and Anatolian context, it was probably meant to rival the image of the royal hero combatting an eagle-or lion-headed griffin carved on reliefs from Persepolis (Doorways of the Hundred-Columned Hall, 5 th century BC; Ghirshmann 1963: Fig. 250251). This kind of theme is present earlier in Lycia, with the male figure combatting a lion on the "Lion Pillar" from Xanthos (dated to the third quarter of the 6 th century BC, British Museum B 286). Thus, it is possible to say that Greek art provided a new iconographic pattern that allowed the revival of a traditional Anatolian or East Mediterranean theme and imagery during the 4 th century BC. Other examples could be presented, e.g. the motif of the apobate related to that of the king in a chariot with charioteer (Demargne 1974b: 75-76).

Finally, based on a close study of the fourth Lycian example, I would like to present another kind of combination: a traditional pattern depicted with a new carving style. The case study is a slab from Xanthos, the Gable end of "Building F" from the Lycian Acropolis at Xanthos, dated to around 470 BC (British Museum B 289; 31 see notably, Metzger 1963: 71-75, Fig. 25, Pl. 48.2;Bruns-Özgan 1987: cat. M 6;Rudolph 2003: 59-61;Draycott 2015: 128-129). In the centre (Fig. 8), a bird-woman stands in a frontal position, on the abacus of a capital surmounting an Ionic column (the volutes are now broken off). The human head of the bird-woman is missing; one would presume that two portions of hair fell onto the shoulders. A short crinkled garment is seen, worn with a belt around the waist (it has the appearance of a chiton, with a lot of folds and hanging sleeves). There are outstretched wings, a tail and bird's legs, with human arms extended in front of the wings. A male figure (in profile) is seated on each side of the column. The one on the left is beardless, the one on the right has a beard with horizontal ridges. They wear garments very similar to a chiton with sleeves, and a wrapped cloak. They hold a staff in one hand with the other hand extended. On the left, the male figure is seated on a kind of low throne with a backrest. This is a unique occurrence of this motif in the Lycian corpus. The bird-woman looks like a Greek siren; the carving style of the male figures recalls the Ionian style (garment with folds, attitude). 32 However, the closest iconographic parallel can be found in a group of Cilician seals, which belongs to the "Lyre player group" dated to the second half of the 8 th century BC [START_REF] Porada | A Lyre Player from Tarsus and his relations[END_REF][START_REF] Boardman | Seals from Ischia and the Lyre-player group[END_REF][START_REF] Boardman | The Lyre player group of seals, an encore[END_REF][START_REF] Poncy | -C.) -Sceaux en verre et cachets anépigraphes d'époque achéménide -Scaraboïdes inscrits -Scarabées et sceaux égyptisants[END_REF] 33 . Five seals currently known are noteworthy, their motif showing the winged sun disc surmounting a sacred tree with crooked volutes, flanked by two seated or kneeling figures. The sacred tree resembles a pillar with volutes above. The gesture of the figures is of one hand raised and the other lowered, which may be a sign of adoration and worship (Porada 1956: 187-188 n. 10, 193, n. 22, Fig. 10-11, Pl. XVII.10-11;Boardman/Buchner 1966: n°83, n°90, n°141, n°160, Fig. 42, Fig. 58;[START_REF] Poncy | -C.) -Sceaux en verre et cachets anépigraphes d'époque achéménide -Scaraboïdes inscrits -Scarabées et sceaux égyptisants[END_REF]: n°15, Pl. I; Fig. 9). We find the same symmetrical composition as on the relief from Xanthos, with sim-32 The style is close to the style of the reliefs from the "Harpy Tomb" at Xanthos (c. (Porada 1956: 192) or from Al Mina (Boardman 1990: 10-11). ilar components. However, at Xanthos, the pattern is "dressed" with a style inspired from Greek art: the pillar with volutes above has become an Ionic column, the winged sun disc has become a bird-woman with outstretched wings wearing a chiton. The original pattern can be found in Mesopotamia (e.g. on seals or on Assyrian reliefs), on Hittite seals, on Neo-Hittite or Syro-Hittite reliefs: two human or hybrid figures, standing or kneeling, are flanking the sacred Tree of Life, surmounted by a winged sun disc (Buchanan 1966: n°630a, Pl. 41, n°990, n°991, Pl. 61;Parrot 1969: 14, Pl. 16;Uzunoğlu 1986: 77, Fig. 7-1, 7-2;Orthmann 1971: 448, Domuztepe 6, Sakçagözü A/1, Pl. 6.c, 49.a). The scene carved on the slab from Xanthos dated to the 5 th century revives a traditional motif well-documented in South Anatolia and in the Near East a couple of centuries earlier. At Xanthos, the pattern is renewed with the help of a carving style inspired by Greek sculpture. The representation of these two seated male figures (one older than the other) can be interpreted in a dynastic, Xanthian context. I would like to point out that this relief attributed to "Building F" belongs to the same period as "Building G" mentioned above -the second quarter of the 5 th century BC -and both buildings were located on the Lycian Acropolis at Xanthos. However, each one displays a different combination of the relief sculptures. This comparison supports the idea of "fluidity" provided by a synchronic study of Lycian images.

CONCLUSION: STUDYING LYCIAN IMAGES Beyond cultural as well as academic boundaries

Following an iconographic and iconological approach, for each scene showing a figurative representation, it is very important to study and analyse the iconographic theme, iconographic pattern, composition, style, and the Lycian way of associating them. Thus, different combinations appear: this is the "fluidity" mentioned above. This method enables us to highlight Lycian choices made in specific contexts. Diachronic comparison shows that borrowings and adaptations were evolving; the synchronic approach emphasizes the diversity of the elements that sustained the creative process. The traditional attitude to studying Lycian art, focusing only on Greek and Persian artistic impact, is inadequate. We can no longer simply say that we find in Lycia "un art grec au service d'une idéologie orientale" (Demargne 1981a). We cannot Art history within Anatolian studies simply see Lycian art as an art "between Occident and Orient". Images also expressed the Anatolian cultural background and were indebted to old contacts within the Eastern Mediterranean. Illuminating and understanding this background can be difficult because of the deliberate and constantly evolving mixture of patterns and/or styles circulating in the Mediterranean and the Achaemenid Empire. To conclude, the proper study of Lycian images requires us to question ancient cultural boundaries, while constantly pushing back the bounds of academic disciplines.

"

  On trouve dans la Haute-Égypte un grand nombre de grottes, qui sans doute étaient consacrées à cet usage; mais aucun de ces monuments n'a autant d'analogie avec ceux de Telmissus, que les tombeaux de Persépolis." 2 "…mais quelle analogie plus frappante encore entre les tombeaux de Persépolis et ceux de Telmissus ! Ces derniers sont de même creusés dans une montagne de roche vive, et à une trop grande hauteur pour qu'on y puisse parvenir sans beaucoup de peine; ils sont en grand nombre, […]: quelques-uns ne sont que de simples trous, d'autres sont plus décorés: mais deux de ces tombeaux, vrais monuments, fixent bientôt les regards. Ils offrent la façade d'un édifice, dont le style prouve que c'est un ouvrage des Grecs, travaillant à l'imitation des Perses ou des Égyptiens." 3 (Fig. 1).

Fabienne

  Fig. 1. Telmessos. At the top, one rock-cut tomb with a front inspired by Greek architecture, below, rock-cut tombs of Lycian traditional type (photo © F. Colas-Rannou).

  5 On a visit to Lycia a couple of years later, Charles Texier arrived at the site of Phellos and expressed his astonishment: "Nous arrivons à la nécropole. Nous sommes dans l'admiration en entrant dans une enceinte carrée toute taillée dans le roc, au milieu de laquelle s'élèvent deux édifices monolithes taillés dans la masse même du rocher. Ce ne sont plus des colonnes et des frontons; c'est un art tout à fait en dehors de ce que nous connaissons de l'antiquité, car il est aussi éloigné de l'égyptien que du grec. Un de ces grands tombeaux a trois portes; son entablement ressemble à des charpentes posées de front, et sur les faces latérales, ce sont d'énormes solives recourbées représentant des becs d'ancre; tout cela taillé dans le rocher." 6

" 8 7

 8 Texier 1849: 189. Here, Charles Texier quoted the opinion expressed by Edward Daniel Clarke who travelled at the beginning of the 19 th century AD. 8 Fellows 1841: 165.

Fig. 3 .

 3 Fig. 3. Drawings of a traditional Lycian rock-cut tomb at Phellos (from Texier 1849: Pl. 203).

"

  Phénomène non pas unique, certes, que celui du contact entre civilisations, de l'acculturation comme on dit aujourd'hui, au bénéfice de celles qui disposent d'une supériorité matérielle et spirituelle : l'Antiquité, […], a connu le phénomène antérieur et inverse de l'orientalisation, le phénomène postérieur et complémentaire de la romanisation." 12

Fig. 4 .

 4 Fig. 4. Satyr from the "satyrs and wild beasts frieze", "Building G", Xanthos (British Museum B 292; photo © F. Colas-Rannou, taken courtesy of the Trustees of the British Museum).

  . The "satyrs and wild beasts frieze" (British Museum B 292-298, Xanthos/Antalya Museum 3533-3534-3341) is attributed to the upper 27 The study of these examples is developed in Colas-Rannou 2020; the last two examples have already been presented in Colas-Rannou 2013.

Fig. 5 .

 5 Fig. 5. Slab from the "parade frieze", "Building G", Xanthos (British Museum B 312; photo © F. Colas-Rannou, taken courtesy of the Trustees of the British Museum).

Fig. 6 .

 6 Fig. 6. Gate of the Heroon at Trysa (in situ), interior side (from Oberleitner 1994: Fig. 17; photography: W. Burger, 1881).

  ; photography: W. Burger, 1881). adorned with reliefs on their upper part and internal side. Only the south wall was adorned with reliefs inside and out, with reliefs on both the internal and external side of the gate. The friezes of the Heroon walls develop an ambitious iconographic programme, with numerous patterns inspired by Greek art (most recently, with previous literature:

Fig. 7 .

 7 Fig. 7. Gate of the Heroon at Trysa (in situ), exterior (from Oberleitner 1994: Fig. 9; photography: F. von Luschan, 1882).

  31 Limestone. L. 1.05 m; H. 0.83 m.

Fig. 8 .

 8 Fig. 8. "Gable slab" from "Building F", Xanthos (British Museum B 289; from Metzger 1963: Pl. 48.2).

Fig. 9 .

 9 Fig. 9. Seal (impression) from the "Lyre player group" (Toronto, Royal Ontario Museum, 926.7.2; from Porada 1956: Pl. XVII.11. Dimensions of the seal: 22.5 × 18.5 × 11 mm).

Choiseul-Gouffier 1842: 196.

Demargne 1974a: 584. In a paper dated 1979 (published in 1981), he used the word "acculturation", however, the notion of periphery still remained(Demargne 1981a: 85).

Fabienne Colas-Rannou

P. Demargne borrowed the expression "archaïsme provincial"/"provincial archaism" from E. Pfuhl(Pfuhl 1926: 154: "provinzieller Archaismus"; see Demargne 1981b: 586 n. 5; Childs/Demargne 1989: 363 n. 92).

P. Demargne still expressed these ideas in an interview in 1992(Demargne et al. 1992: 320-321).

For a Lycian interpretation, see[START_REF] Robinson | The Nereid Monument at Xanthos or the Eliyâna Monument at Arñna?[END_REF]

Titles are significant, e.g.[START_REF] Akurgal | Griechische Reliefs des VI. Jahrhunderts aus Lykien[END_REF], as the adjective "Greek" is employed for reliefs from Lycia dated to the 6 th century BC. In more recent publications, monuments from Xanthos are presented as monuments from Eastern Greece, because of the carving style, thus denying the existence of a Lycian cultural background in the context of ancient Anatolia (for example, the so-called "Harpy Tomb" of Xanthosin Hofstetter 1990: cat. O 61, 243-248).

For a general reflection about the concepts of Hellenization and acculturation, see (in the bibliography in French for example)[START_REF] Will | Influence": note sur un pseudo-concept[END_REF][START_REF] Wachtel | L'acculturation[END_REF][START_REF] Bats | L'acculturation et autres modèles de contacts en archéologie protohistorique européenne[END_REF][START_REF] Roure | Stéréotypes modernes et stéréotypes antiques: la pesanteur du concept d'Hellénisation en Gaule méditerranéenne[END_REF]

In his second book published in 2002, J. Hall takes into consideration cultural facts, see[START_REF] Hall | Hellenicity. Between ethnicity and culture[END_REF]

"[…] l'iconographie s'attache à la reconnaissance, au déchiffrement des images […] l'iconologie cherche à mettre en évidence le rapport qui unit ces images et les formes de pensée d'une société donnée."(Lissarrague 1990: 1).

Currently included in the research centre UMR 8210 -Anhima, Anthropologie et Histoire des Mondes Antiques (Paris).

th century BC, e.g. the Nereid Monument at Xanthos; the Heroon at Limyra.

For a previous comparison of these items, seeColas-Rannou 2013: 54-57, Figs. 5-6.

New York, Metropolitan Museum of Art 74.51.4554.