Anatomy-Aware Self-supervised Fetal MRI Synthesis from Unpaired Ultrasound Images

Fetal brain magnetic resonance imaging (MRI) offers exquisite images of the developing brain but is not suitable for anomaly screening. For this ultrasound (US) is employed. While expert sonographers are adept at reading US images, MR images are much easier for non-experts to interpret. Hence in this paper we seek to produce images with MRI-like appearance directly from clinical US images. Our own clinical motivation is to seek a way to communicate US findings to patients or clinical professionals unfamiliar with US, but in medical image analysis such a capability is potentially useful, for instance, for US-MRI registration or fusion. Our model is self-supervised and end-to-end trainable. Specifically, based on an assumption that the US and MRI data share a similar anatomical latent space, we first utilise an extractor to determine shared latent features, which are then used for data synthesis. Since paired data was unavailable for our study (and rare in practice), we propose to enforce the distributions to be similar instead of employing pixel-wise constraints, by adversarial learning in both the image domain and latent space. Furthermore, we propose an adversarial structural constraint to regularise the anatomical structures between the two modalities during the synthesis. A cross-modal attention scheme is proposed to leverage non-local spatial correlations. The feasibility of the approach to produce realistic looking MR images is demonstrated quantitatively and with a qualitative evaluation compared to real fetal MR images.Comment: MICCAI-MLMI 201

Influence of the nature of cell wall carbohydrates on the anatomico-functional development of the digestive tract in the rabbit

International audienc

Personalized pretreatment QA for intracranial stereotactic treatments using gel dosimetry and 3D printing of phantom: A feasibility study

Introduction.In stereotactic radiotherapy, pretreatment patient-specific quality controls (PSQA) are performed on generic phantoms to check the agreement between the dose calculated by the treatment planning system (TPS) and the measured dose by a point or 2D detector. For those controls, gel dosimetry seems a promising technique as it presents several advantages compared with conventional dosimeters such as 3D absolute dose determination with high spatial resolution [1]. Thus, we investigated the feasibility of gel dosimetry in combination with a patient-based 3D printed phantom for personalized PSQA.Methods. CT images of a patient treated by intracranial stereotactic radiotherapy were processed to generate a STL file. Phantom was 3D printed at scale 1:1 using an Ultimaker 3 extended 3D printer. The phantom consisted in a 1.2mm thick wall made of PET and the nose was printed separately to be used as a plug. This phantom filled with water includes a cylindrical insert at the target location to place a radiochromic gel jar. It was scanned with the patient’s stereotactic mask and the patient plan was recalculated using the phantom CT on the iPlan TPS (BrainLab). The radiochromic gels were manufactured and calibrated according to a protocol developed at IRSN [2]. One treatment fraction was delivered on the phantom with the gel in place using a Novalis TrueBeam STX accelerator. Gels were optically read following the protocol and data analysis was performed using MatLab.Results. A good agreement is found between the dose distribution measured with the gel and calculated with the TPS. For a coronal slice at the center of the gel dosimeter, the local 2D 3 mm-3% gamma-index was evaluated within the central 85% of the cylinder diameter. The gamma passing rate reaches 86.5%. In the same region, the local 3D 3 mm-3% gamma-index passing rate is 95.2%. Within the central 85% of the cylinder volume, 87.2% and 96.2% of points pass the local 2 mm-2% and the global 1 mm-2% gamma-index 3D respectively.Conclusions. This study presents promising results for personalized PSQA for stereotactic radiotherapy and this work could be extended to end-to-end tests. Other cases are currently investigated in order to benchmark the methods and the reproducibility of the measurement protocol

Gestion des doses liées à l’imagerie de positionnement en radiothérapie

International audienceImage-guided radiotherapy (IGRT) has become a standard irradiation technique to improve the clinical outcome of patients in terms of toxicity and local control due to better targeting of radiation during the irradiation fraction. Positioning imaging systems, whether embedded or not, such as kV for 2 x 2D acquisitions and especially kVCBCT for 3D acquisitions are however irradiating in a large volume including the target volume but also healthy tissue, with a theoretical risk of increased toxicity and second cancer. It therefore appears very important both to optimize the absorbed dose due to IGRT practice but also to report it, especially in case of kVCBCT. The AAPM report published in 2018 (>) proposes a management of image guidance doses delivered during radiotherapy. This report is the basis of this focus article that aims at giving orders of magnitude and proposing a management of image guidance doses delivered during radiotherapy inclinical practice. The dose delivered per kVCBCT is about 0.5 to 2 cGy at isocenter according to treatment site. As long as the calculation algorithms are not available in the treatment planning systems, it seems appropriate to use at least the published dose orders of magnitude. This estimate should ultimately allow the clinician to decide on the therapeutic strategy in the event of accumulation of positioning imaging sessions. (c) 2020 Societe francaise de radiotherapie oncologique (SFRO)

Bonnes pratiques de radiothérapie guidée par l’image [Good practice of image-guided radiotherapy]

National audienceLa radiothérapie guidée par l’image vise à prendre en compte les variations anatomiques survenant en cours d’irradiation, par une visualisation directe ou indirecte du volume cible suivie d’une mesure corrective. Les déplacements de cette cible ou au minimum les erreurs de positionnement sont corrigés par un déplacement de la table de traitement, correspondant à la modalité corrective la plus simple et la plus validée de guidage par l’image dans une pratique standard. Les déformations du volume cible et des organes à risque sont cependant beaucoup plus fréquentes, et malheureusement beaucoup plus complexes à prendre en compte, impliquant de générer plusieurs planifications, avant ou pendant le traitement, correspondant aux stratégies de radiothérapie adaptative. Le volume cible prévisionnel doit être méticuleusement choisi en fonction de ces variations anatomiques. Une revue des modalités de radiothérapie guidée par l’image, standard ou en cours d’évaluation, est effectuée selon les différentes localisations tumorales. -- Image-guided radiotherapy (IGRT) aims to take into account the anatomical variations occurring during the course of radiotherapy, by direct or indirect visualization of the target volume followed by a corrective action. The movements of the target, or at least the set-up errors are corrected by moving the treatment table, corresponding to the simplest and most validated IGRT modality in a standard practice. The deformations of the target volume and organs at risk are however much more common, and unfortunately much more complicated to consider, requiring multiple planning before or during the treatment, corresponding to the adaptive radiotherapy strategies. The planning target volume must be carefully chosen according to these anatomic variations. This article reviews the modalities of IGRT, standard or under evaluation, according to the different tumour site