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Resume Les nouvelles techniques d’irradiation permettent de mieux conformer la dose aux contours de la tumeur. Le corollaire est une exigence accrue de precision. Des etudes recentes d’intercomparaison de plans de traitement ont souligne la necessite d’une harmonisation des pratiques de contourage. Une approche plus consensuelle repose sur l’utilisation de modalites d’imagerie adaptees, des recommandations de groupes experts et des atlas de segmentation automatiques, une harmonisation des decisions dosimetriques passant par l’utilisation d’abaques exhaustifs pour les organes a risque, et d’indices pour le choix des plans de traitement optimaux. A un echelon de plus, des programmes d’assurance qualite et de partage des donnees passant par l’utilisation de transferts de donnees DICOM RT (reseaux d’images) sont mis en place. La combinaison de plusieurs techniques d’irradiation differentes (par exemple, radiotherapie conformationnelle par modulation d’intensite [RCMI] + boost en CyberKnife ® et reirradiations), permettant de mieux irradier les tumeurs, necessite une documentation des doses cumulees grâce a des logiciels de sommation de dose. Une reelle prise de conscience s’est faite ces dernieres annees dans le sens de l’amelioration de la qualite des traitements, du partage des donnees et de l’harmonisation des pratiques.

Purpose: To propose an automatic atlas-based segmentation framework of the dental structures, called Dentalmaps, and to assess its accuracy and relevance to guide dental care in the context of intensity-modulated radiotherapy. Methods and Materials: A multi-atlas-based segmentation, less sensitive to artifacts than previously published head-and-neck segmentation methods, was used. The manual segmentations of a 21-patient database were first deformed onto the query using nonlinear registrations with the training images and then fused to estimate the consensus segmentation of the query. Results: The framework was evaluated with a leave-one-out protocol. The maximum doses estimated using manual contours were considered as ground truth and compared with the maximum doses estimated using automatic contours. The dose estimation error was within 2-Gy accuracy in 75% of cases (with a median of 0.9 Gy), whereas it was within 2-Gy accuracy in 30% of cases only with the visual estimation method without any contour, which is the routine practice procedure. Conclusions: Dose estimates using this framework were more accurate than visual estimates without dental contour. Dentalmaps represents a useful documentation and communication tool between radiation oncologists and dentists in routine practice. Prospective multicenter assessment is underway on patients extrinsic to the database. © 2012 Elsevier Inc.

Resume Objectif de l’etude Le risque associe aux soins dentaires est un probleme de pratique quotidienne pour les radiotherapeutes et les chirurgiens dentistes. En cas d’extraction dentaire postirradiation, ce risque est correle avec la dose d’irradiation recue localement. La resolution du probleme, c’est-a-dire la documentation de la dose est fastidieuse (deux heures de delineation manuelle) et imprecise en l’absence d’outil de segmentation automatique dentaire. Materiel et methodes Un outil de segmentation automatique dentaire base sur une methode multi-atlas, Dentalmaps, a ete mis au point a partir d’une base de donnees de patients traites pour cancer de la tete et du cou. Resultats Cet outil informatique permet, simplement et rapidement, une estimation a 2 Gy pres, ce qui est tout a fait pertinent pour l’usage clinique a partir des consoles de planification de radiotherapie. Conclusion cet outil cree une interface entre chirurgiens dentistes et radiotherapeutes d’autant plus necessaire que les nouvelles techniques d’irradiation complexifient l’estimation visuelle de la dose (inhomogeneites, gradients abruptes). Il devrait permettre d’ameliorer la comprehension des complications dentaires et de l’osteoradionecrose.

The purpose of this study is to assess compliance with fluoride gel custom trays in irradiated head and neck cancer patients.One hundred fifty-five consecutive patients on remission following radiation therapy of head and neck cancers were assessed retrospectively for dental care practices prior to radiation and prospectively for long-term compliance with custom trays from November 2009 to January 2010. A five-item questionnaire was filled in by patients in the waiting room, and a 15-item questionnaire by the physician in charge during the corresponding follow-up visit.Ten percent of patients were edentulous at inclusion. Among dentate patients, 17% had total extractions. With a mean follow-up of 24 months, 19% of patients used custom trays for over a year. Primary stage, age, and tobacco consumption were correlated with compliance with custom trays. More than half of dentate patients developed carious lesions, and 8% had stage 1-3 osteoradionecrosis of the whole population of edentulous and dentate patients.Compliance with custom trays was poor in this series. Specific postirradiation dental care follow-up visits and education have demonstrated their utility in the era of 2D irradiation. We currently advocate an 18-month compliance with custom trays in IMRT patients on the basis of the Parsport trial, after which we assess the quality of salivary recovery before recommending prolonged use or interruption. Data with innovative irradiation techniques are however required.

Highly conformal irradiation techniques are associated with steep gradient doses. Accuracy and reproducibility of delineation are required to avoid geometric misses and to properly report dose-volume effects on organs at risk. Guidelines of the International Commission on Radiation Units have largely contributed to high quality treatments. The ICRU endeavors to collect and evaluate the latest data and information pertinent to the problems of radiation measurement and dosimetry. There remains a need for delineation guidelines and automatic segmentation tools in routine practice. Among these tools, atlas-based segmentation has been shown to provide promising results. The methodology used for head and neck cancer patients is illustrated.

International audience; With new irradiation techniques, the dose can be better matched to the contours of the tumour. The corollary is that greater precision is required. Recent intercomparison studies of treatment plans have emphasized the need to harmonise contouring practices. More of a consensus approach is based on using adaptive imaging modalities, expert group recommendations and automatic segmentation atlases, on harmonisation of dosimetric decisions through employing exhaustive nomograms for organs at risk, and on indexes for choosing optimal treatment plans. On another level, quality assurance and data pooling programmes have been set up, making use of DICOM-RT data transfer (image networks). The combination of several irradiation techniques (for example, intensity-modulated conformal radiation therapy plus CyberKnife((R)) boost and re-irradiation), making it possible to irradiate tumours better, requires the cumulative doses to be recorded by dose summation software. Real awareness has been achieved in recent years as regards improving the quality of treatment, pooling data and harmonising practices.

International audience; Radiotherapy planning requires accurate delineations of the critical structures. To avoid manual contouring, atlas-based segmentation can be used to get automatic delineations. However, the results strongly depend on the chosen atlas, especially for the head and neck region where the anatomical variability is high. To address this problem, atlases adapted to the patient's anatomy may allow for a better registration, and already showed an improvement in segmentation accuracy. However, building such atlases requires the definition of a criterion to select among a database the images that are the most similar to the patient. Moreover, the inter-expert variability of manual contouring may be high, and therefore bias the segmentation if selecting only one image for each region. To tackle these issues, we present an original method to design a piecewise most similar atlas. Given a query image, we propose an efficient criterion to select for each anatomical region the K most similar images among a database by considering local volume variations possibly induced by the tumor. Then, we present a new approach to combine the K images selected for each region into a piecewise most similar template. Our results obtained with 105 CT images of the head and neck show that our method reduces the over-segmentation seen with an average atlas while being robust to inter-expert manual segmentation variability.

In atlas-based segmentation, using one single atlas for segmenting all patients introduces a bias. Multi-atlas techniques overcome this drawback by selecting and fusing the most appropriate atlases among a database for a given patient. Globally assessing different multi-atlas strategies provides a biased evaluation of the atlas selection methods. To address this problem, we propose to evaluate atlas selection methods independently from the number of atlases selected and from the atlas fusion step. Briefly, we first cluster the selection methods on the basis of rank correlation and then assess each sub-group of methods with respect to a sub-group of reference selection methods. We apply our method to 105 images of the head and neck region.