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International audience; Complete and homogeneous illumination of the target is necessary for the success of a photodynamic therapy (PDT) procedure. In most applications, light dosimetry is done using detectors placed at strategic locations of the target. In this study we propose a novel approach based on the combination of light distribution modeling with spatial localization of the light applicator for real time estimation and display of the applied dose on medical images. The feasibility approach is demonstrated for intrapleural PDT of malignant pleural mesothelioma.

While breast specialists debate on therapeutic de-escalation in breast cancer, the treatment of benign lesions is also discussed in relation to new percutaneous ablation techniques. The purpose of these innovations is to minimize potential morbidity. Laser Interstitial ThermoTherapy (LITT) is an option for the ablation of targeted nodules. This review evaluated the scientific publications investigating the LITT approach in malignant and benign breast disease. Three preclinical studies and eight clinical studies (2 studies including fibroadenomas and 6 studies including breast cancers) were reviewed. Although the feasibility and safety of LITT have been confirmed in a phase I trial, heterogeneous inclusion criteria and methods seem to be the main reason for LITT not being yet an extensively used treatment option. In conclusion, further development is necessary before this technique can be used in daily practice.

Computer-assisted medical interventions and treatment planning have known an increasing interest and research activity in different fields and applications. However, before the routine deployment of these procedures becomes a reality, in vivo and in silico validations must be undertaken. This paper describes a platform containing multimodality medical images and atlases useful for algorithms evaluation, comparison and validation. The platform contains des-identified data (images, contours and atlases) from the ProstateAtlas and ProstateWeb project: the first morphological and zonal atlas of the prostate, and from clinical data of lymphoma PET (PETWeb). Data are available at the URL: http://www.medataweb.U703.net .

Resume La tomographie par emission de positons (TEP) au 18 F-fluorodesoxyglucose (TEP 18 F-FDG) est une technique d’imagerie nucleaire dont l’interet en oncologie ne cesse de croitre. Dans le cadre d’une radiotherapie externe, l’optimisation du plan de traitement, l’evaluation de la reponse therapeutique, le suivi objectif sont autant d’etapes qui necessitent une quantification precise des volumes d’interet. Dans cet article, nous presentons une nouvelle methode de segmentation quasi-automatique, operateur independant et ne necessitant pas de calibration prealable du tomographe. Cette methode basee sur la theorie des possibilites permet, via l’utilisation de degres d’appartenance, de prendre en compte l’incertitude et l’inexactitude inherentes aux images. Les resultats obtenus sur des images issues d’un fantome (pourcentage d’erreur = 18,4 % (moyenne) ± 9,7 % (ecart-type)) ainsi que sur des donnees simulees (erreur de classification = 23,6 % (moyenne) ± 18,6 % (ecart-type) pour un SUV de 4,5) montrent l’efficacite et la robustesse de la methode.

Resume Objectif Mettre en place un cadre d’evaluation de methodes automatiques de segmentation des volumes tumoraux en TEP. Patient et methodes Les examens TEP de 18 patients presentant un lymphome non hodgkinien ont servi de base de donnees. Une lesion cible a ete designee par patient. Chaque lesion a ensuite ete contouree manuellement trois fois par un groupe de cinq experts. Quatre methodes automatiques (application d’un seuillage fixe egal a 42 % de la SUV maximale, methode MIP-based, methode proposee par Daisne et al., methode proposee par Nestle et al.) ont alors pu etre evaluees par comparaison avec l’ensemble des segmentations manuelles. Resultats Les contours realises par les experts ont permis de conclure a une variabilite intra-operateur moderee et a une reproductibilite interoperateurs assez faible. Par ailleurs, les tests statistiques realises sur divers criteres quantitatifs n’ont mis en evidence aucune difference significative entre la methode MIP-based, la methode de Daisne et al. et celle de Nestle et al. La methode de seuillage fixe a 42 % de la SUV maximale apparait moins performante. Conclusion Ce travail a permis de proposer un protocole d’evaluation et de comparaison de methodes de segmentation. La base de donnees generee pour cette etude pourra etre diffusee en ligne pour la communaute afin de simplifier l’evaluation de toute nouvelle methode de segmentation.

18F-fluorodeoxyglucose positron emission tomography (18FDG PET) has become an essential technique in oncology. Accurate segmentation and uptake quantification are crucial in order to enable objective follow-up, the optimization of radiotherapy planning, and therapeutic evaluation. We have designed and evaluated a new, nearly automatic and operator-independent segmentation approach. This incorporated possibility theory, in order to take into account the uncertainty and inaccuracy inherent in the image. The approach remained independent of PET facilities since it did not require any preliminary calibration. Good results were obtained from phantom images [percent error =18.38% (mean) ± 9.72% (standard deviation)]. Results on simulated and anatomopathological data sets were quantified using different similarity measures and showed the method was efficient (simulated images: Dice index =82.18% ± 13.53% for SUV =2.5 ). The approach could, therefore, be an efficient and robust tool for uptake volume segmentation, and lead to new indicators for measuring volume of interest activity.

Resume Cette etude bibliographique traite des methodes de segmentation utilisees en tomographie par emission de positons pour la determination des volumes tumoraux. Nous proposons ici un etat de l’art sur les techniques se basant sur un seuillage, qu’il soit fixe ou adaptatif. Les methodes trouvees dans la litterature sont analysees du point de vue de leur methodologie, de leurs avantages et inconvenients. Enfin, nous proposons une synthese comparative sous forme de tableaux.

Accurate tumor segmentation in [18F]-fluorodeoxyglucose positron emission tomography is crucial for tumor response assessment and target volume definition in radiation therapy. Evaluation of segmentation methods from clinical data without ground truth is usually based on physicians' manual delineations. In this context, the simultaneous truth and performance level estimation (STAPLE) algorithm could be useful to manage the multi-observers variability. In this paper, we evaluated how this algorithm could accurately estimate the ground truth in PET imaging. Complete evaluation study using different criteria was performed on simulated data. The STAPLE algorithm was applied to manual and automatic segmentation results. A specific configuration of the implementation provided by the Computational Radiology Laboratory was used. Consensus obtained by the STAPLE algorithm from manual delineations appeared to be more accurate than manual delineations themselves (80% of overlap). An improvement of the accuracy was also observed when applying the STAPLE algorithm to automatic segmentations results. The STAPLE algorithm, with the configuration used in this paper, is more appropriate than manual delineations alone or automatic segmentations results alone to estimate the ground truth in PET imaging. Therefore, it might be preferred to assess the accuracy of tumor segmentation methods in PET imaging.

The aim of this study was to evaluate the impact of consensus algorithms on segmentation results when applied to clinical PET images. In particular, whether the use of the majority vote or STAPLE algorithm could improve the accuracy and reproducibility of the segmentation provided by the combination of three semiautomatic segmentation algorithms was investigated. Three published segmentation methods (contrast-oriented, possibility theory and adaptive thresholding) and two consensus algorithms (majority vote and STAPLE) were implemented in a single software platform (Artiview®). Four clinical datasets including different locations (thorax, breast, abdomen) or pathologies (primary NSCLC tumours, metastasis, lymphoma) were used to evaluate accuracy and reproducibility of the consensus approach in comparison with pathology as the ground truth or CT as a ground truth surrogate. Variability in the performance of the individual segmentation algorithms for lesions of different tumour entities reflected the variability in PET images in terms of resolution, contrast and noise. Independent of location and pathology of the lesion, however, the consensus method resulted in improved accuracy in volume segmentation compared with the worst-performing individual method in the majority of cases and was close to the best-performing method in many cases. In addition, the implementation revealed high reproducibility in the segmentation results with small changes in the respective starting conditions. There were no significant differences in the results with the STAPLE algorithm and the majority vote algorithm. This study showed that combining different PET segmentation methods by the use of a consensus algorithm offers robustness against the variable performance of individual segmentation methods and this approach would therefore be useful in radiation oncology. It might also be relevant for other scenarios such as the merging of expert recommendations in clinical routine and trials or the multiobserver generation of contours for standardization of automatic contouring.

Introduction [18F]-Fluorodeoxyglucose PET has become an essential technique in oncology. Accurate segmentation is important for treatment planning. With the increasing number of available methods, it will be useful to establish a reliable evaluation tool. Method Five methods for [18F]-fluorodeoxyglucose PET image segmentation (MIP-based, Fuzzy C-means, Daisne, Nestle and the 42% threshold-based approach) were evaluated on non-Hodgkin’s lymphoma lesions by comparing them with manual delineations performed by a panel of experts. The results were analyzed using different similarity measures. Intraoperator and interoperator variabilities were also studied. Results The maximum of intensity projection-based method provided results closest to the manual delineations set [binary Jaccard index mean (SD) 0.45 (0.15)]. The fuzzy C-means algorithm yielded slightly less satisfactory results. The application of a 42% threshold-based approach yielded results furthest from the manual delineations [binary Jaccard index mean (SD) 0.38 (0.16)]; the Daisne and the Nestle methods yielded intermediate results. Important intraoperator and interoperator variabilities were demonstrated. Conclusion A simple assessment framework based on comparisons with manual delineations was proposed. The use of a set of manual delineations performed by five different experts as the reference seemed to be suitable to take the intraoperator and the interoperator variabilities into account. The online distribution of the data set generated in this study will make it possible to evaluate any new segmentation method.

Fractal geometry may be an efficient tool for texture analysis in medical imaging. However its application is primarily restricted to 2D cases and at the only use of an approximation method of the fractal dimension (FD). Recently, multifractal analysis has showed interesting results in this field. This study focuses on the use of an optimized set of 3D fractal and multifractal features for the epileptogenic focus characterization in SPECT imaging. Our results showed that this optimized set, compared to various texture features, improved the classification rate by Support Vector Machines (SVM). Moreover, results were significantly better than the clinical method: SISCOM (Substraction Ictal SPECT Co-registred to MRI).

A new automatic method for tumor volume segmentation on PET images has been developed. The method introduced in this paper is based on previous works in MRA segmentation and involves both fuzzy set and possibility theories. Visual results prove the method efficiency which is confirmed by obtained Jaccard index.