Introducing interactive inverse FEM simulation and its application for adaptive radiotherapy

International audienceWe introduce a new methodology for semi-automatic deformable registration of anatomical structures, using interactive inverse simulations. The method relies on non-linear real-time Finite Element Method (FEM) within a constraint-based framework. Given a set of few registered points provided by the user, a real-time optimization adapts the boundary conditions and(/or) some parameters of the FEM in order to obtain the adequate geometrical deformations. To dramatically fasten the process, the method relies on a projection of the model in the space of the optimization variables. In this reduced space, a quadratic programming problem is formulated and solved very quickly. The method is validated with numerical examples for retrieving Young's modulus and some pressures on the boundaries. Then, we apply the approach for the registration of the parotid glands during the radiotherapy of the head and neck cancer. Radiotherapy treatment induces weight loss that modifi es the shape and the positions of these structures and they eventually intersect the target volume. We show how we could adapt the planning to limit the radiation of these glands.Nous introduisons une nouvelle méthode de recalage déformable semi-automatique de structures anatomiques, à l'aide de simulations inverses interactives. La méthode est basée sur la méthode des éléments finis(FEM) et revient à résoudre un système de contraintes. Etant donné un ensemble de quelques points fournies par l'utilisateur, une optimisation en temps réel adapte les conditions aux limites et(/ou) des paramètres de la FEM dans le but d'obtenir les déformations géométriques adéquates. Pour accélérer les calculs de manière conséquente, la méthode repose sur une projection du modèle dans l'espace des variables d'optimisation. Dans cet espace réduit, un problème de programmation quadratique est formulé et résolu très rapidement. La méthode est validée par des exemples numériques (récupérer le module de Young et des pressions à appliquer sur le modèle). Ensuite, nous appliquons l'approche pour le recalage des glandes parotides pendant la radiothérapie de la tête et du cou. Un traitement de radiothérapie induit généralement une perte de poids chez le patient qui modifie la forme et la position de ces structures. Structures qui finissent par entrer dans le volume cible. Nous montrons comment nous pourrions adapter la planification afin de limiter le rayonnement de ces glandes

GTV-based prescription in SBRT for lung lesions using advanced dose calculation algorithms

BACKGROUND: The aim of current study was to investigate the way dose is prescribed to lung lesions during SBRT using advanced dose calculation algorithms that take into account electron transport (type B algorithms). As type A algorithms do not take into account secondary electron transport, they overestimate the dose to lung lesions. Type B algorithms are more accurate but still no consensus is reached regarding dose prescription. The positive clinical results obtained using type A algorithms should be used as a starting point. METHODS: In current work a dose-calculation experiment is performed, presenting different prescription methods. Three cases with three different sizes of peripheral lung lesions were planned using three different treatment platforms. For each individual case 60 Gy to the PTV was prescribed using a type A algorithm and the dose distribution was recalculated using a type B algorithm in order to evaluate the impact of the secondary electron transport. Secondly, for each case a type B algorithm was used to prescribe 48 Gy to the PTV, and the resulting doses to the GTV were analyzed. Finally, prescriptions based on specific GTV dose volumes were evaluated. RESULTS: When using a type A algorithm to prescribe the same dose to the PTV, the differences regarding median GTV doses among platforms and cases were always less than 10% of the prescription dose. The prescription to the PTV based on type B algorithms, leads to a more important variability of the median GTV dose among cases and among platforms, (respectively 24%, and 28%). However, when 54 Gy was prescribed as median GTV dose, using a type B algorithm, the variability observed was minimal. CONCLUSION: Normalizing the prescription dose to the median GTV dose for lung lesions avoids variability among different cases and treatment platforms of SBRT when type B algorithms are used to calculate the dose. The combination of using a type A algorithm to optimize a homogeneous dose in the PTV and using a type B algorithm to prescribe the median GTV dose provides a very robust method for treating lung lesions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13014-014-0223-5) contains supplementary material, which is available to authorized users

Development of staffing, workload and infrastructure in member departments of the European Organisation for Research and Treatment of Cancer (EORTC) radiation oncology group

Purpose The EORTC Radiation Oncology Group uses a Facility Questionnaire (FQ) to collect information from its member radiation oncology departments. We analysed the FQ database for patient-related workload, staffing levels and infrastructure to determine developments in radiation oncology departments in the clinical trials community. Materials & Methods We exported the FQ database in August 2019. Departments were included if their FQ was created or updated within the two preceding years. Observations were compared with previous evaluations of the FQ database. Results In total, 161 departments from 24 mostly European countries were analysed. The average number of patients per department increased by 3.0% to 2,453 (2013: 2,381). The annual number of patients decreased by 7.4% to 225 per radiation oncologist (2013: 243) and by 7.9% to 326 per medical physicist (2013: 354). In contrast, the number of patients increased by 23.3% to 106 per radiation therapist (RTT) (2013: 86) and per treatment unit by 3.9 % to 485 (2013: 467). In a pairwise comparison of departments that were available in 2013 and 2019, the number of patients per radiation oncologist (p = 0.02) and per physicist (p = 0.0003) decreased significantly. The number of departments that own a dedicated PET-CT scanner more than doubled (2013: 4%; 2019: 9%) and the availability of stereotactic body radiation therapy (SBRT) increased by 31.8% to 85.7% of the departments (2013: 65%). Conclusion The case-related workload per radiation oncologist and per physicist continues to decrease but increases per RTT and treatment unit. This is likely driven by an increased use of complex techniques, multimodality imaging and the implementation of automation in radiation oncology departments

Re-irradiation in clinical practice:Results of an international patterns of care survey within the framework of the ESTRO-EORTC E²-RADIatE platform

Background: Re-irradiation is an increasingly utilized treatment for recurrent, metastatic or new malignancies after previous radiotherapy. It is unclear how re-irradiation is applied in clinical practice. We aimed to investigate the patterns of care of re-irradiation internationally. Material/Methods: A cross-sectional survey conducted between March and September 2022. The survey was structured into six sections, each corresponding to a specific anatomical region. Participants were instructed to complete the sections of their clinical expertise. A total of 15 multiple-choice questions were included in each section, addressing various aspects of the re-irradiation process. The online survey targeted radiation and clinical oncologists and was endorsed by the European Society for Radiotherapy and Oncology (ESTRO) and the European Organisation for Research and Treatment of Cancer (EORTC).Results: 371 physicians from 55 countries across six continents participated. Participants had a median professional experience of 16 years, and the majority (60%) were affiliated with an academic hospital. The brain region was the most common site for re-irradiation (77%), followed by the pelvis (65%) and head and neck (63%). Prolonging local control was the most common goal (90–96% across anatomical regions). The most common minimum interval between previous radiotherapy and re-irradiation was 6–12 months (45–55%). Persistent grade 3 or greater radiation-induced toxicity (77–80%) was the leading contraindication. Variability in organs at risk dose constraints for re-irradiation was observed. Advanced imaging modalities and conformal radiotherapy techniques were predominantly used. A scarcity of institutional guidelines for re-irradiation was reported (16–19%). Participants from European centers more frequently applied thoracic and abdominal re-irradiation. Indications did not differ between academic and non-academic hospitals. Conclusion: This study highlights the heterogeneity in re-irradiation practices across anatomical regions and emphasizes the need for high-quality evidence from prospective studies to guide treatment decisions and derive safe cumulative dose constraints.</p

Planification de la radiothérapie basée sur TEP/IRM :gestion des incertitudes

Imaging provides the basis for radiotherapy. Multi-modality images are used for target delineation (primary tumor and nodes, boost volume) and organs at risk, treatment guidance, outcome prediction, and treatment assessment. Next to anatomical information, more and more functional imaging is being used. The current paper provides a brief overview of the different applications of imaging techniques used in the radiotherapy process, focusing on uncertainties and QA. The paper mainly focuses on PET and MRI, but also provides a short discussion on DCE-CT. A close collaboration between radiology, nuclear medicine and radiotherapy departments provides the key to improve the quality of radiotherapy. Jointly developed imaging protocols (RT position setup, immobilization tools, lasers, flat table…), and QA programs are mandatory. For PET, suitable windowing in consultation with a Nuclear Medicine Physician is crucial (differentiation benign/malignant lesions, artifacts…). A basic knowledge of MRI sequences is required, in such a way that geometrical distortions are easily recognized by all members the RT and RT physics team. If this is not the case, then the radiologist should be introduced systematically in the delineation process and multidisciplinary meetings need to be organized regularly. For each image modality and each image registration process, the associated uncertainties need to be determined and integrated in the PTV margin. When using functional information for dose painting, response assessment or outcome prediction, collaboration between the different departments is even more important. Limitations of imaging based biomarkers (specificity, sensitivity) should be known.SCOPUS: sh.jinfo:eu-repo/semantics/publishe

Self-absorption correction for (32)p, (198) Au and Re-118 stents: Dose point kernel calculations versus Monte Carlo.

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Dose calculation validation of a convolution algorithm in a solid water phantom.

The dose calculated using a convolution algorithm should be validated in a simple homogeneous water-equivalent phantom before clinical use. The dose calculation accuracy within a solid water phantom was investigated.info:eu-repo/semantics/publishe