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International audience; We present the first results obtained with a detector, called Large Area Pixelized Detector (LAPD), dedicated to the study the ballistic control of the beam delivered to the patient by in-beam and real time detection of secondary particles, emitted during its irradiation in the context of hadrontherapy. These particles are 511 keV γ from the annihilation of a positron issued from the β+ emitters induced in the patient tissues along the beam path. The LAPD basic concepts are similar to a conventional PET camera. The 511 keV γ are detected and the reconstructed lines of response allow to measure the β+ activity distribution. Nevertheless, when trying to use γ from positron annihilation for the ballistic control in hadrontherapy, the large prompt γ background should be taken into account and properly rejected. First reconstruction results, obtained with a phantom filled with a high intensity FDG source at the cancer research centre of Clermont-Ferrand are shown. We also report results of measurements performed at the Heidelberg Ion-Beam Therapy Centre with one third of the detector, using proton and carbon ion beams.

But Les progres techniques autorisent maintenant les traitements conservateurs des melanomes malins de la choroide. L’evolution de la maladie reste dominee par la crainte de metastases, survenant en moyenne apres trois ans. Le but de ce travail est de rapporter deux cas inhabituels de metastases hepatiques de melanome malin de la choroide survenues 11 et 18 ans apres curietherapie. Materiel et methodes Une femme de 40 ans et un homme de 50 ans ont presente un melanome malin de la choroide du pole posterieur de taille T2 et T3. Ils ont ete traites par disque de cobalt. Dans l’annee qui a suivi, les deux tumeurs ont completement regresse. Les patients ont ete suivis regulierement tous les trois mois pendant cinq ans. Resultats Les metastases hepatiques sont apparues respectivement 11 ans et 18 ans plus tard. Discussion et conclusion Ces deux observations semblent indiquer que la dissemination metastatique etait deja presente au moment du diagnostic et que le temps de doublement cellulaire du melanome uveal etait particulierement long. Elles posent le probleme de la duree du melanome uveal et du depistage infraclinique des metastases.

Resume Objectif de l'etude Analyse retrospective des resultats de la radiotherapie de l'adenocarcinome non metastatique de la prostate a l'exclusion des complications. Patients et methodes Les 610 cas de stade T1-T2 repertories ont ete traites par irradiation externe dans 19 instituts, entre janvier 1983 et janvier 1988. Le recul moyen etait de 10,4 ans, la moyenne d'âge au debut du traitement de 68,5 ans. Resultats Un controle local a 10 ans a ete obtenu pour 86 % des cancers classes T1-T2 (81,4 % dans le cas des T2). Le taux de rechute metastatique etait a 5 et 10 ans respectivement de 25,3 et 30 % (29 et 38,1 % pour les T2). A 10 ans, 62,4 % des tumeurs de stade T1-T2 n'avaient pas recidive; par ailleurs, le taux de survie globale etait de 45,8 % et celui de survie specifique de 70,5 %; 29,9 % des patients etaient vivants sans signe de recidive. Il y avait une correlation entre le stade (TNM), le grade, le statut ganglionnaire pelvien, le controle tumoral local, la presence d'une obstruction ureterale, et la survie. L'irradiation pelvienne, la dose, l'etalement, le traitement hormonal neoadjuvant et la resection transuretrale n'avaient pas d'influence sur le pronostic. Conclusion Il n'y a pas de difference entre les deux etudes francaises (1975–1982 et 1983–1988) sur le plan du recrutement et du pronostic. Les resultats releves dans la litterature sont voisins des notres. Cette etude souligne l'importance des facteurs de pronostic inherents a la tumeur et au malade.

Beta Irradiation (106Ru/106Rh) versus Gamma Irradiation (125I): A Comparative Study on the Normal Rabbit Eye. We compared beta irradiation (106Ru/106Rh) to gamma irradiation (125I) on the normal rabbit eye, using ophthalmic plaques to deliver doses similar to those recommended in man for choroidal melanoma treatment. A detailed dosimetry was performed and the animals were followed up by clinical and histological examinations during 1 year. The mean total doses were either comparable, or larger with iodine-125, but the globes treated with ruthenium-106 exhibited more damaging effects: total destruction of the chorioretina on the plaque site, abnormalities of the retinal vessels and of the close nerve fiber layers, cavernous atrophy of the optic nerve. In the eyes treated with iodine-125, only the external retinal layers were destroyed.

International audience; The GATE Monte Carlo simulation platform based on the Geant4 toolkit is under constant improvement for dosimetric calculations. In this study, we explore its use for the dosimetry of the preclinical targeted radiotherapy of melanoma using a new specific melanin-targeting radiotracer labeled with iodine 131. Calculated absorbed fractions and S values for spheres and murine models (digital and CT-scan-based mouse phantoms) are compared between GATE and EGSnrc Monte Carlo codes considering monoenergetic electrons and the detailed energy spectrum of iodine 131. The behavior of Geant4 standard and low energy models is also tested. Following the different authors' guidelines concerning the parameterization of electron physics models, this study demonstrates an agreement of 1.2% and 1.5% with EGSnrc, respectively, for the calculation of S values for small spheres and mouse phantoms. S values calculated with GATE are then used to compute the dose distribution in organs of interest using the activity distribution in mouse phantoms. This study gives the dosimetric data required for the translation of the new treatment to the clinic.

Although cancer of the penis is a rare disease, we have collected 506 cases through a multicentric study. In the present study we analyse the results obtained from 259 patients treated by interstitial brachytherapy from 1959 to 1989. Among the 259 patients, 184 males had exclusive brachytherapy (group A) while 75 received a combination of surgery and brachytherapy and/or external beam irradiation (EBI) (group B). Five- and 10-year survival rates are, respectively: overall survival, 66 and 52%; cause-specific survival, 88 and 88%; disease-free survival, 78 and 67%. One hundred and forty-three patients in group A (78%) and 48 (64%) in group B avoided mutilation of the penis while late side effects occurred in 137/259 patients (53%). Survival depends on the volume of the tumor and the presence of involved nodes; systematic groin dissection does not however seem advisable.

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. This paper gives a detailed description of the design and development of GATE by the OpenGATE collaboration, whose continuing objective is to improve, document and validate GATE by simulating commercially available imaging systems for PET and SPECT. Large effort is also invested in the ability and the flexibility to model novel detection systems or systems still under design. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at http:/www-lphe.epfl.ch/GATE/. Two benchmarks developed for PET and SPECT to test the installation of GATE and to serve as a tutorial for the users are presented. Extensive validation of the GATE simulation platform has been started, comparing simulations and measurements on commercially available acquisition systems. References to those results are listed. The future prospects towards the gridification of GATE and its extension to other domains such as dosimetry are also discussed. ispartof: Physics in medicine and biology vol:49 issue:19 pages:4543-4561 ispartof: location:England status: published

Monte Carlo simulations are increasingly used in scintigraphic imaging to model imaging systems and to develop and assess tomographic reconstruction algorithms and correction methods for improved image quantitation. GATE (GEANT4 application for tomographic emission) is a new Monte Carlo simulation platform based on GEANT4 dedicated to nuclear imaging applications. This paper describes the GATE simulation of a prototype of scintillation camera dedicated to small-animal imaging and consisting of a CsI(Tl) crystal array coupled to a position-sensitive photomultiplier tube. The relevance of GATE to model the camera prototype was assessed by comparing simulated 99mTc point spread functions, energy spectra, sensitivities, scatter fractions and image of a capillary phantom with the corresponding experimental measurements. Results showed an excellent agreement between simulated and experimental data: experimental spatial resolutions were predicted with an error less than 100 microns. The difference between experimental and simulated system sensitivities for different source-to-collimator distances was within 2%. Simulated and experimental scatter fractions in a [98-182 keV] energy window differed by less than 2% for sources located in water. Simulated and experimental energy spectra agreed very well between 40 and 180 keV. These results demonstrate the ability and flexibility of GATE for simulating original detector designs. The main weakness of GATE concerns the long computation time it requires: this issue is currently under investigation by the GEANT4 and the GATE collaborations.

Introduction The GATE Monte-Carlo (MC) simulation platform ( www.opengatecollaboration.org ) based on the GEANT4 toolkit has come into widespread use for simulating Positron Emission Tomography, Single Photon Emission Computed Tomography, Computing Tomography (CT) imaging devices and radiation therapy. In this work, we explore the simulation of an intensity-modulated arc therapy (IMAT) treatment using GATE 6.2. To reach this objective, we first performed a complete modeling of the Varian's Novalis Tx linear accelerator (15MV photon mode) using the multileaf collimator (MLC). Then, the simulation of the geometry was validated in water before experiencing a head-and-neck cancer treatment. Material and methods The first stage is to model the Novalis Tx head with the GATE MC platform using manufacturer's data. We simulated this linac in 15 MV mode and compared depth doses, in-plane and cross-plane profiles with reference measurements (performed with ionization chambers (Semiflex 31013, PTW and LA48 Linear Array, PTW) and PTW60012 Diode E) in water for several field sizes ranging from 1 × 1 to 10 × 10 cm 2 . Target and flattening filter geometries and initial electron beamare adjusted in order to fit simulation calculations with dosemeasurements. In a second stage, the MLC geometry implementation enabled the simulation of clinical IMAT treatment plans compared with the iPlan treatment planning software (BrainLab) calculations. In order to reduce the computing time of GATE calculations, the simulations are executed on a distributed infrastructure using the GateLab ( http://vip.creatis.insa-lyon.fr/ ) platform. Results Weshowa good agreement between measurements and simulated depth dose profiles in liquid water. GATE and iPlan normalized treatment plans were compared using agammaindex of ±2%/mm.The ongoing work concerning treatment plan comparisons demonstrates limits of the iPlan Pencil Beam algorithm close to heterogeneities. Using the distributed infrastructure, space phase file was produced in 14 h for 500 million primary photons generated reaching a gain of a factor 50 comparing to calculations performed on a single CPU. Conclusions This study demonstrates that GATE offers efficient tools to make possible IMAT applications. In a subsequent work a microdosimetry study should be performed for a complete validation.

Purpose: By calibratingbrachytherapy (BT) sources to the TG‐43U1 reference position at 1cm in water, named the nominal absorbed dose‐rate to water, Ḋ w ,1, accuracy and precision for patient treatment will be increased. Traceability must be provided to Ḋ w ,1 ‐primary‐standards; which soon become available. Methods and Materials: Efforts have been made in discussions with fellow scientists from many countries, by reviewing concerned literature, and similarities are drawn from documents (e.g. extending TG‐43U1). Results: From the study of primary photon interaction mechanisms, a need was recognized to classify BT‐photon radiation qualities as: high‐energy >100keV, medium energy 40keV to 100keV, and low energy

International audience