Automatic 3D seed location and orientation in CT images for prostate brachytherapy

International audienceIn prostate brachytherapy, the analysis of the 3D pose information of each individual implanted seed is one of the critical issues for dose calculation and procedure quality assessment. This paper addresses the development of an automatic image processing solution for the separation, localization and 3D orientation estimation of prostate seeds. This solution combines an initial detection of a set of seed candidates in CT images (using a thresholding and connected component method) with an orientation estimation using principal components analysis (PCA). The main originality of the work is the ability to classify the detected objects based on a priori intensity and volume information and to separate groups of seeds using a modified k-means method. Experiments were carried out on CT images of a phantom and a patient aiming to compare the proposed solution with manual segmentation or other previous work in terms of detection performance and calculation time

Distribution angulaire de la réaction 6Li(p, a)3He de 100 à 300 keV

The angular distribution of 3He-particles from the 6Li(p, α) 3He reaction has been measured below 300 keV. The distribution obtained I(θ) ≃ 1 + A cos θ (with A ≃ 0.25) beyond 60° gives preferentially an emission in the forward direction. The compound nucleus theory with two interfering levels (3/2 + at 1.5 MeV and 5/2 — at 1.85 MeV) does not explain the angular distribution observed ; a direct interaction process (pick-up) seems to take place at such a low proton energy.La distribution angulaire des particules 3He de la réaction 6Li(p, α)3He a été mesurée à 144, 171, 215 et 247 keV, de 45° à 150° utilisant un spectromètre α à scintillation ICs et un sélecteur 200 canaux. Les points obtenus sont représentés de 60° à 150° par I(θ) ≃ 1 + A cos θ, avec A ≃ 0,25, montrant une forte prédominance de l'émission des 3He vers l'avant ; en outre, il apparaît une diminution aux plus petits angles. La théorie du noyau composé, utilisant deux niveaux (1,5 MeV, 3/2 +, ondes S) (1,85 MeV, 5/2 —, ondes P) interprète seulement 20 % du coefficient A ; la plus grande partie de l'interaction semble due à un processus de « pick-up» du groupe deuton du 6Li par le proton