Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học Radiation Oncology cung cấp cho các bạn kiến thức về ngành y đề tài: Registration accuracy for MR images of the prostate using a subvolume based registration protocol. | Jonsson et al. Radiation Oncology 2011 6 73 http content 6 1 73 RADIATION ONCOLOGY RESEARCH Open Access Registration accuracy for MR images of the prostate using a subvolume based registration protocol Joakim H Jonsson1 Patrik Brynolfsson1 Anders Garpebring1 Mikael Karlsson1 Karin Soderstrom2 and Tufve Nyholm2 Abstract Background In recent years there has been a considerable research effort concerning the integration of magnetic resonance imaging MRI into the external radiotherapy workflow motivated by the superior soft tissue contrast as compared to computed tomography. Image registration is a necessary step in many applications . in patient positioning and therapy response assessment with repeated imaging. In this study we investigate the dependence between the registration accuracy and the size of the registration volume for a subvolume based rigid registration protocol for MR images of the prostate. Methods Ten patients were imaged four times each over the course of radiotherapy treatment using a T2 weighted sequence. The images were registered to each other using a mean square distance metric and a step gradient optimizer for registration volumes of different sizes. The precision of the registrations was evaluated using the center of mass distance between the manually defined prostates in the registered images. The optimal size of the registration volume was determined by minimizing the standard deviation of these distances. Results We found that prostate position was most uncertain in the anterior-posterior AP direction using traditional full volume registration. The improvement in standard deviation of the mean center of mass distance between the prostate volumes using a registration volume optimized to the prostate was mm p in the AP direction. The optimum registration volume size was 0 mm margin added to the prostate gland as outlined in the first image series. Conclusions Repeated MR imaging of the prostate for therapy .
