![]() ![]() PCA decouples the spatial and temporal components of the DVFs. The salient characteristics in the DVFs are captured in a compact representation through principal component analysis (PCA). DVFs are calculated through deformable image registration (DIR) of a reference 4DCT phase image (typically peak-exhale) to a set of 4DCT images corresponding to different phases of a breathing cycle. The patient-specific motion model is based on a compact representation of lung motion represented in displacement vector fields (DVFs). ![]() In the second step, parameters in the motion model are tuned according to the information in the EPID image. In the first step, a patient-specific motion model is constructed from 4DCT. Methods: The authors adopt a two-step approach to time-varying volumetric image estimation from a single cine EPID image. Purpose: In this work the authors develop and investigate the feasibility of a method to estimate time-varying volumetric images from individual MV cine electronic portal image device ( EPID) images. [Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115 (United States) Li, Ruijiang [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305 (United States) ![]() The mechanical sag during gantry rotation was dependent on the gantry angle and was larger in the in-plane direction, although the patterns were notĪn initial study on the estimation of time-varying volumetric treatment images and 3D tumor localization from single MV cine EPID imagesĮnergy Technology Data Exchange (ETDEWEB) The Gamma evaluation (3%, 3 mm) technique was used to investigate the improvement in alignment of cine EPID images of a fixed field, by comparing both individual images and the sum of images in a series with the reference gantry zero image. The generalized shift patterns were derived from the data and used in an image registration algorithm to correct for the effect of the mechanical sag in the system. The results were monitored for one linear accelerator over a course of 15 months and six other linear-accelerators from two treatment centers were also investigated using this method. The method was applied to compare the effect in clockwise and counter clockwise gantry rotations and different source-to-detector distances (SDDs). The algorithm results were then tested against independent methods. The markers were tracked in EPID images and a robust in-house developed MATLAB code was used to analyse the images and find the EPID sag in three directions as well as the EPID + gantry sag by comparison to the reference gantry zero image. EPID images were acquired during a 360° gantry rotation in cine imaging mode. Three metallic ball bearings were used as markers in the beam: two of them fixed to the gantry head and the third positioned at the isocenter. In this study, an easy experiment setup and accurate algorithm have been introduced to characterize and correct for the effect of EPID and gantry sag during arc delivery. Several studies have investigated the effects of gravity on the sag of these systems but each have limitations. The application of EPIDs for dosimetry in arc treatments requires accurate characterization of the mechanical sag of the EPID and gantry during rotation. Rowshanfarzad, Pejman Sabet, Mahsheed O'Connor, Daryl J McCowan, Peter M McCurdy, Boyd M C Greer, Peter BĮlectronic portal imaging devices ( EPIDs) have been studied and used for pretreatment and in-vivo dosimetry applications for many years. Detection and correction for EPID and gantry sag during arc delivery using cine EPID imaging. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |