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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:17 |
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Conference: Bucharest University Faculty of Physics 2013 Meeting
Section: Biophysics; Medical Physics
Title:
Setup error and its effect in prostate cancer radiation therapy
Authors:
Mihai Daniel Suditu (1,2),Daniela Adam (2), Răducu Popa (1,2),Violeta Ciocaltei (2), Gabriel Rîcu (2), Cristian Barbu (2)
Affiliation:
(1)Faculty of Physics, University of Bucharest
(2)Amethyst Radiology Therapeutic Center, Bucharest
E-mail
suditu.mihai@yahoo.com
Keywords:
Key: prostate cancer, cone beam CT, portal imaging
Abstract:
The prescribed dose to treat prostate cancer using external beam radiation therapy is limited by the dose toxicity to the surrounding organs, rectum and bladder, which are both mobile structures within the pelvis. Target volume placement errors occur due to a combination of patient errors and internal organ motion. Setup errors in positioning the patients influence directly the size of safety margin necessary to obtain a good coverage of the target volume and the organs at risk toxicity. To evaluate the necessary safety margins and how the setup errors in patients positioning affect the coverage of tumor volume and healthy tissue, the positioning images corresponding to ten patients with prostate cancer were selected. The lateral, craniocaudal and anteroposterior setup errors were evaluated using portal imaging and cone beam CT (CBCT) devices. Clipbox registration using bones anatomy was applied, to analyze patient set-up error and mask registration to evaluate prostate motion. The observed systemic error ranged from -7 to + 6 mm in lateral direction, -5 to 4 mm in craniocaudal direction and from -3 to +5 mm in anteroposterior direction. For clinical target volume dose coverage and organs at risk, new treatments plans were created for each patients, with fields isocenter shifted with the average estimated deviation in all direction. Irradiation of the prostate with a 5 mm uniform safety margin, allowing for 90% coverage probability of CTV, was feasible for all patients on condition that the gross systemic error (>2 mm) has to be eliminated by treatment couch position correction.
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