AbstractID: 6648 Title: IMRT Prostate Patient Immobilization and Alignment System
In IMRT treatments, target dose conformity and reduction in normal tissue irradiation are realized by generating
high dose gradients along the target and surrounding normal structures. This necessitates accurate target/organ
localization and patient/organ immobilization during the treatment delivery. In this work a system for
patient/organ immobilization has been developed and have been used clinically to reduce prostate organ and
patient movement. To limit movement, the patient lies in the prone position on top of his impression made by a
vacuum bag which has already been placed (the bag) in a specially designed wooden cradle. Prostate
movement has been reduced by inserting a balloon into the rectum to a specified location and is inflated to 50 cc
of air. In addition the patients are treated with bladder full. A simple plastic alignment device inside which
lead/aluminum markers have been inserted, has been built-in the specially designed wooden cradle and is used
during the CT scan and treatment delivery. Film cassette holders have been incorporated into the alignment
device such that AP and LAT portal film images can be obtain. Examination of over 30 patients portal films
have indicated that the estimated daily setup uncertainty has a mean value of 5 ± 2.5 mm and the reproducibility
of prostate position has been within 5 ± 2 mm.