CT based analysis of dose homogeneity in total body irradiation using lateral beam

Abstract

A CT based treatment planning for total body irradiation is presented and compared with the commonly practiced lateral treatment delivery. TBI regimen has been proved to be an essential conditional regimen for patients undergoing bone marrow transplant. The advantage of TBI regimen with bone marrow transplant (BMT) in hematological malignancies can be offset by toxicities arising from TBI in post-transplant complications. With the increasing survival rates, the evaluation of long-term side effects and the quality of life has become an important area of research interest. There have been several treatment techniques developed over the decades designed to achieve accurate dose delivery, and dose homogeneity. This paper reports on the verification of the dose delivery for standard lateral technique using thermoluminescent detectors (TLD) placed in an anthropomorphic phantom and it correlation with CT-based treatment planning. CT based treatment plans on several patients considered the doses to the whole body and critical organs. This study showed a large variation in dose delivery to the whole body, with some parts of the bone marrow failing to receive the prescribed dose and some critical organs, such as the lungs, receiving excessive doses. Arms placed at the side only partially compensates for the increased transmission of the lungs because they only shadow part of the lung. This study shows that CT based treatment planning for TBI is necessary for precise and accurate dose calculation and to correlate the clinical outcome with dose actually delivered to various organs.