AbstractID: 7937 Title: A Precise and Accurate Method for Pediatric Total Body Irradiation (TBI) using
Static Fields
TBI is often used as a conditioning regimen for Bone Marrow Transplantation (BMT). Our method for simulation and planning this
special pediatric procedure is image based CT. Treatment is at the location of the linac floor, a distance of approximately 220 cm
from the source. 6MV x-rays and an acrylic beam spoiler are used in dose delivery with an (AP/PA) technique. Jaw settings of the
linac are set wide open (40cm x 40 cm @ 100 cm SAD), with patient positioned along the field diagonal. Patients less than 35-40 cm
long are eligible. Alpha cradles(cr) are made at time of simulation with the patient in a “frog legged” position . While the patient is
supine in the AP cradle, the complementary PA cradle is fabricated. The AP and PA CT scan data allows precise and accurate
determination and documentation of required treatment parameters: anatomical site, anatomical thickness, off axis location, and SSD.
Spreadsheet calculations permit multiple calculation point dosimetry and compensator design for mid-plane dose uniformity. Port
films containing fiducial markers are obtained on the first day in order to design full thichkness lung blocks for use in one of four
treatments. Technique details and measured beam data relevant to our method will be presented.