Exhibit Hall | Forum 4
Purpose: VMAT technique has been adapted by more and more clinics for total body irradiation treatment because of its advantages over the conventional TBI treatment. However, since the VMAT-TBI treatment uses plans at multiple ISO centers to cover the whole body, the treatment setup time is highly depending on the imaging modality used and the tolerance allowed in setup. Thus, studying the effect of setup uncertainties to dose coverage in VMAT-TBI treatment assists the optimization of clinical workflow and determines the optimal tolerance for setup.
Methods: For each patient treated in our clinic, ISO centers for VMAT plans at head, chest, abdomen, and pelvis have been shifted by 5mm and 1cm, respectively. Dose DicomRT files were exported and statistical analysis of the dose changes was performed in MatLab. The corresponding impact to the dose coverage of the body has been studied. Percentages of body getting dose over 2%, 5%, and 10% of the prescription dose from the base plan resulting from the shifts of different plans for each patient were analyzed.
Results: Among these shifts of ISOs, the change of dose coverage is more sensitive to the shift for chest plans. For chest plans for all patients, on average the body volume getting 2%, 5%, and 10% dose change from the base plans were 9.25%, 2.64%, and 0.27% for 5mm ISO shift and 12.23%, 6.75%, and 1.29% for 1cm shift. For head plans, these numbers are 2.72%, 0.9%, and 0.14% for 5mm shift and 3.77%, 1.66, and 0.53% for 1cm shift. The shifts of pelvis or abdomen plans also have smaller impact than chest plans.Discussion and
Conclusion: Accurate alignment for the chest plans is crucial in VMAT TBI treatment.
Not Applicable / None Entered.