Room: Exhibit Hall
Purpose: To verify the patient dose for volumetric modulated arc therapy total marrow irradiation (VMAT-TMI) which is a new treatment planning technique in Ramathibodi Hospital.
Methods: Five VMAT-TMI treatment plans were created using Eclipse treatment planning system (TPS): AAA algorithm version 13.6. The planning target volume (PTV) was divided into head, chest and pelvis sub-regions. The number of arc fields depended on the patientâ€™s length, the total of 8-10 arc fields (2-5 arcs per isocenter) with the multiple isocenters were used in this study. The planar dose distribution and absolute point dose for each isocenter and each PTV sub-regions were verified using ArcCHECK and CC13 ionization chamber, respectively. In addition, the EBT3 films were used for verification in the similar region and the junction areas between different PTVs.
Results: The point dose measurements show a good agreement with TPS calculation within Â±5% for all isocenters and PTVs. The ArcCHECK measurements demonstrate excellent agreement with TPS for all isocenters with an average gamma passing rate up to 99.3% Â± 1.4% (3%/3mm). For head, chest and pelvis sub-regions reveal the average gamma passing rates of 98.6% Â± 1.5%, 98.0%Â± 1.4%, 98.7%Â± 1.2%, respectively. The passing rate slightly decreases while using EBT3 films, however, the average value is exceeded 94.1%Â±1.4%.
Conclusion: The remarkable dose distribution and point dose measurement verification show that the VMAT-TMI technique could be implemented for total marrow irradiation in our hospital. However this results is verified only five cases, the more number of VMAT-TMI patients should be evaluated for the further study.
Treatment Verification, Dosimetry, Quality Assurance