Total body irradiation rapid arc planning and dosimetric verification

Abstract

Volumetric modulated arc treatment for the total body irradiation (VMAT TBI) has become the treatment of choice for hematological malignancies from the last two decades. This is because of new technological inventions in simulation procedures, imaging systems, planning optimization and calculation software s, beam delivery devices, different positioning and set up verification devices, and the pre-treatment dose verification equipments etc. In TBI whole body is to be irradiated uniformly. So, to maintain the uniformity and homogeneity in the large target volume, a complexity of the VMAT optimized plan increases. Hence, the measurement of the doses delivered throughout the whole body is a very complex process and pre-treatment verification prior to delivery is the foremost need. Also in-vivo dosimetry for verifying the difference in calculated and delivered dose is required to gain confidence further in planning. As a result various researchers have proposed multiple methodologies for planning and verification. Also different commercially available equipment for dose delivery, pre-treatment verification and positional set up verification are available. In this research work effectiveness of three different combination of fabricated immobilization devices are compared. Also, two different treatment planning software are compared for planning time which include fluence optimization, dose calculation, OAR means doses, and dosimetric conformity and homogeneity indices. For the pre-treatment verification, used equipment is Epiqa, 4D Octavious and IBA dolphin. In-vivo dosimetry at the isocenter and junction of consecutive arcs is done using silicon diode, ionisation chamber, and gafchromic films. Hence, different issues related to whole treatment process are addressed and relevant solutions are proposed with certain assumptions. These addressed issues and solutions are helpful for the planning Medical Physicist, Radiation Oncologist and treating technical staff. newline