Evaluation of Dynamic Axis Optimization for Ablative Radiotherapy

Radiation dose reduction to healthy tissue is a primary objective when treating cancerous disease. Conventional radiotherapy is delivered using a medical linear accelerator (LINAC) that rotates 360 degrees around a patient laying stationary on a treatment couch. The couch can translate and rotate for initial alignment, however literature has shown that rotating it dynamically during treatment offered geometries where greater sparing of healthy brain tissue was possible. The goal of this research is to build on the dynamic algorithm that currently exists for brain treatments, to make it applicable to any site in the body. The main limitation when treating other anatomies with this technique is due to changing "collision zones". A collision zone is defined as a location in the treatment room where the LINAC gantry and couch would physically collide, halting treatment. Treatments to patient extremities (head, feet, or hands) have less collision zones, compared to centralized anatomies. To decrease the collision zones in a centralized treatment (e.g. - breast), the couch could also be dynamically translated laterally and vertically. If this movement is accounted for in the current algorithm, better sparing of healthy tissues (e.g. - heart, for breast treatments) could be realized. These new patient specific collision zones will be tested using human-like phantoms. Phantoms will have radiation sensitive detectors embedded within so new treatments can be delivered in a research setting to compare with the current standard. Successful implementation of this research will allow for widespread adoption of dynamic techniques, by addressing critical needs in the field to reduce dose to healthy tissues and improve long-term patient quality of life. Furthermore, this technique aims to promote dose reductions without requiring completely new radiotherapy infrastructures, and could serve as a foundation for fully automated treatment planning.