Dissertation Defence: The Clinical Applications of 3D Polymer Gel Dosimetry in Commissioning Stereotactic Radiosurgery (SRS) and Spatially Fractionated Radiotherapy (SFRT)

Tenzin Kunkyab, supervised by Dr. Andrew Jirasek, will defend their dissertation titled “The Clinical Applications of 3D Polymer Gel Dosimetry in Commissioning Stereotactic Radiosurgery (SRS) and Spatially Fractionated Radiotherapy (SFRT)” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Medical Physics.

An abstract for Tenzin Kunkyab’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. Registration is not required for in person defences.

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ABSTRACT

Radiation therapy is used to treat various types of cancers. The technologies in radiation delivery continue to advance rapidly. Currently, we are able to accurately target a radiation beam to a tumour volume by conforming the shape of the beam to the complex tumour shape. However, with that, there is a need for radiation dose detection tools that accurately capture the complex dose distribution in 3D space in order to verify the accuracy and precision of a treatment delivery. The purpose of this work is to implement a promising solution to this clinical challenge that utilizes a 3D NIPAM polymer gel dosimetry system with CBCT readout to verify the dosimetric and spatial accuracy of stereotactic radiosurgery (SRS) and spatially fractionated radiotherapy (SFRT) technique.

Three main objectives of this work are 1) to evaluate the reproducibility of a NIPAM gel dosimetry workflow between two institutions, by implementing three identical verification plans in order to demonstrate its wide scale applicability in commissioning advanced radiotherapy techniques. In the study, two separate gel analysis pipelines were utilized based on the individual institution’s preference. 2) to commission two SRS techniques; HyperArc® (Varian Medical Systems, Palo Alto CA) to treat brain metastases and a virtual cone technique to treat trigeminal neuralgia. In the virtual cone study, an end–to–end spatial accuracy test of the treatment delivery was performed using a 3D-printed anthropomorphic phantom. The dosimetric accuracy of the gel dosimetry system was benchmarked against a gold standard, film dosimeter. 3) utilizing a traditional dosimeter solely to verify the treatment delivery accuracy of SFRT is incredibly challenging and inefficient due to the heterogenous dose distribution generated in three-dimensional space.

Therefore, the goal of the final study is to demonstrate the application of the gel dosimetry system to commission SFRT technique. A semi-automated SFRT planning approach was utilized to generate a verification plan on a gel dosimeter for analysis.

This work presents novel applications of a gel dosimetry workflow in two advanced radiotherapy deliveries (SRS and SFRT). The dosimetric and spatial accuracy with this type of gel dosimetry analysis is invaluable for the clinical commissioning process.