Radiotherapy Dosage

The Monaco treatment planning system offers three different dose calculation algorithms for use in calculating 3D treatment plans. These include Monte Carlo (MC), Collapsed Cone (CC) and the pencil beam algorithms. The aim of this study is an in-depth analysis of Monte Carlo and Collapsed Cone dose calculation methods to find the optimal parameters for clinical use for both algorithms.
An end-to-end phantom with inhomogeneities was scanned and the DICOM images were imported into Monaco for contouring and planning. Treatment plans were then created in Monaco for both MC and CC using different permutations of variables for approximately 400 plans. These variables include CT Slice thickness, grid size, statistical uncertainty, and beam energy. Following planning the end-to-end phantom was then irradiated on an Elekta Linac and plans for each beam energy were created. Clinical beam data was then compared to the computed plans for each dose calculation method.

Proton therapy with pencil beam scanning technique is a novel technique to treat cancer patients due to its unique biophysical properties. However, a small error in dose calculation may lead towards undesired greater uncertainties in planed doses. This project aims to create a simulation model of Varian ProBeam Compact using the GEANT4 Monte Carlo simulation tool kit.
Experimental data from the first clinical ProBeam Compact system at South Florida Proton Therapy Institute was used to validate the simulation model. A comparison was made between the experimental and simulated Integrated Depth-Dose curves using a 2%/2mm gamma index test with 100% of points passing. The beam spot standard deviation sizes (s!) were compared using percent deviation. All simulated s! matched the experimental s! within 2.5%, except 70 and 80 MeV. The model can be used to develop a more comprehensive model as an independent dose verification tool and further investigate dose distribution.