Three dimensional verification of the dose distribution in prostate cancer treatment using gel dosimeters and comparing it with the treatment planning techniques
Creators: name: Zhu, Wanxian
Publisher: name: RMIT University
Year: 2024

description: Prostate cancer is the most common form of cancer occurring in males in Australia after skin cancer. External beam radiation therapy (EBRT) is one of the main treatment modalities for prostate cancer. It is a procedure where beams of high-energy radiation are focused from outside the body onto the targeted area (tumor). The goal is to apply maximum damage to the tumor while subjecting minimal damage to the adjacent normal tissues. It is very important that the dose distribution from EBRT can be delivered as accurate as possible. Gel dosimeter is a three-dimensional method used to get the dose distribution, and is considered as a highly promising tool of radiotherapy dosimetry.<br><br> The gels can be produced in similar modalities within the human being prostate by using special containers the size alike the prostate. There should be only monomers when the gels are prepared. Radiation-induced polymerization of monomers generates a polymer producing dose-dependent changes where the configurations and some properties of the system are different with monomers. In this work gel dosimeters will be used to determine the dose distribution, which in this case represented by the gel that is immersed in a water phantom.<br><br>Purpose<br><br>Is to evaluate and compare the dose distribution with conventional Four-Field and Intensity Modulated Radiotherapy (IMRT) plans by different beam energy and different commercial treatment planning systems. The aims of this work is to verify and compare the dose distributions by IMRT and Four-Field techniques, verify the beam energy effects in prostate cancer radiotherapy treatment, and compare Cadplan and Pinnacle 3 treatment planning systems (TPS) by the experimental results. <br> <br>Method <br><br>The PAG gels were prepared at the research laboratory of Professor D. Solomon at the Chemical Engineering Department of Melbourne University by following the procedures according to the literatures. The treatment planning of the gel phantom was planned by both Cadplan and Pinnacle 3 treatment planning systems. Then, the gel dosimeters were irradiated by 6MV and 18MV photon beams using Varian Clinac 2100c linear accelerator. The collected data of the gel dosimeter was performed by a 1.5T magnetic resonance imaging (MRI) scanner. The data analysis was applied with a custom program written by the scientific computational program, Matlab 7.0. <br><br>Results<br><br>The dose distribution differences between IMRT and Four-Field were observed from 4.7% to 7.6% by average, depending on the beam energy, planning dose to planning target volume (PTV) and treatment planning systems upon irradiation. The dose distribution differences from different beam energy were found within 1%, without any significant changes. DVHs (Dose Volume Histogram) calculated by experimental data were used to analyze the TPS differences. It was verified there were no significant differences between both TPSs.<br><br>Conclusions<br><br>IMRT technique is more practical for prostate cancer radiotherapy with higher doses to planning target volume (PTV), while sparing more doses to the surrounding normal tissues. There is no substantial significant evidence that can show any better effects from selecting irradiation beam energy. The effectiveness of the planning systems was evaluated and compared by the experimental data, which shows that both of the planning systems are effective to deliver dose with insignificant differences.<br>