Design and Development of an Anthropomorphic Heterogeneous Female Pelvic (AHFP) Phantom for Dosimetric Verification of Advance Radiotherapy

Abstract

Introduction: The objective of this work is to design a new kind of AHFP phantom to determine if this phantom is a realistic representation of actual cervical cancer patients. This can serve as a stand-in for the dosimetry quality assurance of a real patient. Material and Methods: An anthropomorphic heterogeneous female pelvic phantom was designed which was made of paraffin wax, a female pelvic bone, water, gauze, polyvinyl chloride (PVC) and polymerized siloxanes. The AHFP phantom was scanned using a CT scanner (Toshiba Alexion 16 multi–Slice CT scanner) at 120kVp and 250mAs with a slice thickness of 2mm to assess how accurately the resulting phantom product simulates a real patient. The CT images were transferred to the Eclipse treatment planning system for dosimetry analysis. Results: The AHFP phantom's CT numbers and relative electron densities of the uterus, bladder, rectum, muscles, fat, bones, and cavities were found close to real patients. The mean percentage variations between planned and measured doses of all RapidArc QA plans were of 2.14 % and standard deviation of 0.543 (t=0.135, p= 0.447; p>0.05) for homogeneous phantom¸ and 7.57% & standard deviation 2.358 (t=4.674, p=0.00094; p< .05) for AHFP phantom. Conclusion: It is concluded that the existing algorithms in TPS for dosimetry are working fine for homogeneous phantoms, but it does not work good for heterogeneous (AHFP) phantom. Therefore, patient-specific absolute dosimetry should be performed using a heterogeneous phantom that closely resembles the actual human body in terms of both density and design.

Keywords

• homogeneous phantom
• heterogeneous phantom
• radiation dosimetry