Comparative Studies of Absolute Dose in Water Phantom, Solid Water Phantom and MatriXX with MULTICube Phantom

Introduction: Radiotherapy is one of the important treatment modalities in cancer treatment. To maintain the treatment procedure accuracy, the phantom is an essential tool for absolute dosimetry conformation and Quality Assurance routine cheek up. This work aims to study the absorbed dose of various phantoms and hence to make a comparison of the result with the IAEA recommendation (TRS 398) for daily QA of Linac. Materials and Methods: The experiment has been done at the Institute of Nuclear Medical Physics (INMP), AERE, Savar, Dhaka, under the Bangladesh Atomic Energy Commission. For external beam radiation, 6 MV and 15 MV photon beams of Varian Clinac iX Linear Accelerator (Linac) were used. One dimensional (1D) water phantom, solid water phantom, and MatriXX with MULTICube phantom and associate accessories were used to experiment. Results: We have measured and compared the absorbed dose data of the phantoms. The variation of sold water phantom from the 1D water phantom is +2.8% at 6 MV and +3.5% at 15 MV. The variation MatriXX with MULTIcube phantom from the 1D water phantom is +8.0% at 6 MV and +3.2% at 15 MV. This study revealed that the 1D water phantom was the best absolute dose conformation among the other phantoms and the deviation was within the acceptable limit (±5%), except MatriXX with MULTICube Phantom for low energy beam (8%). Conclusion: It was observed that the accuracy of dose estimation was better in the 1D water phantom rather than the other two. It is also known that the 1D water phantom is low cost but needs a long time to set up for the experimental arrangement. Solid water or MatriXX with MULTICube phantom can be used to overcome this problem, which takes only a few minutes for setup and is comparatively faster than 1D water phantom.