Assessment of four dose calculation algorithms using IAEA-TECDOC-1583 with medium dependency correction factor (K_med)...

Area of Science:

• Medical Physics
• Radiation Dosimetry
• Radiotherapy Quality Assurance

Background:

• Clinical commissioning requires accurate dose measurements for radiotherapy. IAEA-TECDOC-1583 provides guidelines for these tests.
• Monte Carlo (MC) simulations are essential for precise dose calculations, but require accurate input parameters.

Purpose of the Study:

• To evaluate the impact of Monte Carlo modelled medium dependency correction factors (Kmed) on dose measurements in bone and lung tissues.
• To assess the accuracy of dose measurements using the CIRS phantom in clinical commissioning tests.

Main Methods:

• BEAMnrc codes were used to simulate 6 MV and 15 MV photon beams.
• CT images of the CIRS phantom were converted for MC simulation.
• Doses were measured using a PTW 30013 farmer chamber within the MC modelled phantom.
• Kmed factors were calculated for Dm.m and Dw.w algorithms in bone and lung media.

Main Results:

• In bone media, Kmed for Dm.m were 0.976 (6 MV) and 0.979 (15 MV); for Dw.w, they were 0.990 and 0.992.
• In lung media, Kmed for Dm.m were 1.020 (6 MV) and 1.022 (15 MV); for Dw.w, they were 1.010 and 1.012.
• These correction factors showed variations depending on the medium and algorithm type.

Conclusions:

• Applying Kmed significantly impacts dose measurement accuracy in clinical commissioning.
• The study underscores the importance of Kmed for reducing dose differences between calculated and measured values during dose audits.