Evaluation of conformal radiotherapy dosimetry uncertainty three dimensions and intensity modulated radiation therapy in several radiotherapy centers: preliminary study

Radiotherapy is still the main choice of cancer therapy both in the world and in Indonesia. Medical treatment with radiotherapy begins with the planning stage in the Treatment Planning System (TPS). This planning is absolutely necessary for avoid radiation accidents in the form of over dose or under dose received by the patient. The aim of this research is to evaluate the dosimetry uncertainty in the 3D-CRT and MRT technique in order to know accuracy and the amount of deviation radiation dose received by the patient with the dose planned at the TPS. Study for the 3D-CRT technique using phantom CIRS thoracic models 002LFC and IMRT using solid water phantom following standard testing protocols according to IAEA-TECDOC-1583, 2008 and testing according to the recommendations of AAPM Task Group 119. Dose measurement was carried out using an active volume ionization chamber of 0.65 cm³ on Linac energy 6 MV at seven Linacs. The deviation of the dose calculated by TPS with the dose the measurement results for 3D-CRT on the seven consecutive Linacs are 1.849±5.462, 0.061±7.413, 3.870±9.518, -1.075±2.565, -4.195±11,529, 1.817±36,256, and 6.513±20.82. Some Linacs exceed tolerances because the TPS algorithm can't generate the model properly the use of the wedge. The dose deviation for the 3D-CRT is outside the tolerance range generally occurs in the four test cases for point 10, which in its design uses a tangential beam on an inhomogeneous material, test case 6 using blocks and inhomogeneous materials. The results of research on techniques IMRT, the confidence limit (CL) value that describes the suitability of the measurement results dose with planning results, for IMRT planning point dose measurement at the high-dose area in Linac A to Linac F respectively, 3.95 %, 2.83 %, 6.30 %, 2.33 %, 5.49 %, and 9.27 % with the limits set by TG 119 are 4.07 %. CL dose measurement result of IMRT planning point in low dose area in Linac A to Linac F respectively 4.64 %, 3.96 %, 4.88 %, 5.05 %, 3.33 %, and 10.40 % with the limit set by TG 119 is 4.05 %. IMRT test result, show that Linac using the AAA algorithm generally produces a deviation that are within the tolerance range, while those using the superposition algorithm are many measurements with deviations that are outside the tolerance range. Volume effect from the Farmer ionization booth may result in inaccurate measurements for clinical verification of IMRT planning, due to the lack of spatial resolution of the detector used for radiation beam data collection. (author)