Background and Objective:The planning dose distribution of intensity-modulated radiation therapy(IMRT) has to be verified before clinical implementation.The commonly used verification method is to measure the beam flu...Background and Objective:The planning dose distribution of intensity-modulated radiation therapy(IMRT) has to be verified before clinical implementation.The commonly used verification method is to measure the beam fluency at 0 degree(0°) gantry angle with a 2-dimensional(2D) detector array,but not the composite dose distribution of the real delivery in the planned gantry angles.This study was to investigate the angular dependence of a 2D diode array(2D array) and the feasibility of using it to verify the composite dose distribution of IMRT.Methods:Angular response of the central detector in the 2D array was measured for 6 MV X-ray,10 cm × 10 cm field and 100 cm source axis distance(SAD) in different depths.With the beam incidence angle of 0°-60°,at intervals of 10°,and inherent buildup of the 2D array(2 g/cm2),the array was irradiated and the readings of the central diode were compared with the measurement of thimble ionization chamber.Using a combined 30 cm × 30 cm × 30 cm phantom which consisted of solid water slabs on top and underlying the 2D array,with the diode detectors placed at 8 g/cm2 depth,measurements were taken for beam angles of 0°-180° at intervals of 10° and compared with the calculation of treatment planning system(TPS) that pre-verified with ion chamber measuring.Results:Differences between the array detector and thimble chamber measurements were greater than 1% and 3.5% when the beam angle was larger than 30° and 60°,respectively.The measurements in the combined phantom were different from the calculation as high as 20% for 90° beam angle,2% at 90°± 5° and less than 1% for all the other beam angles.Conclusions:The 2D diode array is capable of being used in composite dose verification of IMRT when the beam angles of 90°± 5° and 270°± 5° are avoided.展开更多
基金Wu Jie-ping Medical Foundation (No. WKJ2005-3-006-7)
文摘Background and Objective:The planning dose distribution of intensity-modulated radiation therapy(IMRT) has to be verified before clinical implementation.The commonly used verification method is to measure the beam fluency at 0 degree(0°) gantry angle with a 2-dimensional(2D) detector array,but not the composite dose distribution of the real delivery in the planned gantry angles.This study was to investigate the angular dependence of a 2D diode array(2D array) and the feasibility of using it to verify the composite dose distribution of IMRT.Methods:Angular response of the central detector in the 2D array was measured for 6 MV X-ray,10 cm × 10 cm field and 100 cm source axis distance(SAD) in different depths.With the beam incidence angle of 0°-60°,at intervals of 10°,and inherent buildup of the 2D array(2 g/cm2),the array was irradiated and the readings of the central diode were compared with the measurement of thimble ionization chamber.Using a combined 30 cm × 30 cm × 30 cm phantom which consisted of solid water slabs on top and underlying the 2D array,with the diode detectors placed at 8 g/cm2 depth,measurements were taken for beam angles of 0°-180° at intervals of 10° and compared with the calculation of treatment planning system(TPS) that pre-verified with ion chamber measuring.Results:Differences between the array detector and thimble chamber measurements were greater than 1% and 3.5% when the beam angle was larger than 30° and 60°,respectively.The measurements in the combined phantom were different from the calculation as high as 20% for 90° beam angle,2% at 90°± 5° and less than 1% for all the other beam angles.Conclusions:The 2D diode array is capable of being used in composite dose verification of IMRT when the beam angles of 90°± 5° and 270°± 5° are avoided.
