A study of enhanced dynamic wedge dosimetry using a 2D ion chamber array detector

Abstract

The purpose of this work was to study the dosimetric properties of the enhanced dynamic wedge using a Seven29 ion chamber array. The PTW Seven29 ion chamber array and solid water phantoms were used for the study. Primarily, the solid water phantoms with the two-dimensional (2D) array were scanned using a computed tomography scanner at different depths. Using these scanned images, planning was performed for different wedge angles at 6 and 15 MV. A dose of 100 CGy was delivered in each case. For each delivery, the required monitoring units (MUs) were calculated. Using the same setup with a Varian Clinac iX, the calculated MU was delivered for different wedge angles. Subsequently, the different wedged dose distributions that had been obtained were analysed using Verisoft software. A shoulder-like region was observed in the profile; this region reduced as depth increased. The percentage deviation between the planned and measured doses at the shoulder region fell within the range of 0·9–4·3%. The standard deviation between planned and measured doses at shoulder region in the profile fell within 0·08±0·02 at different depths. The standard deviations between planned and measured wedge factors for different depths (2·5, 5, 10 and 15 cm) were 0·0021, 0·0007, 0·0050 and 0·0001 for 6 MV and 0·0024, 0·0191, 0·0013 and 0·0005 for 15 MV, respectively. On the basis of the studies that we performed, it can be concluded that the 2D ion chamber array is a good tool for enhanced dynamic wedge dosimetry.