Relative dosimetrical verification in high dose rate brachytherapy using two-dimensional detector array IMatriXX

For high dose rate (HDR) brachytherapy, independent treatment verification is needed to ensure that the treatment is performed as per prescription. This study demonstrates dosimetric quality assurance of the HDR brachytherapy using a commercially available two-dimensional ion chamber array called IMatriXX, which has a detector separation of 0.7619 cm. The reference isodose length, step size, and source dwell positional accuracy were verified. A total of 24 dwell positions, which were verified for positional accuracy gave a total error (systematic and random) of -0.45 mm, with a standard deviation of 1.01 mm and maximum error of 1.8 mm. Using a step size of 5 mm, reference isodose length (the length of 100% isodose line) was verified for single and multiple catheters of same and different source loadings. An error <= 1 mm was measured in 57% of tests analyzed. Step size verification for 2, 3, 4, and 5 cm was performed and 70% of the step size errors were below 1 mm, with maximum of 1.2 mm. The step size <= 1 cm could not be verified by the IMatriXX as it could not resolve the peaks in dose profile.