Monte Carlo simulations and radiation dosimetry measurements of peripherally applied HDR 192Ir breast brachytherapy D-shaped applicators.

Conformal dose coverage for accelerated partial breast irradiation or radiotherapy boost can be obtained with AccuBoost D-shaped brachytherapy applicators using a flattened surface positioned near the patient. Three D-shaped applicators (D45/D53/D60) were dosimetrically characterized using Monte Carlo methods (MCNP5), air ionization chambers (Farmer and Markus), and radiochromic film (GafChromic EBT) in polystyrene and ICRU 44 breast tissue. HDR 192Ir source dwell times were either constant or optimized to improve skin dose uniformity. Scatter dose decreased as depth decreased. 10 mm beyond the applicator aperture, dose reductions of 90% and 51% were observed at depths of 0 and 30 mm, respectively. Similarly, planar dose uniformity improved as depth decreased and was also due to scatter and applicator geometry. Dose uniformity inside the applicator aperture was approximately 11% and 15% for all three applicators at the skin and 30 mm deep, respectively. Depth dose measurements in polystyrene using ion chamber and radiochromic film agreed with Monte Carlo results within 2%. Discrepancies between film and Monte Carlo dose profiles at 30 mm depth were within 1%.