Assessment of geometric distortions and dosimetric impact from implementing 2D-T2-PROPELLER and 3D-T1-LAVA-FLEX in an MRI-only gynecological brachytherapy workflow

An average geometric distortion of 2.4mm was measured for both the 2D-T2-PROPELLER and T1-3D-LAVA-Flex sequence reconstructions; maximum distortions were 7.5 and 6.4mm respectively. Larger geometric distortions are attributed to obtaining measurements on the periphery of the field-of-view and not in the region of applicator and catheter reconstruction. Gamma pass rates of 96.1±2.8% and 96.6±3.1% were found for the 2D-T2-PROPELLER and 3D-T1- LAVA-Flex MRI reconstructions when compared to CT reconstructions. Minimum gamma pass rates were 90.2% and 90.5% respectively. Significant differences in gamma pass rates were not found between T2-2D-PROPELLER and T1-3D-LAVA-FLEX; however, T1-3D-LAVA-FLEX results were skewed towards higher pass rates. T1-3D-LAVA-FLEX also performed significantly better than T2-2D-PROPELLER for a larger number of catheters.