Fifty-seventh annual meeting of the American association of physicists in medicine
SU-E-P-38: Comparison of Capri Applicator HDR Planning Methods to Meet the NCCN Uterine Neoplasm 2.2015 Guidelines
To establish a systematic planning approach for Capri intravaginal multichannel balloon applicators that meet updated Version 2.2015 NCCN guidelines for uterine neoplasms, which dictate delivery of 400 to 600 cGy in 2 to 3 fractions prescribed to the vaginal mucosa for HDR combined with EBRT as well as a regimen of 600 cGy × 5 (to the vaginal mucosa) for HDR brachytherapy alone.
Studies have shown three different channel configurations of the Capri applicator are optimal for dosimetric conformity: central channel combined with the six inner ring channels (R12), all inner and outer ring channels (R23), or all thirteen channels (R123). To minimize the dose to the vaginal mucosa, a traditional 0.5cm expansion contour from the Capri surface was created. Optimization limits were set to push 600 cGy to 100% of the Capri volume, while simultaneously restricting dose to the expansion contour.
Plans were created using all three configurations (R12, R23, R123) and evaluated to determine which was best for delivering 600 cGy to the vaginal mucosa. Our criteria was: Capri V100 > 98%, Vaginal Mucosa Dmax < 125%, Bladder Dmax < 100%, Rectum Dmax < 100%. All configurations show Capri V100 values greater than 98.5%, with differences between plans varying by less than 1%. Vaginal mucosal Dmax values showed differences of roughly 5% of prescription. The R12 configuration proved the lowest vaginal mucosa Dmax, on average. The OAR Dmax values showed an average dose difference of roughly 2% of prescription, with the R23 configuration having the best results.
The R12 channel configuration optimally fits our planning criteria and NCCN guidelines for 600 cGy prescribed to the vaginal mucosa. On average, it produced the highest Capri V100, the lowest vaginal mucosal Dmax, and a marginally higher OAR Dmax doses compared to the R23 and R123 plans.