Dosimetric comparison of perineal and intra-vaginal interstitial template in image guided high dose rate brachytherapy for carcinoma cervix

The purpose of this study is to introduce a novel brachytherapy template called the Medanta anterior oblique‑lateral oblique template (MAOLOT), which has been designed for carcinoma cervix, and conduct its dosimetric comparison with Martinez universal perineal interstitial template (MUPIT).

Ten patients were chosen for this study with twelve intracavitary (IC) and/or interstitial (IS) applications. Plans were generated with basal points (BP), target points (TP), and inverse plan simulated annealing (IPSA) along with local graphical optimization (LGrO). Dosimetric and volumetric quantifiers including conformal index (COIN), dose non-uniformity ratio (DNR), dose homogeneity index (DHI), target dose homogeneity index (TDHI), and overdose volume index (OVI) were evaluated.

IPSA provided a better solution for DNR (range 0.25-0.48, p=0.04) in MUPIT and BP+LGrO method was appreciable (p=0.08) in OVI. Mean doses of D90, D95, and D98 of targets of LGrO plan were greater than their respective counterparts. Dose to 1cc and 2cc bladder was the highest for IPSA+LGrO plans as compared to forward optimization plans. Better COIN values were obtained for BP and TP plans with LGrO (p=0.043 (BP+LGrO), p=0.022 (TP+LGrO)). Mean EQD2 dose of 1cc and 2cc bladder was the highest for the IPSA plan as compared to other forward optimization plans.

In IC+IS application, small adjustments using LGrO improves the target coverage and reduces the normal structure dose. IPSA provides better results if plan evaluation is performed carefully. MAOLOT creates the intracavitary and interstitial dose distribution, which is comparable to MUPIT.