Dose optimization in gynecological 3D image based interstitial brachytherapy using martinez universal perineal interstitial template (MUPIT) -an institutional experience

Abstract

The aim of this study was to evaluate the dose optimization in 3D image based gynecological interstitial brachytherapy using Martinez Universal Perineal Interstitial Template (MUPIT). Axial CT image data set of 20 patients of gynecological cancer who underwent external radiotherapy and high dose rate (HDR) interstitial brachytherapy using MUPIT was employed to delineate clinical target volume (CTV) and organs at risk (OARs). Geometrical and graphical optimization were done for optimum CTV coverage and sparing of OARs. Coverage Index (CI), dose homogeneity index (DHI), overdose index (OI), dose non-uniformity ratio (DNR), external volume index (EI), conformity index (COIN) and dose volume parameters recommended by GEC-ESTRO were evaluated. The mean CTV, bladder and rectum volume were 137 +- 47cc, 106 +- 41cc and 50 +- 25cc, respectively. Mean CI, DHI and DNR were 0.86 +- 0.03, 0.69 +- 0.11 and 0.31 +- 0.09, while the mean OI, EI, and COIN were 0.08 +- 0.03, 0.07 +- 0.05 and 0.79 +- 0.05, respectively. The estimated mean CTV D90 was 76 +- 11Gy and D100 was 63 +- 9Gy. The different dosimetric parameters of bladder D2cc, D1cc and D0.1cc were 76 +- 11Gy, 81 +- 14Gy, and 98 +- 21Gy and of rectum/recto-sigmoid were 80 +- 17Gy, 85 +- 13Gy, and 124 +- 37Gy, respectively. Dose optimization yields superior coverage with optimal values of indices. Emerging data on 3D image based brachytherapy with reporting and clinical correlation of DVH parameters outcome is enterprizing and provides definite assistance in improving the quality of brachytherapy implants. DVH parameter for urethra in gynecological implants needs to be defined further.