Determination of variation in dosimetric parameters of treatment planning with Co-60 and Ir-192 sources in high dose rate brachytherapy of cervical carcinoma

Abstract

AimTo determine the differences in dosimetric parameters in patients of intracavitary brachytherapy and interstitial HDR brachytherapy using Co-60 and Ir-192 sources. Materials and methodsComputed tomography (CT) based treatment plans of 20 cervical carcinoma patients treated with intracavitary and interstitial high dose rate brachytherapy were retrospectively studied. Patients were planned using Co-60 and Ir-192 sources, keeping the same dwell positions and dose objectives. The dosimetric parameters such as V100, D90, homogeneity index (HI) and conformal index (CI) for target and D2cc, D1cc and D0.1cc for organs at risk (OAR) were compared for both sources. ResultsFor interstitial brachytherapy plans, HR-CTV mean V100 values for Co-60 and Ir-192-based plans were 97.03 ± 1.93% and 96.42 ± 2.18%, respectively. There was no significant difference found in target coverage (p = 0.370). Ir-192 based plans were more homogeneous (HI = 0.68 ± 0.09) than the Co-60 plans (HI = 0.59 ± 0.10). However, the conformity was similar with both the sources. No significant difference was found between D2cc, D1cc, and D0.1cc values of bladder and rectum. In intracavitary brachytherapy plans, we did not find any significant difference in the dosimetric parameters such as point A values, D90, V100, and OAR doses on comparing plans from both sources. ConclusionThere are no significant differences in dosimetric parameters and no clinical advantage of using Co-60 over Ir-192-based brachytherapy. However, when it comes to cost management, Co-60 has a longer half-life, which reduces the cost of frequent source replacement and disposal.