Dosimetric comparison of AcurosBV with AAPM TG43 dose calculation formalism in cervical intraductal high‐dose‐rate brachytherapy using three different applicators

Abstract

To compare the dosimetric effects of American Association of Physicists in Medicine (AAPM) TG43 dose formalism and AcurosBV ( grid-based Boltzmann solver ,GBBS) formalism on High-dose-rate(HDR) brachytherapy planning for cervical cancer patients irradiated using three different applicators. MethodsA TG43 plan and a AcurosBV plan were generated for each of the 30 patients. twenty patients who had undergone whole pelvic radiotherapy followed by cervical HDR brachytherapy and the remaining 10 patients who underwent total hysterectomy only gave HDR brachytherapy also were enrolled in this study. The patients were divided into three groups according to the types of applicators used: tandem and ovoid (T&O), tandem and ring (T&R), and Cylinder. To compare the dosimetric parameters, the cumulative dosevolume histograms (DVHs) were measured. We also compared the doses at 90% of the volume (D 90% ), the volume receiving 100% and 150% of the prescribed dose (V 100% and V 150% ) for the clinical target volume (CTV-HR) and the doses of point A, the dose receiving 0.1 cc and 2 cc of the volume (D 0.1cc and D 2cc ) for the organs-at-risk (OARs). ResultsIn this study, compared with the AcurosBV plans, TG43 plans predicted higher D 90% , V 100% , and V 150% of CTV-HR, dose of point A and D 0.1cc and D 2cc of OARs in three types of applicators. Except D 2cc of sigmoid in T&R and Cylinder applicators, the D 90% , V 100% , and V 150% of CTV-HR; the Dose of point A and the D 0.1cc and D 2cc of bladder, recutum and small bowel exhibited signi cant discrepancies (P > 0.05). The effects of the three types of applicators on the dose distribution were quite different due to the difference of the materials: The dose difference of CTV-HR and OARs was greatest (around 10%) for T&O applicators but only 1%-5% for T&R and Cylinder applicators. ConclusionsThis study demonstrated that AcurosBV was more accurate in calculating the doses in the air cavity and high-density substance than TG43. In the clinical setting, the AcurosBV exhibited different dosimetric distributions in the cervix plans for HDR brachytherapy, especially in treatment planning when using T&O applicators. The AcurosBV algorithm should be considered when using T&O applicators or some other materials with a much higher or lower density (metal or air) than soft tissue. Howevere, If the density is close to the soft tissue, considering AcurosBV algorithm requires more calculation time, TG43 could still be selected when using applicators in clinical.