Abstract
PURPOSE: This retrospective analysis was completed to investigate the use of a model-based dose calculation algorithm (MBDCA) AcurosBV, for use in HDR BT treatments for locally advanced cervical cancer treated with tandem and ovoid applicators with interstitial needles. METHODS: A cohort of 32 patients receiving post-EBRT HDR brachytherapy boost with a prescription dose of 5.5 Gy × 5 fractions to the high-risk clinical target volume (CTV(HR)) were selected for this study. For standard TG43 dose calculation, applicators were manually digitized on the planning images, while for AcurosBV calculations, solid renderings of Titanium Fletcher Suite Delclos (FSD) applicators included in BrachyVision were matched to those used clinically and Ti needles were manually digitized. The dose was recalculated using Varian's AcurosBV 13.5 and dose-to-medium-in-medium (D(m,m)) was reported. EQD2 values for targets and organs at risk were compared between dose calculation formalisms. D(90%) and D(98%) values were reported for the high and intermediate-risk CTVs, and D2 cm3 values were reported for OARs including bladder, rectum, sigmoid, bowel, and vagina. Due to variability within the patient cohort, the dosimetric impact of AcurosBV was investigated corresponding to planning image modality (CT vs. CBCT), presence of Ti needles, and contrast within vaginal balloons used to stabilize implants. AcurosBV showed lower dosimetric values for all plans compared to TG43. RESULTS: The average ± standard deviation of dosimetric reduction in D(90%) was 4.33 ± 0.09% for CTV(HR) and 4.12 ± 0.09% for CTV(IR). The reduction to OARs D2 cm3 was: 4.99 ± 0.15% for bladder, 7.87 ± 0.16% for rectum, 5.79 ± 0.17% for sigmoid, 6.91 ± 0.14% for bowel, and 4.55 ± 0.14% for vagina. CONCLUSIONS: AcurosBV should be utilized for HDR BT GYN cases, treated with tandem and ovoid applicators, with high degrees of heterogeneity and calculated in tandem with TG43.