Whole brain radiotherapy with hippocampal sparing using Varian HyperArc.

The purpose of this work was to evaluate using Varian HyperArc as a planning and treatment solution for whole brain radiotherapy (WBRT) with hippocampal sparing following Radiation Therapy Oncology Group (RTOG) 0933 dosimetric criteria. Ten patients previously treated for intracranial lesions were retrospectively planned for WBRT with hippocampal sparing using HyperArc and a 2-arc coplanar VMAT technique. The whole brain and hippocampus were delineated on fused MRI and CT datasets. The planning target volume (PTV), defined as the whole brain excluding the hippocampal avoidance region, was prescribed 30 Gy in 10 fractions. Plans were evaluated using dosimetric parameters which included the volume of 105% of the prescription dose (V105%) and the maximum dose to the PTV, and the minimum dose to the hippocampus. The planning time, delivery time, and delivery quality assurance (QA) results were also evaluated. Statistical significance was performed between the HyperArc and coplanar VMAT metrics using the Wilcoxon signed-rank test with a significance level of 0.05. All plans met RTOG 0933 dosimetric criteria. HyperArc plans demonstrated significant improvements in PTV dosimetric quality which included a reduced V105% of 6 ± 7% and decreased maximum dose of 1.3 ± 0.3 Gy, compared to coplanar VMAT. Significant OAR sparing was also found for HyperArc plans that included a decreased minimum dose to the hippocampus of 0.3 ± 0.3 Gy. Coplanar VMAT plans resulted in significantly shorter planning and delivery times, compared to HyperArc, by 2.4 minutes and 1.5 minutes, respectively. No significant difference was found between the delivery QA results. This study demonstrated using Varian HyperArc as a planning and treatment solution for WBRT with hippocampal sparing following RTOG 0933 dosimetric criteria. The primary advantages of WBRT with hippocampal sparing using HyperArc, compared to coplanar VMAT, are the gains in OAR sparing and reduced high dose volumes to the PTV.

Investigation of accelerated partial breast patient alignment and treatment with helical tomotherapy unit.

PURPOSE: To determine the precision of megavoltage computed tomography (MVCT)-based alignment of the seroma cavity for patients undergoing partial breast irradiation; and to determine whether accelerated partial breast irradiation (APBI) plans can be generated for TomoTherapy deliveries that meet the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39/Radiation Therapy Oncology Group (RTOG) 0413 protocol guidelines for target coverage and normal tissue dose limitations. METHODS AND MATERIALS: We obtained 50 MVCT images from 10 patients. An interuser study was designed to assess the alignment precision. Using a standard helical and a fixed beam prototype ("topotherapy") optimizer, two APBI plans for each patient were developed. RESULTS: The precision of the MVCT-based seroma cavity alignment was better than 2 mm if averaged over the patient population. Both treatment techniques could be used to generate acceptable APBI plans for patients that fulfilled the recommended NSABP B-39/RTOG-0413 selection criteria. For plans of comparable treatment time, the conformation of the prescription dose to the target was greater for helical deliveries, while the ipsilateral lung dose was significantly reduced for the topotherapy plans. CONCLUSIONS: The inherent volumetric imaging capabilities of a TomoTherapy Hi-Art unit allow for alignment of patients undergoing partial breast irradiation that is determined from the visibility of the seroma cavity on the MVCT image. The precision of the MVCT-based alignment was better than 2 mm (+/-standard deviation) when averaged over the patient population. Using the NSABP B-39/RTOG-0413 guidelines, acceptable APBI treatment plans can be generated using helical- or topotherapy-based delivery techniques.