Delivery confirmation of bolus electron conformal therapy combined with intensity modulated x-ray therapy

Abstract

Bolus ECT and mixed beam therapy dose delivery to the phantom were more accurate than IMXT delivery, adding confidence to the use of planning, fabrication, and delivery for bolus ECT tools either alone or as part of mixed beam therapy. The methodology reported in this work could serve as a basis for future standardization of the commissioning of bolus ECT or mixed beam therapy. When applying this technology to patients, it is recommended that an electron dose algorithm more accurate than the pencil beam algorithm, e.g., a Monte Carlo algorithm or analytical transport such as the pencil beam redefinition algorithm, be used for planning to ensure the desired accuracy.

Evaluation of a mixed beam therapy for postmastectomy breast cancer patients: Bolus electron conformal therapy combined with intensity modulated photon radiotherapy and volumetric modulated photon arc therapy

“…For plans without VMAT component, the prescription dose was changed from 40 to 50 Gy for the BECT and supraclavicular IMRT fields to make them clinically comparable. Consistent with previous study, 17 the mixed beam reduced the hot spots within and outside the target at the expense of increased low dose outside PTV. Figures 5-7 show the dose distributions and dose volume histograms (DVHs) for patients CW2 and CW6 from mixed beam therapy.…”

“…Smoothing the machineable wax bolus reduced some of the dose heterogeneities, but not all could be removed because of bolus surface following the curvature of chest wall. Mixing VMAT with BECT + IMRT (1:4) reduced, but did not eliminate dose heterogeneities, as was the case reported previously …”

“…The IMRT beams were optimized to deliver 40 Gy to supraclavicular PTV and limit dose to OARs using the direct machine parameter optimization (DMPO) optimization After the BECT PTV and supraclavicular PTV were covered by their 40 Gy prescription, the VMAT component of the plan was determined using the VMAT planning technique identical to that described previously with the exception it was optimized on top of the initial mixed beam dose distributions. The purpose of the 10 Gy VMAT component was to reduce dose heterogeneities in the mixed beam plan due to the irregular bolus surface, 16,17 the abutting electron and photon beams, and the parallel opposed photon beams in the supraclavicular region.…”

“…Mixing VMAT with BECT + IMRT (1:4) reduced, but did not eliminate dose heterogeneities, as was the case reported previously. 17 The mean PTV evaluation metrics are summarized in Table IV. All of the mixed beam and VMAT treatment plans were deemed clinically acceptable by the radiation oncologist.…”

Accuracy of pencil‐beam redefinition algorithm dose calculations in patient‐like cylindrical phantoms for bolus electron conformal therapy

“…26 With the recent commercial availability of bolus ECT, knowing the accuracy of the PBA and PBRA dose calculations in the presence of bolus is of clinical interest. A recent study of the accuracy of the dose delivery of bolus ECT and mixed beam therapy (intensity-modulated x-ray therapy optimized on top of bolus ECT dose distributions) to chest wall and parotid PTVs embedded in a homogeneous cylindrical phantom by Kavanaugh et al 27 showed for the bolus ECT dose component that the PBA calculations agreed with measured data to within 4% or 2 mm for 98.8% and 97.3% of points for parotid and chest wall plans, respectively. Kavanaugh 28 showed similar accuracy for the PBRA, i.e., dose calculations agreed with measured data to within 4% or 2 mm for 98.9% and 98.7% of points for the same parotid and chest wall plans, respectively.…”