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We report our experience of performing an extra, earlier physics plan check as recommended by the American Association of Physicists in Medicine Task Group 100 and Task Group 275 reports. We assessed utilization and timing of the extra check as well as the time required in a medium-sized clinic.We retrospectively extracted and analyzed timestamp data from the record and verify system for the quality checklist (QCL) items related to treatment planning and physics "prechecks" for 3487 patients treated at our institution from February 2017 to February 2021. The dosimetry staff was interviewed for their perception of the value and efficacy of the practice.Physics prechecks were requested for 19.0% of plans. The number of requests declined from 43.9% of cases in 2017 to 18.4% in 2018. The introduction of automated plan-check tools and a dosimetrist checklist further contributed to a drop in number of precheck requests to 3.5% in 2019. For patients who received a physics precheck, the treatment planning process was a median 3.6 hours longer compared with those without (P.001). A total of 12.9% of the precheck requests were canceled by the dosimetrist after waiting a median time of 5.3 hours. There was a strong positive correlation (0.899) between a precheck being requested and the time remaining until treatment start. Higher complexity plans and plans with a specific concern (eg, possible collision) were more likely to have a precheck requested.Physics prechecks have become standard practice for certain cases in our clinic. However, the perception in the department was that, as a universal practice, waiting for a precheck was not worth the time saved redoing work on the few cases in which an error was caught. Dosimetrist access to automated checking tools and checklists, which were motivated by the precheck process, contributed to this perception.

We present an example when profile measurement and modeling of an Elekta Agility multileaf collimator (MLC) had a large effect specifically on arc therapy plan quality assurance (QA) results using ArcCheck. ArcCheck absolute dose measurements of these plans were systematically lower than planned by 3–10%. Failing QA results were seen even with unmodulated static and conformal arcs. Furthermore, the effect was found to be dependent on collimator angle, with worse results associated with near‐zero collimator angles. In contrast, step‐and‐shoot QA results were not affected. Changing the beam model to match steeper profile measurements obtained using a different measurement device resolved the problem. This case study demonstrates that conventional gamma index analysis can be sensitive to small profile modeling changes.

Breast-conserving therapy consisting of segmental mastectomy followed by whole-breast irradiation (WBI) has become widely accepted as an alternative to mastectomy as a treatment for women with early-stage breast cancer. Accelerated partial-breast irradiation (APBI) is a shorter, alternative radiation technique for select patients with favorable early-stage breast cancer. We review here the different modalities of APBI delivery and discuss the possible benefits and harms associated with these treatments.

Recent recommendations by the American Association of Physicists in Medicine Task Group 186 emphasize the importance of understanding material properties and their effect on inhomogeneity-corrected dose calculation for brachytherapy. Radiographic contrast is normally injected into breast brachytherapy balloons. In this study, the authors independently estimate properties of contrast solution that were expected to be incorrectly specified in a commercial brachytherapy dose calculation algorithm.The mass density and atomic weight fractions of a clinical formulation of radiographic contrast solution were determined using manufacturers' data. The mass density was verified through measurement and compared with the density obtained by the treatment planning system's CT calibration. The atomic weight fractions were used to determine the photon interaction cross section of the contrast solution for a commercial high-dose-rate (HDR) brachytherapy source and compared with that of muscle.The density of contrast solution was 10% less than that obtained from the CT calibration. The cross section of the contrast solution for the HDR source was 1.2% greater than that of muscle. Both errors could be addressed by overriding the density of the contrast solution in the treatment planning system.The authors estimate the error in mass density and cross section parameters used by a commercial brachytherapy dose calculation algorithm for radiographic contrast used in a clinical breast brachytherapy practice. This approach is adaptable to other clinics seeking to evaluate dose calculation errors and determine appropriate density override values if desired.