Medical Physicist-Patient Consultation Enhances the Reproducibility of Treatment Delivery in Radiation Therapy for Breast Cancer: An EPID-Based In Vivo Transit Dosimetry Study

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• Picked for Medical Physics (top studies of the week, 11 October 2026): Physicist‑patient consult improves QA reproducibility, EPID dosimetry

Abstract

PURPOSE: Previous studies have suggested that direct interaction between medical physicists and patients may improve patient understanding of radiation therapy and reduce treatment-related anxiety. However, the potential impact of physicist-patient consultations on the technical reproducibility of radiation therapy delivery has not been extensively investigated. This study evaluates whether a pretreatment consultation with a medical physicist can improve interfraction treatment reproducibility in breast cancer radiation therapy using Electronic Portal Imaging Device (EPID)-based In-Vivo Transit Dosimetry (IVTD). METHODS AND MATERIALS: Breast cancer radiation therapy treatments were delivered using intensity modulated radiation therapy and volumetric modulated arc therapy techniques with surface guided radiation therapy and image guided radiation therapy for patient setup and positioning verification. EPID-based In-Vivo Transit Dosimetry was performed during each treatment fraction. The first treatment fraction was used as a patient-specific reference baseline, and integrated EPID images from subsequent fractions were compared against this baseline using gamma analysis with a 3%/4-mm criterion. A total of 40 patients were included in the analysis. Twenty patients underwent a structured pretreatment consultation with a medical physicist before radiation therapy initiation, whereas 20 patients were treated according to the standard clinical workflow without such consultation. Interfraction reproducibility was assessed by comparing Gamma Passing Rate (GPR) values and setup corrections between the 2 groups. Translational (vertical, longitudinal, lateral) and rotational (pitch, roll, yaw) setup variations were analyzed. Statistical comparisons were performed using the Mann-Whitney U test. RESULTS: Patients who underwent a pretreatment consultation with a medical physicist showed significantly higher GPR values compared with the control group (99.25% vs 96.97%, P = 3.1 × 10⁻⁶). Significant reductions in translational setup variations were observed in the consultation group for vertical (0.24 cm vs 0.31 cm, P = 0.030) and longitudinal shifts (0.17 cm vs 0.22 cm, P = 0.048). Lateral shifts showed a nonsignificant trend toward reduction (P = .116). No statistically significant differences were observed in rotational setup corrections (pitch, roll, yaw). CONCLUSIONS: Pre-treatment consultations between medical physicists and patients may improve the reproducibility of radiation therapy delivery in breast cancer treatments. The consultation group demonstrated significantly improved treatment delivery reproducibility, as evidenced by higher GPRs relative to the first-fraction baseline and reduced translational setup variability.

Abstract as published, via PubMed.