A Multi-Institutional Epid-Based 3D Dose Reconstruction Model in a Virtual Phantom for Standardized Patient QA, Benchmarking and Auditing for Stereotactic Radiosurgery

Authors

• Benjamin Zwan
• Emily Searle
• Cameron Stanton
• Ching-Ling Teng
• Seng Boh Lim
• Andrew Dipuglia
• Richard Popple
• Michael Lovelock
• Ashley Cullen
• Conor K McGarry
• Victoria Robinson
• Sergei Zavgorodni
• Baozhou Sun
• Xiaodong Zhao
• Matthew Schmidt
• Juan-Francisco Calvo-Ortega
• Gemma Warner
• Andrew Cousins
• Michael Barnes
• Peter Greer

Language

English

Publication Date

5-1-2026

Journal

Physics and Imaging in Radiation Oncology

DOI

10.1016/j.phro.2026.100979

PMID

42088602

PMCID

PMC13137042

PubMedCentral® Posted Date

4-25-2026

PubMedCentral® Full Text Version

Post-print

Abstract

Background and purpose: For single-isocentre multi-target (SIMT) stereotactic radiosurgery (SRS), benchmarking, auditing and inter-institutional standardisation of dose verification remain challenging as they require specialized equipment and expertise. This work aims to develop and validate an electronic portal imaging device (EPID)-based technique to determine 3D dose in a virtual spherical phantom which is applicable across institutions for SIMT SRS dose verification.

Materials and methods: Small-field output factors from 11 international centres were measured in-water for the TrueBeam linear accelerator, including jaw-defined and high-definition multi-leaf collimator (MLC) fields from 0.5 × 0.5 to 20 × 20 cm2 and depths from 1.5-20 cm. Matching EPID images were collected at each centre. Utilising the average-centre data, jaw-derived and MLC-derived models were created to convert EPID images to three-dimensional dose in a virtual spherical phantom. Models were validated by comparing EPID-derived dose with film in a three-dimensional-printed spherical phantom for 11 non-coplanar SIMT SRS plans.

Results: Output factors estimated from EPID-to-dose models were within 1.8% (jaw-derived) and 1.0% (MLC-derived) of measured factors at 10 cm depth. For SIMT SRS plans, target dose differences were -0.3 ± 2.4% (mean ± standard deviation) and gamma pass rates were 99.6 ± 1.7% (5%/1.5 mm) for the jaw-derived model compared to film. For the MLC-derived model, -0.2 ± 2.1% dose differences and 99.7 ± 1.2% pass rates (5%/1.5 mm) were achieved.

Conclusions: The EPID-based three-dimensional dose reconstruction method was modelled using multi-institutional data and validated for static and SIMT SRS deliveries. This method requires no specialised equipment and can be applied across institutions for benchmarking, auditing and standardised patient-specific quality assurance for SRS.

Keywords

Stereotactic Radiosurgery, Electronic Portal Imaging Device, Quality Assurance, Dose Reconstruction, Small-field Dosimetry, Auditing

Published Open-Access

yes

Recommended Citation

Zwan, Benjamin; Searle, Emily; Stanton, Cameron; et al., "A Multi-Institutional Epid-Based 3D Dose Reconstruction Model in a Virtual Phantom for Standardized Patient QA, Benchmarking and Auditing for Stereotactic Radiosurgery" (2026). Faculty, Staff and Students Publications. 7838.
https://digitalcommons.library.tmc.edu/baylor_docs/7838