Experimental verification of clinical dose and LET maps for LET-informed proton therapy
In brief
Proton film detector's linear energy transfer pass rate fell below 50% once
In tests at two proton centers, an optically stimulated luminescence film system measured dose and dose-averaged linear energy transfer; phantom gamma pass rates were 75% to 100% for dose and 45% to 95% for linear energy transfer, with one layer below 50%. The results support benchmarking treatment-planning calculations, but discrepancies at distal, high-transfer edges leave further validation needed before routine commissioning.
- Journal
- Physics in medicine and biology (Q1)
- Published
- 6 November 2026
- Study design
- Unclassified
- Evidence level
- Level 5, Expert Opinion (CEBM 5)
- Authors
- Mads Lykke Jensen, Michelle Van Heerden, Liliana Stolarczyk, Michele Togno, Francesca Albertini, Niels Bassler, et al.
- PMID
- 42994092
- DOI
- 10.1088/1361-6560/aebf1d
Why clinicians should know about it
- Picked for Medical Physics (top studies of the week, 8 November 2026): Experimental phantom verification of proton dose and LET maps
Abstract
Objective:Linear energy transfer (LET)-informed proton therapy has the potential to improve biological treatment planning beyond the conventional, constant-RBE assumption. Its clinical translation, however, requires experimental tools capable of verifying spatially resolved dose and dose-averaged LET (LETD) distributions under clinically relevant conditions. We recently introduced an optically stimulated luminescence (OSL) film-based detector system that simultaneously measures two-dimensional (2D) absorbed dose and LETD. This work provides a first assessment of the system for verifying dose and LETDdistributions from clinical proton therapy plans.

Approach:The system was tested at two proton therapy centers, ranging from simple uniform fields to more complex geometries, including Bragg curve measurements and a clinically realistic anthropomorphic head phantom treatment plan. Measured dose and LETDdistributions were compared against commercial treatment planning system (TPS) calculations and, for selected fields, to external Monte Carlo particle transport simulations due to the absence of traceability of LETD. For non-uniform irradiations, agreement was assessed using gamma analysis with 3%/2 mm and 5%/2 mm criteria for dose and LETD, respectively.

Main results:For uniform fields, measured dose and LETDdistributions generally agreed with TPS and independent Monte Carlo simulations across a range of clinically relevant irradiation conditions. In the Bragg curve measurement, gamma pass rates were 96.6% for dose and 99.7% for LETD, with the largest dose discrepancy observed near the Bragg peak, consistent with a current over-correction of detector quenching in high-LET regions to be improved in future work. In the anthropomorphic phantom, gamma pass rates ranged from 75% to 100% for dose and from 45% to 95% for LETD, with a single layer showing a sub-50% pass rate for LETD. Failing regions were confined to high-dose superior layers for dose and distal-edge, high-LET regions for LETD.

Significance:The presented results support the detector system's use as an experimental benchmarking tool for TPS-calculated dose and LETDmaps. Given this and the system's ability to simultaneously measure 2D dose and LETDmaps with high spatial resolution and minimal field perturbation, the system shows promise for future commissioning workflows for LET-informed proton therapy.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.