# Ultra‐fast dosimetric data collection with a commercial plastic scintillation detector in an MR‐linac

## TL;DR

This study shows that a commercial plastic scintillation detector can quickly and accurately measure radiation doses in an MR-linac, outperforming traditional methods in speed.

## Contribution

The study demonstrates the first ultra-fast dosimetric commissioning using a commercial plastic scintillation detector in an MR-linac.

## Key findings

- All PDD and profile gamma passing rates were 100% at 2%/2 mm criteria.
- Measurement times were 5 to 14 times shorter with the PSD compared to traditional detectors.
- Gamma analysis results were better for smaller fields and at slower movement speeds.

## Abstract

Plastic scintillation detectors (PSD) are widely used for detecting and measuring ionizing radiation. These detectors are versatile, with high efficiency, fast response and the ability to provide real‐time measurements.

Evaluate the suitability of Blue Physics PSD (BP‐PSD) for performing ultra‐fast dosimetric commissioning measurements with high accuracy and precision in a very short time.

Ultra‐fast measurements were performed in water using a BP‐PSD on an Elekta Unity MR‐linac. Percentage depth doses (PDD) and profiles at different depths were measured at two movement velocities, 10 mm/s and 20 mm/s, for field sizes ranging from 10 × 10 cm2 to 1 × 1 cm2. Gamma analysis was conducted to compare these measurements with those obtained during machine commissioning using a PTW Semiflex 3D ionization chamber (for PDD) and a PTW micro‐Diamond detector (for PDD and profiles). Gamma criteria of 2%/2 mm and 1%/1 mm dose difference/distance to agreement were studied, alongside field size, penumbra, and measurement time.

All PDD and profile gamma passing rates were 100% at 2%/2 mm. At the stricter 1%/1 mm criteria, all PDD showed a passing rate above 96.97% for both velocities, with most of the profiles exceeding 95% at 10 mm/s and 90% at 20 mm/s. Gamma analysis results were superior for smaller fields (1 × 1 cm2 and 2 × 2 cm2) and generally better at 10 mm/s. On average, the penumbra measurements obtained with the PSD were greater than those achieved with the micro‐Diamond detector. Measurement times were found to be between 7 and 14 times shorter for PDD, and between 5 and 9 times shorter for profiles at speeds of 10 mm/s and 20 mm/s, respectively.

Ultra‐fast measurements using the Blue Physics PSD are suitable for acquiring dosimetric commissioning data with high accuracy and precision, and can be performed in a much shorter timeframe than with commonly used detectors.