Quantitative helium-beam radiograph of an anthropomorphic head phantom acquired with thin silicon pixel detectors: comparison to digitally reconstructed radiographs based on X-ray CT modalities
Abstract
For the mitigation of uncertainties in ion-beam radiotherapy, ion-beam radiography promises to be a powerful imaging technique. In contrast to clinically used imaging modalities employing X-rays, it measures water-equivalent thickness (WET), so the integrated relative stopping power (RSP) along the beam direction, directly. This contribution presents a quantitative helium-beam radiograph of an anthropomorphic head phantom and compares it to WET-maps calculated based on X-ray CT modalities.The detection system for ion-beam radiography measurements was developed in-house and consists of thin silicon pixel detectors which track the position and direction of single ions and measure their energy deposition. Firstly, calibration measurements were conducted at the Heidelberg Ion-beam Therapy center (HIT). A phantom made from polymethyl methacrylate (PMMA) with well-known WET values was used to connect those with the energy deposition values measured by the detection system. Subsequently, the calibration curves were applied to an image of an anthropomorphic head phantom acquired with the same setup. In this way, a quantitative helium-beam radiograph of the anthropomorphic head phantom showing WET information could be obtained.
The helium-beam radiograph of the anthropomorphic head phantom reached a mean WET accuracy of (1.076 ± 0.019) % compared to the gold standard based on a digitally reconstructed radiograph (DRR) of an X-ray dual-energy computed tomograph (DECT). However, in many facilities, X-ray single-energy computed tomography (SECT) is used as a standard. As this also deviated from the gold standard by (0.667 ± 0.014) %, the presented imaging method offers a competitive WET accuracy.
Resources
- The presentation file of this talk is not available for download.
- No recordings of this talk are available.