A Proton Computed Tomography Demonstrator for Stopping Power Measurements

TL;DR

This paper presents a proton computed tomography demonstrator that measures stopping power directly, aiming to improve treatment planning accuracy in particle therapy by reducing conversion errors from x-ray CT scans.

Contribution

Development and testing of a new pCT system with upgraded hardware, demonstrating direct RSP measurement and initial imaging results in a phantom.

Findings

Achieved RSP measurement accuracy of 0.59%.

RSP resolution within the phantom was 9.3%.

Successfully recorded a 3D tomogram with 80 projections.

Abstract

Particle therapy is an established method to treat deep-seated tumours using accelerator-produced ion beams. For treatment planning, the precise knowledge of the relative stopping power (RSP) within the patient is vital. Conversion errors from x-ray computed tomography (CT) measurements to RSP introduce uncertainties in the applied dose distribution. Using a proton computed tomography (pCT) system to measure the SP directly could potentially increase the accuracy of treatment planning. A pCT demonstrator, consisting of double-sided silicon strip detectors (DSSD) as tracker and plastic scintillator slabs coupled to silicon photomultipliers (SiPM) as a range telescope, was developed. After a significant hardware upgrade of the range telescope, a 3D tomogram of an aluminium stair phantom was recorded at the MedAustron facility in Wiener Neustadt, Austria. In total, 80 projections with 6.5x10^5 primary events were acquired and used for the reconstruction of the RSP distribution in the phantom. After applying a straight-line approximation for the particle path inside the phantom, the most probable value (MPV) of the RSP distribution could be measured with an accuracy of 0.59%. The RSP resolution inside the phantom was only 9.3% due to a limited amount of projections and measured events per projection.