Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

1 Publication

Improved accuracy of prompt-gamma-based range verification system enabling validation of CT-based stopping-power prediction

Berthold, J.; Khamfongkhruea, C.; Petzoldt, J.; Thiele, J.; Hölscher, T.; Wohlfahrt, P.; Pausch, G.; Janssens, G.; Smeets, J.; Richter, C.



To improve the accuracy of range verification with prompt-gamma-ray imaging (PGI), enabling the validation of CT-based stopping-power prediction in patients.
Material & Methods:
A PGI-slit-camera system was modified to enhance its positioning accuracy, now using a floor-based docking station. The camera position is calibrated with orthogonal X-rays and its reproducibility was validated with X-ray measurements at two different days with ten repositioning iterations each. To determine the PGI simulation accuracy, the camera position derived with the X-Ray system and PGI-based range shift determination in a PMMA phantom (measured vs. simulated PGI profiles) was correlated.
Subsequently, the PGI system was clinically applied to monitor absolute proton ranges for a 1.5Gy field during eight fractions of a hypo-fractionated prostate-cancer treatment using pencil beam scanning (Fig.1). For all monitored fractions, in-room control CT scans were acquired in treatment position, enabling PGI-based range analysis for the actual patient anatomy.
The reproducibility of the camera position in beam direction was ±0.55mm (1σ) over different days. A 1.1mm offset in absolute range determination was found. It can be directly identified as simulation accuracy and is corrected in subsequent clinical application. The overall PGI range measurement uncertainty of about 2mm (averaging over multiple spots for global-shift determination) is well below the range prediction uncertainty (3.5%∙Range+2mm). Evaluation of the clinical slit-camera application and the verification of the applied stopping-power prediction using dual-energy CT is ongoing.
The accuracy of PGI-based range verification was improved to enable the verification of CT-based stopping-power prediction in patients, potentially allowing for a future reduction of currently used range uncertainties.

  • Lecture (Conference)
    PTCOG58 - 58th Annual Conference of the Particle Therapy Co-operative Group, 10.-15.06.2019, Manchester, Großbritannien


Years: 2023 2022 2021 2020 2019 2018 2017 2016 2015