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ST: Fachverband Strahlen- und Medizinphysik

ST 2: Medical Imaging Concepts

ST 2.5: Talk

Tuesday, March 21, 2023, 18:00–18:15, ZEU/0146

A Two-plane Spectral Proton Radiography System using Silicon Pixel Detectors — •Jana Hohmann, Kevin Kröninger, Isabelle Schilling, Hendrik Speiser, Jens Weingarten, and Jolina Zillner — TU Dortmund University, Germany

To take advantage of the locally high dose in proton therapy the irradiation must be planned precisely. X-Ray CT images are used for this purpose. However, when Hounsfield units are converted to the stopping power of the material, this entails a range uncertainty in the treatment plan, which can lead to unintentional radiation damage in healthy tissue or to missing dose in the tumor.

To avoid this, the stopping power of the protons can be determined via imaging techniques with protons themselves. This could be used to verify and adjust the existing irradiation plan.

One attempt is a two-plane system that is designed to measure the water equivalent thickness (WET) directly, from which the stopping power can be calculated. Two pixelated silicon detectors with an absorber in between track the deposited energies of individual protons. With a reference measurement and the initial proton energy, the WET of a phantom can thus be determined.

The detector design is simulated and optimized in GEANT4. This is then used to determine the 2D WET distribution of a known phantom. The talk summarizes the simulation results and provides a comparison to the single plane method.