Bortfeldt, Jonathan

Englbrecht, Franz Siegfried

Gianoli, Chiara

Hartmann, Jens

Herault, Joel

Hofverberg, Petter

Meyer, Sebastian

Parodi, Katia

Schnürle, Katrin

Schreiber, Jörg

Vidal, Marie

Würl, Matthias

English

Open Access LMU

Abstract for poster presentation at the Joint Conference of the ÖGMP, DGMP and SGSMP, Dreiländertagung der Medizinischen Physik, September 19-22, 2021, Digital Conference Published in: Abstactband, Joint Conference of the ÖGMP, DGMP & SGSMP Dreiländertagung der Medizinischen Physik, Editors: Univ.-Prof. Dr. DI Dietmar Georg, ao. Univ.-Prof. Dr. Mag. Wolfgang Birkfellner, ISBN: 978-3-948023-16-4   Development of scatter correction for integration mode proton imaging for a small animal irradiation platform  Schnürle, K.1, Bortfeldt, J.1, Englbrecht, F. S.1, Gianoli, C.1, Hartmann,  J.1, Hofverberg, P.5 , Meyer, S.1,3, Vidal, M.2, Hérault, J.2 , Schreiber, J.1, Parodi, K.1 and Würl, M.1  1Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, Garching, Germany 2 Centre Antoine-Lacassagne, Nice, France  3Department of Radiology, University of Pennsylvania, Philadelphia, United States  Introduction A novel system for pre-clinical proton therapy studies foresees proton imaging for set-up and accurate treatment planning. In integration mode, imaging at modern synchrocyclotron-based proton therapy centers with high instantaneous particle flux is possible. Commercially available detectors, such as large-area CMOS sensors allow the determination of the object’s water-equivalent thickness (WET). However, image quality is strongly affected by multiple Coulomb scattering. We present experimental results and methods for proton scatter correction. Materials & Methods Image contrast is achieved by recording the proton energy deposition in the detector pixels for several incoming beam energies and a signal decomposition method that retrieves the WET. A single planar 114x65mm2 CMOS sensor (49.5μm pixel pitch) behind the imaged object was used. The 65MeV beam at Centre Antoine-Lacassagne (Nice, France) was passively degraded to produce probing energies suitable for small-animal sized objects. To assess WET accuracy, a micro-CT calibration phantom with 10 inserts of tissue-mimicking materials was imaged (see Figure 1). The phantom-to-detector distance was 0.3, 1.3 and 3.3cm. Several methods (Monte Carlo-based and analytical) for proton scatter correction were investigated, some using a CBCT image of the phantom as prior knowledge. Results The average relative WET error compared to ground truth was <1% for 0.3cm spacing and <2% for 1.3cm. For the worst case of 3.3cm distance, preliminary results showed that WET relative error was improved from 30% to only 3% using scatter correction. Spatial resolution was better than 0.2mm, when scatter correction is applied. Summary A pixelated CMOS detector and post-processing methods enable proton radiographic imaging for small-animal-sized objects with reasonable WET accuracy and excellent spatial resolution by exploiting prior knowledge.  Supported by ERC. 

Development of scatter correction for integration mode proton imaging for a small animal irradiation platform

https://epub.ub.uni-muenchen.de/92774/1/KS_Abstract_DGMP2021_LMU.pdf

Development of scatter correction for integration mode proton imaging for a small animal irradiation platform

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