Birkfellner, Wolfgang

Bortfeldt, Jonathan

Georg, Dietmar

Gianoli, Chiara

Hu, Guyue

Liubchenko, Grigory

Meyer, Sebastian

Parodi, Katia

Schnürle, Katrin

Würl, Matthias

English

Open Access LMU

  Abstract of an oral presentation at the Joint Conference of the ÖGMP, DGMP and SGSMP, Dreiländertagung der Medizinischen Physik, 19.-22. September 2021, Digital Conference. Published in: Dietmar Georg and Wolfgang Birkfellner (eds.), Abstractband. ISBN: 978-3-948023-16-4   Expansion of a Small-Animal Proton CT Reconstruction Framework  and Studies of Energy Dependence of Relative Stopping Power  G. Hu1, K. Schnürle1, S. Meyer1,2, G. Liubchenko1, J. Bortfeldt1, C. Gianoli1, K. Parodi1, and M. Würl1  1 Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, Garching b. München, Germany  2 Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, USA  Introduction We present a reconstruction framework for pre-clinical proton computed tomography (pCT) and investigate the energy dependence of reconstructed relative (to water) stopping power (RSP) for proton energies relevant for small-animal imaging.  Materials and Methods Proton radiographies were obtained from FLUKA Monte-Carlo (MC) simulations with 75MeV pencil beams using the beamline model of a clinical proton therapy facility. The in-silico detector model consisted of two gas-based tracking detectors, perpendicular to the beam’s axis, registering position and direction of individual protons before entering and after exiting the phantom and a time-projection-chamber-based range telescope for residual range measurement. Cylindrical phantoms of various tissue-mimicking materials with different radii varying from 5mm to 20mm were studied. For each phantom, the RSP image of a central slice with 10mm thickness and 0.2×0.2mm2 pixel size was reconstructed, using 180 projections in 2° increments with 106 initial protons per projection scanning along a 4cm field covering the phantom diameter. A total variation superiorization ordered-subset simultaneous algebraic reconstruction technique (TVS-OS-SART) algorithm was implemented in C++. Proton trajectories within the phantom were estimated using straight-line and cubic-spline path models.  Results Implementation of pCT reconstruction in C++ considerably reduced computation time by a factor of 3 compared to our previous MATLAB-based reconstruction. Mean reconstructed RSP showed minor difference below 0.3% relative to ground truth for all studied materials. A comparison of different cylinder radii has shown that the energy dependence of the RSP is negligible for proton energies relevant for small-animal imaging. Figure 1 shows results for one of the employed materials.  Summary We developed a small-animal pCT reconstruction code faster than our previous MATLAB-based implementation. Energy dependence of the RSP at low proton energies has shown no substantial impact on the imaging performance.  Supported by ERC grant 725539 (SIRMIO).           Appendix                          Figure 1: Mean reconstructed RSP of liver cylinders with varying radius.     

Expansion of a Small-Animal Proton CT Reconstruction Framework and Studies of Energy Dependence of Relative Stopping Power

https://epub.ub.uni-muenchen.de/103670/1/dgmp2021_hu.pdf

Expansion of a Small-Animal Proton CT Reconstruction Framework and Studies of Energy Dependence of Relative Stopping Power

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