Englbrecht, Franz Siegfried

Meyer, Sebastian

Moskal, Ines

Parodi, Katia

Pinto, Marco

Schreiber, Jörg

Würl, Matthias

English

Universität München: Elektronischen Publikationen

 Abstract of a presentation at the 49. Jahrestagung der Deutschen 
Gesellschaft für Medizinische Physik, 19. – 22. September 2018, Nürnberg. 
Published in: Christoph Bert, Michael Wucherer, Frederik B. Laun, 49. 
Jahrestagung Deutsche Gesellschaft für Medizinische Physik und 21. 
Jahrestagung der Deutschen Sektion der International Society for Magnetic 
Resonance in Medicine - Abstractband. ISBN: 978-3-9816002-5-4 
Feasibility study for small-animal proton radiography using passive energy variation and 
a single planar detector 
 
M. Würl1, I. Moskal1, M. Carriço1,2, S. Meyer1, F. Englbrecht1, M. Pinto1, J. Schreiber1, K. Parodi1 
 
1Ludwig-Maximilians-Universität München, Lehrstuhl für Medizinische Physik, Garching b. München, 
Deutschland 
2Universidade de Coimbra, Departamento de Física, Coimbra, Portugal 
 
Introduction 
Image-guidance is of great importance to improve the precision of small-animal proton irradiation 
experiments. We present a method for position verification and direct measurement of the two-
dimensional water-equivalent thickness (WET) distribution of small-animal sized objects, based on 
passive energy variation and a single planar pixel detector (similar to [1]). 
 
Materials & Methods 
An extensive simulation study to examine the feasibility and to explore different beam characteristics 
and setup geometries was performed using the FLUKA Monte-Carlo (MC) code. Fan-beams and mini-
beams at 51 proton energies ranging from 45 to 70MeV were scanned over a 20x20x20mm³ water 
phantom with four different material inserts (3x3x20mm³ each). Energy deposition was scored in a 
model of a commercially available, pixelated CMOS detector (1024x512 pixels, 48μm pixel pitch, 2μm 
sensitive thickness), which was placed at varying distances downstream of the phantom. For each 
detector pixel, signal versus proton energy was recorded and converted to WET by a linear signal 
decomposition [2] using a MC-based lookup-table matrix. 
 
Results 
Due to multiple Coulomb scattering in the phantom and surrounding air, the image quality decreases 
with increasing phantom-detector-distance. A compromise between acceptable spatial resolution 
(<0.5mm) and practicability (geometrical constraints, acquisition time) in a future experimental setup 
was found using fan-beams and a phantom-detector-distance of 1.5cm. With these settings, 
differences between reconstructed and true WET were below 2% for the entire phantom, aside from 
pixels close to material interfaces (fig.1). 
 
Summary 
According to MC simulation results, our proposed method for small-animal proton radiography is 
suitable for fairly accurate WET-determination at a good spatial resolution. Based on these promising 
results, we are aiming to further improve radiographic performance and then extent this method 
towards tomographic imaging. 
 
Supported by ERC grant 725539. 
 
Appendix       
Fig.1: True/Reconstructed WET-
distribution.  
 
Literature 
 [1] Telsemeyer et al: 
PMB57(2012), 7957-7971 
 [2] Meyer et al: 
PMB62(2017), 1096-1112 


Feasibility study for small-animal proton radiography using passive energy variation and a single planar detector

https://epub.ub.uni-muenchen.de/70698/1/Wuerl_Feasibility%20study%20for%20small-animal%20proton%20radiography%20using%20passive%20energy%20variation%20and%20a%20single%20planar%20detector.pdf

Feasibility study for small-animal proton radiography using passive energy variation and a single planar detector

Abstract

Similar works

Full text

Available Versions

Universität München: Elektronischen Publikationen