Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomography
Purpose: Proton computed (transmission) tomography (pCT) refers to the process of imaging an object by letting protons pass through it, while measuring their energy after, and their position and (optionally) direction both before and after their traversal through that object. The so far experimental...
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| Format: | Article |
| Language: | English |
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Elsevier
2022-02-01
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| Series: | Zeitschrift für Medizinische Physik |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S0939388920300313 |
| _version_ | 1797385302927474688 |
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| author | Stephan Radonic Roger A. Hälg Uwe Schneider |
| author_facet | Stephan Radonic Roger A. Hälg Uwe Schneider |
| author_sort | Stephan Radonic |
| collection | DOAJ |
| description | Purpose: Proton computed (transmission) tomography (pCT) refers to the process of imaging an object by letting protons pass through it, while measuring their energy after, and their position and (optionally) direction both before and after their traversal through that object. The so far experimental technique has potential to improve treatment planning of proton therapy by enabling the direct acquisition of a proton stopping power map of tissue, thus removing the need to obtain it by converting X-ray CT attenuation data and thereby eliminating uncertainties which arise in the mentioned conversion process. The image reconstruction in pCT requires accurate estimates of the proton trajectories. In experimental pCT detector setups where the direction of the protons is not measured, the air gap between the detector planes and the imaged object worsens the spatial resolution of the image obtained. In this work we determined the mean proton paths and the corresponding spatial uncertainty, taking into account the presence of the air gap. Methods: We used Monte Carlo simulations of radiation transport to systematically investigate the effect of the air gap size between detector and patient on the spatial resolution of proton (ion) computed tomography for protons with an energy of 200 MeV and 250 MeV as well as for helium ions (He-4) with an energy of 798 MeV. For the simulations we used TOPAS which itself is based on Geant4. Results: For all particles, which are detected at the same entrance and exit coordinate, the average ion path and the corresponding standard deviation was computed. From this information, the dependence of the spatial resolution on the air gap size and the angular confusion of the particle beam was inferred. Conclusion: The presence of the airgap does not pose a problem for perfect fan beams. In realistic scenarios, where the initial angular confusion is around 5 mrad and for typical air gap sizes up to 10 cm, using an energy of 200 MeV a spatial resolution of about 1.6 mm can be achieved. Using protons with E = 250 MeV a spatial resolution of about 1.1 mm and using helium ions (He-4) with E = 798 MeV even a spatial resolution below 0.7 mm respectively is attainable. |
| first_indexed | 2024-03-08T21:52:09Z |
| format | Article |
| id | doaj.art-b13d2e1ae56e496ca6de2ba12603bdf1 |
| institution | Directory Open Access Journal |
| issn | 0939-3889 |
| language | English |
| last_indexed | 2024-03-08T21:52:09Z |
| publishDate | 2022-02-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Zeitschrift für Medizinische Physik |
| spelling | doaj.art-b13d2e1ae56e496ca6de2ba12603bdf12023-12-20T07:33:07ZengElsevierZeitschrift für Medizinische Physik0939-38892022-02-01321120128Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomographyStephan Radonic0Roger A. Hälg1Uwe Schneider2Department of Physics, University of Zurich, Zurich, Switzerland; Corresponding author: Stephan Radonic, Radiotherapy Hirslanden, Witellikerstrasse 40, 8032 Zürich, SchweizDepartment of Physics, University of Zurich, Zurich, Switzerland; Radiotherapy Hirslanden AG, Rain 34, Aarau, SwitzerlandDepartment of Physics, University of Zurich, Zurich, Switzerland; Radiotherapy Hirslanden AG, Rain 34, Aarau, SwitzerlandPurpose: Proton computed (transmission) tomography (pCT) refers to the process of imaging an object by letting protons pass through it, while measuring their energy after, and their position and (optionally) direction both before and after their traversal through that object. The so far experimental technique has potential to improve treatment planning of proton therapy by enabling the direct acquisition of a proton stopping power map of tissue, thus removing the need to obtain it by converting X-ray CT attenuation data and thereby eliminating uncertainties which arise in the mentioned conversion process. The image reconstruction in pCT requires accurate estimates of the proton trajectories. In experimental pCT detector setups where the direction of the protons is not measured, the air gap between the detector planes and the imaged object worsens the spatial resolution of the image obtained. In this work we determined the mean proton paths and the corresponding spatial uncertainty, taking into account the presence of the air gap. Methods: We used Monte Carlo simulations of radiation transport to systematically investigate the effect of the air gap size between detector and patient on the spatial resolution of proton (ion) computed tomography for protons with an energy of 200 MeV and 250 MeV as well as for helium ions (He-4) with an energy of 798 MeV. For the simulations we used TOPAS which itself is based on Geant4. Results: For all particles, which are detected at the same entrance and exit coordinate, the average ion path and the corresponding standard deviation was computed. From this information, the dependence of the spatial resolution on the air gap size and the angular confusion of the particle beam was inferred. Conclusion: The presence of the airgap does not pose a problem for perfect fan beams. In realistic scenarios, where the initial angular confusion is around 5 mrad and for typical air gap sizes up to 10 cm, using an energy of 200 MeV a spatial resolution of about 1.6 mm can be achieved. Using protons with E = 250 MeV a spatial resolution of about 1.1 mm and using helium ions (He-4) with E = 798 MeV even a spatial resolution below 0.7 mm respectively is attainable.http://www.sciencedirect.com/science/article/pii/S0939388920300313Proton computed tomographyMonte CarloProton radiographyTOPASComputational physics |
| spellingShingle | Stephan Radonic Roger A. Hälg Uwe Schneider Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomography Zeitschrift für Medizinische Physik Proton computed tomography Monte Carlo Proton radiography TOPAS Computational physics |
| title | Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomography |
| title_full | Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomography |
| title_fullStr | Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomography |
| title_full_unstemmed | Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomography |
| title_short | Investigation of the effect of air gap size on the spatial resolution in proton- and helium radio- and tomography |
| title_sort | investigation of the effect of air gap size on the spatial resolution in proton and helium radio and tomography |
| topic | Proton computed tomography Monte Carlo Proton radiography TOPAS Computational physics |
| url | http://www.sciencedirect.com/science/article/pii/S0939388920300313 |
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