Three dimensional reconstruction of therapeutic carbon ion beams in phantoms using single secondary ion tracks
Carbon ion beam radiotherapy enables a very localised dose deposition. However, even small changes in the patient geometry or positioning errors can significantly distort the dose distribution. A live, non-invasive monitoring system of the beam delivery within the patient is therefore highly desirab...
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| Hauptverfasser: | , , |
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| Dokumenttyp: | Article (Journal) |
| Sprache: | Englisch |
| Veröffentlicht: |
22 May 2017
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| In: |
Physics in medicine and biology
Year: 2017, Jahrgang: 62, Heft: 12 |
| ISSN: | 1361-6560 |
| DOI: | 10.1088/1361-6560/aa6aeb |
| Online-Zugang: | Verlag, Volltext: http://dx.doi.org/10.1088/1361-6560/aa6aeb Verlag, Volltext: http://stacks.iop.org/0031-9155/62/i=12/a=4884 
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| Verfasserangaben: | Anna Merle Reinhart, Claudia Katharina Spindeldreier, Jan Jakubek and Mária Martišíková |
| Zusammenfassung: | Carbon ion beam radiotherapy enables a very localised dose deposition. However, even small changes in the patient geometry or positioning errors can significantly distort the dose distribution. A live, non-invasive monitoring system of the beam delivery within the patient is therefore highly desirable, and could improve patient treatment. We present a novel three-dimensional method for imaging the beam in the irradiated object, exploiting the measured tracks of single secondary ions emerging under irradiation. The secondary particle tracks are detected with a TimePix stack—a set of parallel pixelated semiconductor detectors. We developed a three-dimensional reconstruction algorithm based on maximum likelihood expectation maximization. We demonstrate the applicability of the new method in the irradiation of a cylindrical PMMA phantom of human head size with a carbon ion pencil beam of ##IMG## [http://ej.iop.org/images/0031-9155/62/12/4884/pmbaa6aebieqn001.gif] $226$ MeV u −1 . The beam image in the phantom is reconstructed from a set of nine discrete detector positions between ##IMG## [http://ej.iop.org/images/0031-9155/62/12/4884/pmbaa6aebieqn002.gif] $-80^\circ$ and ##IMG## [http://ej.iop.org/images/0031-9155/62/12/4884/pmbaa6aebieqn003.gif] $50^\circ$ from the beam axis. Furthermore, we demonstrate the potential to visualize inhomogeneities by irradiating a PMMA phantom with an air gap as well as bone and adipose tissue surrogate inserts. We successfully reconstructed a three-dimensional image of the treatment beam in the phantom from single secondary ion tracks. The beam image corresponds well to the beam direction and energy. In addition, cylindrical inhomogeneities with a diameter of ##IMG## [http://ej.iop.org/images/0031-9155/62/12/4884/pmbaa6aebieqn004.gif] $2.85$ cm and density differences down to ##IMG## [http://ej.iop.org/images/0031-9155/62/12/4884/pmbaa6aebieqn005.gif] $0.3$ g cm −3 to the surrounding material are clearly visualized. This novel three-dimensional method to image a therapeutic carbon ion beam in the irradiated object does not interfere with the treatment and requires knowledge only of single secondary ion tracks. Even with detectors with only a small angular coverage, the three-dimensional reconstruction of the fragmentation points presented in this work was found to be feasible. |
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| Beschreibung: | Gesehen am 09.05.2018 |
| Beschreibung: | Online Resource |
| ISSN: | 1361-6560 |
| DOI: | 10.1088/1361-6560/aa6aeb |