Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout
Purpose: To date, no universally accepted technique for the evaluation of the overall dosimetric performance of hybrid integrated magnetic resonance imaging (MR) – linear accelerators (linacs) is available. We report on the suitability and reliability of a novel phantom with modular inserts for comb...
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| Format: | Article |
| Language: | English |
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Elsevier
2022-08-01
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| Series: | Zeitschrift für Medizinische Physik |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S093938892200006X |
| _version_ | 1797385312879509504 |
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| author | Lukas Nierer Florian Kamp Michael Reiner Stefanie Corradini Moritz Rabe Olaf Dietrich Katia Parodi Claus Belka Christopher Kurz Guillaume Landry |
| author_facet | Lukas Nierer Florian Kamp Michael Reiner Stefanie Corradini Moritz Rabe Olaf Dietrich Katia Parodi Claus Belka Christopher Kurz Guillaume Landry |
| author_sort | Lukas Nierer |
| collection | DOAJ |
| description | Purpose: To date, no universally accepted technique for the evaluation of the overall dosimetric performance of hybrid integrated magnetic resonance imaging (MR) – linear accelerators (linacs) is available. We report on the suitability and reliability of a novel phantom with modular inserts for combined polymer gel (PG) and ionisation chamber (IC) measurements at a 0.35 T MR-linac. Methods: Three 3D-printed, modular head phantoms, based on real patient anatomy, were used for repeated (2 times) PG irradiations of cranial treatment plans on a 0.35 T MR-linac. The PG readout was performed on two 1.5 T diagnostic MR-scanners to reduce scanning time. The PG dose volumes were normalised to the IC dose (normalised dose N1) and to the median planning target volume dose (normalised dose N2). Linearity of the PG dose response was validated and dose profiles, centres of mass (COM) of the 95% isodoses and dose volume histograms (DVH) were compared between planned and measured dose distributions and a 3D gamma analysis was performed. Results: Dose linearity of the PG was good (R2 > 0.99 for all linear fit functions). High agreement was found between planned and measured dose volumes in the dose profiles and DVHs. The largest dose deviation was found in the intermediate dose region (mean dose deviation 0.2 Gy; 5.6%). A mean COM offset of 1.2 mm indicated high spatial accuracy. Mean 3D gamma passing rates (2%, 2 mm) of 83.3% for N1 and 91.6% for N2 dose distributions were determined. When comparing repeated PG measurements to each other, a mean gamma passing rate of 95.7% was found. Conclusion: The new modular phantom was found practical for use at a 0.35 T MR-linac. In contrast to the high dose region, larger mean deviations were found in the mid dose range. The PG measurements showed high reproducibility. The MR-linac performed well in a non-adaptive setting in terms of spatial and dosimetric accuracy. |
| first_indexed | 2024-03-08T21:52:16Z |
| format | Article |
| id | doaj.art-d19d379d41a64961b52c748c14bd7ccc |
| institution | Directory Open Access Journal |
| issn | 0939-3889 |
| language | English |
| last_indexed | 2024-03-08T21:52:16Z |
| publishDate | 2022-08-01 |
| publisher | Elsevier |
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| series | Zeitschrift für Medizinische Physik |
| spelling | doaj.art-d19d379d41a64961b52c748c14bd7ccc2023-12-20T07:33:15ZengElsevierZeitschrift für Medizinische Physik0939-38892022-08-01323312325Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readoutLukas Nierer0Florian Kamp1Michael Reiner2Stefanie Corradini3Moritz Rabe4Olaf Dietrich5Katia Parodi6Claus Belka7Christopher Kurz8Guillaume Landry9Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany; Corresponding author: Lukas Nierer, Department of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, GermanyDepartment of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany; Department of Radiation Oncology, University Hospital Cologne, Kerpener Str. 62, 50937 Cologne, GermanyDepartment of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, GermanyDepartment of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, GermanyDepartment of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, GermanyDepartment of Radiology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, GermanyDepartment of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, 85748 Garching, GermanyDepartment of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, Germany; German Cancer Consortium (DKTK), partner site Munich, Munich, GermanyDepartment of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, GermanyDepartment of Radiation Oncology, University Hospital, LMU Munich, Marchioninistr. 15, 81377 Munich, GermanyPurpose: To date, no universally accepted technique for the evaluation of the overall dosimetric performance of hybrid integrated magnetic resonance imaging (MR) – linear accelerators (linacs) is available. We report on the suitability and reliability of a novel phantom with modular inserts for combined polymer gel (PG) and ionisation chamber (IC) measurements at a 0.35 T MR-linac. Methods: Three 3D-printed, modular head phantoms, based on real patient anatomy, were used for repeated (2 times) PG irradiations of cranial treatment plans on a 0.35 T MR-linac. The PG readout was performed on two 1.5 T diagnostic MR-scanners to reduce scanning time. The PG dose volumes were normalised to the IC dose (normalised dose N1) and to the median planning target volume dose (normalised dose N2). Linearity of the PG dose response was validated and dose profiles, centres of mass (COM) of the 95% isodoses and dose volume histograms (DVH) were compared between planned and measured dose distributions and a 3D gamma analysis was performed. Results: Dose linearity of the PG was good (R2 > 0.99 for all linear fit functions). High agreement was found between planned and measured dose volumes in the dose profiles and DVHs. The largest dose deviation was found in the intermediate dose region (mean dose deviation 0.2 Gy; 5.6%). A mean COM offset of 1.2 mm indicated high spatial accuracy. Mean 3D gamma passing rates (2%, 2 mm) of 83.3% for N1 and 91.6% for N2 dose distributions were determined. When comparing repeated PG measurements to each other, a mean gamma passing rate of 95.7% was found. Conclusion: The new modular phantom was found practical for use at a 0.35 T MR-linac. In contrast to the high dose region, larger mean deviations were found in the mid dose range. The PG measurements showed high reproducibility. The MR-linac performed well in a non-adaptive setting in terms of spatial and dosimetric accuracy.http://www.sciencedirect.com/science/article/pii/S093938892200006XPolymer gel dosimetryMR-guided radiotherapyMultimodality phantomDosimetric accuracy |
| spellingShingle | Lukas Nierer Florian Kamp Michael Reiner Stefanie Corradini Moritz Rabe Olaf Dietrich Katia Parodi Claus Belka Christopher Kurz Guillaume Landry Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout Zeitschrift für Medizinische Physik Polymer gel dosimetry MR-guided radiotherapy Multimodality phantom Dosimetric accuracy |
| title | Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout |
| title_full | Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout |
| title_fullStr | Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout |
| title_full_unstemmed | Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout |
| title_short | Evaluation of an anthropomorphic ion chamber and 3D gel dosimetry head phantom at a 0.35 T MR-linac using separate 1.5 T MR-scanners for gel readout |
| title_sort | evaluation of an anthropomorphic ion chamber and 3d gel dosimetry head phantom at a 0 35 t mr linac using separate 1 5 t mr scanners for gel readout |
| topic | Polymer gel dosimetry MR-guided radiotherapy Multimodality phantom Dosimetric accuracy |
| url | http://www.sciencedirect.com/science/article/pii/S093938892200006X |
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