Eine neue Bildgebungstechnik für die Strahlentherapie mit Ionenstrahlen: Die Ionenstrahlbasierte Computertomographie
Zusammenfassung der Projektergebnisse
Ion beams offer favorable interaction properties in matter for high selective radiation therapy, particularly owing to the possibility to concentrate most of the energy deposition in a narrow region – so called Bragg peak - at their end of their range. However, uncertainties in the determination of the beam range in the patient still pose an unsolved challenge for full clinical exploitation of the therapeutic advantages offered by ion beams in clinical practice. A major source of range uncertainty lies in the calibration of X-ray Computed Tomography images of the patient into ion stopping power of tissue relative to water for treatment planning. A possibility to overcome this uncertainty would be to image the patient using the same radiation quality as for therapy, exploiting the fact that the ion stopping power ratio is approximately independent of the energy used for therapy (with the Bragg peak stopped in the tumour) or imaging (with the Bragg peak stopped in a detector beyond the patient). However, to date no commercial solution for transmission ion imaging exists, and most investigations ongoing worldwide are focused on expensive instrumentation tailored to the more scattering proton beams. In contrast, this project investigated the feasibility of a cost-effective solution based on a detector concept originally designed for dosimetry, featuring 61-channels large area parallel plate ionization chambers interleaved with 3mm plastic degraders. When applied to the less scattering carbon ions, the proposed system, in combination with advanced post-processing methods, enabled the achievement of reasonable accuracy in (integrated) stopping power ratio estimations, with relative errors below 1.5%. While in some cases the applied dose levels exceeded the values acceptable for clinical treatment, improvement possibilities of the hardware instrumentation and software data processing were identified, which are expected to allow a further reduction of the imaging dose down to clinically acceptable levels, while retaining comparable accuracy. Hence, this project highlighted challenges but also promises of ion-based transmission imaging as a viable method to eliminate the aforementioned sources of range uncertainty in the current practice of ion beam therapy. In particular, the results of this project build the basis for further ongoing projects and investigations, which might enable in the near future a possible translation to clinical application with carbon ion beams, as well as an extension to imaging with the more scattering lighter ion beams. In this latter effort, the project also indicated the promise of helium ion beams, meanwhile experimentally available at the Heidelberg Ion Beam Therapy Center and receiving increasing interest in the particle therapy community, as a good compromise solution between proton and carbon ion beams for imaging purposes to reduce range uncertainties of ion beam therapy. Parts of the project results with related acknowledgement to the DFG support have been advertised to the general audience and scholars in public lectures.
Projektbezogene Publikationen (Auswahl)
- A method to increase the nominal range resolution of a stack of parallel-plate ionization chambers, Phys Med Biol. 59 (2014) 5501-15
Rinaldi I, Brons S, Jäkel O, Voss B, Parodi K
(Siehe online unter https://doi.org/10.1088/0031-9155/59/18/5501) - Experimental investigations on carbon ion scanning radiography using a range telescope, Phys Med Biol. 59 (2014) 3041-57
Rinaldi I, Brons S, Jäkel O, Voss B, Parodi K
(Siehe online unter https://doi.org/10.1088/0031-9155/59/12/3041) - On the role of ion-based imaging methods in modern ion beam therapy, XIII Mexican Symposium on Medical Physics AIP Conf. Proc. 1626 (2014) 142-146
Magallanes L, Brons S, Tiago M, Takechi M, Voss B, Jäkel O, Rinaldi I, Parodi K
(Siehe online unter https://doi.org/10.1063/1.4901379) - An advanced image processing method to improve the spatial resolution of ion radiographies, Phys Med Biol. 60 (2015) 8525-47
Krah N, Testa M, Brons S, Jäkel O, Parodi K, Voss B, Rinaldi I
(Siehe online unter https://doi.org/10.1088/0031-9155/60/21/8525) - Comparative Monte Carlo study on the performance of integration- and list-mode detector configurations for carbon ion computed tomography, Phys Med Biol. 62 (2017) 1096-1112
Meyer S, Gianoli C, Magallanes L, Kopp B, Tessonnier T, Landry G, Dedes G, Voss B, Parodi K
(Siehe online unter https://doi.org/10.1088/1361-6560/aa5602) - Initial development of goCMC: a GPU-oriented fast cross-platform Monte Carlo engine for carbon ion therapy, Phys Med Biol. 62 (2017) 3682-3699
Qin N, Pinto M, Tian Z, Dedes G, Pompos A, Jiang SB, Parodi K, Jia X
(Siehe online unter https://doi.org/10.1088/1361-6560/aa5d43) - Low material budget floating strip Micromegas for ion transmission radiography, Nucl Instrum Methods Phys Res A845 (2017) 210–214
Bortfeldt J, Biebel O, Flierl B, Hertenberger R, Klitzner F, Lösel Ph, Magallanes L, Müller R, Parodi K, Schlüter T, Voss B, Zibell A
(Siehe online unter https://doi.org/10.1016/j.nima.2016.05.003) - Low-dose ion-based transmission radiography and tomography for optimization of carbon ion-beam therapy, PhD Thesis, LMU Munich, 2017
Lorena Magallanes
