Monomer consumption in MAGIC-type polymer gels in the Bragg-peak of proton beams observed by volume selective 1H MR-spectroscopy (MRS): proof of principle for high resolution MRS-methodology with a sensitive rf-detector

7th International Conference on 3D Radiation Dosimetry

Schmid, A.I.^1,2 ; Laistler, E.^1,2 ; Sieg, J.^1,2 ; Dymerska, B.^1,2,3 ; Wieland, M.^1,2,4 ; Naumann, J.^5 ; Jaekel, O.^5 ; Berg, A.^1,2

Center for Medical Physics and Biomedical Eng., Med. University of Vienna, Vienna, Austria^1

High-Field MR-Centre of Excellence, Medical University of Vienna, Austria^2

Institute of Solid State Physics, Gdansk University of Technology, Poland^3

Institut für Radioonkologie, Sozialmedizinisches Zentrum Ost - Donauspital Wien, Austria^4

Heidelberg Ion Therapy Center (HIT), Heidelberg, Germany^5

关键词: Energetic protons;    Hardware components;    High linear energy transfers;    Methacrylic acids;    Polymerization process;    Proof of principles;    Short measurement time;    Spatial resolution;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/444/1/012096/pdf
DOI  :  10.1088/1742-6596/444/1/012096

来源: IOP

【 摘 要 】

Mono-energetic proton and heavy ion beams for tumour therapy feature high dose gradients laterally and at its penetration depth, characterized by the Bragg-peak. The 3-dimensional dosimetry of such Hadron particle beams poses high demands on the spatial resolution of the imaging methodology and linearity of the polymer gel dose response in a wide dose range and at high linear energy transfer (LET). In almost all polymer gels the Bragg-peak dose response is therefore quenched. Volume selective MR-spectroscopy is in principle capable of delivering information on the polymerization process. We here present the MR-methodology to obtain MR-spectroscopic (MRS) data on the monomer consumption at the very small voxel volumes necessary for resolving e.g. the Bragg-peak area. Using additional hardware components, i.e. a strong gradient system and a very sensitive rf-detector at a high field human 7T scanner, MR-microimaging and MRS with 600 μm depth resolution can be implemented at very short measurement time. The vinyl groups of methacrylic acid in a MAGIC-type polymer gel can be resolved by volume selective MRS. The complete monomer consumption in the Bragg-peak due to polymerization is demonstrated selectively in the Bragg-peak indicating one main reason for Bragg-peak quenching in the investigated polymer gel.