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| Home > Publications database > Development of phantom materials with independently adjustable CT- and MR-contrast at 0.35, 1.5 and 3T. |
| Journal Article | DKFZ-2020-02940 |
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2021
IOP Publ.
Bristol
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Please use a persistent id in citations: doi:10.1088/1361-6560/abd4b9
Abstract: Quality assurance in magnetic resonance (MR)-guided radiotherapy (RT) lacks anthropomorphic phantoms that represent tissue-equivalent imaging contrast in both computed tomography (CT) and MR imaging. In this study, we developed phantom materials with individually adjustable CT value as well as T1- and T2-relaxation times in MR imaging at three different magnetic field strengths. Additionally, their experimental stopping power ratio (SPR) for carbon ions was compared with predictions based on single- and dual-energy CT. Ni-DTPA doped agarose gels were used for individual adjustment of T1and T2at 0.35,1.5 and 3.0 T. The CT value was varied by adding potassium chloride (KCl). By multiple linear regression, equations for the determination of agarose, Ni-DTPA and KCl concentrations for given T1, T2and CT values were derived and employed to produce nine specific soft tissue samples. Experimental T1, T2and CT values of these soft tissue samples were compared with predictions and additionally, carbon ion SPR obtained by range measurements were compared with predictions based on single- and dual-energy CT. The measured CT value, T1and T2of the produced soft tissue samples agreed very well with predictions based on the derived equations with mean deviations of less than 3.5 %. While single-energy CT overestimates the measured SPR of the soft tissue samples, the dual-energy CT-based predictions showed a mean SPR deviation of only (0.2±0.3) %. To conclude, anthropomorphic phantom materials with independently adjustable CT values as well as T1and T2relaxation times at three different magnetic field strengths were developed. The derived equations describe the material specific relaxation times and the CT value in dependence on agarose, Ni-DTPA and KCl concentrations as well as the chemical composition of the materials based on given T1,T2and CT value. Dual-energy CT allows accurate prediction of the carbon ion range in these materials.
Keyword(s): MR-guided radiotherapy (MRgRT) ; end-to-end tests ; magnetic resonance imaging (MRI) and computed tomography (CT) contrast ; phantom materials ; quality assurance
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