Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), INF 280, Heidelberg, Germany.
National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany.
Phys Med Biol. 2021 Feb 3;66(4):045013. doi: 10.1088/1361-6560/abd4b9.
Quality assurance in magnetic resonance (MR)-guided radiotherapy 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 [Formula: see text]- and [Formula: see text]-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 [Formula: see text] and [Formula: see text] at [Formula: see text] 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 [Formula: see text] [Formula: see text] and CT values were derived and employed to produce nine specific soft tissue samples. Experimental [Formula: see text] [Formula: see text] and 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, [Formula: see text] and [Formula: see text] of the produced soft tissue samples agreed very well with predictions based on the derived equations with mean deviations of less than [Formula: see text] 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 [Formula: see text] To conclude, anthropomorphic phantom materials with independently adjustable CT values as well as [Formula: see text] and [Formula: see text] relaxation 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 [Formula: see text] and CT value. Dual-energy CT allows accurate prediction of the carbon ion range in these materials.
磁共振（MR）引导放射治疗中的质量保证缺乏在计算机断层扫描（CT）和 MR 成像中均具有组织等效成像对比的人体模型。在这项研究中，我们开发了具有可单独调节 CT 值以及在三种不同磁场强度的 MR 成像中 [Formula: see text]-和 [Formula: see text]-弛豫时间的体模材料。此外，还比较了它们的实验性碳离子阻止本领比（SPR）与基于单能和双能 CT 的预测值。使用 Ni-DTPA 掺杂琼脂糖凝胶来单独调整 [Formula: see text]和 [Formula: see text]在 [Formula: see text]和 3.0 T 下。通过添加氯化钾（KCl）来改变 CT 值。通过多元线性回归，为确定给定 [Formula: see text] [Formula: see text]和 CT 值的琼脂糖、Ni-DTPA 和 KCl 浓度导出了方程，并将其用于生产 9 种特定的软组织样本。这些软组织样本的实验 [Formula: see text] [Formula: see text]和 CT 值与预测值进行了比较，并且还比较了基于射程测量获得的碳离子 SPR 与基于单能和双能 CT 的预测值。所生产的软组织样本的测量 CT 值、[Formula: see text]和 [Formula: see text]与基于所导出的方程的预测值非常吻合，平均偏差小于 [Formula: see text]虽然单能 CT 高估了软组织样本的实测 SPR，但基于双能 CT 的预测值仅显示出平均 SPR 偏差为 [Formula: see text]总之，开发了具有可独立调节 CT 值以及在三种不同磁场强度下的 [Formula: see text]和 [Formula: see text]弛豫时间的人体模型材料。所导出的方程描述了材料特定的弛豫时间和 CT 值与琼脂糖、Ni-DTPA 和 KCl 浓度以及基于给定 [Formula: see text]和 CT 值的材料化学成分的关系。双能 CT 允许准确预测这些材料中的碳离子射程。
