Bulanov Petr, Menshchikov Petr, Grimm Johannes A, Lutz Max, Orzada Stephan, Boyd Philip S, Bachert Peter, Ladd Mark E, Korzowski Andreas, Schmitter Sebastian
Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany.
Magn Reson Med. 2025 Oct;94(4):1604-1615. doi: 10.1002/mrm.30557. Epub 2025 May 24.
To explore the feasibility of CEST imaging in the human liver at 7 T with shimming.
CEST MRI was performed on a 7 T whole-body scanner with a parallel transmission (pTx) system in five healthy volunteers. Static pTx ( shimming) was applied to locally maximize the magnitude per input power within a given region of interest (ROI) of approximately 30 mm diameter (ROI). Relaxation-compensated inverse magnetization transfer ratio (MTR) values were quantified for amide protons, guanidino protons, and relayed nuclear Overhauser effect signals based on five-pool Lorentzian fit analysis. MTR values were corrected for B inhomogeneities using an absolute, accurate MR fingerprinting-based mapping technique.
Within the ROI, reliable MTR values could be calculated for an average of 85% of voxels. The mean MTR values and corresponding coefficient of variations across the group are: 0.113 ± 0.009, 8.8% for amide; 0.167 ± 0.010, 6.3% for nuclear Overhauser effect; and 0.079 ± 0.010, 12.9% for guanidino. MTR values exhibit low variation between subjects, as reflected by low coefficient of variations.
In this study, we have demonstrated for the first time the feasibility of acquiring and quantifying relaxation-compensated CEST contrasts in the human liver at ultrahigh field. The application of static pTx effectively eliminates dropouts and allows for accurate CEST contrast quantification within the selected ROI. In addition, the proposed mapping technique shows efficacy for enhanced MTR B corrections in the abdomen.
探讨在7T磁场下通过匀场实现化学交换饱和转移（CEST）成像在人体肝脏中的可行性。
在一台配备并行发射（pTx）系统的7T全身扫描仪上，对5名健康志愿者进行CEST磁共振成像（MRI）检查。应用静态pTx（匀场）在直径约30mm的给定感兴趣区域（ROI）内局部最大化每输入功率的场强。基于五池洛伦兹拟合分析，对酰胺质子、胍基质子和中继核Overhauser效应信号的弛豫补偿反转磁化转移率（MTR）值进行量化。使用基于绝对准确的磁共振指纹图谱的场图绘制技术对MTR值进行磁场不均匀性校正。
在ROI内，平均85%的体素可计算出可靠的MTR值。该组的平均MTR值及其相应的变异系数分别为：酰胺为0.113±0.009，8.8%；核Overhauser效应为0.167±0.010，6.3%；胍基为0.079±0.010，12.9%。MTR值在受试者之间的变异较低，变异系数较低即反映了这一点。
在本研究中，我们首次证明了在超高场下在人体肝脏中获取和量化弛豫补偿CEST对比的可行性。静态pTx的应用有效消除了信号丢失，并允许在选定的ROI内进行准确的CEST对比量化。此外，所提出的场图绘制技术在腹部增强MTR磁场校正方面显示出有效性。
