Stabinska Julia, Cronenberg Tom, Wittsack Hans-Jörg, Lanzman Rotem Shlomo, Müller-Lutz Anja
Department of Diagnostic and Interventional Radiology, Medical Faculty, University Dusseldorf, Moorenstr. 5, 40225, Düsseldorf, Germany.
MAGMA. 2017 Oct;30(5):505-516. doi: 10.1007/s10334-017-0625-0. Epub 2017 May 31.
The goal of this study was to quantify CEST related parameters such as chemical exchange rate and fractional concentration of exchanging protons at a clinical 3T scanner. For this purpose, two CEST quantification approaches-the AREX metric (for 'apparent exchange dependent relaxation'), and the AREX-based Ω-plot method were used. In addition, two different pulsed RF irradiation schemes, using Gaussian-shaped and spin-lock pulses, were compared.
Numerical simulations as well as MRI measurements in phantoms were performed. For simulations, the Bloch-McConnell equations were solved using a two-pool exchange model. MR experiments were performed on a clinical 3T MRI scanner using a cylindrical phantom filled with creatine solution at different pH values and different concentrations.
The validity of the Ω-plot method and the AREX approach using spin-lock preparation for determination of the quantitative CEST parameters was demonstrated. Especially promising results were achieved for the Ω-plot method when the spin-lock preparation was employed.
Pulsed CEST at 3T could be used to quantify parameters such as exchange rate constants and concentrations of protons exchanging with free water. In the future this technique might be used to estimate the exchange rates and concentrations of biochemical substances in human tissues in vivo.
本研究的目的是在临床3T扫描仪上对与化学交换饱和转移（CEST）相关的参数进行定量，如化学交换率和交换质子的分数浓度。为此，使用了两种CEST定量方法——AREX指标（“表观交换依赖弛豫”）和基于AREX的Ω图方法。此外，还比较了使用高斯形状脉冲和自旋锁定脉冲的两种不同脉冲射频照射方案。
进行了数值模拟以及体模中的磁共振成像（MRI）测量。对于模拟，使用双池交换模型求解布洛赫-麦康奈尔方程。在临床3T MRI扫描仪上，使用填充有不同pH值和不同浓度肌酸溶液的圆柱形体模进行MR实验。
证明了Ω图方法以及使用自旋锁定准备的AREX方法用于测定定量CEST参数的有效性。当采用自旋锁定准备时，Ω图方法取得了特别有前景的结果。
3T时的脉冲CEST可用于量化诸如交换速率常数和与自由水交换的质子浓度等参数。未来，该技术可能用于估计人体组织中生物化学物质的体内交换速率和浓度。
