Department of Radiology, University of Cambridge, Cambridge, United Kingdom.
Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom.
Magn Reson Med. 2020 Oct;84(4):1817-1827. doi: 10.1002/mrm.28238. Epub 2020 Mar 13.
Calibration of hyperpolarized C-MRI is limited by the low signal from endogenous carbon-containing molecules and consequently requires C-enriched external phantoms. This study investigated the feasibility of using either Na-MRI or H-MRI to calibrate the C excitation.
Commercial C-coils were used to estimate the transmit gain and center frequency for C and Na resonances. Simulations of the transmit B profile of a Helmholtz loop were performed. Noise correlation was measured for both nuclei. A retrospective analysis of human data assessing the use of the H resonance to predict [1- C]pyruvate center frequency was also performed. In vivo experiments were undertaken in the lower limbs of 6 pigs following injection of hyperpolarized C-pyruvate.
The difference in center frequencies and transmit gain between tissue Na and [1- C]pyruvate was reproducible, with a mean scale factor of 1.05179 ± 0.00001 and 10.4 ± 0.2 dB, respectively. Utilizing the H water peak, it was possible to retrospectively predict the C-pyruvate center frequency with a standard deviation of only 11 Hz sufficient for spectral-spatial excitation-based studies.
We demonstrate the feasibility of using the Na and H resonances to calibrate the C transmit B using commercially available C-coils. The method provides a simple approach for in vivo calibration and could improve clinical workflow.
由于内源性含碳分子的信号较弱，因此极化 13 C-MRI 的校准受到限制，这就需要使用 13 C 富集的外部 phantom。本研究旨在探讨使用 Na-MRI 或 H-MRI 来校准 13 C 激发的可行性。
使用商用 13 C 线圈来估计 13 C 和 11 Na 共振的发射增益和中心频率。模拟了亥姆霍兹线圈的发射 B 分布。测量了两种核的噪声相关性。还对人体数据进行了回顾性分析，评估了使用 H 共振预测 [1-13 C]丙酮酸中心频率的能力。在注射极化 13 C-丙酮酸后，对 6 头猪的下肢进行了体内实验。
组织 11 Na 和 [1-13 C]丙酮酸的中心频率和发射增益之间的差异具有可重复性，平均标度因子分别为 1.05179±0.00001 和 10.4±0.2 dB。利用 H 水峰，可以回顾性地预测 13 C-丙酮酸的中心频率，其标准偏差仅为 11 Hz，足以满足基于谱-空间激发的研究。
我们证明了使用商用 13 C 线圈通过 11 Na 和 H 共振来校准 13 C 发射 B 的可行性。该方法为体内校准提供了一种简单的方法，并可能改善临床工作流程。
