Linz Peter, Santoro Davide, Renz Wolfgang, Rieger Jan, Ruehle Anjuli, Ruff Jan, Deimling Michael, Rakova Natalia, Muller Dominik N, Luft Friedrich C, Titze Jens, Niendorf Thoralf
Interdisciplinary Center for Clinical Research, Nikolaus-Fiebiger-Center for Molecular Medicine, Friedrich-Alexander-University Erlangen-Nürnberg, Germany.
NMR Biomed. 2015 Jan;28(1):54-62. doi: 10.1002/nbm.3224. Epub 2014 Oct 18.
Skin sodium (Na(+) ) storage, as a physiologically important regulatory mechanism for blood pressure, volume regulation and, indeed, survival, has recently been rediscovered. This has prompted the development of MRI methods to assess Na(+) storage in humans ((23) Na MRI) at 3.0 T. This work examines the feasibility of high in-plane spatial resolution (23) Na MRI in skin at 7.0 T. A two-channel transceiver radiofrequency (RF) coil array tailored for skin MRI at 7.0 T (f = 78.5 MHz) is proposed. Specific absorption rate (SAR) simulations and a thorough assessment of RF power deposition were performed to meet the safety requirements. Human skin was examined in an in vivo feasibility study using two-dimensional gradient echo imaging. Normal male adult volunteers (n = 17; mean ± standard deviation, 46 ± 18 years; range, 20-79 years) were investigated. Transverse slices of the calf were imaged with (23) Na MRI using a high in-plane resolution of 0.9 × 0.9 mm(2) . Skin Na(+) content was determined using external agarose standards covering a physiological range of Na(+) concentrations. To assess the intra-subject reproducibility, each volunteer was examined three to five times with each session including a 5-min walk and repositioning/preparation of the subject. The age dependence of skin Na(+) content was investigated. The (23) Na RF coil provides improved sensitivity within a range of 1 cm from its surface versus a volume RF coil which facilitates high in-plane spatial resolution imaging of human skin. Intra-subject variability of human skin Na(+) content in the volunteer population was <10.3%. An age-dependent increase in skin Na(+) content was observed (r = 0.78). The assignment of Na(+) stores with (23) Na MRI techniques could be improved at 7.0 T compared with current 3.0 T technology. The benefits of such improvements may have the potential to aid basic research and clinical applications designed to unlock questions regarding the Na(+) balance and Na(+) storage function of skin.
皮肤钠（Na⁺）储存作为一种对血压、容量调节乃至生存具有重要生理意义的调节机制，最近被重新发现。这促使了磁共振成像（MRI）方法的发展，以在3.0 T场强下评估人体的Na⁺储存情况（（²³）Na MRI）。本研究探讨了在7.0 T场强下进行高平面空间分辨率的皮肤（²³）Na MRI的可行性。提出了一种为7.0 T场强（f = 78.5 MHz）的皮肤MRI量身定制的双通道收发射频（RF）线圈阵列。进行了比吸收率（SAR）模拟和对RF功率沉积的全面评估，以满足安全要求。在一项体内可行性研究中，使用二维梯度回波成像对人体皮肤进行了检查。研究了正常成年男性志愿者（n = 17；平均±标准差，46 ± 18岁；范围，20 - 79岁）。使用0.9×0.9 mm²的高平面分辨率，通过（²³）Na MRI对小腿的横向切片进行成像。使用覆盖Na⁺浓度生理范围的外部琼脂糖标准物测定皮肤Na⁺含量。为了评估受试者内的可重复性，每位志愿者接受了三到五次检查，每次检查包括5分钟的步行以及受试者的重新定位/准备。研究了皮肤Na⁺含量的年龄依赖性。与体部RF线圈相比，（²³）Na RF线圈在其表面1 cm范围内提供了更高的灵敏度，这有利于对人体皮肤进行高平面空间分辨率成像。志愿者群体中人体皮肤Na⁺含量的受试者内变异性<10.3%。观察到皮肤Na⁺含量随年龄增加（r = 0.78）。与当前的3.0 T技术相比，在7.0 T场强下使用（²³）Na MRI技术对Na⁺储存的定位可以得到改善。这些改进的益处可能有助于基础研究和临床应用，以解决有关皮肤Na⁺平衡和Na⁺储存功能的问题。
