Code R F, Harrison J E, McNeill K G
Department of Physics, University of Toronto, Ontario, Canada.
J Bone Miner Res. 1990 Mar;5 Suppl 1:S91-4. doi: 10.1002/jbmr.5650051341.
We have developed a localized noninvasive nuclear magnetic resonance (NMR) method for determining the accumulated bone fluoride content in human index fingers. Using a 27 MHz "split-ring" resonator probe, we measure the total fluoride (F) content within a 6.5 cm length of the distal end of the index finger from a calibrated determination of the intensity of the observed 19F free induction decay (FID) signal. Since fluoride impurities accumulate almost exclusively in bone mineral, the 19F resonance signal is broadened by rigid lattice magnetic dipole-dipole interactions, causing the FID signal to have a relatively short lifetime of approximately 75 microseconds. This short signal lifetime, plus the weakness of the signal strength prevents conventional magnetic resonance imaging equipment from observing the 19F in bone mineral. Nevertheless, we have achieved an in vivo sensitivity of +/- 0.5 mg fluoride in an observation period of 30 min. Assuming an index finger has between 0.25 and 0.5 g of bone calcium, this sensitivity is just sufficient to detect fluorides in the index finger of most adults whose bone fluoride concentration is greater than 2.0 mg fluoride/g calcium (0.8 mg/g ash weight). We are particularly interested in using this new NMR technique to monitor the rate of bone fluoride accumulation in osteoporotic patients receiving therapeutic levels of fluoride in their diets.
我们已经开发出一种局部非侵入性核磁共振（NMR）方法，用于测定人类食指中累积的骨氟含量。使用一个27 MHz的“裂环”谐振器探头，通过对观测到的19F自由感应衰减（FID）信号强度进行校准测定，我们测量食指远端6.5厘米长度内的总氟（F）含量。由于氟杂质几乎只在骨矿物质中累积，19F共振信号因刚性晶格磁偶极 - 偶极相互作用而展宽，导致FID信号的寿命相对较短，约为75微秒。这种短信号寿命加上信号强度较弱，使得传统磁共振成像设备无法观测到骨矿物质中的19F。尽管如此，我们在30分钟的观测期内实现了体内±0.5毫克氟的灵敏度。假设食指含有0.25至0.5克骨钙，这种灵敏度刚好足以检测大多数骨氟浓度大于2.0毫克氟/克钙（0.8毫克/克灰重）的成年人食指中的氟化物。我们特别感兴趣的是使用这种新的NMR技术来监测接受饮食中治疗水平氟化物的骨质疏松患者的骨氟累积速率。
