Beravs K, White D, Sersa I, Demsar F
Jozef Stefan Institute, University of Ljubljana, Slovenia.
Magn Reson Imaging. 1997;15(8):909-15. doi: 10.1016/s0730-725x(97)00038-6.
Current density imaging (CDI) has been shown to be a feasible method to map spatial distribution of electric currents through bone structures and for studying osteoporosis and bone fracture models. For the osteoporosis model, bone sample was moistened in a solution of a sodium salt of ethylendiamintetraacetic acid (EDTA) which causes chemical reaction with hydroxyapatite Ca2+ ions and lowers the mineralisation degree of the solid bone. This enables clear visualisation of conventional magnetic resonance imaging and CDI. Sensitivity of conventional magnetic resonance and CD images of bone was improved by immersing the bone samples into physiological saline containing contrast agent Gd-DTPA prior to imaging. To stimulate effects of bone fracture on electric current conductivity through bone, a transverse cut was made through the bone, and the resulting gap was filled with an insulator. Electric current density images under these conditions have shown that regions of strong conductivity can be distinguished from regions of no conductivity at the site where the insulator restricts electric current. Real bone fracture was imaged as well. To demonstrate influence of electrolyte concentration on electric current spatial distribution, the bone samples were imaged after being immersed in various saline concentrations. The same contrast in current density images was produced with the combinations of higher electrolyte concentrations and lower voltages. Our observations demonstrate the feasibility of the method in mapping current density in bone structures, which could have implications in understanding and monitoring the effects of the electrical stimulation.
电流密度成像（CDI）已被证明是一种可行的方法，可用于绘制电流通过骨骼结构的空间分布，并用于研究骨质疏松症和骨折模型。对于骨质疏松症模型，将骨样本在乙二胺四乙酸（EDTA）钠盐溶液中湿润，该溶液会与羟基磷灰石Ca2+离子发生化学反应并降低固体骨的矿化程度。这使得传统磁共振成像和CDI能够清晰显示。在成像前将骨样本浸入含有造影剂钆喷酸葡胺（Gd-DTPA）的生理盐水中，可提高骨骼的传统磁共振和CD图像的灵敏度。为了刺激骨折对通过骨骼的电流传导性的影响，在骨头上进行横向切割，并在产生的间隙中填充绝缘体。在这些条件下的电流密度图像显示，在绝缘体限制电流的部位，可以区分强导电区域和不导电区域。真实的骨折也进行了成像。为了证明电解质浓度对电流空间分布的影响，将骨样本浸入不同浓度的盐水中后进行成像。较高的电解质浓度和较低的电压组合在电流密度图像中产生了相同的对比度。我们的观察结果证明了该方法在绘制骨骼结构中电流密度方面的可行性，这可能对理解和监测电刺激的效果有影响。
