Ashok Kumar Neeta, Chauhan Munish, Kandala Sri Kirthi, Sohn Sung-Min, Sadleir Rosalind J
School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona, USA.
Magn Reson Med. 2020 Oct;84(4):2103-2116. doi: 10.1002/mrm.28273. Epub 2020 Apr 16.
Deep brain stimulation electrodes composed of carbon fibers were tested as a means of administering and imaging magnetic resonance electrical impedance tomography (MREIT) currents. Artifacts and heating properties of custom carbon-fiber deep brain stimulation (DBS) electrodes were compared with those produced with standard DBS electrodes.
Electrodes were constructed from multiple strands of 7-μm carbon-fiber stock. The insulated carbon electrodes were matched to DBS electrode diameter and contact areas. Images of DBS and carbon electrodes were collected with and without current flow and were compared in terms of artifact and thermal effects in phantoms or tissue samples in 7T imaging conditions. Effects on magnetic flux density and current density distributions were also assessed.
Carbon electrodes produced magnitude artifacts with smaller FWHM values compared to the magnitude artifacts around DBS electrodes in spin echo and gradient echo imaging protocols. DBS electrodes appeared 269% larger than actual size in gradient echo images, in sharp contrast to the negligible artifact observed in diameter-matched carbon electrodes. As expected, larger temperature changes were observed near DBS electrodes during extended RF excitations compared with carbon electrodes in the same phantom. Magnitudes and distribution of magnetic flux density and current density reconstructions were comparable for carbon and DBS electrodes.
Carbon electrodes may offer a safer, MR-compatible method for administering neuromodulation currents. Use of carbon-fiber electrodes should allow imaging of structures close to electrodes, potentially allowing better targeting, electrode position revision, and the facilitation of functional imaging near electrodes during neuromodulation.
测试由碳纤维组成的深部脑刺激电极作为施加和成像磁共振电阻抗断层成像（MREIT）电流的一种手段。将定制的碳纤维深部脑刺激（DBS）电极的伪影和加热特性与标准DBS电极产生的伪影和加热特性进行比较。
电极由多股7μm碳纤维材料制成。绝缘碳电极与DBS电极的直径和接触面积相匹配。在有电流和无电流情况下采集DBS电极和碳电极的图像，并在7T成像条件下，就体模或组织样本中的伪影和热效应进行比较。还评估了对磁通密度和电流密度分布的影响。
在自旋回波和梯度回波成像协议中，与DBS电极周围的幅度伪影相比，碳电极产生的幅度伪影具有更小的半高宽值。在梯度回波图像中，DBS电极看起来比实际尺寸大269%，这与在直径匹配的碳电极中观察到的可忽略不计的伪影形成鲜明对比。正如预期的那样，与同一体模中的碳电极相比，在长时间射频激发期间，DBS电极附近观察到更大的温度变化。碳电极和DBS电极的磁通密度和电流密度重建的幅度和分布相当。
碳电极可能为施加神经调节电流提供一种更安全、与磁共振兼容的方法。使用碳纤维电极应能对靠近电极的结构进行成像，有可能实现更好的靶点定位、电极位置修正，并便于在神经调节期间对电极附近进行功能成像。
