Tronnier Helena T, Melchert Uwe, Petersen Dirk, Tronnier Volker M
Department of Medical Engineering, University of Lübeck, Lübeck, Germany.
Stereotact Funct Neurosurg. 2015;93(3):182-9. doi: 10.1159/000375175. Epub 2015 Apr 1.
Cortical epidural stimulation is used for the treatment of different neuropsychiatric disorders such as chronic neuropathic pain, tinnitus, movement disorders, and psychiatric diseases. While preoperative magnetic resonance imaging (MRI) is considered the imaging tool of choice for planning the approach and electrode placement, postoperative MRI is still a contraindication with implanted paddle leads due to the risk of thermal damage or current induction creating seizures or neurological deficits.
In this feasibility in vitro study the temperature changes and induction were determined as well as the artifacts caused by 2 parallel paddle leads (Resume II, Model 3587 A; Medtronic, Minneapolis, Minn., USA), commonly used in clinical practice with and without a pulse generator (Prime Advanced, Model 7489; Medtronic).
An ultrasound gel-filled head phantom with 2 paddle leads mimicking the surgical scenario was used to evaluate temperature changes as well as induced currents in a 1.5- and 3-tesla MR scanner. In addition, 1 patient underwent a 3-tesla MRI with an implanted subdural paddle lead.
Negligible temperature changes were detected with turbo spin echo sequences in the 1.5- and 3-tesla scanner using a head and body coil. Induced voltages up to 6 V were measured. The imaging artifacts in the phantom were well tolerable. The patient's imaging was uneventful under the settings which are accepted for deep brain stimulation imaging.
MRI under the conditions described here seems to be safe with the implants used in this study. In particular, the induced temperature is much lower with paddle compared to conventional leads due to the different electrode design. The induced voltage does not carry any risks. However, these findings cannot automatically be transferred to other implants or other scanning conditions, and further studies are needed. The biomedical companies should be encouraged to develop MR-conditional paddle leads. Also, further research is necessary to study the mechanism of action of cortical stimulation in the future.
皮质硬膜外刺激用于治疗多种神经精神疾病，如慢性神经性疼痛、耳鸣、运动障碍和精神疾病。虽然术前磁共振成像（MRI）被认为是规划手术入路和电极放置的首选成像工具，但术后MRI对于植入的板状电极仍属禁忌，因为存在热损伤风险或电流感应导致癫痫发作或神经功能缺损。
在这项体外可行性研究中，确定了温度变化和感应情况，以及由两根平行的板状电极（Resume II，型号3587 A；美敦力公司，美国明尼苏达州明尼阿波利斯）所引起的伪影，这两根电极在临床实践中常用于有或没有脉冲发生器（Prime Advanced，型号7489；美敦力公司）的情况。
使用一个填充有超声凝胶、带有两根模拟手术场景的板状电极的头部模型，在1.5特斯拉和3特斯拉的磁共振扫描仪中评估温度变化以及感应电流。此外，1例患者植入了硬膜下板状电极后接受了3特斯拉的MRI检查。
在1.5特斯拉和3特斯拉扫描仪中，使用头部和体部线圈的涡轮自旋回波序列检测到的温度变化可忽略不计。测量到的感应电压高达6伏。模型中的成像伪影可良好耐受。在用于深部脑刺激成像的可接受设置下，患者的成像过程顺利。
在本研究中使用的植入物的情况下，此处所述条件下的MRI似乎是安全的。特别是，由于电极设计不同，与传统电极相比，板状电极引起的温度要低得多。感应电压不存在任何风险。然而，这些发现不能自动推广到其他植入物或其他扫描条件，还需要进一步研究。应鼓励生物医学公司开发符合磁共振条件的板状电极。此外，未来还需要进一步研究以探讨皮质刺激的作用机制。
