Alexander E, Moriarty T M, Kikinis R, Black P, Jolesz F M
Department of Surgery (Neurosurgery), Brigham & Women's Hospital, Dana-Farber Cancer Institute, Boston, Mass., USA.
Stereotact Funct Neurosurg. 1997;68(1-4 Pt 1):10-7. doi: 10.1159/000099896.
We have worked in conjunction with scientists from the General Electric Corporation over 6 years to develop an open-bore MR imaging system (0.5 T) enabling optimal vertical access of surgeon and assistant to the patient, and real-time imaging during major neurosurgical procedures.
The intraoperative MR system (MRT) is located in a specially modified operative suite that combines the features of an MR-imaging suite with a fully functional operating room. An MR-compatible anesthesia machine and patient-monitoring device are located next to the magnet. The position of instruments, platforms and supports may be mapped in the operative field using 3 charge-coupled device video cameras mounted in the overhead support truncheon that follow various light-emitting diodes on the devices (Pixsys). The MR image plane can be defined as the axial, coronal or sagittal views through a point along the vector beneath the Pixsys tripod. A variety of surface coils were designed to take full advantage of full open patient access. The software, implemented by a technologist located outside the MR room, is now equivalent to that available on the commercial 0.5-tesla Signa Advantage system. Development of very robust 3-dimensional software in conjunction with the Surgical Planning Laboratory (SPL) at the Brigham & Women's Hospital is the subject of significant effort. The MRT system has been shown to possess imaging capabilities comparable, or even slightly superior (by 10%), to a conventional 0.5-tesla MR scanner. Two modified liquid-crystal display screens are mounted on the magnet housing for the surgeon to monitor the images during the procedures. Projection into larger screens or the operating microscope is under development.
We have performed 110 neurosurgical cases in MRT as of January 29, 1997, including 47 biopsies, 6 catheter placements, 4 cyst drainages, 47 craniotomies for resection, 3 spinal cases (1 syrinx drainage), and 3 laser tumor ablations.
MRT is especially useful in guiding biopsies and resections near cysts, ventricles and critical vascular structures where preoperative images with framed/frameless techniques would be inadequate to show anatomic changes during the procedure. Real-time images of a biopsy needle within the abnormal area are very useful in cases of subtle pathologic change. More complete resection of infiltrative tumor is readily accomplished. SPL image fusion of SPECT and neurofunctional data (e.g. from magnetic stimulation preoperatively) into the imaging space enables the surgeon to better visualize tumor invasion or neural function in real-time imaging during resection. Imaging of thermal gradients for cryoprobe or laser ablation, and combination with endoscopy and robotics will offer additional benefit in the performance of difficult neurosurgical procedures.
我们与通用电气公司的科学家合作超过6年，研发出一种开放式磁共振成像系统（0.5T），该系统能使外科医生及其助手最佳地垂直接触患者，并在重大神经外科手术过程中进行实时成像。
术中磁共振系统（MRT）位于一个经过特殊改造的手术室中，该手术室兼具磁共振成像室和功能完备的手术室的特点。一台与磁共振兼容的麻醉机和患者监测设备放置在磁体旁边。仪器、平台和支架的位置可通过安装在头顶支撑横杆上的3个电荷耦合器件摄像机在手术区域进行标记，这些摄像机跟踪设备（Pixsys）上的各种发光二极管。磁共振图像平面可通过沿Pixsys三脚架下方矢量上的一点定义为轴向、冠状或矢状视图。设计了多种表面线圈以充分利用完全开放的患者通道。由磁共振室外的技术人员操作的软件，目前等同于商用0.5特斯拉Signa Advantage系统上的软件。与布莱根妇女医院的手术规划实验室（SPL）联合开发非常强大的三维软件是一项重要工作。MRT系统已被证明具有与传统0.5特斯拉磁共振扫描仪相当甚至略优（高10%）的成像能力。在磁体外壳上安装了两个经过改造的液晶显示屏，供外科医生在手术过程中监测图像。投影到更大屏幕或手术显微镜上的工作正在开发中。
截至1997年1月29日，我们已在MRT中进行了110例神经外科手术，包括47例活检、6例导管置入、4例囊肿引流、47例开颅切除术、3例脊柱手术（1例脊髓空洞症引流）和3例激光肿瘤消融术。
MRT在引导囊肿、脑室和关键血管结构附近的活检和切除术方面特别有用，在这些情况下，术前使用框架/无框架技术的图像不足以显示手术过程中的解剖变化。在病理变化细微的情况下，活检针在异常区域内的实时图像非常有用。浸润性肿瘤更容易实现更完整的切除。将SPECT和神经功能数据（如术前磁刺激数据）进行SPL图像融合到成像空间，使外科医生在切除过程中的实时成像中能更好地观察肿瘤浸润或神经功能。对冷冻探头或激光消融的热梯度进行成像，并与内窥镜和机器人技术相结合，将在困难的神经外科手术中带来更多益处。
