Martel A L, Heid O, Slomczykowski M, Kerslake R, Nolte L P
Department of Medical Physics, University Hospital, Nottingham, U.K.
Comput Aided Surg. 1998;3(1):40-4. doi: 10.1002/(SICI)1097-0150(1998)3:1<40::AID-IGS6>3.0.CO;2-L.
The objective of this research was to determine whether a fast 3-dimensional (3-D) gradient echo magnetic resonance imaging (MRI) sequence could be used to acquire images suitable for image guided surgery of the spine. The main difficulty with MRI is that inhomogeneities in the static magnetic field lead to geometric distortions in the images. We used a very fast 3-D MRI sequence with a wide bandwidth and short echo time (TE) to minimize these distortions. Fiducial markers that could be localized in MRI and computed tomography (CT) images and in physical space were attached to a phantom in order to assess the accuracy of a landmark based registration method. The effect of varying the MRI parameters on image contrast was also investigated. The results demonstrate that the registration can be undertaken with an accuracy of 0.4 mm using the 3-D MRI. This is comparable to the accuracy of 0.3 mm obtained with CT and is a significant improvement over the accuracy of the 2-D MRI techniques (> 1.0 mm). In vivo images demonstrating good contrast between the spine and surrounding soft tissues such as fat, intervertebral disks, and cerebrospinal fluid were obtained. The MRI acquired using the sequence described in this article shows promise for use in computer assisted surgery of the spine.
本研究的目的是确定快速三维（3-D）梯度回波磁共振成像（MRI）序列是否可用于获取适合脊柱图像引导手术的图像。MRI的主要难点在于静磁场中的不均匀性会导致图像出现几何失真。我们使用了具有宽带宽和短回波时间（TE）的非常快速的3-D MRI序列来尽量减少这些失真。将可在MRI和计算机断层扫描（CT）图像以及物理空间中定位的基准标记附着到模型上，以评估基于地标的配准方法的准确性。还研究了改变MRI参数对图像对比度的影响。结果表明，使用3-D MRI进行配准的精度可达0.4毫米。这与CT获得的0.3毫米精度相当，并且相对于二维MRI技术（>1.0毫米）的精度有显著提高。获得了体内图像，显示出脊柱与周围软组织（如脂肪、椎间盘和脑脊液）之间具有良好的对比度。使用本文所述序列获得的MRI显示出在脊柱计算机辅助手术中的应用前景。
