Jödicke A, Springer T, Böker D-K
Department of Neurosurgery, University Medical Centre, Justus-Liebig-Universität, Giessen, Germany.
Acta Neurochir (Wien). 2004 Nov;146(11):1211-20. doi: 10.1007/s00701-004-0352-y. Epub 2004 Sep 20.
In brain surgery, intraoperative brain deformation is the major source of postimaging inaccuracy of neuronavigation. For intraoperative imaging of brain deformation, we developed a platform for the integration of ultrasound imaging into a navigation system.
A commercially available ultrasound system was linked to a light-emitting-diode- (LED) based neuronavigation system via rigid fixation of a position localiser to the ultrasound probe and ultrasound image transfer into the navigation system via a S-VHS port. Since the position of the ultrasound image co-ordinate system is not readily defined within the navigation reference co-ordinate system (REF CS), a transformation which links both co-ordinate systems has to be defined by a calibration procedure. Calibration of the ultrasound probe within the REF CS was performed via a cross-wire phantom. The phantom target was defined within the navigation co-ordinate system (by pointer under microscopic control) and imaged by ultrasound. Ultrasound presets were optimised (digital beam focusing, gain intensity) to attain a small echoic target for manual target definition. The transformation was derived from 150 ultrasound measures and iteration. Accuracy was calculated as mean linear error (LE; in X(REF), Y(REF), or Z(REF) direction), overall mean LE (linear errors of all axes X(REF) to Z(REF)) and Euclidean error (EE; vectorial distance from the physical target).
Optimised ultrasound presets (8 MHz frequency, digital beam focusing, 20% gain intensity) enabled a low interobserver error (mean: 0.5 mm, SD: 0.28) for target definition within the 2-D ultrasound image. Mean accuracy of pointer-based physical target definition in the REF CS was 0.7 mm (RMSE; SD: 0.23 mm). For navigated ultrasound, the overall mean LE was 0.43 mm (SD: 1.36 mm; 95%CL: 3.13 mm) with a mean EE of 2.26 mm (SD: 0.97 mm; 95%CL: 4.21 mm).
Using a single target cross-wire phantom, a highly accurate integration of ultrasound imaging into neuronavigation was achieved. The phantom accuracy of integration lies within the range of application accuracy of navigation systems and warrants clinical studies.
在脑外科手术中，术中脑形变是神经导航术后成像不准确的主要来源。为了对脑形变进行术中成像，我们开发了一个将超声成像集成到导航系统中的平台。
通过将位置定位器牢固地固定在超声探头上，将市售超声系统与基于发光二极管（LED）的神经导航系统相连，并通过S - VHS端口将超声图像传输到导航系统中。由于超声图像坐标系的位置在导航参考坐标系（REF CS）中不易确定，因此必须通过校准程序定义一个连接两个坐标系的变换。通过十字线模型在REF CS内对超声探头进行校准。在导航坐标系中（通过显微镜控制下的指针）定义模型靶点，并进行超声成像。优化超声预设（数字波束聚焦、增益强度）以获得用于手动定义靶点的小回声靶点。通过150次超声测量和迭代得出变换。准确性计算为平均线性误差（LE；在X(REF)、Y(REF)或Z(REF)方向）、总体平均LE（所有轴X(REF)到Z(REF)的线性误差）和欧几里得误差（EE；与物理靶点的矢量距离）。
优化的超声预设（8 MHz频率、数字波束聚焦、20%增益强度）使得在二维超声图像内定义靶点时观察者间误差较低（平均值：0.5 mm，标准差：0.28）。在REF CS中基于指针的物理靶点定义的平均准确性为0.7 mm（均方根误差；标准差：0.23 mm）。对于导航超声，总体平均LE为0.43 mm（标准差：1.36 mm；95%置信区间：3.13 mm），平均EE为2.26 mm（标准差：0.97 mm；95%置信区间：4.21 mm）。
使用单个靶点十字线模型，实现了超声成像与神经导航的高度精确集成。集成的模型准确性在导航系统的应用准确性范围内，值得进行临床研究。
