Gebhart Steven C, Jansen E Duco, Galloway Robert L
Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee 37235-1631, USA.
Med Phys. 2005 Jan;32(1):209-20. doi: 10.1118/1.1828672.
Surgical resection remains the treatment of choice for brain tumors with infiltrating margins but is currently limited by visual discrimination between normal and neoplastic marginal tissues during surgery. Imaging modalities such as computed tomography, magnetic resonance, positron emission tomography, and optical techniques can accurately localize tumor margins. We believe coupling the fine resolution of current imaging techniques with the precise cutting of midinfrared lasers through image-guided neurosurgery can greatly enhance tumor margin resection. This paper describes a feasibility study designed to optically track in three-dimensional space the articulated arm delivery of a noncontact ablative laser beam. To enable optical tracking of the laser beam focus, infrared-emitting diodes (IREDs) were attached to a handpiece machined for the distal end of the articulated arm of a surgical carbon dioxide laser. Crosstalk between the ablative laser beam and the tracking diodes was measured. The geometry of the adapted laser handpiece was characterized to track an externally attached passive tip and the laser beam focus. Target localization accuracies were assessed for both instrument points-of-interest and the sources of tracking errors were investigated. Stray infrared laser light did not affect optical tracking accuracy. The mean target registration errors while optically tracking the laser handpiece with a passive tip and the laser beam focus were 1.31+/-0.50 mm and 2.31+/-0.92 mm, respectively, and were equivalent to the errors tracking a 24-IRED pen probe from Northern Digital in a side-by-side comparison. The majority of error during ablation tracking derived from registration accuracy between physical space and the defined space of the ablation phantom and from an inability to freehand align the laser focus with the target in a consistent manner. While their magnitudes depend on spatial details of the tracking setup (e.g., number and distribution of fiducial points, working distance from the camera, etc.), these errors are inherent to any freehand laser surgery.
手术切除仍然是具有浸润性边缘的脑肿瘤的首选治疗方法，但目前在手术过程中，正常边缘组织与肿瘤边缘组织之间的视觉辨别限制了其应用。计算机断层扫描、磁共振成像、正电子发射断层扫描和光学技术等成像方式可以精确地定位肿瘤边缘。我们认为，将当前成像技术的高分辨率与通过图像引导神经外科手术实现的中红外激光精确切割相结合，可以大大提高肿瘤边缘切除率。本文描述了一项可行性研究，旨在在三维空间中光学跟踪非接触式消融激光束的关节臂输送。为了实现对激光束焦点的光学跟踪，将红外发光二极管（IRED）连接到为手术二氧化碳激光关节臂远端加工的手持件上。测量了消融激光束与跟踪二极管之间的串扰。对适配的激光手持件的几何形状进行了表征，以跟踪外部连接的无源尖端和激光束焦点。评估了仪器感兴趣点的目标定位精度，并研究了跟踪误差的来源。杂散红外激光不会影响光学跟踪精度。在用无源尖端光学跟踪激光手持件和激光束焦点时，平均目标配准误差分别为1.31±0.50毫米和2.31±0.92毫米，在并排比较中，这与跟踪北方数字公司的24个IRED笔式探头的误差相当。消融跟踪过程中的大部分误差源于物理空间与消融模型定义空间之间的配准精度，以及无法以一致的方式徒手将激光焦点与目标对齐。虽然这些误差的大小取决于跟踪设置的空间细节（例如，基准点的数量和分布、与相机的工作距离等），但这些误差是任何徒手激光手术所固有的。
