Zhaowei Jiang

Image-guided insertion of transpedicular screws. A laboratory set-up.

Study design A computer-assisted system allowing precise preoperative planning and real-time intraoperative image localization of surgical instruments is tested in a laboratory setup. Objectives The purpose of this study is to assess the applicability, functionality, and accuracy of this transpedicular spinal fixation technique. Summary of background data Most techniques in transpedicular spinal fixation rely on the identification of predefined targets with the help of anatomic landmarks and on the intraoperative use of image intensifiers. Various studies report considerable screw misplacement rates which may lead to serious clinical sequelae such as permanent nerve damage. Methods The proposed system was tested in an in vitro setup drilling 20 pedicle pilot holes in lumbar vertebrae. The accuracy was assessed using precision cuts through the pedicles and simulation of a 6-mm pedicle screw insertion. Results An ideal screw position was found in 70 of 77 cuts, and in no case was an injury to the pedicular cortex observed. Conclusions The presented technique provides a safe, accurate, and flexible basis for transpedicular screw placement in the spine. This approach should be further evaluated in clinical applications.

Interactive intraoperative localization using an infrared-based system.

We discuss new methods of localizing and treating brain lesions for both the conventional method of a base-ring fixed to the patients skull (referred to as frame-based procedures) and the new method of frameless procedures (no base ring). Frame-based procedures are used for finding a precise instrument position during neurosurgical procedures, such as stereotactic biopsy of deep-seated lesions, placing electrodes for functional stereotaxis or catheters with radioactive seeds for brachytherapy, or even the placement of a stereotactic retractor or endoscope for removal or internal decompression of lesions. In such procedures, the intraoperative image localization of instruments becomes useful as it tracks instruments as they travel through the preplanned trajectory. Additional intraoperative digitization of surgical instruments, e.g., bipolar suction, biopsy forceps, microscope, ultrasound probe, etc, can be achieved during the stereotactic resection of eloquent areas or deep intracranial lesions by adding an infrared-based system. Frameless procedures broaden the range of surgical approaches, image guidance planning, and operative procedures, since no ring is attached to the patients head which might interfere with the surgical approach, and offers logistic advantages in scheduling diagnostic studies. Frameless diagnostic studies employ anatomical markers and/or surface matching techniques for data registration in the computer software surgical preplanning program. This simplifies scheduling of the procedures since the image study does not need to be acquired the same day as surgery. Frameless diagnostic studies allow for the use of more than one type of imaging data for planning and optimization of surgical procedures, and greatly improve patient tolerance and comfort during these procedures and during surgery, as compared with frame-based procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer-assisted neurosurgery system: Wayne state university hardware and software configuration

Computer-assisted neurosurgery uses the latest technological advancements in imaging, computers, mechanics, and electronics to improve the accuracy and reduce the invasiveness and risk of neurosurgical procedures. We describe the Wayne State University, Detroit, Michigan, computer-assisted neurosurgical system with the emphasis on software and discuss the theory guiding the development of this system and its application in real-time position tracking systems. Our system consists of the Neurological Surgery Planning System (NSPS) software which we developed at our medical center and three types of position tracking systems: the Zamorano-Dujovny (Z-D) are digitizer for frame-based procedures, an articulated arm, and an infrared-based digitizer for frameless procedures. The NSPS software is designed to offer neurosurgeons a safe and accurate method to approach intracranial lesions by preoperatively planning a surgical trajectory. Software consisting of the most advanced technologies in computer vision, computer imaging/graphics, and stereotactic numeric analysis forms the core of the system. Capabilities for correlating data from imaging studies to facilitate image reconstruction, image mapping, and three-dimensional (3D) visualization of target volumes enable the neurosurgeon to simulate surgical procedures into a preoperative protocol to be used during surgery, both to follow the preplanned trajectory and to track the position of surgical instruments in real-time on the computer monitor. The tracking systems position and orient the surgical instruments relative to the patients head. With these devices, the display of the surgical instruments together with the virtual images create an excellent intraoperative tool.

Application Accuracy Study of a Semipermanent Fiducial System for Frameless Stereotaxis

The accuracy of a semipermanent fiducial marker system developed at Wayne State University in collaboration with Fisher-Leibinger (Freiburg, Germany) was compared with reference to a standard stereotactic frame (Zamorano-Dujovny Localizing Unit; Fisher-Leibinger). For each patient in our study, 10 semipermanent markers were placed on the skull through a small incision and a pilot hole drilled for the marker; five markers were used for registration, and five were used for comparison. Gadolinium-enhanced magnetic resonance imaging was performed, and, upon registration using both ring and fiducial markers, 184 random points were collected by infrared digitization. All three-dimensional measurements (x, y, z) were converted into distance values correlating each value to the origin by the formula dij = SQRT (xij2 + yij2 + zij2). The mean difference of fiducial coordinates vs. absolute image coordinates was 1.72 +/- 0.42 mm (P = .0001), implying no significant difference. The mean difference in dij of the stereotactic ring coordinates vs. the absolute image coordinates was 3.35 +/- 0.59 mm (P = .00011). The mean difference in the fiducial markers vs. the stereotactic ring coordinates was 2.95 +/- 0.45 mm (P = .0001). All tests were declared significant at alpha = .016. The combination of interactive guidance with semipermanent fiducial markers allows for accurate localization of intracranial targets (as accurate or even more accurate than the stereotactic frame). Semipermanent fiducial markers facilitate the procedure logistically, allow for staged procedures (i.e., at the skull base or in epilepsy), and provide access for combined supra- and infratentorial approaches. We believe that the semipermanent fiducial markers system might represent an important development leading toward widespread use of interactive image guidance in conventional neurosurgery.

Three‐dimensional magnetic resonance angiography in the planning of aneurysm surgery

Standard planning for intracranial aneurysm surgery relies on the surgeons intellectual reconstruction of the three-dimensional (3D) surgical field on the basis of a two-dimensional (2D) imaging modality, biplanar cerebral angiography. This method is relatively imprecise, and it relies on previous experience for optimal results. We describe a stereotactic magnetic resonance angiographic (MRA)-guided method based on computer segmentation techniques for the planning of aneurysm surgery that has the potential of bringing a 3D perspective to the lesion. The method has been evaluated retrospectively on 20 surgical patients in whom the aneurysm orientation and relationship to parent vessels were shown to match presurgical 3D stereotactic display. When it is adapted to frameless interactive surgical navigation, this method may become a useful adjunct in the surgical obliteration of these life-threatening lesions.

The Application Accuracy of the Frameless Implantable Marker System and Analysis of Related Affecting Factors

The purpose of this study was to determine the application accuracy of a new frameless marker system for interactive intraoperative localization of intracranial lesions. The influence of image quality, registration error, repeatability, and marker distribution on the application accuracy were analyzed and compared. A phantom was mounted with the standard Z-D ring and also implanted with frameless marker system, which randomly distributed on the surface. The phantom was scanned as routine with 1 mm and 2 mm sections. The pixel sizes were used 1.18×1.18 and 0.59×0.59. The two systems were tested under different image quality and registration. The target point was digitized and the coordinates were recorded and compared with reference points. The difference between two systems were tested with paired t-test. Image data were loaded into a SUN Workstation and registered with NSPS.4.0 software. The coordinate of each fiducial marker was recorded into a file as the reference. The tip of each semi-invasive fiducial marker was digitized to achieve a frameless transformation matrix, and the special points on the Z-D ring were digitized to achieve a frame-based transformation matrix. The differences from the reference points were used as the deviation from “true point”. The mean square root (RMS) was calculated to show the sum of vectors. The results of 2 mm section group showed that the registration error of frame-based system is 3.42±0.22 mm and the error of the frameless system is 1.01±0.63 mm (P<0.001). The RMS are 2.57±0.54 mm and 1.53±0.65 mm respectively (P<0.001). The RMS of error registration (one point off 5 mm) are 5.01±0.26 mm and 2.23±0.13 mm respective (P=0.003). The results of 1mm section group showed that the RMS are 1.20±0.42 mm and 0.90±0.47 mm respectively (P=0.121). The higher the quality (the thinner scan thickness) of image it is, the better the application accuracy will be (P=0.001 and 0.032 respectively). These preliminary results showed that the frameless semi-invasive fiducial marker system can provide clinical acceptable accurate localization as the frame based surgical localization system did. There is no significant difference between the experimental and clinical results. The higher the quality of image it is, the better the application accuracy will be. But there is no significant difference between 1mm sections and 3 mm sections of MRI images.

Use of Surgical Wands in Neurosurgery

Recent technological developments in neuroimaging and surgical techniques, including the use of interactive image-guided surgical procedures, have opened new frontiers in neurosurgery. Advances in imaging techniques have created the need for more precise navigational assistance, in order to approach image-defined lesions. Several methods that transform coordinates from imaging studies to the surgical field have been developed and used in intraoperative guidance systems.

Advanced Neurosurgical Navigation Using a Robotic Microscope Integrated with an Infrared-Based System

Advanced neuronavigational techniques include the use of interactive image guidance during surgical procedures. Imaging data acquisition, software, and a digitizer device are the minimal requirements. We present our experience using a system in which a microscope was coupled to a robotic holder. Limitations encountered were related to the need to maintain the patient’s head in a fixed position and to easy loss of registration in deep areas. These limitations were overcome by integrating an infrared system that allowed movement of the patient’s head during surgery while tracking the accuracy of intraoperative registration. The optoelectronic integration of these two devices gives a “true” navigational system. The technical details of the system, methodology, and preliminary clinical experience are presented.

Computer-Assisted Insertion of Pedicle Screws

The possible complications of a pedicle screw fixation system include injury to neurologic and vascular structures resulting from inaccurate placement of the instrumentation. In a review of 617 surgical cases in which pedicle screw implants were used, Esses and co-authors reported a overall complication rate of 27.4%. The most common intraoperative problem was unrecognized screw misplacement (5.2%). Fracturing the pedicle during screw insertion and iatrogenic cerebrospinal fluid leak occurred in 4.2% of cases. Such a complication rate is not acceptable in clinical practice. In this paper, we discuss a computer-assisted spine surgery system designed for real-time intraoperative localization of surgical instruments on precaptured images used during surgery. Localization was achieved by combining image-guided stereotaxis with advanced opto-electronic position sensing techniques. The insertion of pedicle screws can be directly monitored by interactive navigation using specially equipped surgical tools. Our preliminary results showed no misplacement of pedicle screw, which have further confirmed the clinical potential of this system.

Influence of different medical images on the application accuracy during image-guided surgery

Application accuracy is a crucial factor for stereotactic surgical localization systems. The different qualities of medical images can produce different influences on the application accuracy. However there are a lot of factors that can have an effect on the application accuracy. In this study, we compared the influences of different section thickness of MRI and CT images on the application accuracy during image-guided surgery. An implantable frameless marker system was used. CT scans were taken using 2 kinds of thickness, 1 and 2 mm, and with 2 resolution 256 X 256, 512 X 512. T1 weighted MRI images were used with 3 kinds of thickness, 1 and 3 and 10mm. The IR tracking systems and the Neurosurgery Planning System software were used to do image registration and intraoperative digitization. The differences among the mechanical measurements, image digitization from the computer and the measurement through the tracking systems were compared. The mechanical measurement was used as the most accurate measurement. A statistical study was used to analyze the results. In the CT group, there was a significant difference between 1mm and 2mm sections. There was also a difference found between the 256 X 256 and 512 X 512 image quality groups. In the MRI group, there was a significant difference between 10mm and 1mm or 3mm sections, but no difference between 1mm and 3mm sections. When compares CT and MRI with 1mm thickness, there was no significant difference. For the evaluation of the application accuracy during image-guided surgery, the quality of the medical image is an important factor to be dealt with. The thickness of section is usually used factor to analyze the influence. It is commonly accepted that the thinner the thickness, the better the application accuracy. However there is a limitation. Our results showed that for CT images the thickness when reduced from 2mm to 1mm can still significantly improve the application accuracy. But in MRI image when the thickness were reduced from 3mm to 1mm, the application accuracy remained the same. These results may reflect the difference of machines producing these medical images. The quality of medical images do have influences on the application accuracy during image guided surgery.