Hamid Reza Abbasi

Clinical fluoroscopic fiducial-based registration of the vertebral body in spinal neuronavigation.

We present a system involving a computer-instrumented fluoroscope for the purpose of 3D navigation and guidance using pre-operative diagnostic scans as a reference. The goal of the project is to devise a computer-assisted tool that will improve the accuracy, reduce risk, minimize the invasiveness, and shorten the time it takes to perform a variety of neurosurgical and orthopedic procedures of the spine. For this purpose we propose an apparatus that will track surgical tools and localize them with respect to the patients 3D anatomy and pre-operative 3D diagnostic scans using intraoperative fluoroscopy for in situ registration and embedded fiducials. Preliminary studies have found a fiducial registration error (FRE) of 1.41 mm and a Target Localization Error (TLE) of 0.48 mm. The resulting system leverages equipment already commonly available in the operating room (OR), providing an important new functionality that is free of many current limitations, while keeping costs contained.

Development of fluoroscopic registration in spinal neuronavigation

We present a system involving a computer-instrumented fluoroscope for the purpose of 3D navigation and guidance using pre-operative diagnostic scans as a reference. The goal of the project is to devise a computer-assisted tool that will improve the accuracy, reduce risk, minimize the invasiveness, and shorten the time it takes to perform a variety of neurosurgical and orthopedic procedures of the spine. For this purpose we propose an apparatus that will track surgical tools and localize them with respect to the patients 3D anatomy and pre-operative 3D diagnostic scans using intraoperative fluoroscopy for in situ registration and localization of embedded fiducials. Preliminary studies have found a fiducial registration error (FRE) of 1.41 mm and a Target Localization Error (TLE) of 0.48 mm. The resulting system leverages equipment already commonly available in the operating room (OR), providing an important new functionality that is free of many current limitations, such as the inadequacy of skin fiducials for spinal neuronavigation, while keeping costs contained.

Computerized lateral endoscopic approach to spinal pathologies

Abstract Spinal surgery is often necessary to ease back pain symptoms. Neuronavigation (NN) allows the surgeon to localize the position of his instruments in 3D using pre-operative CT scans registered to intra-operative marker positions in cranial surgeries. However, this tool is unavailable in spinal surgeries for a variety of reasons. For example, because of the spines many degrees of freedom and flexibility, the geometric relationship of the skin to the internal spinal anatomy is not fixed. Guided by the currently available imperfect 2D images, it is difficult for the surgeon to correct a patients spinal anomaly; thus, surgical relief of back pain is sometimes only temporary. The Image Guidance Laboratorys (IGL) goal is to combine the direct optical control of traditional endoscopy with the 3D orientation of NN. This powerful tool requires registration of the patients anatomy to the surgical navigation system using internal landmarks rather than skin markers. Pre-operative CT scans matched with intraoperative fluoroscopic images can overcome the problem of spinal movement in NN registration. The combination of endoscopy with fluoroscopic registration of vertebral bodies in a NN system provides a 3D intra-operative navigational system for spinal neurosurgery to visualize the internal surgical environment from any orientation in real time. The accuracy of this system integration is being evaluated by assessing the success of nucleotomies and marker implantations guided by NN-guided endoscopy.

Expected versus observed error in a computer-aided navigation system for spine surgery

Abstract Error analysis of surgical navigation is extremely important in systems intended for clinical use. Knowledge of the overall clinical accuracy is vital for physicians during the preoperative planning process. Recent results in error analysis give us an idea of the expected impact of fiducial placement on overall clinical error (IEEE Trans. Med. Imaging 17 (1998)). We discuss this impact with respect to an end-to-end system for image-guided spine surgery. We show that fiducial placements have a definite effect on the clinical accuracy of our spine surgery system. Our results agree with the prediction that areas outside of the “bounding box” of fiducials are subject to greater clinical error.

Computerized lateral endoscopic approach to invertebral bodies

Spinal surgery is often necessary to ease back pain symptoms. Neuronavigation (NN) allows the surgeon to localize the position of his instruments in 3D using pre- operative CT scans registered to intra-operative marker positions in cranial surgeries. However, this tool is unavailable in spinal surgeries for a variety of reasons. For example, because of the spines many degrees of freedom and flexibility, the geometric relationship of the skin to the internal spinal anatomy is not fixed. Guided by the currently available imperfect 2D images, it is difficult for the surgeon to correct a patients spinal anomaly; thus surgical relief of back pain is often only temporary. The Image Guidance Laborators (IGL) goal is to combine the direct optical control of traditional endoscopy with the 3D orientation of NN. This powerful tool requires registration of the patients anatomy to the surgical navigation system using internal landmarks rather than skin markers. Pre- operative CT scans matched with intraoperative fluoroscopic images can overcome the problem of spinal movement in NN registration. The combination of endoscopy with fluoroscopic registration of vertebral bodies in a NN system provides a 3D intra-operative navigational system for spinal neurosurgery to visualize the internal surgical environment from any orientation in real time. The accuracy of this system integration is being evaluated by assessing the success of nucleotomies and marker implantations guided by NN-registered endoscopy.

Evaluation of accuracy in frame-based versus fiducial-based registration for stereotaxy in Parkinson's deep electrode implantation

After several years of levodopa treatment, patients with Parkinsons Disease (PD) can develop difficult-to-control motor fluctuations and levodopa-induced dyskinesias (LID). Surgical options for these medically intractable PD patients include deep nucleus lesioning and stimulation. Because it is adjustable and reversible, deep brain stimulations (DBS) is preferable to ablative procedures. Traditionally, frame- based stereotaxy has been used to register these patients during deep electrode implantation. This study investigated the accuracy of the less invasive frameless registration method in 9 patients and found an overall mean error of 1.9mm (range: 1.1mm min, 2.7mm max) with an overall SD of 0.7mm. This error range is not acceptable for the submillimeter precision needed in microelectrode implantation. The lab is currently investing the accuracy of the frameless bone-screw marker method that is still less invasive and cumbersome than the frame-based system.

A Comparative Statistical Error Analysis of Neuronavigation Systems in a Clinical Setting

The use of neuronavigation (NN) in neurosurgery has become ubiquitous. A growing number of neurosurgeons are utilizing NN for a wide variety of purposes, including optimizing the surgical approach (macrosurgery) and locating small areas of interest (microsurgery). The goal of our team is to apply rapid advances in hardware and software technology to the field of NN, challenging and ultimately updating current NN assumptions. To identify possible areas in which new technology may improve the surgical applications of NN, we have assessed the accuracy of neuronavigational measurements in the RadionicsTM and BrainLabTM systems. Using a phantom skull, we measured the accuracy of the navigational systems, taking a total of 2616 measurements. We found that, despite current NN tenets, the six marker count does not yield optimal accuracy in either system, and the spreaded marker setting yields best accuracy in both systems. Placing fewer markers around the region of interest (ROI) minimizes registration error, and active tracking does not necessarily increase accuracy. Comparing the two systems, we also found that accuracy of NN machines differs both overall and in different axes. As researchers continue to apply technological advances to the NN field, an increasing number of currently held tenets will be revised, making NN an even more useful neurosurgical tool.