Biomedical subjects

H R Abbasi

Publications and source records attributed to H R Abbasi.

5 recordsLinked to original sources

PubMed2001

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 patient's 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.

Artificial Intelligence↗

PubMed2001

A comparative statistical 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 Radionics and BrainLab systems. Using a phantom skull, we measured how accurate the visualization of a navigational probe's tip was in these systems, taking a total of 2180 measurements. We found that, despite current NN tenets, error is maximal at the six marker count and minimal in the spreaded marker setting; that is, placing less markers around the area of interest maximizes accuracy 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 tool in neurosurgery.

Factor Analysis, Statistical↗

PubMed2001

Quantification of the gravity-dependent change in the C-arm image center for image compensation in fluoroscopic spinal neuronavigation.

In the quest to develop a viable, frameless spinal navigation system, many researchers are utilizing the C-arm fluoroscope. However, there is a significant problem with the C-arm that must be quantified: the gravity-dependent sag effect resulting from the geometry of the C-arm and aggravated by the inequity of weight at each end of the C-arm. This study quantified the C-arm sag effect, giving researchers the protocol and data needed to develop a program that accounts for this distortion. The development of spinal navigation algorithms that account for the C-arm sag effect should produce a more accurate spinal navigation system.

Artifacts↗

PubMed2001

Neuronavigational epilepsy focus mapping.

The localization of a seizure focus for resective surgery often requires invasive monitoring for precise localization of the target as well as structures to avoid. We report on the use of intra-operative surgical navigation to precisely localize and co-register subdural electrodes to regions of know radiographic pathology. Additionally, the navigation system was used to develop intra-operative electrode maps. These maps were subsequently used in the sub-acute recording phase to assign electrographic pathology and function (e.g. speech) to a specific cortical surface anatomy. This permitted for more precise planning of surgery and better assessment of potential risk, based on functional as well as anatomical criterion.

Artificial Intelligence↗

PubMed1999

Telepathology in neurosurgery.

In most tumor cases of neurosurgery, we need to have a rapid section diagnostic of the tumor during the course of surgery. When we have received the results that diagnose the exact dignity of the tumor, we devise the operation strategy for the continuing course of surgery. The tissue sample is sent by taxi to the pathological institute in Heidelberg. It takes approximately 45-60 min until we receive the results by telephone. Many centers are far away from a pathological institute and the patient may need to be re-operated on there. In stereotaxy it is still more important. We need approximately 15-25 specimens during a stereotaxy, so we can be sure we have a sample with some of the tumor tissue present. With direct contact to a pathological institute we could reduce this dramatically. We prepared a methylen blue slide and used a histological microscope with a video camera attached to it and a digitizer interface for digitized pictures. By use of a modem we send the pictures by telephone line to the pathological institute, where they are assessed. We currently have direct contact with a pathologist so they can tell us from which part of the tumor we should send the other histological pictures. The procedure takes about twenty minutes. By using this procedure the distance to the pathological institute is irrelevant. The system costs approximately $10,000, covering the cost mostly of the microscope and the camera (but we already had the microscope) and can be built by anybody with minimal requirements.

Brain Diseases↗