hamid abbasi - Academia.edu (original) (raw)

Papers by hamid abbasi

Research paper thumbnail of Rectifying Reverse Polygonization of Digital Curves for Dominant Point Detection

A polygonal approximation technique using reverse polygonization is presented in this paper. This... more A polygonal approximation technique using reverse polygonization is presented in this paper. This method rectifies the reverse polygonization in previous publications since it captures an efficient approximation independent to all initial points of curves. previous algorithms do not account for this, the algorithm presented in this article is more accurate than previous, specially when specified dominants for deleting are near to each other and follow a particular pattern. Our new approach starts from an initial set of dominant points i.e. break points and dominant points are deleted (one in each iteration) in a way that the maximal perpendicular distance of an approximating straight line from an original curve is minimized. The deletion is performed in a way that optimizes the results of approximation. Leftover points will be considered as dominant points that are not related to the starting point. Finally, a comparative study with former algorithms is provided which prove that under usage of this new technique better approximation results are obtainable.

Research paper thumbnail of Bio-inspired computation: success and challenges of IJBIC

International Journal of Bio-Inspired Computation, 2014

It is now five years since the launch of the International Journal of Bio-Inspired Computation (I... more It is now five years since the launch of the International Journal of Bio-Inspired Computation (IJBIC). At the same time, significant new progress has been made in the area of bio-inspired computation. This review paper summarises the success and achievements of IJBIC in the past five years, and also highlights the challenges and key issues for further research.

Research paper thumbnail of 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 neuros... more 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.

Research paper thumbnail of Expected versus observed error in a computer-aided navigation system for spine surgery

International Congress Series, 2001

Error analysis of surgical navigation is extremely important in systems intended for clinical use... more 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. D

Research paper thumbnail of A Flouroscopic X-Ray Registration Process for Three-Dimensional Surgical Navigation

We describe a system involving a computer-instrumented fluoroscope for the purpose of 3D navigati... more We describe 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 anatomy and pre-operative 3D diagnostic scans using intraoperative fluoroscopy for in situ registration. The resulting system leverages equipment already commonly available in the Operating Room (OR), allowing us to provide important new functionality that is free of many current limitations, while keeping costs contained.

Research paper thumbnail of Development of fluoroscopic registration in spinal neuronavigation

International Congress Series, 2001

Research paper thumbnail of Computerized lateral endoscopic approach to spinal pathologies

International Congress Series, 2001

Spinal surgery is often necessary to ease back pain symptoms. Neuronavigation (NN) allows the sur... more 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 spine's 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 patient's spinal anomaly; thus, surgical relief of back pain is sometimes only temporary. The Image Guidance Laboratory's (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 patient's 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. D

Research paper thumbnail of Bio-Inspired Computation: Success and Challenges of IJBIC

It is now five years since the launch of the International Journal of Bio-Inspired Computation (I... more It is now five years since the launch of the International Journal of Bio-Inspired Computation (IJBIC). At the same time, significant new progress has been made in the area of bio-inspired computation. This review paper summarizes the success and achievements of IJBIC in the past five years, and also highlights the challenges and key issues for further research.

Research paper thumbnail of Rectifying Reverse Polygonization of Digital Curves for Dominant Point Detection

A polygonal approximation technique using reverse polygonization is presented in this paper. This... more A polygonal approximation technique using reverse polygonization is presented in this paper. This method rectifies the reverse polygonization in previous publications since it captures an efficient approximation independent to all initial points of curves. previous algorithms do not account for this, the algorithm presented in this article is more accurate than previous, specially when specified dominants for deleting are near to each other and follow a particular pattern. Our new approach starts from an initial set of dominant points i.e. break points and dominant points are deleted (one in each iteration) in a way that the maximal perpendicular distance of an approximating straight line from an original curve is minimized. The deletion is performed in a way that optimizes the results of approximation. Leftover points will be considered as dominant points that are not related to the starting point. Finally, a comparative study with former algorithms is provided which prove that under usage of this new technique better approximation results are obtainable.

Research paper thumbnail of Bio-inspired computation: success and challenges of IJBIC

International Journal of Bio-Inspired Computation, 2014

It is now five years since the launch of the International Journal of Bio-Inspired Computation (I... more It is now five years since the launch of the International Journal of Bio-Inspired Computation (IJBIC). At the same time, significant new progress has been made in the area of bio-inspired computation. This review paper summarises the success and achievements of IJBIC in the past five years, and also highlights the challenges and key issues for further research.

Research paper thumbnail of 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 neuros... more 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.

Research paper thumbnail of Expected versus observed error in a computer-aided navigation system for spine surgery

International Congress Series, 2001

Error analysis of surgical navigation is extremely important in systems intended for clinical use... more 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. D

Research paper thumbnail of A Flouroscopic X-Ray Registration Process for Three-Dimensional Surgical Navigation

We describe a system involving a computer-instrumented fluoroscope for the purpose of 3D navigati... more We describe 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 anatomy and pre-operative 3D diagnostic scans using intraoperative fluoroscopy for in situ registration. The resulting system leverages equipment already commonly available in the Operating Room (OR), allowing us to provide important new functionality that is free of many current limitations, while keeping costs contained.

Research paper thumbnail of Development of fluoroscopic registration in spinal neuronavigation

International Congress Series, 2001

Research paper thumbnail of Computerized lateral endoscopic approach to spinal pathologies

International Congress Series, 2001

Spinal surgery is often necessary to ease back pain symptoms. Neuronavigation (NN) allows the sur... more 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 spine's 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 patient's spinal anomaly; thus, surgical relief of back pain is sometimes only temporary. The Image Guidance Laboratory's (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 patient's 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. D

Research paper thumbnail of Bio-Inspired Computation: Success and Challenges of IJBIC

It is now five years since the launch of the International Journal of Bio-Inspired Computation (I... more It is now five years since the launch of the International Journal of Bio-Inspired Computation (IJBIC). At the same time, significant new progress has been made in the area of bio-inspired computation. This review paper summarizes the success and achievements of IJBIC in the past five years, and also highlights the challenges and key issues for further research.