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Showing papers presented at "Computer Assisted Radiology and Surgery in 2003"


Proceedings Article
01 Jan 2003
TL;DR: A method is presented that allows the two aspects of measurement accuracy to be disentangled, so that the resultant trueness properly represents the systematic, non-reducible part of the measurement error, and the resultant precision (or repeatability) represents only the statistical, reducible part.
Abstract: Electromagnetic tracking systems have found increasing use in medical applications during the last few years. As with most non-trivial spatial measurement systems, the complex determination of positions and orientations from their underlying raw sensor measurements results in complicated, non-uniform error distributions over the specified measurement volume. This makes it difficult to unambiguously determine accuracy and performance assessments that allow users to judge the suitability of these systems for their particular needs. Various assessment protocols generally emphasize different measurement aspects that typically arise in clinical use. This can easily lead to inconclusive or even contradictory conclusions. We examine some of the major issues involved and discuss three useful calibration protocols. The measurement accuracy of a system can be described in terms of its 'trueness' and its 'precision'. Often, the two are strongly coupled and cannot be easily determined independently. We present a method that allows the two to be disentangled, so that the resultant trueness properly represents the systematic, non-reducible part of the measurement error, and the resultant precision (or repeatability) represents only the statistical, reducible part. Although the discussion is given largely within the context of electromagnetic tracking systems, many of the results are applicable to measurement systems in general.

177 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: An MR compatible ambidextrous robot capable of both microneurosurgery and stereotaxy and seamless integration of robotics with iMRI will further revolutionize neurosurgery.
Abstract: Introduction: Technologies such as microscopy have pushed surgeons to the limits of their dexterity and endurance. Robotic advances such as tremor filtration and motion scaling permit maximal use of magnification, and enable precise, tremor-free tool manipulation during microsurgery. To our knowledge, however, no such device exists for image-guided, ambidextrous microneurosurgery, prompting us to develop our own system. Methods: We approached a company with exceptional experience in space robotics to design and construct an appropriate system. A systematic and structured approached was followed for the design of neuroArm. Engineers studied the operating room environment with the assistance of surgeons and nursing staff. A preliminary design was developed, and subsequently evaluated by surgical staff. Selected materials were tested at 3.0 T to ensure MR compatibility and performance characteristics of the robot actuators and encoders were evaluated. Results: We have developed an MR compatible ambidextrous robot capable of both microneurosurgery and stereotaxy. The design is based on a SCARA configuration and has 8-DOF (including tool actuation). The end-effector is designed to interface with standard neurosurgical tools and is equipped with a 3-DOF optical force sensor for haptic feedback. Comprehensive testing of materials was conducted in a 3-T magnet to ensure compatibility. Breadboard testing results suggest a tool tip resolution of 30 μm. Discussion: A systematic approach has been applied to the development of a unique and dexterous neurosurgical robot. The system promises to enhance surgical performance, reduce fatigue, and improve surgical outcomes. This seamless integration of robotics with iMRI will further revolutionize neurosurgery.

92 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: Two novel approaches for segmentation of the lung tissues from the surrounding structures in the chest cavity, and detection of the abnormalities in the lungs tissues are presented.
Abstract: This research aims at developing a fully automatic Computer-Assisted Diagnosis (CAD) system for lung cancer screening using chest spiral CT scans. This paper presents two novel approaches for segmentation of the lung tissues from the surrounding structures in the chest cavity, and detection of the abnormalities in the lung tissues. The segmentation algorithm is hierarchical. The first step is to isolate the background from the chest cavity. The second step is to isolate the lungs from the surrounding structures (e.g., ribs, liver, and other organs that may appear in chest CT scans) by using Gibbs–Markov Random Field (GMRF). The third step is to isolate the abnormality (lung nodules), arteries, vines, bronchi, and bronchioles from the normal tissues. Finally, the abnormalities in the lungs are detected by using adaptive template matching; its parameters (mean, variance…) are estimated from the given data. In order to increase the speed of detecting lung nodules, we use genetic algorithms (GAs) to determine the target position in the observed image and to select an adequate template image from several reference patterns.

58 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: A technique that combines visualization with haptic rendering to provide real-time assistance to medical gestures is presented, and a system that provides haptic feedback to the surgeon using patient specific data is developed.
Abstract: The VRAI group at EPFL is conducting research in the fields of virtual reality and haptics (force-feedback) for medical applications. In particular, we have developed visualization techniques for medical images from various sources, and a high-performance haptic interface. In this paper, we present a technique that combines visualization with haptic rendering to provide real-time assistance to medical gestures. To demonstrate this technique, we have developed the BiopsyNavigator, a system that provides haptic feedback to the surgeon using patient specific data. Before the biopsy, it provides the surgeon with the ability to simulate the intervention. During the biopsy, haptic feedback is used to first help the surgeon to find the target and to define the optimal trajectory, then to physically guide the surgical gesture along the chosen path. Finally, haptic information is used to indicate that the target has been reached. Future developments will include real-time update of the patient model from various sources, including C-arm mounted CT and ultrasonic probes.

53 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: A new technique to measure the overall application accuracy of image-guided stereotactic systems has been used to measureThe Pathfinder neurosurgical robot, which uses a robot-mounted camera to triangulate fiducial skin markers, virtually eliminating line-of-sight problems experienced by other optical localisation methods.
Abstract: We have developed a new technique to measure the overall application accuracy of image-guided stereotactic systems. It has been used to measure the accuracy of the Pathfinder neurosurgical robot, which uses a robot-mounted camera to triangulate fiducial skin markers, virtually eliminating line-of-sight problems experienced by other optical localisation methods. A phantom consisting of plastic spheres on stalks was used. The targets are the centre of the spheres. Points on a sphere's surface were automatically selected on CT images, from which the centre of the sphere was calculated in image space to greater precision than the CT voxel dimensions. A depth gauge was attached to Pathfinder in place of a biopsy needle and driven to the target as defined on CT. Pathfinder then moved to several points over the sphere, moving perpendicular to the trajectory in a grid pattern. By considering the depth gauge reading, 3D points on the sphere's surface were measured in robot space and the centre of the sphere was found. The difference between the actual and planned targets yields the overall accuracy. Preliminary experiments show that the application accuracy of Pathfinder is 2.7 mm. Further calibrations of the robot are expected to improve this value significantly.

48 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: An evaluation of three Hessian-based filters for enhancement of the central axis of coronary arteries in multi-detector CT images acquired with contrast injection found that these filters analyze the main modes of 2nd-order variation in image intensity to determine the type of local structure present in the image.
Abstract: This work describes an evaluation of three Hessian-based filters for enhancement of the central axis of coronary arteries in multi-detector CT images acquired with contrast injection. These filters analyze the main modes of 2nd-order variation in image intensity to determine the type of local structure present in the image (tubular-like). The average filter response obtained with different parameter configurations was measured at fixed distances from a reference central axis determined manually. Results were compared with two objective measures, namely the response decay rate at the center and the overall response within 5 mm.

48 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: Two detection approaches for architectural distortions existing around skinline and within mammary glandular tissues are developed and it is concluded that these methods were effective to detect architectural distortions.
Abstract: The architectural distortion is a very important finding in interpreting breast cancers as well as microcalcification and mass on mammograms. However, it is more difficult for physicians to detect architectural distortion than microcalcification and mass. The purpose of this study is to develop two detection approaches for architectural distortions existing around skinline and within mammary glandular tissues. The detection methods for depressed areas around skinline consisted of three steps. The binarization technique was performed to extract the mammary gland region. In order to determine suspect areas, the top-hat processing was performed. The false positives were eliminated by the features of their sizes and positions. The distorted areas within mammary gland region were detected by the following steps. The structure of mammary gland was extracted by using curvature. The candidates were determined by concentration index. The false positives were eliminated by their isotropy indexes, sizes, pixel values and contrast. Our image database consisted of 17 cases with focal retraction areas around skinlines (case A) and 38 cases with architectural distortions within mammary glands (case B). As a result, the sensitivities were 94% and 84% in case A and case B, respectively. It was concluded that our methods were effective to detect architectural distortions.

47 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: The first steps in realizing soft tissue models through the development of an automated laparoscopic grasper and tissue cutting equipment to characterize grasping and cutting tasks in minimally invasive surgery (MIS) are taken.
Abstract: The modeling of grasping and cutting in surgery are two fundamental tasks that must be achieved for the development of a reality-based haptic interface in robot-assisted surgery. Currently, the lack of these models with soft tissue has limited the accuracy of such interfaces in surgery. As a result, we have taken the first steps in realizing soft tissue models through the development of an automated laparoscopic grasper and tissue cutting equipment to characterize grasping and cutting tasks in minimally invasive surgery (MIS). The grasper is capable of generating force feedback that can be felt through a haptic interface device thereby allowing a user to feel the stiffness of the tissue that is being grasped. The cutting equipment employs a surgical scalpel attached to a six-axis force/torque sensor to measure the forces during cutting. The scalpel follows a linear motion created by a DC motor and leadscrew assembly.

37 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: This study serves as a first step towards the long-term goal of using skin motion to predict internal organ motion, which may lead to more precise radiation treatment delivery for mobile target volumes.
Abstract: The purpose of this study is to report and analyze patient skin motion data collected during CyberKnife stereotactic radiosurgery (SRS). The CyberKnife is a radiation treatment system that incorporates a robotic arm to precisely position a linear accelerator. While this capability is not currently commercially available, the CyberKnife could be programmed to move the radiation beam in real time to compensate for organ motion. This study serves as a first step towards our long-term goal of using skin motion to predict internal organ motion. This may lead to more precise radiation treatment delivery for mobile target volumes. To date, we have collected and analyzed skin motion data on four patients (two sacrum, one lung, one pancreas). The movement amplitudes of individual skin markers ranged from 3.1 to 14.8 mm with a median of 7.5 mm.

35 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: The presented validation shows that the AAM method combines a high robustness with clinically acceptable accuracy, and therefore is a promising tool to further automate the integral quantitative analysis of cardiac MR patient examinations.
Abstract: This paper describes a multi-view Active Appearance Model (AAM) for coherent segmentation of multiple cardiac views. Cootes' AAM framework was adapted by considering shapes and intensities from multiple views as single shape and intensity samples, while eliminating trivial difference in object pose in different views. This way, the coherence in organ shape and intensities between different views is modeled and utilized during image search. In a leave-one-out validation study on a combination of four-chamber, two-chamber and short-axis cardiac MR views from 29 patients, low border positioning errors were found comparing manual and computer detected borders, whereas no statistically significant difference in contour area was present. The presented validation shows that the method combines a high robustness with clinically acceptable accuracy, and therefore is a promising tool to further automate the integral quantitative analysis of cardiac MR patient examinations.

33 citations


Journal ArticleDOI
01 Jun 2003
TL;DR: Although focussed on cranio-maxillofacial surgery planning, the method presented herein is well suited for cutting any ( manifold or non-manifold) polygonal model in a free-form manner.
Abstract: We present a novel approach on computer-assisted 3D planning of arbitrarily shaped osteotomies on polygonal bone models. Osteotomy lines can be drawn ‘free-hand’ onto a 3D geometry, either by stroke projection or by the use of several control points, that are automatically connected in a shortest way, approximating osteotomy lines across a triangulated surface representation. Polygonal surface models are cut and retriangulated accordingly. In cases where inner structures have to be cut as well, cut surfaces are generated from closed contour lines. These surfaces again serve as an additional input for a downstream surface cut algorithm. Although focussed on cranio-maxillofacial surgery planning, the method presented herein is well suited for cutting any (manifold or non-manifold) polygonal model in a free-form manner.

Journal ArticleDOI
01 Jun 2003
TL;DR: The simultaneous extraction of epi- and endocardial contours is used to illustrate the operation of a set of coupled active contours to handle and exploit a geometrical relation between neighbouring boundaries.
Abstract: Active contours are a popular method for extraction of object boundaries in medical images. However, they may fail to give correct results if there are other edges in the neighbourhood. To handle and even exploit a geometrical relation between neighbouring boundaries, we propose to use a set of coupled active contours. In this paper, the simultaneous extraction of epi- and endocardial contours is used to illustrate the operation of a set of coupled active contours.

Journal ArticleDOI
01 Jun 2003
TL;DR: This work has developed an automated lung segmentation method based on gray-level thresholding techniques and applied this method as a pre-processing step for automated lung nodule detection and as the foundation for a computer-assisted technique to measure the extent of pleural mesothelioma.
Abstract: Automated segmentation of the lungs in thoracic computed tomography (CT) scans represents an essential process in the development of computer-aided diagnostic (CAD) methods and computer-assisted quantification techniques. A core segmentation process may be developed for general application; however, modifications may be required for specific clinical tasks. We have developed such an automated lung segmentation method based on gray-level thresholding techniques and have applied this method (1) as a pre-processing step for automated lung nodule detection and (2) as the foundation for a computer-assisted technique to measure the extent of pleural mesothelioma. In the automated detection of lung nodules, we have developed a method that has achieved 71% nodule detection sensitivity with an average of 0.4 false-positive detections per section on a database of 38 CT scans. Our method for the computer-assisted quantification of mesothelioma achieved a correlation coefficient of 0.97 with the average manual measurements of four observers based on 134 measurement sites in 22 CT scans. Important differences exist in the specific approaches to automated lung segmentation required for these two clinical tasks.

Journal ArticleDOI
01 Jun 2003
TL;DR: A web-based solution that integrates the digital images of the PACS, the EPR/HIS/RIS data and a built-in teleconferencing functionality and has been successfully tested with three different commercial RIS and HIS products.
Abstract: Medical images are currently created digitally and stored in the radiology department's picture archiving and communication system (PACS). Reports are usually stored in the electronic patient record (EPR) of other information systems, such as the radiology information system (RIS) or the hospital information system (HIS). But high-quality service can only be provided if the EPR data is integrated with the PACS digital images. The clinician should be able to access both systems' data in an integrated and consistent way as part of the regular working environment, the HIS or the RIS. Additionally, this system should allow for teleconferences with other users, e.g., for consultations with a specialist in the radiology department. This paper describes a web-based solution that integrates the digital images of the PACS, the EPR/HIS/RIS data and a built-in teleconferencing functionality. The integration has been successfully tested with three different commercial RIS and HIS products.

Journal ArticleDOI
01 Jun 2003
TL;DR: A neural network identification method is proposed that takes mass-spring structure into account and uses only two neural networks to identify these parameters, which are usually nonlinear functions.
Abstract: In this paper, we use a mass-spring system to simulate facial soft tissue deformation resulting from the bone realignment at the lower jaw area. Since the materials concerned often exhibit significant nonlinearity, correct simulation parameters are needed to capture the nonlinear characteristics in order to achieve satisfying simulation accuracy. We propose a neural network identification method that takes mass-spring structure into account and uses only two neural networks to identify these parameters, which are usually nonlinear functions. An adaptive learning rate formula is also introduced to improve the simulation accuracy and convergence speed.

Journal ArticleDOI
01 Jun 2003
TL;DR: A new method for extracting bronchus regions from 3D chest X-ray CT images based on structural features of the bronchu based on a sharpening operation and segments each bronchial branch by recognizing the tree structure starting from the trachea is presented.
Abstract: This paper presents a new method for extracting bronchus regions from 3D chest X-ray CT images based on structural features of the bronchus. This method enhances bronchial walls by applying a sharpening operation and segments each bronchial branch by recognizing the tree structure starting from the trachea. During the extraction process, the volumes of interests (VOI) which contain the bronchial branch currently being processed are defined. Region growing is performed only inside a VOI so that a bronchial branch is extracted by a suitable threshold value. The final bronchus region is obtained by unifying the extracted branches. The tree structure of the bronchus is also extracted simultaneously. The proposed method was applied to three cases of 3D chest X-ray CT images. The experimental results showed that the method significantly improved extraction accuracy. About 82% of the branches is extracted for the 4th-order bronchi, 49% for 5th-order bronchi, and 20% for 6th-order bronchi, compared to 45%, 16%, and 3% by the previous method using the region-growing method with a constant threshold value.

Journal ArticleDOI
01 Jun 2003
TL;DR: A remote-controlled laparoscope manipulator system, Naviot™ (Hitachi), is newly developed and introduced to a laparoscopic cholecystectomy for seven patients, believed to be feasible in clinical use and enables surgeons to perform “solo-surgery” in the near future.
Abstract: A remote-controlled laparoscope manipulator system, Naviot™ (Hitachi), is newly developed and introduced to a laparoscopic cholecystectomy for seven patients. This system consists of a specific laparoscope with a zoom lens, a flexible arm, an actuator, a five-bar linkage mechanism, and a hand controller. A surgeon can easily use the zoom lens and move the laparoscope into the eight directions by pushing the buttons of a hand controller. The zoom can be 5.07 magnifications. The moving range is 45° in the horizontal directions and 25° in the vertical ones. All procedures were performed safely and smoothly. We believe that this new system is feasible in clinical use and enables surgeons to perform “solo-surgery” in the near future.

Journal ArticleDOI
01 Jun 2003
TL;DR: In this article, the performance of image intensifier (II)-equipped C-arm systems for 3D imaging was investigated in terms of spatial resolution (modulation transfer function, MTF), contrast resolution, geometrical accuracy and homogeneity depending on the image intensifiers format, focal spot size, number of projections and the angular span covered during the data acquisition.
Abstract: The performance of image intensifier (II)-equipped C-arm systems for three-dimensional (3D) imaging was investigated. The three-dimensional image quality was evaluated in terms of spatial resolution (modulation transfer function, MTF), contrast resolution, geometrical accuracy and homogeneity depending on the image intensifier format, focal spot size, number of projections and the angular span covered during the data acquisition. Experiments have been performed on a vascular C-arm system equipped with a 38-cm image intensifier. Several objects, including CT performance, MTF and pelvis phantoms, were scanned under various conditions. It was shown that for reasonable acquisition parameters, a contrast resolution below 100 HU could be obtained with standard acquisition strategies. Focusing on the spatial resolution, an almost isotropic three-dimensional resolution of up to 22 lp/cm at 10% modulation could be obtained when a 17-cm II was used. The homogeneity in the resulting images was limited by the remaining scatter and truncations. The resulting geometrical accuracy was in the order of the voxel size.

Journal ArticleDOI
01 Jun 2003
TL;DR: The use of an ensemble of SVM classifiers with bagging (bootstrap aggregation), built on different feature subsets, is intended to improve classification performance when compared to single SVMs and to reduce the number of false positive detections.
Abstract: In this paper, we propose a new classification scheme for computer-aided detection (CAD) of colonic polyps in CT colonography (CTC). The scheme involves an ensemble of support vector machines (SVMs) for classification, a smoothed leave-one-out (SLOO) cross-validation method for obtaining error estimates, and the use of a bootstrap aggregation method for training and model selection. Our use of an ensemble of SVM classifiers with bagging (bootstrap aggregation), built on different feature subsets, is intended to improve classification performance when compared to single SVMs and to reduce the number of false positive detections. The bagging technique has the effect of a virtual increase in the training set size and, as a consequence, also helps to reduce the bias of error estimates when combined with a leave-one-out cross-validation approach. The bootstrap-based model selection technique is used for tuning the SVM parameters.

Journal ArticleDOI
01 Jun 2003
TL;DR: New algorithms developed in the framework of CRANIO project are presented, especially related to the manipulation of 3-D geometry data of the skull for planning and definition of craniotomy.
Abstract: Computer-assisted planning, navigation, and robotic craniotomy, with optional skull reconstruction using customized implants are of increasing clinical interest in craniofacial and neurosurgery. The aim of the CRANIO project presented in the first part of this paper is to develop a system that integrates the entire surgical process, from planning, customized implant manufacturing, optional robot programming, up to intraoperative navigation and robot-assisted execution. In the second part of the paper, we present new algorithms developed in the framework of CRANIO project. This work is especially related to the manipulation of 3-D geometry data of the skull for planning and definition of craniotomy. The results of our work are presented, together with results and objectives for further development.

Journal ArticleDOI
01 Jun 2003
TL;DR: A new approach based on a three-dimensional finite element software and an elastic constitutive equation, able to predict realistic results is presented, applied to soft tissues deformation, namely lamb kidney and human uterus.
Abstract: Laparoscopy is a surgical technique that requires fine control from the surgeon point of view. Up to this day, this experience can only be obtained by intensive training. That is why a lot of training simulators have been developed in the medical area. We present here a new approach based on a three-dimensional finite element software and an elastic constitutive equation, able to predict realistic results. This software has been applied to soft tissues deformation, namely lamb kidney and human uterus, and the numerical results are compared to experimental ones.

Journal ArticleDOI
01 Jun 2003
TL;DR: A new type of hydraulic-driven flexible manipulator for neurosurgery has been developed by using only physiological saline for drive system that assures safety, especially in pressure, to brain tissue as well has the advantage of MRI compatibility.
Abstract: Minimally invasive surgery has recently become a key word in medical engineering. In this operation, to introduce instruments, spatulas, which push tissues aside and retain the approach path to the affected area and workspace for introducing instruments, are necessary. So, a new type of hydraulic-driven flexible manipulator for neurosurgery has been developed. With a balloon put on, by using only physiological saline for drive system that assures safety, especially in pressure, to brain tissue as well has a simple mechanism. In addition, this gives the advantage of MRI compatibility. We first designed and made the prototype, and then evaluated it.

Journal ArticleDOI
01 Jun 2003
TL;DR: The security of PACS is presented as a mechanism by which organization can manage and protect all information assets by ensuring data confidentiality, integrity and accessibility according to ISO17799 and BS7799 standards.
Abstract: In picture archiving and communication systems (PACS) [H.K. Huang, PACS: Basic Principles and Application, 1st ed., Wiley-Liss (1998); K.J. Dreyer, A. Mehta, J.H. Thrall, PACS: A Guide to the Digital Revolution, 1st ed., Springer Verlag (2001)], digital image data were stored and retrieved centrally. Clinicians and radiologists have the convenience of instant and simultaneous access to images and reports from multiple locations. In a filmless hospital [E.L. Siegel, R.M. Kolodner, Filmless Radiology, Reprint ed., Springer Verlag (2001)], with the availability of image servers, integrity of data and security of the system were the most important tasks during the design of a PACS. However, there is no single solution for the security of PACS. A comprehensive information security management system (ISMS) is required for the monitoring of the security of PACS. In this paper, the security of PACS is presented as a mechanism by which organization can manage and protect all information assets by ensuring data confidentiality, integrity and accessibility according to ISO17799 and BS7799 standards. Implementation of the ISMS involved system redesign, change of workflow, staff retraining, communication, social engineering and documentation control.

Journal ArticleDOI
01 Jun 2003
TL;DR: The design and development experiences that a group of us at Simon Fraser University has gained during the past 7 years are presented, including evolutionary designs from the one degree of freedom haptic feedback design to more complex four degrees of freedom.
Abstract: This paper presents an overview of the design and development of electromechanical haptic devices that can be used as a part of the training environment of laparoscopic surgeons (minimally invasive surgery, MIS). The paper first presents results of the experimental study of measuring the expected forces that the user hand can experience when using long stem surgical tools that are used in laparoscopic surgery. In general and in performing laparoscopic procedures, the user can feel reaction forces arising from the interaction of the surgical tools with the organs along four dominant directions and also to some extent between the palm and the fingers of the hand. Design challenges are to develop a high-bandwidth system which allows the creation of such a force feedback along the desired degrees of freedom. This paper presents the design and development experiences that a group of us at Simon Fraser University has gained during the past 7 years. We present evolutionary designs from the one degree of freedom haptic feedback design to more complex four degrees of freedom. Some comparisons have also been made between the proposed design and commercially available ones.

Journal ArticleDOI
01 Jun 2003
TL;DR: The proposed method consists of initial detection of nodule candidates using shape features of lung nodules and reduction process of false positive regions using a minimum directional difference filter called Min-DD from the initial candidates.
Abstract: This paper describes a method for detecting small nodules from three-dimensional chest X-ray CT images. The proposed method consists of two submodules: (a) initial detection of nodule candidates using shape features of lung nodules and (b) reduction process of false positive regions using a minimum directional difference filter called Min-DD from the initial candidates. The performance of the proposed method was evaluated by using six cases of chest X-ray CT images including five abnormal cases where multiple lung cancers are observed. The experimental results showed that sensitivity and FP regions are 71% and 7.4 regions in average per case for nodules of 2 mm in diameter (361 regions in total).

Journal ArticleDOI
01 Jun 2003
TL;DR: A force measuring system with the trocar type of the overcoat method is constructed to measure the tip-loaded force of the surgical instrument in relation to the pose and motion of the instrument.
Abstract: For fine surgical operation by slave robot, master robot needs the information of the contact force loaded on the tip of the surgical instrument. One of major problems in sensing the force is frictional disturbance between the trocar and the instrument. One of authors proposed a new method named overcoat method where the whole instrument is supported by force sensors. This paper tried to construct a force measuring system with the trocar type of the overcoat method. It discussed about the compensations of gravity and acceleration force of the instrument in relation to the pose and motion of the instrument. The tried system measured the tip-loaded force in absolute accuracy about 0.3 N and in sensitivity about 0.05 N.

Journal ArticleDOI
01 Jun 2003
TL;DR: Taking advantage of the 4D deformation field knowledge, a new clinical application in rotational X-ray angiography called “stabilized display” is proposed, presenting a focused and centered display of 3D points of interest.
Abstract: We present a new method to automatically compute a (3D+t) 4D parametric deformation field of coronary arteries from one single rotational X-ray angiography acquisition. We first build 3D centerline models of the coronary arteries and then compute 4D deformations that make the 3D model fit the entire sequence, at all cardiac cycle phases. Taking advantage of the 4D deformation field knowledge, we propose a new clinical application in rotational X-ray angiography called “stabilized display”, presenting a focused and centered display of 3D points of interest. Results on patient data sets are presented.

Journal ArticleDOI
Tetsuya Fujii, Hiroshi Emoto, Nobuo Sugou1, Toshiaki Mito1, Iekado Shibata1 
01 Jun 2003
TL;DR: This paper introduces blood vessels into the path searching because the authors cannot give them damages during operation and shows that the path obtained by the proposed method is better than searching without vessel structure.
Abstract: This paper describes an improvement of automatic neurosurgical path searching algorithm which incorporates the structure of blood vessels. We have proposed an automatic searching method for surgical path planning on neurosurgery to realize minimally invasive operations within the range of soft tissues. This path searching is based on importance values we defined, and an anatomical structure database generated from MRI images and surgeon experiences. This paper introduces blood vessels into the path searching because we cannot give them damages during operation. We first obtain the structure of blood vessels from MRA, then also give them importance values, and finally incorporate the structure into path searching. Experimental results show that the path obtained by the proposed method is better than searching without vessel structure.

Journal ArticleDOI
01 Jun 2003
TL;DR: A novel fiducial marker system was constructed which attaches to a dental biteblock and has fiducials surrounding the surgical field of interest (the ears/temporal bones) and accuracy was tested by fitting the device to a cadaveric skull and embedding targets near anatomically important locations.
Abstract: Application of image-guided surgical systems to otologic surgery has been limited by the need for submillimeter accuracy via a fiducial system that is easily useable (i.e. noninvasive and nonobstructive). To overcome these limitations and demonstrate the feasibility of image-guided otologic surgery, a novel fiducial marker system was constructed which attaches to a dental biteblock and has fiducial markers surrounding the surgical field of interest (the ears/temporal bones). Accuracy was tested by fitting the device to a cadaveric skull and embedding targets near anatomically important locations. High-resolution CT scanning (thickness=0.5 mm) was then performed. Marker and target locations were measured in physical space using an infrared, imageacquisition system. These measurements were used in calculating target registration error—the error associated with identification of the surgical targets. This error was minimized when the maximum number of fiducial markers was used (nine fiducials surrounding each ear). Submillimeter target registration error was repeatedly achieved with five markers surrounding the ear of interest and one marker centrally located on the contralateral side. D 2003 Published by Elsevier Science B.V.

Journal ArticleDOI
01 Jun 2003
TL;DR: It could be concluded that the entropy-based methods mutual information and normalized mutual information (NMI) with a number of histogram bins of 64 or 128 using partial volume interpolation perform robustly for rigid registration of ultrasound volumes of brain tumours.
Abstract: Intraoperative brain deformation is one of the most contributing factors to the inaccuracy of image-guided surgery systems. One option for correcting this deformation is to acquire 3D ultrasound images during surgery and using these to update the information provided by the preoperatively acquired MR data. To compare ultrasound volumes acquired at different stages of surgery, non-rigid registration techniques are necessary. As a first step towards this approach, the accuracy and robustness of entropy-based rigid registration methods for ultrasound volumes have been examined. From the robustness measurements on patient data, it could be concluded that the entropy-based methods mutual information and normalized mutual information (NMI) with a number of histogram bins of 64 or 128 using partial volume interpolation perform robustly for rigid registration of ultrasound volumes of brain tumours. When no brain deformations occur between the two ultrasound acquisitions, accuracies of around 0.5 mm can be achieved.