Showing papers by "Michael W. Vannier published in 1996"
TL;DR: The results suggest that depression is associated with hippocampal atrophy, perhaps due to a progressive process mediated by glucocorticoid neurotoxicity.
Abstract: Hippocampal volumes of subjects with a history of major depressive episodes but currently in remission and with no known medical comorbidity were compared to matched normal controls by using volumetric magnetic resonance images. Subjects with a history of major depression had significantly smaller left and right hippocampal volumes with no differences in total cerebral volumes. The degree of hippocampal volume reduction correlated with total duration of major depression. In addition, large (diameter > or = 4.5 mm)-hippocampal low signal foci (LSF) were found within the hippocampus, and their number also correlated with the total number of days depressed. These results suggest that depression is associated with hippocampal atrophy, perhaps due to a progressive process mediated by glucocorticoid neurotoxicity.
1,856 citations
TL;DR: In experiments with synthetic noise-free and additive noisy projection data of dental phantoms, it is found that both simultaneous iterative algorithms produce superior image quality as compared to filtered backprojection after linearly fitting projection gaps.
Abstract: Iterative deblurring methods using the expectation maximization (EM) formulation and the algebraic reconstruction technique (ART), respectively, are adapted for metal artifact reduction in medical computed tomography (CT). In experiments with synthetic noise-free and additive noisy projection data of dental phantoms, it is found that both simultaneous iterative algorithms produce superior image quality as compared to filtered backprojection after linearly fitting projection gaps. Furthermore, the EM-type algorithm converges faster than the ART-type algorithm in terms of either the I-divergence or Euclidean distance between ideal and reprojected data in the authors' simulation. Also, for a given iteration number, the EM-type deblurring method produces better image clarity but stronger noise than the ART-type reconstruction. The computational complexity of EM- and ART-based iterative deblurring is essentially the same, dominated by reprojection and backprojection. Relevant practical and theoretical issues are discussed.
419 citations
TL;DR: The algorithms in this research create individualized, subject-specific atlases of the head, created from MRI scans and labeled by experts, using an annotated volume of images, charts or tables that systematically illustrate an anatomical part.
Abstract: An anatomical atlas is an annotated volume of images, charts or tables that systematically illustrate an anatomical part. Atlas annotations often include structure names, descriptions, locations and functions, as well as other information specific to the atlas anatomy. Individualized digital atlases can be generated by using a computer to transform the shape of the atlas into the shape of images taken of the individual. Generalized electronic atlases of the head, created from MRI scans and labeled by experts, are currently available. The algorithms in this research create individualized, subject-specific atlases.
147 citations
Journal Article•
TL;DR: Computer-simulated surgery does affect the choice of intervention for patients with complex craniofacial anomalies, and further evaluation of the process is needed to determine the influence of surgical simulation and planning on outcome.
118 citations
TL;DR: General pattern matching of a digital brain atlas to an individual MR image is a mathematically robust method of measurement that is reproducible and less variable than manual measurement.
Abstract: PURPOSE: To determine the repeatability and validity of a pattern-matching method for the segmentation and measurement of hippocampi on magnetic resonance (MR) images. MATERIALS AND METHODS: Comparable two-dimensional MR images obtained in 18 subjects (nine healthy control subjects [six men, three women; aged 24-54 years] and nine patients with schizophrenia [six men, three women; aged 22-61 years]) were twice segmented manually and twice segmented by using pattern matching with digital atlas transformation. The atlas transformation was accomplished in two steps: global followed by local matching. Global matching was performed with use of landmarks; local matching was performed with use of a viscous fluid model. RESULTS: The mean percentage of difference between two atlas-based measurements was 1.33% +/- 1.23 (+/- standard deviation); that between two manual measurements was 4.67% +/- 4.71. The validity of the atlas transformation measurements was demonstrated by means of the high correlation (intraclass ...
110 citations
TL;DR: It was hypothesized that the three major etiologies of plagiocephaly could be unambiguously differentiated by means of endocranial threedimensional CT osscous surface re‐formations, and errors were made in differentiation of unilambdoid synostosis and plagioCEphaly withoutsynostosis in the “error” cases.
Abstract: Plagiocephaly is a descriptive term that connotes an asymmetrically oblique or twisted head. Such cranial dysmorphology has a number of etiologies, the most common of which are unicoronal synostosis, unilambdoid synostosis, and plagiocephaly without synostosis. Use of the term plagiocephaly in the literature is often ambiguous in that at times it is used inclusively for all etiologies while at other times it is used exclusively as a synonym for unicoronal synostosis. Although differentiation by physical examination among unicoronal synostosis, unilambdoid synostosis, and plagiocephaly without synostosis usually is possible for an experienced observer, inexperienced observers often have difficulty making an anatomically accurate diagnosis even with the assistance of conventional skull radiographs. High-resolution CT scans, including three-dimensional osseous surface re-formations, have become a standard element in the evaluation of craniofacial anomalies in many centers. We hypothesized that the three major etiologies of plagiocephaly could be unambiguously differentiated by means of endocranial three-dimensional CT osseous surface re-formations. Archival pretreatment CT data on 15 unicoronal synostosis, 4 unilambdoid synostosis, and 15 plagiocephaly without synostosis patients were reviewed to define, qualitatively and quantitatively, the characteristics of the endocranial base morphologies for each group; in addition to visual dysmorphology specific to each group, there was a statistically significant difference in the angle of deviation from the midlines of the anterior and posterior cranial fossae among unicoronal synostosis, unilambdoid synostosis, and plagiocephaly without synostosis. Four radiologists experienced in reading images of craniofacial anomalies were oriented to the group characteristics and then instructed to perform differential diagnosis for each of the 34 patients using only the endocranial three-dimensional CT images. The raters were blind to all other clinical and diagnostic information. The raters correctly diagnosed unicoronal synostosis. Errors were made in differentiation of unilambdoid synostosis and plagiocephaly without synostosis. These errors resulted from the raters' reliance on image inspection rather than quantitation of anteroposterior fossae midline angulation. Such quantitation unambiguously differentiated between unilambdoid synostosis and plagiocephaly without synostosis in the "error" cases. The endocranial base dysmorphology of patients with plagiocephaly is etiology-specific for unicoronal synostosis, unilambdoid synostosis, and plagiocephaly without synostosis. Three-dimensional CT endocranial base images can assist differential diagnosis of plagiocephaly.
104 citations
TL;DR: It is concluded that the 3-D displacements of MRI tag lines may be reconstructed accurately; however, the strain solution magnifies the small errors in locating tag lines and reconstructing 3- D displacements.
Abstract: A method is developed and validated for approximating continuous smooth distributions of finite strains in the ventricles from the deformations of magnetic resonance imaging (MRI) tissue tagging "tag lines" or "tag surfaces." Tag lines and intersections of orthogonal tag lines are determined using a semiautomated algorithm. Three-dimensional (3-D) reconstruction of the displacement field on tag surfaces is performed using two orthogonal sets of MRI images and employing spline surface interpolation. The 3-D regional ventricular wall strains are computed from an initial reference image to a deformed image in diastole or systole by defining a mapping or transformation of space between the two states. The resultant mapping is termed the measurement analysis solution and is defined by determining a set of coefficients for the approximating functions that best fit the measured tag surface displacements. Validation of the method is performed by simulating tag line or surface deformations with a finite element (FE) elasticity solution of the heart and incorporating the measured root-mean-square (rms) errors of tag line detection into the simulations. The FE-computed strains are compared with strains calculated by the proposed procedure. The average difference between two-dimensional (2-D) FE-computed strains and strains calculated by the measurement analysis was 0.022 +/- 0.009 or 14.2 +/- 3.6% of the average FE elasticity strain solution. The 3-D displacement reconstruction errors averaged 0.087 +/- 0.002 mm or 2.4 +/- 0.1% of the average FE solution, and 3-D strain fitting errors averaged 0.024 +/- 0.011 or 15.9 +/- 2.8% of the average 3-D FE elasticity solution. When the rms errors in tag line detection were included in the 2-D simulations, the agreement between FE solution and fitted solution was 24.7% for the 2-D simulations and 19.2% for the 3-D simulations. We conclude that the 3-D displacements of MRI tag lines may be reconstructed accurately; however, the strain solution magnifies the small errors in locating tag lines and reconstructing 3-D displacements.
67 citations
TL;DR: The hypothesized presence of diagnosis specific mandibular dysmorphology in UCS and PWS is confirmed and forms the baseline for study of the effects of unperturbed growth or therapeutic interventions upon the dentoskeletal Dysmorphology of these anomalies.
Abstract: Patients with unicoronal synostosis (UCS) or plagiocephaly without synostosis (PWS) have distinctive skull dysmorphologies. Associated mandibular dymorphologies have been suspected but not quantified. This study was performed to test the hypothesis that discrete mandibular dysmorphology exists in both UCS and PWS. All patients at a tertiary referral center at a medical school-affiliated children's hospital with confirmed diagnosis of UCS or PWS with adequate pretreatment CT data were included in the study population, which population was comprised of 20 UCS, 23 PWS, and 8 normal infants. Each patient had a head CT scan using 2-mm slices. 3-D images were created using Analyze, a biomedical imaging program. The mandibles were isolated, and the coordinates of 8 landmarks were sampled from each mandible by a single investigator: a single volume value was measured, and 9 linear distances and 4 angles were calculated. Corresponding measurements from each hemimandible were expressed as ratios of ipsilateral/contralateral side. In UCS, the affected side was defined as the side ipsilateral to the synostosis; In PWS, the affected side was defined as the side ipsilateral to the occipital flattening. The results from both groups were t tested for statistical significance. For UCS, statistically significant (p < .001) findings included: ipsilateral hemimandibular volume 5% smaller than contralateral; affected hemimandibular body length 1.9% shorter; affected gonial angle 2.6% more acute; affected coronoid process tilted anteriorly 2.5%; and distances from condylion and tip of the coronoid process to the chin landmarks 4% shorter on the affected side. For PWS, significant findings included: affected hemimandibular volume 3.8% larger; ramal height 3.5% shorter; mandibular body length 3% longer; and coronoid process tilted anteriorly by 2.3% on the affected side. In the UCS/PWS comparison, findings included: affected hemimandibular volume in UCS 8.7% less; affected gonial angle in UCS 3% more acute; affected mandibular corpus length in UCS 5% shorter; distances from the condylion and the tip of the coronoid process to the chin landmarks 4% shorter on the affected side in UCS. The hypothesized presence of diagnosis specific mandibular dysmorphology in UCS and PWS is confirmed. This analysis forms the baseline for study of the effects of unperturbed growth or therapeutic interventions upon the dentoskeletal dysmorphology of these anomalies.
61 citations
TL;DR: Data indicate that UCS affects the development of the osseous orbit as well as its soft-tissue contents in patients with unilateral coronal synostosis, and it seems to permit normalization of previously impaired growth.
Abstract: Unilateral coronal synostosis (UCS) produces overt craniofacial dysmorphology. UCS surgery in infancy aims to release the osseous restriction and normalize the fronto-orbital deformity. The quantitative effect of this surgery on the orbit and its contents is unknown. This study was conducted to quantify the preoperative orbital dysmorphology and its surgical outcome in patients with unilateral coronal synostosis. Twenty-eight UCS patients had preoperative three-dimensional computerized tomographic (CT) scans (at mean age 4.0 months), cranio-orbital reconstructive surgery (at 4.7 months), and postoperative scans (at 18.1 months). The CT data were analyzed using a computer workstation and AnalyzeTM(??) biomedical imaging software. Four measurements were performed on both ipsilateral (same side as synostosis) and contralateral (opposite to synostosis) orbits of each scan: orbital index (OI, 100 × height/width of orbit), orbital cavity volume (OV), ocular globe volume (GV), and ventral globe index (V...
56 citations
TL;DR: The fuzzy c‐means (FCM) statistical clustering algorithm was extended to estimate and retrospectively correct a multiplicative inhomogeneity field in T1‐weighted head MR scans, which improved overall image uniformity and separability of gray and white matter intensities.
Abstract: Signal inhomogeneities in volumetric head MR scans are a major obstacle to segmentation and neuromorphometry. The fuzzy c-means (FCM) statistical clustering algorithm was extended to estimate and retrospectively correct a multiplicative inhomogeneity field in T1-weighted head MR scans. The method was tested on a mathematically simulated object and on seven whole head 3D MR scans. Once initial parameters governing operation of the algorithm were chosen for this class of images, results were obtained without intervention for individual MR studies. Post-acquisition inhomogeneity correction by extended FCM clustering improved overall image uniformity and separability of gray and white matter intensities.
45 citations
TL;DR: Stereology was used to measure frontal lobe volume on magnetic resonance imaging (MRI) scans in a multi-observer repeated-measures trial in 17 adults and yielded high repeatability and precision, and was time efficient for the raters.
Abstract: Stereology was used to measure frontal lobe volume on magnetic resonance imaging (MRI) scans in a multiobserver repeated-measures trial in 17 adults. Prior to measurement, MR image volumes were reoriented into coronal sections perpendicular to the bicommissural plane. Three observers blinded to subject identity repeatedly used fixed grid stereology to estimate frontal lobe volumes, defined as all sections of the frontal lobe anterior to the anterior commissure. The lateral ventricles were excluded. Stereological measurement yielded high repeatability and precision, and was time efficient for the raters. The coefficient of error was 0.03. The inter-rater correlation coefficient = 0.95 for three raters; intea-rater correlation coefficients = 0.95–0.98. A comparison was made between stereological and traditional edge tracing measurement of the frontal lobe volumes. The overall correlation between the two methods was 0.95. The use of internal landmarks to define orientation and 3-D orthogonal views to define frontal lobe boundaries on 3-D images was critical to obtaining repeatable measurements. Frontal lobe volumetry by brain MR used to estimate small differences postulated to occur in certain psychiatric and neurologic disorders requires high precision and repeatability. Stereology, a semi-automated method, can reliably estimate frontal lobe volumes. This method may distinguish small frontal lobe volume differences within individuals and between groups.
TL;DR: These measurement systems were found to be substantially equivalent in terms of repeatability and precision for measurement of lower extremity residua.
TL;DR: An approach is described to use as input a volumetric spiral computed tomography image of the Nucleus electrode array to unwrap it, and to measure its implanted length given starting and end points, to improve speech processor programming to maximize speech recognition.
Abstract: Multielectrode, intracochlear implants were designed for individuals with profound sensorineural hearing loss who derive little or no benefit from acoustic hearing aids. Determination of each electrode's position in a patient's inner ear may improve speech processor programming to maximize speech recognition. In this paper, an approach is described to use as input a volumetric spiral computed tomography (CT) image of the Nucleus electrode array (Cochlear Pty. Ltd, Lane Cove, NSW, Australia) to unwrap it, and to measure its implanted length given starting and end points. Representative curvilinear structures were digitally synthesized in image volumes of isotropic 0.1-mm voxels. The electrode array was spirally CT-scanned in vitro and in vivo, and reconstructed on an isotropic grid in 0.1-mm steps. Two algorithms were constructed to track and measure these curvilinear structures. The first algorithm is Karhunen-Loeve (K-L)-transform based, in which the K-L transform is locally applied at a current main aids position to determine the eigenvectors of the main axis voxels, the next main axis position is estimated from the current position along the principal eigendirection, adjusted to the mass center of the orthogonal cross section passing through the estimated position, and then scaled to have a prespecified step. The second algorithm is similar to the first one but avoids use of the K-L transform, in the second algorithm, the next position is directly estimated along the local direction and then processed with the same correction and scaling operations. With user-specified starting and end points as well. As a local direction at the starting point, a curvilinear structure can be automatically tracked using either of the algorithms. The first algorithm is more robust, while the second one is more efficient. In the numerical and in vitro studies, the lengths of the curvilinear structures were accurately measured. Given local directions determined in the tracking process, an electrode array image can be unwrapped into a linear array with the central electrode axis as the abscissa. The unwrapping approach allows longitudinally and cross-sectionally accurate measurement and better visualization of cochlear implant images. With preimplantation knowledge of length, width, and center electrode distance, the position of individual electrodes can be estimated after unwrapping.
TL;DR: Registration of CT volumetric data sets to quantify residual-limb soft-tissue envelope change in lower-limB prosthetics is precise and can be used to detect the effect of prosthesis shape alterations.
Abstract: PURPOSE: To perform quantitative evaluation of lower-extremity prosthesis fit by using spiral computed tomography (CT). MATERIALS AND METHODS: Two spiral CT scans were obtained at each of two different sessions in seven adult patients who had undergone amputation below the knee. A rigid-body transformation of the tibia was computed and used to align paired (intra- and intersession) spiral CT data sets for each individual in a common coordinate system. Paired scans in each individual were compared to assess registration and precision of soft-tissue change measurement. Clinical prosthesis fit evaluation was demonstrated in an adult amputee volunteer who underwent CT evaluation while wearing two different prostheses. RESULTS: In the seven patients examined, more than 90% of the measured soft-tissue volume displacements between sessions could be explained as true differences. Precision error of soft-tissue volume change was approximately 13 cm3, or approximately 1% error relative to the mean volume. Volumetri...
TL;DR: It is concluded that plate rigid fixation at the nasion provides superior stability for bandeau advancement compared with bone graft/suture fixation, and surgical outcomes in the plate group were significantly better than those in the bone graft /suture group.
Abstract: Fronto-orbital dysmorphology in nonsyndromic bilateral coronal synostosis includes frontal flattening, supraorbital recession, and ocular globe protrusion. Surgical advancement of the supraorbital region (bandeau) is performed to correct these deformities. A retrospective analysis of 10 consecutive patients with nonsyndromic bilateral coronal synostosis was performed to assess the effect of two types of bandeau fixation at the nasion. The advanced bandeau was fixed medially at the nasion with a calvarial bone graft and polyglycolic acid sutures (bone graft/suture group, five patients) or with a microplate (plate group, five patients) and bilaterally at pterion with calvarial bone grafts and polyglycolic acid sutures (all patients). The cranio-orbital dysmorphology and the surgical results were studied using pre-, peri-, and postoperative three-dimensional computed tomographic (CT) data. Reformation, manipulation, editing, and quantitative measurements of the CT data were performed on a computer workstation and Analyze imaging program. Four measurements were performed to evaluate the fronto-orbital morphology : the length :width ratio of anterior cranial fossa, ventral globe index, cornea position, and supraorbital rim lag. The ventral globe index assessed the degree of eyeball protrusion out of the orbital cavity. Measurements of the cornea position and supraorbital rim lag were performed on the longitudinal orbital projections of the CT data. Six normal skull CT scans were available for same measurement and comparison. Measurements of the preoperative fronto-orbital dysmorphology in bilateral coronal synostosis were significantly different from those of normal subjects. One year after the surgery, the length :width ratio of the anterior cranial fossa was normalized in both groups. The ventral globe index was improved but not normalized in both groups, whereas the cornea position and supraorbital rim lag were improved in the bone graft/suture group but were normalized in the plate group. Based on the quantitative data, the surgical outcomes in the plate group were significantly better than those in the bone graft/suture group. Major relapse of surgical advancement in the bone graft/suture group seemed to occur in perioperative period. In summary, at 1 year postoperatively, the bandeau advancement improved but did not entirely normalize the fronto-orbital dysmorphology of nonsyndromic bilateral coronal synostosis in either group. We conclude that plate rigid fixation at the nasion provides superior stability for bandeau advancement compared with bone graft/suture fixation.
TL;DR: The validity of graphically rendered CT or MR scanned images is carefully measured by simulating craniofacial surgical procedures and testing each step in the process.
Abstract: Interactive computer graphics visualization allows simulation of craniofacial procedures before surgical intervention. Two simulation modes are currently available: physical replicas created with CT data applied to numerically controlled milling machines or stereolithography machines; and 3D graphical images created from tomographic data. The validity of graphically rendered CT or MR scanned images is carefully measured by simulating craniofacial surgical procedures and testing each step in the process.
21 Jun 1996
TL;DR: A new method for non-rigid registration of a normal infant CT head atlas with CT data of infants with abnormal skull shape is presented and the CT atlas was transformed into the shape of several infants with various types of craniofacial deformities.
Abstract: A new method for non-rigid registration of a normal infant CT head atlas with CT data of infants with abnormal skull shape is presented. An individualized atlas is synthesized by computing a volume transformation from the normal atlas to the target data set shape. This process begins rigidly by eliminating translation and rotation differences and proceeds non-rigidly to eliminate anatomical shape differences. Operator specified anatomical landmarks are used to find the initial rigid transformation. Non-rigid registration is achieved by constraining the transformation by the low frequency modes of vibration of a 3D linear-elastic solid while minimizing the squared intensity difference between atlas and target CT image volumes. Results are presented in which the CT atlas was transformed into the shape of several infants with various types of craniofacial deformities.
Journal Article•
TL;DR: In a study conducted with 13 persons with below knee (BK) amputation, the OSS system was compared to calipers, electromagnetic digitizer, and volumetric computed tomography with better than 1 mm precision on plaster positive casts and approximately 2 mm on the residual limbs.
Abstract: A three-dimensional (3-D) noncontact optical surface range sensing imaging system that captures the entire circumferential and distal end surfaces of lower limb residua in less than 1 second has been developed. The optical surface scanner (OSS) consists of four charge injection device (CID) cameras and three white light projectors, mounted on a rigid frame surrounding the subject's residuum, allowing 360 degrees surface coverage of the lower residual limb. Anatomic 3-D computer graphics reconstruction of a residuum surface, recorded with the OSS imaging system, is used for visualization and measurement. One cubical and two spherical calibration test objects were used to obtain a system precision of less than 1 mm. In a study conducted with 13 persons with below knee (BK) amputation, the OSS system was compared to calipers, electromagnetic digitizer, and volumetric computed tomography with better than 1 mm precision on plaster positive casts and approximately 2 mm on the residual limbs.
TL;DR: Castleman's and Rüttimann's matching algorithms perform equally well in correcting digital image contrast in digital dental images while Histogram flattening was less effective.
Abstract: OBJECTIVES To compare the results or two methods of histogram matching and two methods of histogram flattening for their ability to correct for contrast variations in digital dental images. METHODS A custom-built, aluminium stepwedge with 0.1, 0.5 and 1.0 mm steps was placed over Ektaspeed films and exposed for 0.06, 0.12 and 0.25 s, respectively. Radiographs were digitized at 50 microns spatial resolution and 12-bit contrast resolution. Contrast corrections were performed using Ruttimann et al.'s algorithm (1986) for one method of matching (RM) and flattening (RF) and Castleman's algorithm (1979) for the other method of matching (CM) and flattening (CF). Mean pixel grey-scale values were determined for each step. The 0.12 s exposure was considered to be the target image exposure. Absolute differences in pixel grey-scale values between the target images and the modified images were determined. RESULTS The median values of the absolute differences in pixel grey-scale values between the target images and th...
TL;DR: It is proved that the maximum volume coverage is reached with a pitch of square root of 2.4 in spiral CT scanning with a heat-limited tube and for a specified image quality in terms of slice thickness and image noise.
01 Jan 1996
TL;DR: A combination of iso-surface generation, spatial region growing and interactive graphics tools are used to extract small structures interactively in CT scans.
Abstract: This paper presents a new interactive method for segmentation and visualization of small structures in CT scans. A combination of iso-surface generation, spatial region growing and interactive graphics tools are used to extract small structures interactively. A practical example of segmentation of the dentition in a CT scan is shown.
Journal Article•
TL;DR: If new investigators are able to avoid common mistakes and misconceptions, their proposals will improve in quality and they will be able to spend their time more effectively in proposal preparation, the BLRC expects.
Abstract: New and aspiring investigators often ask the same questions of experts as proposals are formulated, written, and submitted to the National Library of Medicine (NLM) for peer review. The NLM's Division of Extramural Programs (EP) provides support to medical libraries, academic medical centers, individuals, and industry through numerous types of grants and contracts. A complex set of processes and procedures is in place and is familiar to established and funded researchers, but to few others. A collection of frequently asked questions (FAQ) and their answers on these issues has been prepared by the Biomedical Library Review Committee (BLRC), a standing advisory group to the NLM that meets three times a year to review and score proposals. The BLRC and two experts on National Institutes of Health (NIH) grants and contracts compiled their advice in an electronic FAQ that has been edited and abridged as an introduction to NLM EP for investigators from medical library science, informatics, and biotechnology. The BLRC expects that if new investigators are able to avoid common mistakes and misconceptions, their proposals will improve in quality and they will be able to spend their time more effectively in proposal preparation.
22 Sep 1996
TL;DR: The entire abdomen may now be continuously scanned within a single breath-hold with spiral CT, and a semi-automatic approach was developed for fly-through and unraveling in vivo.
Abstract: Gastrointestinal (GI) tract examination with computed tomography (CT) is currently performed by slice-based visual inspection despite the volumetric nature of the problem. The entire abdomen may now be continuously scanned within a single breath-hold with spiral CT. The GI tract can be computationally extracted from spiral CT images, the lumen explicitly unraveled onto a plane, and colonoscopy virtually simulated via fly-through display. A semi-automatic approach was developed for fly-through and unraveling in vivo. Automation of this approach was investigated in numerical simulation. The techniques are promising for colon cancer screening.
16 Apr 1996
TL;DR: Three-dimensional optical surface and SXCT imaging systems are feasible for capturing the comprehensive 3D surface geometry of BK residua, and provide distance measurements statistically equivalent to calipers, which can readily distinguish internal soft tissue and bony structure of the residuum.
Abstract: Accurate and reproducible geometric measurement of lower extremity residua is required for custom prosthetic socket design. We compared spiral x-ray computed tomography (SXCT) and 3D optical surface scanning (OSS) with caliper measurements and evaluated the precision and accuracy of each system. Spiral volumetric CT scanned surface and subsurface information was used to make external and internal measurements, and finite element models (FEMs). SXCT and OSS were used to measure lower limb residuum geometry of 13 below knee (BK) adult amputees. Six markers were placed on each subject's BK residuum and corresponding plaster casts and distance measurements were taken to determine precision and accuracy for each system. Solid models were created from spiral CT scan data sets with the prosthesis in situ under different loads using p-version finite element analysis (FEA). Tissue properties of the residuum were estimated iteratively and compared with values taken from the biomechanics literature. The OSS and SXCT measurements were precise within 1% in vivo and 0.5% on plaster casts, and accuracy was within 3.5% in vivo and 1% on plaster casts compared with caliper measures. Three-dimensional optical surface and SXCT imaging systems are feasible for capturing the comprehensive 3D surface geometry of BK residua, and provide distance measurements statistically equivalent to calipers. In addition, SXCT can readily distinguish internal soft tissue and bony structure of the residuum. FEM can be applied to determine tissue material properties interactively using inverse methods.
Journal Article•
TL;DR: Newer imaging systems, especially ultrasound, magnetic resonance imaging,'6 and digital fluoroscopy are used for neurosurgery, oncology, cardiothoracic and abdominal surgery, and each modality offers specific qualities that subserve specific needs in diagnosis, planning, intraoperative navigation and evaluation.
Abstract: Imaging i.n.surgery. is used for diagnosis, planning, intraoperative navigation and post-operative evaluation, DIgItal medical imaging modalities mclude computed tomography (CT), magnetic resonance Imaging (MRI), MR therapy (MRT), fluoroscopy and ultrasound.t These modalities are applied singly or jointly (multimodality) Surgical requirements differ according to the nature of intervention, and real-time guidance? is sometimes needed such that a sequence of images is generated and displayed as acquired, Soft copy display on CRTscreens is satisfactory for intraoperative use, while hardcopy film images or physical replica modeling may be needed in other cases. Computed tomography/ developed more than 20 years ago, remains important in craniofacial'v" and orthopedic surgery." Newer imaging systems, especially ultrasound, magnetic resonance imaging,'6 and digital fluoroscopy are used for neurosurgery, oncology, cardiothoracic and abdominal surgery. Each modality offers specific qualities that subserve specific needs in diagnosis, planning, intraoperative navigation and evaluation (Table 1).
TL;DR: In this article, the question of how an endocast (or brain) is oriented within a skull that is positioned in the Frankfurt plane was investigated for African great apes, early hominids, and modern humans using a 3SPACE digitizer.
Abstract: The question of how an endocast (or brain) is oriented within a skull that is positioned in the Frankfurt plane is investigated for African great apes, early hominids STS 71, KNM-ER 1813 and KNM-ER 1470, and modern humans using a 3SPACE digitizer. Our results suggest that, rather than being positioned in the orientation in which isolated brains (endocasts) are conventionally illustrated, brains within skulls that are oriented in the Frankfurt plane tend to be inclined so that the frontal pole is higher than the occipital pole, especially inHomo. These preliminary findings have implications for interpreting early hominid endocasts such as that of AL 162-28.