Advances in radiologic image analysis from MICCAI 2005.
Explore the source record for details and available documents.
Algorithms↗
Biomedical subjects
Martin Styner
Publications and source records attributed to Martin Styner.
Reduced relationship to cortical white matter volume revealed by tractography-based segmentation of the corpus callosum in young children with developmental delay.
OBJECTIVE: The corpus callosum is the primary anatomical substrate for interhemispheric communication, which is important for a range of adaptive and cognitive behaviors in early development. Previous studies that have measured the corpus callosum in developmental populations have been limited by the use of rather arbitrary methods of subdividing the corpus callosum. The purpose of this study was to measure the corpus callosum in a clinical group of developmentally delayed children using a subdivision that more accurately reflected the anatomical properties of the corpus callosum. METHOD: The authors applied tractography to subdivide the corpus callosum into regions corresponding to the cortical regions to and from which its fibers travel in a clinical group of very young children with developmental delay, a precursor to general mental retardation, in comparison with typically developing children. RESULTS: The data demonstrate that the midsagittal area of the entire corpus callosum is reduced in children presenting with developmental delay, reflected in the smaller area of each of the fiber-based callosal subdivisions. In addition, while the area of each subdivision was strongly and significantly correlated with the corresponding cortical white matter volume in comparison subjects, this correlation was prominently absent in the developmentally delayed group. CONCLUSIONS: A fiber-based subdivision successfully separates lobar regions of the corpus callosum, and the areas of these regions distinguish a developmentally delayed clinical group from the comparison group. This distinction was evident both in the area measurements themselves and in their correlation to the white matter volumes of the corresponding cortical lobes.
Atrophy↗
Morphometric analysis of lateral ventricles in schizophrenia and healthy controls regarding genetic and disease-specific factors.
The structural variability of lateral ventricles is poorly understood notwithstanding that enlarged size has been identified as an unspecific marker for psychiatric illness, including schizophrenia. This paper explores the effects of heritability and genetic risk for schizophrenia reflected in ventricular size and structure. We examined ventricular size and shape in the MRI studies of monozygotic (MZ) twin pairs discordant for schizophrenia (DS), healthy MZ twin pairs, healthy dizygotic twin pairs, and healthy nonrelated subject pairs. Heritability and effect due to disease were analyzed in two tests. First, heritability was examined by ventricle similarity between pairs of co-twins. Results show that co-twin ventricle shape similarity decreases with decreasing genetic identity, an effect not seen in the volume analysis. Co-twin shape similarity of healthy MZ twins did not differ from DS MZ twins. Second, the disease effect was examined through the ventricular differences of DS subjects to a template shape representing healthy subjects. Affected DS twins showed shape differences from healthy subjects on the left and right sides. Interestingly, unaffected DS twins also showed significant shape differences from healthy subjects for both sides. Volume comparisons did not show differences between these groups. Locality of shape difference suggests that the ventricular shape of the anterior and posterior regions is under genetic influence in both healthy controls and schizophrenia patients. Affected and unaffected groups demonstrate main shape differences, compared with healthy controls, only in the posterior region. Our results suggest that genetics have a stronger influence on the shape of lateral ventricles than do the disease-related changes in schizophrenia.
Adult↗
Automatic method to assess local CT-MR imaging registration accuracy on images of the head.
BACKGROUND AND PURPOSE: Precise registration of CT and MR images is crucial in many clinical cases for proper diagnosis, decision making or navigation in surgical interventions. Various algorithms can be used to register CT and MR datasets, but prior to clinical use the result must be validated. To evaluate the registration result by visual inspection is tiring and time-consuming. We propose a new automatic registration assessment method, which provides the user a color-coded fused representation of the CT and MR images, and indicates the location and extent of poor registration accuracy. METHODS: The method for local assessment of CT-MR registration is based on segmentation of bone structures in the CT and MR images, followed by a voxel correspondence analysis. The result is represented as a color-coded overlay. The algorithm was tested on simulated and real datasets with different levels of noise and intensity non-uniformity. RESULTS: Based on tests on simulated MR imaging data, it was found that the algorithm was robust for noise levels up to 7% and intensity non-uniformities up to 20% of the full intensity scale. Due to the inability to distinguish clearly between bone and cerebro-spinal fluids in the MR image (T1-weighted), the algorithm was found to be optimistic in the sense that a number of voxels are classified as well-registered although they should not. However, nearly all voxels classified as misregistered are correctly classified. CONCLUSION: The proposed algorithm offers a new way to automatically assess the CT-MR image registration accuracy locally in all the areas of the volume that contain bone and to represent the result with a user-friendly, intuitive color-coded overlay on the fused dataset.
Algorithms↗
New method to assess the registration of CT-MR images of the head.
Due to their complementary information content, both x-ray computed tomography (CT) and magnetic resonance (MR) imaging are employed in certain clinical cases to improve the understanding of pathology involved. o spatially relate the two datasets, image registration and image fusion are employed. However, registration errors, either global or local, are common and are nonuniform within the image volume. In this paper, we propose a new algorithm that assesses the quality of the registration locally within the CT-MR volume and provides visual, color-coded feedback to the user about the location and extent of good and bad correspondence between the two images. The proposed registration assessment algorithm is based on a correspondence analysis of bone structures in the CT and MR images. For that purpose, a custom segmentation algorithm for bone in MR images has been developed that is based on a stochastic threshold computation method. This segmentation method for MR images and the CT-MR registration assessment algorithm were validated on simulated MR datasets and real CT-MR image pairs of the head. Some partial-volume effects occur at the borders of the bone structures and at the bone interfaces with air, which cannot be separated from bone in the MR image. The presented assessment method of CT-MR image registration offers the user a new tool to evaluate the overall and local quality of the registration. With this information, the user does not have to blindly trust the fused CT-MR datasets but can easily identify areas of inaccurate correspondence. The application of the algorithm is so far limited to T1-weighted MR and CT images of the head area.
Algorithms↗
Boundary and medial shape analysis of the hippocampus in schizophrenia.
Statistical shape analysis has become of increasing interest to the neuroimaging community due to its potential to precisely locate morphological changes and thus potentially discriminate between healthy and pathological structures. This paper describes a combined boundary and medial shape analysis based on two different shape descriptions applied to a study of the hippocampus shape abnormalities in schizophrenia. The first shape description is the sampled boundary implied by the spherical harmonic SPHARM description. The second one is the medial shape description called M-rep. Both descriptions are sampled descriptions with inherent point correspondence. Their shape analysis is based on computing differences from an average template structure analyzed using standard group mean difference tests. The results of the global and local shape analysis in the presented hippocampus study exhibit the same patterns for the boundary and the medial analysis. The results strongly suggest that the normalized hippocampal shape of the schizophrenic group is different from the control group, most significantly as a deformation difference in the tail region.
Brain Mapping↗
A-mode ultrasound-based registration in computer-aided surgery of the skull.
OBJECTIVE: To evaluate the integration and accuracy of A (amplitude)-mode ultrasound-based surface matching for noninvasive registration of the head into a frameless computer-aided surgery system for otorhinology and skull base surgery. DESIGN: Experimental study and case series. SETTING: Academic medical center. PATIENTS: Twelve patients underwent anterior and paranasal skull base surgery with the routine use of a computer-aided surgery system. INTERVENTIONS: A computer-aided surgery system, based on an optoelectronic localizer, was used to track the skull and the surgical tools, including the A-mode ultrasound probe. The A-mode probe was a 10-MHz immersion transducer. An acoustic lens attached to the transducer focused the ultrasonic beam to a depth of 1 to 10 mm. Accuracy tests were performed for the ultrasound setup. Different surface point distributions were evaluated with respect to matching accuracy on a human cadaver skull specimen equipped with fiducial markers. The matching comparison was based on the fiducial registration error. For the clinical evaluation, the laboratory setup was transferred to the operating room. MAIN OUTCOME MEASURES: Noninvasive registration of the skull by using A-mode ultrasound in computer-aided surgery (practical and clinical measurements). RESULTS: The accuracy tests on the human skull specimen revealed that the mean +/- SD fiducial registration error was 1.00 +/- 0.19 mm in the best series for A-mode ultrasound surface matchings and was robust with respect to different sets of surface points. The mean +/- SD root mean square error from the 12 A-mode ultrasound matchings in the patient study was 0.49 +/- 0.20 mm. CONCLUSION: A-mode ultrasound surface matching can be used as a noninvasive and accurate registration procedure in computer-aided surgery of the head.
Bias↗
Computer-assisted arthroplasty using bioengineered autografts.
Explore the source record for details and available documents.
Ankle Joint↗
A comparison study assessing the feasibility of ultrasound-initialized deformable bone models.
This article presents a feasibility and evaluation study for using 2D ultrasound in conjunction with our statistical deformable bone model within the scope of computer-assisted surgery. The final aim is to provide the surgeon with enhanced 3D visualization for surgical navigation in orthopedic surgery without the need for preoperative CT or MRI scans. We unified our earlier work to combine several automatic methods for statistical bone shape prediction and ultrasound segmentation and calibration to provide the intended rapid and accurate visualization. We compared the use of a tracked digitizing pointer and ultrasound for acquiring landmarks and bone surface points for the estimation of two cast proximal femurs.
Bone and Bones↗
Intraoperative three-dimensional fluoroscopic cholangiography.
Precise intraoperative assessment of the architecture of the biliary tree could reduce lesions to intra- or extrahepatic bile ducts. The aim of this study was to test feasibility of intraoperative three-dimensional imaging during liver resections. Isocentric C-arm fluoroscopy acquires three-dimensional images during a 190 degrees orbital rotation. The bile ducts were displayed three-dimensionally by realtime rotational projections or multiplanar reconstructions. The technique was established ex vivo in a preserved cadaveric human liver. Intraoperative three-dimensional cholangiography was performed in five patients with centrally located liver malignancies. Complete data acquisition in 3 patients depicted precise anatomical details of the architecture of the biliary tree up to third order divisions. Biliary imaging can be improved by the application of real-time intraoperative three-dimensional cholangiography. For the development of computer-aided navigation in hepatobiliary procedures, this technique could be an important prerequisite for defining landmarks of the liver in a three-dimensional space.
Aged↗