PubMed Health⌕ Search

Biomedical subjects

Gordon Harris

Publications and source records attributed to Gordon Harris.

5 recordsLinked to original sources
PubMed2005

MRI-based surface-assisted parcellation of human cerebellar cortex: an anatomically specified method with estimate of reliability.

We revisit here a surface assisted parcellation (SAP) system of the human cerebellar cortex originally described in Makris, N., Hodge, S.M., Haselgrove, C., Kennedy, D.N., Dale, A., Fischl, B., Rosen, B.R., Harris, G., Caviness, V.S., Jr., Schmahmann, J.D., 2003. Human cerebellum: surface-assisted cortical parcellation and volumetry with magnetic resonance imaging. J Cogn Neurosci 15, 584-599. This system preserves the topographic and morphologic uniqueness of the individual cerebellum and allows for volumetric analysis and representation of multimodal structural and functional data on the cerebellar cortex. This methodology integrates features of automated routines of the program FreeSurfer as well as semi-automated and manual procedures of the program Cardviews to create 64 cerebellar parcellation units based on fissure information and anatomical landmarks of the cerebellar surface. Using this technique, we undertook the parcellation of ten cerebella by two independent raters. The reliability of the resulting parcellation units (64 total) was high, with an average Intraclass Correlation Coefficient (ICC) of 0.724 in the vermis and 0.853 in the hemispheres. Clusters of parcellation units were then created, based on lobar and connectivity data and functional hypotheses. These 36 clusters, when treated as anatomical units, had an average ICC of 0.933. Whereas the individual units provide a high level of detail and anatomical specificity, the clusters add flexibility to the analysis by providing higher reliability.

Algorithms↗
PubMed2005

Multi-detector row CT in evaluation of 94 living renal donors by readers with varied experience.

PURPOSE: To retrospectively assess the accuracy of four-section multi-detector row computed tomography (CT) in the evaluation of renal transplant donors when scans are read by one of multiple readers with varied levels of expertise, by using surgery as the reference standard. MATERIALS AND METHODS: This retrospective study was approved by the institutional review board and complied with the Health Insurance Portability and Accountability Act. Informed consent was waived. Between October 1999 and March 2003, 94 renal donors (42 men, 52 women; mean age, 44 years) underwent four-section multi-detector row CT. Unenhanced scanning of the abdomen was performed with 5-mm section thickness and table speed of 15 mm per rotation. Next, 135-150 mL of nonionic iodinated (300 mg/mL) contrast material was injected intravenously at a rate of 4-5 mL/sec. Contrast material-enhanced CT was initiated 20-25 seconds, 65-70 seconds, and 10 minutes after start of injection. Arterial phase scanning was performed with 1.25-mm section thickness and 7.5-mm table speed. Venous and excretory phase scanning was performed with 2.5-mm section thickness and 15-mm table speed. Each scan was evaluated independently by one of 11 readers for renal vascular and ureteral anatomic variants. Findings at CT were compared with those at surgery. Sensitivity and specificity (with 95% confidence intervals) and accuracy of CT were calculated on the basis of presence or absence of variant anatomy at surgery. RESULTS: CT depicted 107 of 114 renal arteries confirmed at surgery; seven accessory arteries were missed in six donor kidneys. CT depicted 95 of 98 renal veins confirmed at surgery. Sensitivity and specificity of CT were 66% and 100%, 75% and 100%, and 50% and 100%, and overall accuracy was 94%, 97%, and 99%, for identification of variant anatomy of renal arteries, veins, and ureters, respectively. CONCLUSION: Multi-detector row CT as the sole imaging technique in the preoperative evaluation of living renal donors is accurate even when images are read by multiple readers with varied levels of expertise.

Adult↗
PubMed2004

Overt propositional speech in chronic nonfluent aphasia studied with the dynamic susceptibility contrast fMRI method.

This study examined activation levels in the left (L) supplementary motor area (SMA) and the right (R) SMA (separately), and activation in nine R perisylvian language homologues during overt, propositional speech in chronic nonfluent aphasia patients. Previous functional imaging studies with a variety of chronic aphasia patients have reported activation in these regions during different language tasks, however, overt propositional speech has not been examined. In the present research, four nonfluent aphasia patients were studied during overt elicited propositional speech at 4-9 years post-single L hemisphere stroke, which spared the SMA. The dynamic susceptibility contrast (DSC) method of functional MRI was used to calculate relative cerebral blood volume (relCBV) for cortical regions of interest (ROIs) during the first-pass bolus of gadolinium during two conditions: (1) pattern (silent viewing of checkerboard patterns) and (2) story (overt, elicited propositional speech describing sequential pictures, which formed a story). During the story condition, controls had significantly higher relCBV in L SMA than in R SMA; aphasics, however, had significantly higher relCBV in R SMA than in L SMA. During the pattern condition, no significant differences were observed between the L SMA and the R SMA for either controls or aphasics. In addition, aphasics had significantly higher relCBV in the R sensorimotor mouth during story than pattern. This R sensorimotor mouth relCBV was also significantly higher in aphasics than controls during story, and the two groups did not differ during pattern. The overall mean relCBV for the nine R perisylvian ROIs was significantly higher for aphasics than controls during both story and pattern. These results suggest that poor modulation, including possible over-activation of R sensorimotor mouth and other R perisylvian language homologues may underlie in part, the hesitant, poorly articulated, agrammatic speech associated with nonfluent aphasia.

Adult↗
PubMed2003

Human cerebellum: surface-assisted cortical parcellation and volumetry with magnetic resonance imaging.

We describe a system of surface-assisted parcellation (SAP) of the human cerebellar cortex derived from neural systems functional and behavioral anatomy. This system is based on MRI and preserves the unique morphologic and topographic features of the individual cerebellum. All major fissures of the cerebellum were identified and traced in the flattened representation of the cerebellar cortex using the program "FreeSurfer." Parcellation of the cerebellar cortex followed using the fissure information in conjunction with landmarks using the program "Cardviews" to create 64 gyral-based cerebellar parcellation units. Computer-assisted algorithms enable the execution of the cerebellar parcellation procedure as well as volumetric measurements and topographic localization. The SAP technique makes it possible to represent multimodal structural and functional imaging data on the flattened surface of the cerebellar cortex as illustrated in one functional MRI experiment.

Adult↗