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Biomedical subjects

S W Yu

Publications and source records attributed to S W Yu.

32 records · Page 2Linked to original sources
PubMed1988

Anulus fibrosus in bulging intervertebral disks.

In this investigation the association of radial tears of the anulus fibrosus and bulging of the intervertebral disk was studied. An index of disk bulging was measured in sagittal anatomic sections in 149 lumbar disks from 31 cadavers. The indexes of disk bulging were correlated with stages of disk development and the presence of an annular tear. The largest disk-bulging indexes were always associated with radial tears of the anulus. Eighty-four percent of the disks with radial tears had disk-bulging indexes greater than 2.5 mm. Most normal adult disks had an index of less than 2.5 mm. The results challenge the concept that the anulus fibrosus is intact in bulging disks, although ruptured in herniated disks.

Adult↗
PubMed1988

Truncation artifact in MR images of the intervertebral disk.

A cadaver's vertebral column, a phantom, and a volunteer were imaged on a 1.5-T MR scanner to study the thin, uniform, dark, transverse lines that characterize some intervertebral disks. An artifactual dark line appears when the field of view (FOV) and matrix steps (n) are chosen so that d = FOV/n, where d equals the intervertebral disk height, or spacing between phantom vertebrae. The artifact is caused by the truncation effect. An artifactual dark line is differentiated from a dark line caused by anatomic variables, and means for reducing such lines by modifying imaging parameters are discussed.

Cadaver↗
PubMed1988

MR and cryomicrotomy of C1 and C2 roots.

Paramedian sagittal MR images and cryotome sections in four cadavers were correlated with eight clinical MR studies to analyze the appearance of the C1 and C2 nerve roots and adjacent tissue. The C2 nerve roots and anatomically related venous plexus were identified. The C1 root, although not visualized by MR, could be localized by its relation to the vertebral artery, C1 lateral mass, and posterior arch.

Adult↗
PubMed1987

Facet joint menisci of the cervical spine: correlative MR imaging and cryomicrotomy study.

An analysis of the cervical facet joint menisci was done in which cryomicrotomy sections were correlated with magnetic resonance (MR) images. In parasagittal anatomic sections in ten cadavers, 10-69 years of age at death, four types of meniscus were defined. Type 1 was a thin washer of dense connective tissue covering 50% or more of the joint space. Type 2 in sagittal section appeared as a wedge of connective tissue containing collagen in the tapering free edge and fat in the peripheral portion attached to the joint capsule. Type 3 had no meniscuslike connective tissue extending into the joint. Type 4 had irregular, thick masses of collagen, fat, and cartilage in the periphery of the joint space. Menisci in the child were predominantly type 1. In adults type 2 menisci predominated at C1-2 and type 3 in the lower cervical facet joints. The few type 4 menisci found were in association with facet joint degeneration. Types 2 and 4 menisci could be demonstrated with MR imaging. In MR images the collagenous portion of the menisci were of low signal intensity, and the fat was of higher signal intensity. Few menisci conform to the traditional anatomic description.

Adult↗
PubMedDate not supplied

Age-related changes in the cervical facet joints: studies with cryomicrotomy, MR, and CT.

The cervical facet joints of 20 cadavers were studied systematically with MR, CT, cryomicrotomy, and histologic sections to determine the anatomic changes that occur with age. Uniform layers of cartilage and subarticular cortical bone characterize the cervical facet joints in cadavers under 20 years of age. Most adult cervical facet joints have only a discolored or microscopically thin layer of cartilage and have irregularly thickened subarticular cortical bone. The appearance of the cervical facet joints changes significantly with aging.

Adult↗
PubMedDate not supplied

An experimental model to study contrast enhancement in MR imaging of the intervertebral disk.

MR imaging after IV gadolinium-DTPA administration has demonstrated contrast enhancement in traumatized lumbar intervertebral disks. To characterize the morbid anatomy that correlates with the contrast enhancement, we developed a canine model of traumatized intervertebral disks. Diskectomy was performed with a nucleotome and the spines were imaged biweekly with MR and Gd-DTPA. The spines were studied at necropsy, and their anatomic abnormalities correlated with contrast enhancement detected by MR imaging. Our preliminary results indicate that contrast enhancement occurs where granulation tissue develops in traumatized intervertebral disks.

Animals↗
PubMedDate not supplied

MR appearance of gray and white matter at the cervicomedullary region.

To study the appearance of gray and white matter in the cervicomedullary region, six fresh cadavers were imaged with a 1.5-T MR scanner and then sectioned with a cryomicrotome. The pyramidal tracts, fasciculus cuneatus and gracilis, inferior olivary nuclei, supraspinal nuclei, spinal trigeminal nuclei, and medial lemnisci were identified by MR in the cervicomedullary region.

Adult↗
PubMedDate not supplied

Comparison of MR and diskography in detecting radial tears of the anulus: a postmortem study.

Radial tears of the anulus fibrosus, which anatomic studies suggest are a primary event in disk degeneration, can be detected by diskography or MR imaging. We compared the sensitivity of MR and diskography in the detection of anular tears. MR, diskography, and cryomicrotomy anatomic sectioning were performed in eight cadaver lumbar spines. Diskography demonstrated 15 radial tears in 36 intervertebral disks. MR demonstrated 10 of the 15, a sensitivity of 67%. MR (T2-weighted images) in each of the diskographically normal disks showed the high signal intensity characteristic of normal disks. Thirteen of 15 disks from which contrast medium extravasated at diskography had diminished signal intensity in MR images. We conclude that although MR may demonstrate some radial tears of the anulus, and associated changes in the disk, it cannot be used as effectively as diskography to visualize a radial tear.

Aged↗
PubMedDate not supplied

Fibrous structure in the intervertebral disk: correlation of MR appearance with anatomic sections.

To correlate the MR appearance of the disk with its fibrous structure, we studied the lumbar intervertebral disks in 10 cadavers with MR, CT, cryomicrotome anatomic sections, and, in selected disks, with histologic and dried sections. In MR images the predominantly fibrous tissues such as Sharpey's fibers had a low signal intensity while the fibrocartilagenous tissues with a mucoid matrix in the intervertebral disk had a high signal intensity. In the equator of the adult disk was a well-defined fibrous plate that contained collagenous, elastic, and reticular fibers with little ground substance. This plate appeared to develop progressively from the periphery of the nucleus toward the center, starting in the second decade of life. The fibrous plate was also distinguished as a lower signal intensity in the MR images.

Adult↗
PubMedDate not supplied

Tears of the anulus fibrosus: correlation between MR and pathologic findings in cadavers.

Tears of the anulus fibrosus, which have been implicated in back pain, have not been studied systematically with MR imaging. We correlated MR images with cryomicrotome sections to study the lumbar anulus fibrosus in 20 cadavers. Three distinct types of tears of the anulus were identified: concentric tears, characterized by fluid-filled spaces between adjacent lamellae; radial tears, characterized by a rupture of all layers in the anulus between the nucleus and the surface of the disk; and transverse tears, characterized by a rupture of Sharpey's fibers in the periphery of the anulus, near the ring apophysis. In each type, fluid or mucoid material was present in the tear. MR demonstrated the transverse and radial tears. We conclude that MR imaging provides an accurate means for investigating tears of the anulus.

Cadaver↗
PubMedDate not supplied

The MR appearance of gray and white matter in the cervical spinal cord.

Artifacts that can distort the appearance of the cervical spinal cord are caused by data truncation during MR image reconstruction. We used a phantom and then correlated anatomic sections with MR images in cadavers and normal volunteers to evaluate the effect of truncation artifacts on the MR appearance of the spinal cord. When truncation artifacts are minimized, the gray matter and major white-matter columns in the cervical cord can be recognized. T2-weighted gradient-echo MR techniques can best differentiate gray from white matter.

Humans↗