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T L Richards

Publications and source records attributed to T L Richards.

44 records · Page 3Linked to original sources
PubMed1987

Lipid/water ratio of bone marrow measured by phase-encoded proton nuclear magnetic resonance spectroscopy.

Proton NMR spectroscopy (spatially resolved) at 0.7 Tesla with a whole body superconducting magnet was performed on bone marrow from human lumbar spine to measure the lipid/water ratio. Phase-encoded proton spectroscopy was performed by using (1) a spin-echo sequence with selective 90 degrees and 180 degrees rf pulses on the Z and X axes; (2) 64 different phase encodes along the Y axis; and (3) echo acquisition with no gradient. The lipid/water ratios also were measured by the Folch chemical extraction technique. The set of phase-encoded spectra obtained from the spine demonstrates the chemical difference between the vertebral disk (large water peak and no lipid peak) and the marrow (smaller water peak and detectable lipids). Lipid/water ratios were lower than the chemically measured ratios. The phase-encoded proton spectroscopic technique presented in this study allowed rapid acquisition of localized spectra from the bone marrow in each of three vertebral bodies of the intact human spine. This technique provided a measure of the mobile lipid/water ratio weighted by relaxation times.

Body Water↗
PubMed1985

In vivo sodium-23 magnetic resonance surface coil imaging: observing experimental cerebral ischemia in the rat.

Sodium-23 magnetic resonance imaging can be used to detect and assess experimental cerebral ischemia in the rat. An imaging technique utilizing a surface coil is described to produce sodium magnetic resonance images of good quality and resolution within 10 min. A novel method of hemispheric occlusion showed edema in the right brain of the rat head within 3 hr after injury. The edema was especially pronounced by 12 hr with effects in the right brain, eye and surrounding muscle evident.

Animals↗
PubMed1981

Midtrimester amniocentesis. Subjective maternal responses.

Studies, through questionnaire and interview, of couples who elect or decline midtrimester amniocentesis demonstrate that both groups cope well with new decisions surrounding this procedure. The pregnancy monitored by genetic amniocentesis does not appear to receive special status as viewed by the parents, nor is the developing fetus placed in a special category during the pregnancy.

Adult↗
PubMedDate not supplied

Partial volume effects in volume-localized phased-array proton spectroscopy of the temporal lobe.

MRS techniques can aide in confirming the location of seizure foci in temporal lobe epilepsy. N-acetyl aspartate (NAA), creatine plus phosphocreatine, choline-containing compounds, and lactate are most often the clinically relevant metabolites in these studies. We examined the importance of partial volume effects from tissue heterogeneity in temporal lobe spectroscopy on the metabolite ratios. Our study shows that localized spectroscopy, using three different voxel sizes, centered on the anterior body of the hippocampus, produces significantly different values for the NAA to the creatine ratio. The spectroscopy was performed at 1.5 T using the PRESS pulse sequence and a phased-array coil system specifically designed for the temporal lobe. The data exhibits a clear trend of increasing NAA to creatine ratios with increasing voxel size. This trend demonstrates that partial volume effects can contribute to variation of NAA to creatine ratios in healthy subjects.

Artifacts↗
PubMedDate not supplied

Magnetic resonance imaging and spectroscopy in fetal ethanol exposed Macaca nemestrina.

Magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (1H-MRS) offer noninvasive ways to observe structural and biochemical changes which might serve as valuable diagnostic markers for detecting brain damage from prenatal ethanol teratogenesis. Cranial MR imaging and spectroscopy were performed on 20 nonhuman primates (Macaca nemestrina) with known prenatal ethanol exposures and well-documented cognitive and behavioral levels of performance. The choline: creatine ratio detected by 1H-MRS in the brain increased significantly with increasing duration of in utero ethanol exposure. These signal alterations occurred in the absence of gross structural brain anomalies (detectable by MRI) and were significantly correlated with alcohol-related cognitive and behavioral dysfunction. These observations are consistent with reports of elevated choline: creatine ratios associated with various neurologic insults and disease states. The association observed between brain choline:creatine ratios and in utero ethanol exposure suggest a role for 1H-MRS in elucidating mechanisms of ethanol teratogenicity.

Analysis of Variance↗
PubMedDate not supplied

Cerebral N-acetylaspartate is low in patients with multiple sclerosis and abnormal visual evoked potentials.

PURPOSE: Our purpose was to compare cerebral proton MR metabolite changes in patients with multiple sclerosis (MS) and abnormal visual evoked potentials (VEPs) with those in MS patients with normal VEPs. METHODS: Seventeen subjects with clinically definite MS were studied with VEPs and MR spectroscopic imaging. Proton MR metabolites were measured using a fast spectroscopic imaging technique called proton echo-planar spectroscopic imaging (PEPSI). Kurtzke's Expanded Disability Status Scale (EDSS) score was also ascertained for each subject to obtain a clinical rating. Twelve regions of interest within the visual pathway of the cerebrum were evaluated for levels of N-acetylaspartate (NAA), choline, creatine, and the presence or absence of MR-detectable lesions. RESULTS: PEPSI NAA values (water-normalized, CSF-corrected) were significantly lower in MS subjects with abnormal VEPs than in subjects with normal VEPs. MR-detectable lesion fractions and EDSS scores were also significantly different between the two VEP groups, but NAA comparison had a P value 100 times less than either of these measures. CONCLUSION: In patients with MS, NAA measurements in the optic pathways of the brain were sensitive to VEP abnormalities. NAA was more sensitive to VEP changes than were choline, creatine, MR-detectable lesions, and EDSS score.

Adult↗