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Biomedical subjects

R N Bryan

Publications and source records attributed to R N Bryan.

At least 91 records · Page 5Linked to original sources

Magnetic resonance imaging diagnosis of an intracranial metastasis of adenocarcinoma of the prostate: case report.

Adenocarcinoma of the prostate is the second most common cancer of American males over age fifty. However, the reported instances of cerebral metastases have been exceedingly rare and are usually diagnosed at postmortem. This report describes an unusual case of brain metastasis from an occult adenocarcinoma of the prostate confirmed by craniotomy and tumor resection.

Adenocarcinoma↗

Phosphorus magnetic resonance spectroscopy of patients with mitochondrial cytopathies demonstrates decreased levels of brain phosphocreatine.

The hypothesis that brain mitochondria are directly affected in several phenotypes associated with disordered oxidative phosphorylation was tested using phosphorus 31 (31P) magnetic resonance spectroscopy. Abnormal phosphorylation potentials in skeletal muscle have been demonstrated by 31P magnetic resonance spectroscopy in patients with mitochondrial cytopathies (heritable disorders of oxidative phosphorylation), but abnormalities of phosphorylation potentials in other organs have not been documented. Several lines of evidence suggest that these mutations may affect mitochondria in nonmuscle tissue. In this study we found that phosphocreatine-to-ATP ratios in brain were significantly reduced and that calculated brain ADP concentrations, phosphorylation potentials, and percentage of maximal rate of ATP synthesis were significantly altered in the 5 patients examined. This study indicates a primary abnormality of mitochondrial function in the brain, even in the absence of clinically evident cerebral dysfunction.

Adenosine Triphosphate↗

Bright lesions on sellar/parasellar T1-weighted scans.

Eighty-seven patients with sellar and parasellar pathology were evaluated by magnetic resonance imaging to categorize lesions with hyperintensity on T1-weighted images. Postoperative fat packing after transsphenoidal hypophysectomy, intratumoral subacute or chronic hemorrhage in pituitary adenomas, and hemorrhagic or fat-containing craniopharyngiomas accounted for 33 of 35 abnormalities with short T1 values. Forty-three percent of nonsurgically treated pituitary adenomas had subacute intratumoral hemorrhage present. Using T2-weighted images to distinguish fat from subacute hemorrhage and attempting to identify the normal anterior pituitary gland on T1-weighted images may help to differentiate these three entities. T1-weighted images alone were not sufficient to distinguish between all sellar and parasellar masses.

Adenoma↗

Acquired immunodeficiency syndrome: correlation of radiologic and pathologic findings in the brain.

The appearance on magnetic resonance (MR) and computed tomographic (CT) images of specific central nervous system disorders associated with acquired immunodeficiency syndrome in 12 cases was correlated with autopsy findings. There were three cases of human immunodeficiency virus (HIV) encephalopathy; three, primary lymphoma; three, toxoplasmosis; one, cryptococcosis; one, cytomegalovirus infection; and one, progressive multifocal leukoencephalopathy. MR imaging demonstrated the various cranial lesions more clearly than did CT. On the basis of MR imaging characteristics, HIV encephalopathy could be distinguished from other lesions, particularly progressive multifocal leukoencephalopathy. Basal ganglia were the most common sites of involvement in opportunistic infections and primary lymphoma. Reliable distinguishing features among lesions of the basal ganglia were not found, except for cryptococcal lesions, which had a unique appearance.

AIDS Dementia Complex↗

[Encephalic lesions in neurofibromatosis: clinical manifestations and typical magnetic resonance findings].

Neurofibromatosis is the commonest neuroectodermal disease. It is characterized by dysplasias and/or tumors of organs and tissues derived from the embryonic ectoderm, mesoderm and endoderm, and most frequently presents with nervous system and cutaneous lesions. It can be classified as neurofibromatosis type 1 (NF-1 or von Recklinghausen disease) and neurofibromatosis type 2 (NF-2 or bilateral acoustic neurofibromatosis). In order to assess clinical presentation of the disease and diagnostic value of Magnetic Resonance Imaging (MRI), the authors retrospectively evaluated the clinical records and the cranial MR studies of 21 patients with neurofibromatosis (18 with NF-1 and 3 with NF-2). Distinctive abnormalities between the two types were found in both clinical presentation and MR studies. Clinically, NF-1 patients presented most often with blindness, while NF-2 patients were deaf and had fewer cutaneous lesions. The evaluation of MR studies showed that NF-1 patients were more likely to be affected with intracranial gliomas, predominantly of the optic pathways. Moreover, foci of prolonged T2 relaxation were frequently observed, primarily in the globus pallidus of the basal ganglia and in the dentate nucleus of the cerebellum. Some of the foci in the globi pallidi exhibited increased signal intensity on T1-weighted images as well. NF-2 patients more frequently presented with bilateral acoustic schwannomas, meningiomas and cerebral white matter foci of prolonged T2 relaxation, but they did not have dentate and basal ganglia lesions. The authors conclude that as a rule the manifestations of NF-1 and NF-2 on cranial MRI are separate and distinct; they do not overlap. MRI is an useful clinical tool for the diagnosis and the follow-up of patients with neurofibromatosis.

Adolescent↗

Characterization of fluid flow using low-spatial-resolution velocity spectra from NMR images.

Flow velocity distributions or spectra may be obtained by NMR imaging using an anisotropic three-dimensional Fourier transform pulse sequence in which the low-resolution direction encodes perpendicular velocity. Velocity spectra from regions of interest covering the entire lumens of pipes in a flow phantom containing straight sections, a jet, and a constriction suggest that velocity spectra provide useful information even when the vessels are not spatially well-resolved. The flow in the phantom was characterized and limited measurements were made.

Blood Flow Velocity↗

Pituitary adenomas: possible role of bromocriptine in intratumoral hemorrhage.

Magnetic resonance (MR) images of 68 patients examined for adenomas of the pituitary gland were retrospectively reviewed for the presence of hyperintensity on T1-weighted images because of recent reports suggesting that bromocriptine treatment may affect T1 values. Twenty-seven patients were examined after either surgery or radiation therapy, 29 were receiving bromocriptine, and 22 had not received any treatment at the time of MR imaging. MR imaging criteria showed evidence of subacute or chronic intratumoral hemorrhage in 18 patients, five of whom had hemorrhage proved at surgery. Ten of the 18 patients were asymptomatic from the hemorrhage; eight had headaches, visual field cuts, or cranial nerve deficits. Although an increased frequency of intratumoral hemorrhage was noted in prolactinomas and macroadenomas and in patients undergoing bromocriptine therapy, the effect of bromocriptine on bleeding was the only significant correlation (P less than .01).

Adenoma↗

T2 effect of hemoglobin concentration: assessment with in vitro MR spectroscopy.

T2 values were measured at 0.23 and 4.7 T for deoxygenated blood samples (43%-73% O2 saturation) with hematocrits of 18%-100%. An increase in the hematocrit produced a marked reduction in T2 at both field strengths. Cell lysis did not abolish the T2 effect at either field strength. The authors conclude that the increase in hemoglobin concentration caused by formation of a retracted clot is a cause of the hypointense appearance of acute hemorrhage compared with brain on T2-weighted clinical magnetic resonance images. This is particularly important on low-field-strength systems, which are not sensitive to the T2 shortening effects of paramagnetic intracellular deoxyhemoglobin.

Animals↗

MR imaging of susceptibility-induced magnetic field inhomogeneities.

A 90 degrees-tau 1-90 degrees-tau 2-image acquisition pulse sequence allows spatial mapping of resonant frequency. This sort of sequence has previously been used for magnet shimming, and its use in chemical-shift imaging has been proposed. The authors used this sequence in magnetic resonance imaging of a phantom to demonstrate the magnetic field gradients arising from susceptibility differences within the phantom and allow those gradients to be measured. Gradients may arise near interfaces between substances that cannot support the same magnetic flux density. The pulse sequence was found to work well in lower-field-strength instruments.

Brain↗

A comparative analysis of the NMR relaxation times of two human colon cancer cell lines.

Two human colon cancer cell lines grown in tissue culture were found to have significantly different Nuclear Magnetic Resonance (NMR) relaxation times of water protons in the fresh, intact state and after fragmentation into subcellular fractions. Differences in the protein composition of the subcellular fractions were also demonstrated by protein analysis and gel chromatography. In further studies, these cell lines may be useful to investigate the biochemical basis for the disparity in relaxation times of water protons between tissues which constitutes the basis for Magnetic Resonance Imaging (MRI) tissue contrast.

Cell Division↗

Retrospective study of Gen-Probe rapid diagnostic system for detection of legionellae in frozen clinical respiratory tract samples.

The Gen-Probe Rapid Diagnostic System for legionellae, which uses 125I-labeled cDNA directed against the rRNAs of legionellae, was evaluated for its ability to detect members of the genus by using clinical specimens which had been frozen at -70 degrees C for 2 to 8 years. Culture and direct immunofluorescence (DFA) results obtained at the time of specimen collection were used to categorize samples. The specimens tested were 112 samples culture positive for legionellae and 230 samples negative on culture and DFA tests. They were tested in a blinded and randomized fashion. Results were expressed in terms of the ratio of counts per minute of the sample to the counts per minute of the provided negative control. A ratio of greater than or equal to 4.0 was picked for optimal specificity. Of the 112 previously positive specimens, 63 (57%) were positive by the probe assay, and of the 230 previously negative samples, 228 (99.1%) were negative. The 51 discrepant specimens were reexamined by culture and DFA testing if adequate amounts remained; this was possible for 34 specimens. On repeat culture, 22 of 33 previously culture-positive samples yielded legionellae and 11 were negative. Ten of the positive repeat cultures yielded two or fewer colonies per plate. One probe-positive but previously culture-negative sample was overgrown by contaminants on repeat culture. Reanalysis of data after exclusion of the 17 unavailable, 11 repeat culture-negative, and 1 unevaluable specimen gave a probe sensitivity of 74% and specificity of 100%. The Gen-Probe test is therefore specific and is of useful sensitivity.

DNA↗

Typing of herpes simplex virus with synthetic DNA probes.

Three single-stranded oligonucleotide probes, 22 bases long, homologous to unique regions of herpes simplex virus (HSV) types 1 (HSV-1) and 2 (HSV-2) and a region common to both were chemically synthesized with use of a modified phosphochloridite protocol. For hybridization experiments each probe was labeled with use of polynucleotide kinase and [gamma-32P] ATP to a specific activity of approximately 2 X 10(9) cpm/micrograms. Two hundred one clinical isolates of HSV (96 HSV-1 and 105 HSV-2) collected from vesicles in the mucocutaneous junction of the mouth or from the genital area were analyzed. There was a 99% (199 of 201) agreement between hybridization and monoclonal antibody typing; the two discrepant isolates of HSV-2 that were negative by monoclonal antibody typing were confirmed as HSV-2 by restriction endonuclease analysis. The probes detected between 10(4) and 10(5) HSV infectious units and from 150 to 600 HSV-infected Vero cells. No binding was detected between any of the three probes and isolates of cytomegalovirus, Epstein-Barr virus, and varicella-zoster virus.

Animals↗

Myocardial infarct size quantification by MR imaging early after coronary artery occlusion in dogs.

The feasibility of using magnetic resonance (MR) imaging to estimate myocardial infarct size was explored in an in vitro model using only the inherent differences in contrast between infarcted and noninfarcted myocardium. Eight dogs underwent coronary occlusion; their hearts were removed 6 hours later. Estimates of T2 for normal and infarcted myocardium were derived from MR images. Infarct size was quantified anatomically using triphenyltetrazolium-chloride (TTC) staining and compared with MR estimates. The T2 values derived from the images clearly discriminated between infarcted (126 +/- 22 msec) and normal myocardium (88 +/- 10 msec, P less than .05), providing images with good contrast between normal and infarcted myocardium. Comparable differences in T2 values were also noted from spectrometric determinations. Estimates of infarct size by MR imaging compared well with TTC estimates (r = 0.98) over a wide range of infarct sizes from 3% to 29% of the left ventricular mass. These results suggest the potential for in vivo quantification of infarct size based on the inherent contrast difference between infarcted and normal myocardium.

Animals↗

Phase alterations of spin echoes by motion along magnetic field gradients.

Using a Taylor series expansion of the phase shift of a moving isochromatic spin group in the presence of a magnetic field gradient, the refocusing effects of the Carr-Purcell-Meiboom-Gill pulse sequence on stationary nuclei and those with constant, rectilinear velocity are readily demonstrated. Continuing the analysis to higher orders of motion reveals that nuclei with a constant, rectilinear acceleration have a phase shift at the spin echoes which increases linearly with echo number. Constant, rectilinear jerk (the time rate of change of acceleration) leads to an increase in phase shift from echo to echo which is quadratic in nature with an overlying reduction of the odd-numbered echoes by a constant amount. Motion parameters may be measured by parameter identification techniques. These principles may be applied to phase-sensitive NMR imaging.

Magnetic Resonance Spectroscopy↗