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Biomedical subjects

R L Wolf

Publications and source records attributed to R L Wolf.

At least 37 records · Page 2Linked to original sources
PubMed1995

Error in MR volumetric flow measurements due to ordered phase encoding in the presence of flow varying with respiration.

Respiratory ordered phase encoding is often employed in MRI studies to reduce image artifacts due to breathing motion. The purpose of this work was to evaluate error caused by the use of respiratory ordering of phase encoding in MR cine phase-contrast (CPC) volumetric flow measurements when the flow rate is sensitive to respiration. It was hypothesized that this effect is due to the systematic biasing of a respiratory-induced phase modulation function in k-space. A theoretical model for the effects of respiration was developed and then tested in flow phantom studies and in normal volunteer studies. In phantom experiments, the use of respiratory ordering induced an error of as much as 13% in CPC volumetric flow measurements. In preliminary volunteer studies, error was as high as 26% in superior vena cava flow measurements versus less than 1% error in the ascending aorta. It is concluded that a potential for error exists in CPC volumetric flow measurements obtained with the use of respiratory ordering schemes. Volunteer studies with larger numbers are warranted. Clinical applications in which this effect may be important include flow measurements in vessels subject to variations in flow due to respiration, such as the venae cavae, pulmonary vasculature, and portal vein.

Aorta↗
PubMed1993

Analysis of systematic and random error in MR volumetric flow measurements.

The spatial aspects of error in 2D MR cine phase-velocity mapping are considered in order to define acquisition strategies which will minimize error in measuring volumetric flow. Error was separated into two categories: systematic and random. Potential sources of systematic error examined were intravoxel phase dispersion (IVPD), partial volume effects, misalignment of flow axis and flow-encoding gradients, and improper choice of vessel voxels for flux calculations. Random error was addressed using analysis of propagation of variance. Analytical expressions for sources of error were derived; and computer models were used to test the analytical models. Flow phantom studies examining error in MR volumetric flow measurements were performed and compared with error predicted by the analytical models. Expected error in several clinical situations of interest was then derived to find appropriate acquisition strategies. Spatial resolution, signal to noise ratio, velocity sensitivity and the ratio of the modulus of moving isochromats to that of static isochromats were found to be the most important parameters in controlling error and were found to cause competing effects with respect to systematic and random error.

Artifacts↗
PubMed1993

Volumetric flow rates in the portal venous system: measurement with cine phase-contrast MR imaging.

OBJECTIVE: The purposes of this study were to (1) validate the accuracy of cine phase-contrast MR flow measurements within the portal vein, (2) develop a suitable protocol for using this method to measure volumetric flow rate in the portal venous system, and (3) use this protocol, with Doppler sonography as a reference, to measure portal venous flow in healthy volunteers and in patients with protal venous hypertension. SUBJECTS AND METHODS: Flow determinations were obtained in a model of fluid movement approximating blood-flow conditions in the portal venous system. A suitable protocol was based on consideration of the theoretical effects of (1) spatial resolution, (2) obliquity of the imaging plane to the direction of flow, and (3) signal-to-noise ratio of the signed quantitative velocity images (in three volunteers) on the accuracy and precision of flow measurements. This protocol was used to obtain cine phase-contrast MR images of the portal venous system in five volunteers and six patients. RESULTS: Values obtained with a flow phantom showed good accuracy of cine phase-contrast-measured vs actual volumetric flow rate (r = .995; p = .0001; MR rate = [0.94 x actual rate] + 65.6 ml/min; standard error of the y estimate = 67.3 ml/min). Velocity encoding and section thickness substantially influenced the signal-to-noise ratio of the velocity images, whereas flip angle and matrix size had only minimal effect. In volunteers and patients, portal volumetric flow rates determined by using MR images and Doppler sonography showed good correlation (r = .94; p = .0003). CONCLUSION: Our results indicate that cine phase-contrast MR imaging is a practical noninvasive method for measuring volumetric flow rates in the portal venous system.

Adult↗
PubMed1993

Measurement of normal renal artery blood flow: cine phase-contrast MR imaging vs clearance of p-aminohippurate.

OBJECTIVE: The purpose of this study was to compare cine phase-contrast MR imaging with renal clearance of p-aminohippurate for measuring normal renal blood flow. A reliable technique for evaluation of renal hemodynamics would be useful for studying renal vascular diseases and the effects of treatment. Measurements of renal blood flow based on renal clearance of p-aminohippurate are limited in that the kidneys are not studied separately, temporal resolution is poor, and normal renal function is required. SUBJECTS AND METHODS: Bilateral oblique sagittal cine phase-contrast MR images were obtained simultaneously in 10 healthy adult volunteers, with the imaging planes oriented perpendicular to the left and right renal arteries in order to measure through-plane flow. Velocity encoding was 150 cm/sec (seven of 10 volunteers) and 100 cm/sec (eight of 10 volunteers). Axial cine phase-contrast images of the abdominal aorta above and below the origins of the renal arteries were obtained in six volunteers. In these cases, renal blood flow was determined by measuring the difference between suprarenal and infrarenal aortic flow. For all volunteers, renal clearance of p-aminohippurate was determined immediately after MR measurements. RESULTS: Renal blood flow measurements determined by using cine phase-contrast MR imaging were in close agreement with those determined by using clearance of p-aminohippurate. At a velocity encoding of 150 cm/sec, the mean difference was 69 ml/min (95% confidence interval, -31 to 169 ml/min). At a velocity encoding of 100 cm/sec, the mean difference was 39 ml/min (95% confidence interval, -100 to 177 ml/min). Aortic flow measurements using cine phase-contrast MR imaging appeared to be less reliable for determining renal blood flow than measurements in the individual renal arteries, with a mean difference of -75 ml/min (95% confidence interval, -381 to 231 ml/min) compared with renal blood flow determined by using clearance of p-aminohippurate. CONCLUSION: We conclude that cine phase-contrast MR imaging is a promising technique for noninvasive measurement of renal blood flow. Measurements agreed closely with those obtained by using clearance of p-aminohippurate. In addition, the MR technique is faster, can be used to measure unilateral or bilateral renal blood flow, and does not depend on renal function.

Adult↗
PubMed1993

Neurocognitive efficiency following left temporal lobectomy: standard versus limited resection.

Decreased memory and learning efficiency may follow left temporal lobectomy. Debate exists as to whether the acquired deficit is related to the size of the surgical resection. This study addresses this question by comparing changes in cognitive performance to the extent of resection of both mesial temporal structures and lateral cortex. The authors retrospectively reviewed 47 right-handed patients who underwent left temporal lobectomy for medically intractable seizures. To examine the effects of the extent of mesial resection, the patients were divided into two groups: those with resection at the anterior 1 to 2 cm of mesial structures versus those with resection greater than 2 cm. To examine the effects of the extent of lateral cortical resection, patients were again divided into two groups: those with lateral cortex resections of 4 cm or less versus those with resections greater than 4 cm. Statistical analyses showed no difference in cognitive outcome between the groups defined by the extent of mesial resection. Likewise, no difference in cognitive outcome was seen between the groups defined by the extent of lateral cortical resection. Associated data analyses did, however, reveal a negative correlation of cognitive change with patient age at seizure onset. These results showed that the neurocognitive consequences of extended mesial resections were similar to those of limited mesial resections, and that the neurocognitive consequences of extended lateral cortical resections were similar to those of limited lateral cortical resections. The risk of cognitive impairment depends more on age at seizure onset than on the extent of mesial or lateral resection.

Adult↗
PubMed1992

Blood flow imaging through detection of temporal variations in magnetization.

Two hypotheses were tested: (a) that view-to-view variations in bulk phase and modulus of magnetization in vascular volume elements can indicate the presence of disordered blood flow, and (b) that a substantial loss of signal intensity on magnetic resonance (MR) angiograms of poststenotic regions is due to view-to-view changes in magnetization. To test these hypotheses, a technique was developed in which view-to-view variations in transverse magnetization were used to create angiographic projection images, which showed only disordered flow (disordered flow maps) in vitro and in vivo. In phantom studies, this technique recovered signal intensity downstream from stenoses. A combination of disordered flow maps with morphologic images improved visualization of stenotic regions and provided information on characteristics of local flow. These results show that view-to-view variations in transverse magnetization occur in regions of disordered flow and are an important cause of loss of signal intensity. This technique can provide information about dynamic blood flow and improve depiction of anatomic structures on MR angiograms.

Blood Circulation↗
PubMed1988

Human placental cells that regulate lymphocyte function.

We examined normal human placenta for an immunologic function by measuring the release of soluble inhibitory factor (SIF). SIF is a product of normal T lymphocytes and of the JEG-3 choriocarcinoma cell line, and blocks proliferative and antibody-producing responses of mononuclear cells. SIF can be further characterized by a noncovalently linked subcomponent, lipid suppressor substance. The villous surfaces of six normal human placentae were digested with collagenase to obtain a population of predominantly multinucleated giant cells. These cells were maintained in standard culture for 5 days after which the cell-free conditioned culture medium was assayed for SIF content by measuring suppression of [3H]thymidine incorporation into lymphocytes stimulated by low-dose phytohemagglutinin. Undiluted placental SIF induced 88% inhibition of this response (p less than 0.001). The placental SIF was found to contain lipid suppressor substance, as does SIF from mononuclear cells. We determined this by thin-layer chromatography where a peak of suppressive activity occurred at Rf 0.32 [( 3H]thymidine incorporation reduced from 21810 +/- 308 to 4121 +/- 214 cpm); this is the position on thin-layer chromatography to which mononuclear cell lipid suppressor substance migrates. Ion exchange chromatography comparing the elution patterns of lymphocyte-SIF and placental-SIF indicated that both eluted in the fraction of 40-50 mM PO4 means buffer, further suggesting identity between these two substances. SIF from placental and lymphocyte sources functioned by inducing the presence of suppressor cells in culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1987

Unusual arteritis causing myocardial infarction in a child.

A 5-year-old girl presented with a diffuse inflammatory disease that consisted of fever, lymphadenopathy, splenomegaly, and anterior uveitis. A chest x-ray film indicated an apparently nodular infiltrate. Her condition deteriorated abruptly, and she died of acute myocardial infarction. Autopsy revealed an extensive vasculitis that involved the aorta, pulmonary arteries, and coronary vessels. An aneurysm of the left coronary artery was noted. We present and discuss this case as an unusual arteritis in childhood, closely resembling Takayasu's disease. The presence of extensive erythrophagocytosis in sinus histiocytes hinted at a viral or immunologic origin for this child's disease.

Aortic Diseases↗
PubMed1986

In vitro biological activities of Escherichia coli-derived bovine interferons-alpha, -beta, and -gamma.

The infectious yields of several bovine viruses were inhibited in bovine cells treated with purified preparations of E. coli-derived bovine interferons (BoIFNs)-alpha, -beta, and -gamma. BoIFN-beta 2, encoded by one member of the BoIFN-multigene family, had more potent antiviral and antiproliferative activities than the product of one member of the class-I IFN-alpha gene family (BoIFN-alpha I1). BoIFN-beta 2 also completed more effectively than BoIFN-alpha I1 with HuIFN-alpha I2 for cell-surface receptors on bovine cells. Despite these differences, the kinetics of maximal antiviral activity were similar for BoIFN-alpha I1, BoIFN-beta 2, and HuIFN-alpha I2. In comparison to BoIFN-alpha I1 and BoIFN-beta 2, BoIFN-gamma had the least in vitro antiviral activity and required the longest contact with cells to achieve maximal protection against virus infection, but had a dramatically greater antiproliferative activity.

Animals↗
PubMed1983

Characterization of an immune suppressor from transformed human trophoblastic JEG-3 cells.

Cultured human choriocarcinoma JEG-3 cells secrete an immunosuppressor that inhibits lymphocyte proliferation stimulated by either an antigen or a mitogen. In this study, the immunosuppressive factor was characterized by three methods: ion-exchange and exclusion chromatography, partition in organic solvents, and thin-layer chromatography on silicic acid. This JEG-3 cell factor appeared to be a protein complex of about 150,000-200,000 Da that contained an immunologically active polar lipid. The structural and functional characteristics of JEG-3 cell immunosuppressor are similar if not identical to those of SIF, a suppressor lymphokine derived from T cells. These secretions from transformed trophoblastic cells may correspond to normal placental products or represent a function of malignant cells.

Cell Line↗
PubMed1983

Chemosurgical reports: perineural spread of basal-cell carcinoma.

Basal-cell carcinoma with perineural invasion is a rare occurrence. Ten patients with this phenomenon are described. Review of our cases and cases in the literature indicates that perineural spread of basal-cell carcinoma is most common in men with recurrent tumors. The horizontally cut frozen sections that are utilized in Mohs surgery maximize the chances of discovering basal-cell carcinoma with undiagnosed involvement.

Aged↗
PubMed1983

Developing new options in home-delivered meals: the SMOC demonstration elderly nutrition project.

The purpose of this project was to design and test alternative approaches to in-home nutrition services for the elderly. Two meals systems--weekly delivery of five frozen meals and the daily delivery of hot meals--were evaluated for client approval, effect on clients' social contacts, and costefficiency. The alternative frozen meals system met with clients' acceptance, maintained clients' usual social patterns, and produced a cost savings of at least 16%. The development of a more flexible approach to home-delivered meals offers possibilities both for better serving clients' needs and for improving cost efficiency. It therefore has implications for elderly nutrition services nationwide.

Aged↗
PubMed1979

Role of lipids in the immune response. I. Localization to a lipid-containing fraction of the active moiety of an inhibitor (SIF) of lymphocyte proliferation.

By further study, a previously described inhibitor of lymphocyte proliferation and immunoglobulin synthesis, soluble inhibitory factor (SIF), has been shown to comprise two moieties; a nondialyzable protein, apparently inert with regard to inhibition of proliferation, and a polar lipid bound to the protein fraction, presumably by hydrophobic interaction. The lipid contained the activity responsible for inhibition of PHA-induced DNA synthesis. It was tentatively identified as a lipid with an as yet unidentified polar group, on the basis of mobility on thin layer chromatographic plates and behavior on silicic acid.

Amino Acids↗
PubMed1979

Role of lipids in the immune response. II. An enhancer of antibody production (APS) that is a lipid closely associated with lymphocyte mitogenic factor (LMF).

Lymphocyte mitogenic factor (LMF) is a lymphokine produced by dividing T cells. An activity coeluting with LMF from a Sephadex resin is extractable from LMF with chloroform-methanol. It enhances but does not initiate antibody formation measured by generation of plaque-forming cells (PFC). It does not cause proliferation of B cells. This activity elutes from a silicic acid column and produces a pattern on thin layer chromatography that suggests that the compound(s) responsible for the activity is a polar lipid.

Antibody Formation↗