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Biomedical subjects

F Schmitt

Publications and source records attributed to F Schmitt.

At least 73 records · Page 4Linked to original sources
PubMed1992

Image reconstruction for echo planar imaging with nonequidistant k-space sampling.

Echo planar imaging is characterized by scanning the 2D k-space after a single excitation. Different sampling patterns have been proposed. A technically feasible method uses a sinusoidal readout gradient resulting is measured data that does not sample k-space in an equidistant manner. In order to employ a conventional 2D-FFT image reconstruction, the data have to be converted to a cartesian grid. This can be done either by interpolation or alternatively by a generalized transformation. Filtering methods are described to minimize ghosting artifact that is typical in echo planar imaging. Results both from computer simulation and from experiments will be presented. Experimental images were obtained using a 2-T whole-body research system.

Artifacts↗
PubMed1992

Renal effects of angiotensin II in normotensive subjects on short-term cilazapril treatment.

In 13 normotensive subjects on a normal sodium diet, we studied renal vascular, blood pressure, and hormonal changes induced by infusion of exogenous angiotensin II (Ang II) (5 ng/kg/min) during baseline conditions and after 5 days of cilazapril administration. In both conditions, Ang II elicited a slight pressor response accompanied by renal hemodynamic and hormonal changes that were similar. This suggests that hourly changes in Ang II concentrations and/or in Ang II receptor density after short-term administration of the angiotensin-converting enzyme (ACE) inhibitor cilazapril does not significantly affect renal vascular reactivity. In addition, these results also indirectly suggest that most of the renal effects of ACE inhibition are mediated through suppression of Ang II formation.

Adult↗
PubMed1992

Renal interstitial foam cells are macrophages.

Immunohistochemical studies on renal biopsies from eight patients with various types of glomerulonephritis showed that the interstitial foam cells belonged to the monocyte-macrophage lineage. There was a strong association between hypercholesterolaemia and the presence of renal interstitial foam cells.

Adolescent↗
PubMed1992

Psychological profile of somatizing patients attending the integrative clinic.

OBJECTIVE: A clinic to evaluate and treat referred somatizing patients was established in the medicine clinic of a university medical center. METHOD: Fifty-four patients were evaluated and compared to an age- and sex-matched non-somatizing patient group. RESULTS: Somatizing patients had increased rates of psychiatric and alcohol and substance abuse histories. Somatizing patients scored high on all subscales of the SCL-90 and were most frequently found in the Anxious/Moody Cluster of the MBHI. These patients also endorsed highly beliefs in medical problems as a focus of their lives. CONCLUSIONS: These patients' psychological beliefs set the stage for conflict in the medical setting. The implications of these results are discussed in relation to liaison clinics, early identification, and treatment approaches.

Academic Medical Centers↗
PubMed1991

Neurobehavioral outcomes in diseases of childhood. Individual change models for pediatric human immunodeficiency viruses.

The growing incidence of human immunodeficiency virus-1 (HIV-1) and acquired immunodeficiency syndrome (AIDS) in children is a major public health problem. Current research emphasizes treatments for ameliorating deleterious effects on the child's neurological and behavioral development. This article outlines approaches to the assessment of individual change that may provide alternatives to more traditional approaches to the assessment of neurobehavioral outcomes in children with chronic diseases. These approaches provide more precise conceptualizations of changes that lead directly to statistical designs and measurement strategies for assessing effects of HIV-1 and AIDS on development. Such assessments can be superimposed on current clinical trial methodologies to evaluate the efficacy of pharmacological and behavioral interventions designed to improve quality of life in HIV-1 infected children.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Does lithium affect renal sodium handling and renal haemodynamics in normal man?

Renal haemodynamics, sodium excretion, and free-water clearance were evaluated at baseline and after acute frusemide administration in nine moderately volume-expanded healthy volunteers receiving a single administration of either 750 mg lithium carbonate or placebo. Lithium plasma concentration under 0.29 mmol/l exerted no significant effect on renal haemodynamics, on absolute, fractional, or cumulative sodium excretion, or on free-water and chloride clearances at baseline or after frusemide administration. Despite previous volume expansion and presumably depressed proximal reabsorption, frusemide decreased the fractional reabsorption of lithium significantly, suggesting that a small but significant part of lithium may be reabsorbed in the thick ascending limb of Henle's loop. By contrast, frusemide did not change renal haemodynamics or plasma renin activity. Using combined free-water and lithium clearances at baseline and after frusemide administration, fractional reabsorption of sodium in the (FRTAL) was calculated as delta CH2O/CLi, where delta CH2O, the difference in free water clearance before minus after frusemide, is taken as an index of sodium reabsorption in the thick ascending limb, and lithium clearance as an estimation of sodium delivery to the thick ascending limb. FRTAL was calculated in these volume-expanded subjects to lie from 11% to 20% depending on whether some lithium is assumed to be in the thick ascending limb.

Adult↗
PubMed1989

Sleep quality and pulmonary function in the healthy elderly.

Loss of sleep causes deterioration of pulmonary function and ventilatory responsiveness in normal humans and in patients with chronic obstructive pulmonary disease. To evaluate the effects of variations in sleep quality on breathing, we studied 48 healthy elderly volunteers (mean age, 70 years). Electroencephalographically derived indices of sleep quality were correlated with spirometric performance, MIP, MEP, and waking SaO2. We found significant correlations between several indices of sleep quality and the spirometric measurements in the group as a whole, and striking correlations between sleep quality and PFTs in those with sleep efficiency less than or equal to 70 percent. We conclude that sleep disturbance may be related to poor performance on PFTs. These results suggest that spirometry should be performed on well-rested patients. The results also point to sleep quality as a potentially important variable in the management of patients with pulmonary disease.

Aged↗
PubMed1989

Monitoring of heart allograft rejection by simultaneous measurement of serum beta 2-microglobulin and urinary neopterin.

In patients with heart transplant, the combined determination of serum beta 2-microglobulin and urinary neopterin, as rejection marker, prevented the interference by renal function and cyclosporin therapy. Unfortunately, the simultaneous measurement of these two parameters cannot distinguish between a rejection episode and the early stage of viral infection.

Biopterins↗
PubMed1989

Sleep apnea: prevalence of risk factors in a general population.

People with snoring, excessive daytime somnolence, and nocturnal breath cessation are very likely to have sleep apnea, particularly if they are obese or hypertensive. We collected epidemiologic data to determine the frequency of these findings in an unselected adult population. Respondents in a random digit dialing telephone survey included 685 people (356 women and 329 men, with a mean age of 50 years). Snoring was reported by 37%, gasping by 8%, excessive daytime somnolence by 36%, and hypertension by 28%; all symptoms were more prevalent in respondents older than 50 years. Snoring and gasping were more common in men than in women. Six persons (1%) had all four risk factors, plus a body mass index of one standard deviation above the mean. Eleven respondents (2%) had all four risk factors, but lower weight. We conclude that all risk factors for sleep apnea are more prevalent in persons over the age of 50 years, and that the incidence of sleep apnea in the general population may be 1%.

Age Factors↗
PubMed1987

Flow visualisation studies of aerodynamic characteristics of an open-top chamber.

Studies to determine potential locations of ingress of ambient air into an open-top chamber, using flow visualisation, are described. Rates of chamber ventilation necessary to avoid ambient air entrainment have been estimated from wind tunnel experiments. The dependence of the exit velocity of air from the chamber on the ambient air velocity was non-linear, so that for low wind speeds other mechanisms are more important than for high ambient air flows. Wind speeds ranged from 0.5m s(-1)<Uo<12m s(-1) outgoing atmospheric boundary layer had little effect on the probability of entrainment.

Journal Article↗
PubMed1984

Development of an organic affective syndrome during a hyperbaric diving experiment.

The authors describe the clinical and pharmacologic management of a patient who developed an organic affective syndrome during a simulated deep-diving experiment. The physiological complexities of deep-diving research are reviewed, as well as the neuropsychiatric symptoms of the high pressure nervous syndrome.

Atmosphere Exposure Chambers↗
PubMedDate not supplied

Echo-planar imaging of the central nervous system at 1.0 T.

Echo-planar imaging (EPI) on the authors' 1-T prototype imager provides high-quality 100-msec images of the central nervous system. Contrast parameters can be chosen freely. Three-dimensional EPI sequences provide isotropically resolved data sets with 1-mm resolution. Brain perfusion and blood-brain barrier disruption can be assessed in time-course studies with gadopentetate dimeglumine. The current state of development of the authors' midfield research EPI system is discussed and its image quality illustrated through selected patient studies.

Blood-Brain Barrier↗
PubMedDate not supplied

Echo-planar MR imaging of human brain oxygenation changes.

Echo-planar magnetic resonance (MR) imaging was used to observe signal intensity changes in the human brain during hypoxia. Increasing arterial blood levels of deoxyhemoglobin (0%-42%) during prolonged apnea were monitored with a pulse oximeter and correlated with gray matter and white matter signal attenuation of 13% and 20%, respectively. The results suggest the possibility of using deoxyhemoglobin boluses as a physiologic, intravascular susceptibility contrast agent for assessment of local cerebral oxygen utilization.

Brain↗
PubMedDate not supplied

Three-dimensional modeling of tree-like anatomical structures.

In this paper a method for creating geometrical models of tree-like anatomical structures is described. This method is basically interactive and thus it takes advantage of the user's expertise to define highly-structured models even when using nonhomogeneous data sets. First, tubular cavities are reconstructed sequentially; then, junctions between these cavities are provided in such a way that resulting models are continuously shaped (we characterize this property by the G1-continuity (i.e., a tangent plane can be defined at any point on the surface).

Computer Graphics↗
PubMedDate not supplied

Radiometric homogenization of the color cryosection images from the VHP lungs for 3D segmentation of blood vessels.

This work deals with the problem of radiometric inhomogeneities found on the physical color images of the anatomical cryosections from the Visible Human Project (VHP) male body. Our goal is to extract very thin structures, like the blood vessel tree from the lungs. Current segmentation methods applied to VHP color images are disturbed by discontinuous, inter-slice radiometric variations; we thus devised an adaptive correction that is propagated along a series of parallel slices, taking advantage of the structural coherence between consecutive slices. No blurring is introduced, and fine details and texture are respected. Results of 3D segmentation of fine blood vessels on the corrected volume are presented.

Anatomy, Cross-Sectional↗
PubMedDate not supplied

Correction of spatial distortion in MR imaging: a prerequisite for accurate stereotaxy.

With magnetic resonance (MR) imaging, accurate spatial information--critical for effective stereotaxy--demands a homogeneous static field and linear gradients. Inhomogeneities and nonlinearities induced by eddy currents during the pulse sequences distort the images and produce spurious displacements of the stereotactic coordinates in both the x-y plane and the z axis. These errors in position can be assessed by means of two phantoms placed within the stereotactic guidance system--a "two-dimensional phantom" displaying "pincushion" distortion in the image (i.e., x, y) plane, and the "three-dimensional phantom" displaying displacement, warp, and tilt of the image plane itself. The pincushion distortion can be "corrected" (reducing displacements from 5 to 1-2 mm) by calculations based on modeling the distortion as a fourth order two-dimensional polynomial. Based on these corrected images, errors in the z coordinate and tilt of image planes may be corrected by adjustment of the gradient shimming currents. Such correction not only implements stereotaxy under MR guidance but also provides for the accurate transfer of anatomic/pathologic information between MR and CT images.

Humans↗