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Biomedical subjects

M Sprenger

Publications and source records attributed to M Sprenger.

35 records · Page 2Linked to original sources
PubMed1994

Phase-contrast cine MR imaging of normal aqueductal CSF flow. Effect of aging and relation to CSF void on modulus MR.

Cine phase-contrast MR imaging was used to study pulsatile CSF flow in the aqueduct in 11 young controls (mean age 30 years) and 9 old controls (mean age 69 years). A high-resolution gradient echo technique and an oblique imaging plane, perpendicular to the aqueduct, was used to avoid volume averaging. Phantom studies confirmed that the technique was accurate. Aqueductal velocity and flux in old controls was higher than in young controls, but the differences were not significant. For all controls together, the averaged peak velocity was 4.2 +/- 1.5 cm/s in rostral and -7.8 +/- 4.9 cm/s in caudal direction; for the flux it was 0.16 +/- 0.10 cm3/s in rostral and -0.29 +/- 0.19 cm3/s in caudal direction. Phase-contrast measurements were significantly related to flow-void on modulus MR images, but not with ventricular size or cortical atrophy. The present technique avoids underestimation of aqueductal flow, and therefore reveals higher aqueductal velocity and flux values than previous studies. Factors other than age or atrophy seem to determine aqueductal CSF flow.

Adult↗
PubMed1993

Nontriggered magnetic resonance velocity measurement of the time-average of pulsatile velocity.

The feasibility of the determination of the time-average of pulsatile velocity obtained via a nontriggered magnetic resonance (MR) acquisition is studied. The advantage of this method, in comparison with a triggered acquisition, is a considerable reduction (approximately 15x) in acquisition time. However, pulsatility causes image artifacts, known as ghosts, and the Fourier transform technique required for the imaging procedure accomplishes time-averaging of the complex MR signal. Both effects can result in errors in the velocity determined. Calculations show that these errors depend on the velocity time function and the acquisition parameters. In vivo comparison of triggered and nontriggered MR velocity measurements in the femoral artery of volunteers (n = 7) shows larger statistical and systematic errors in the latter, which depend on the excitation angle. Therefore, this nontriggered average velocity measurement is only useful as a fast and rough estimation of the time-averaged velocity.

Blood Flow Velocity↗
PubMed1992

Influence of health care systems on the market for picture archiving and communication systems.

An analysis is given of the relation between health care systems and the PACS market. Two driving forces exist in the market: quality and price. It is argued that the quality driven market is mainly independent of the health care system and will be the force that drives the introduction of the health care system and will be the force that drives the introduction of PACS in the forthcoming years. Finally a change of focus is suggested from only archiving and communication to a more general concept of image networking, serving more goals than only the goal of working filmlessly.

Delivery of Health Care↗
PubMed1991

[Oral administration of activated charcoal-sorbitol suspension as first aid in prevention of poison resorption?].

Due to its paramount adsorption capacity, activated charcoal is supposed to be the remedy of choice for binding a variety of drugs in the gastrointestinal tract. Hence it is surprising--at least according to the advice of German textbooks--that activated charcoal is only recommended for administration after time-consuming treatments like induced emesis and gastric lavage. Particularly with infants at home, a ready-for-use suspension of activated charcoal would allow the early management of acute poisoning. In such cases, inactivation of the poison by adsorption could be particularly helpful, since the period after ingestion is usually short. The charcoal-sorbitol-suspension (30 g activated charcoal in 150 ml of 70% sorbitol) is a creamy preparation which is easy to drink, because density and viscosity prevent sedimentation. The prescription-free drugs can be dispensed by each pharmacist. The present study was undertaken to investigate the influence of sorbitol on the adsorption capacity of activated charcoal. To this end, adsorption isotherms were established in vitro and compared with results in volunteers to whom NAPAP, diphenhydramine or codeine was administered separately. These drugs are gaining increasing importance in medicinal toxicology since they are constituents of various analgesics and cold remedies. To determine absorption, the cumulative urinary excretion was estimated of the parent drugs and their main metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaminophen↗
PubMed1991

An in vivo validation of quantitative blood flow imaging in arteries and veins using magnetic resonance phase-shift techniques.

Magnetic resonance (MR) techniques have recently been introduced, allowing quantitative measurement of blood flow with high spatial and temporal resolutions. These techniques are based on the phase of the MR signal rather than on the amplitude, and are referred to as MR phase or velocity mapping. Clinical validation is still lacking. We therefore performed an in vivo validation of such a technique in 17 healthy volunteers. Velocity maps were acquired at 50 ms intervals over the cardiac cycle in the aorta, superior and inferior vena cava. Plots were made of flow velocity and volume flow vs time and used for calculation of left ventricular stroke volume (SV), cardiac output (CO) and venous return. Comparison with Doppler ultrasound (x) yielded y = -7.5 + 1.1x (r = 0.76) for SV measurements (ml), and y = 0.3 + 0.9x (r = 0.86) for CO calculations (1 min-1). Comparison between MR SV (x) and MR determination of venous return (y), obtained by summation of the flow volumes per cardiac cycle in the superior and inferior vena cava, was close to identity, y = 1.3 + 1.0x (r = 0.91). Also, preliminary applications are presented in patients with aortic diseases. The findings of this study show that magnetic resonance velocity imaging can be accurately applied in vivo as a non-invasive means of measuring flow.

Aortic Dissection↗
PubMed1990

Value of gadolinium-diethylene-triamine pentaacetic acid dynamics in magnetic resonance imaging of acute myocardial infarction with occluded and reperfused coronary arteries after thrombolysis.

The use of the paramagnetic contrast agent gadolinium-diethylene-triamine pentaacetic acid (DTPA) was evaluated in magnetic resonance imaging (MRI) of 18 patients with an acute myocardial infarction after thrombolysis. The patency of the infarct-related vessel was assessed by coronary angiography. At 58 +/- 9 hours after infarction MRI was performed before and after bolus injection of 0.1 mmol/kg gadolinium-DTPA. Myocardial signal intensities were measured using a circumferential profile. Normal and infarcted myocardium showed a maximum signal intensity enhancement of 35 and 66%, respectively. Signal intensity of infarcted relative to normal myocardium (I/N) increased from 1.06 +/- 0.16 before to a maximum of 1.39 +/- 0.13 after gadolinium-DTPA (p less than 0.001), whereas the contrast between normal myocardium and a pseudo-infarct region in 2 healthy volunteers did not change. Between patients with reperfused infarct-related vessels and occluded vessels without collaterals, maximum I/N did not differ. However, observing I/N as a function of time after injection of gadolinium-DTPA, the reperfusion group differed from the occlusion group on images acquired directly after injection (1.29 +/- 0.10 vs 1.14 +/- 0.05, p less than 0.02). Thus, gadolinium-DTPA enhanced the visualization of acute myocardial infarction on relatively longitudinal (T1)-weighted MR images and its dynamics seem of potential value for the noninvasive assessment of coronary artery reperfusion after thrombolysis.

Adult↗
PubMed1989

Carbon-fiber electrodes and leads for electrocardiography during MR imaging.

In an effort to minimize distortion and artifacts on magnetic resonance images obtained with electrocardiographic (ECG) gating, the authors tested the use of ECG electrodes and leads made of carbon fiber. These materials caused no image degradation and, because the leads were reinforced with plastic, were less vulnerable to bending than leads made of graphite.

Carbon↗
PubMed1988

Evaluation of magnetic resonance imaging for determination of left ventricular ejection fraction and comparison with angiography.

Left ventricular ejection fraction was measured by magnetic resonance imaging (MRI) and compared with standard monoplane left ventriculography in 46 patients with various cardiac diseases. Two different MRI strategies were used. In 28 patients (group 1), ejection fraction was determined using a single slice comparable with the right anterior oblique projection of the ventriculogram. Comparison of left ventricular ejection fraction yielded a poor correlation between single slice MRI (y) and ventriculography (x) (y = 28.7 + 0.47 x, r = 0.65). In 18 patients (group 2), a multiple contiguous slice MRI technique was used to allow ejection fraction and stroke volume determination by summing up the volumes of ventricular cavity intersections. Regression analysis showed a high correlation between multiple slice MRI (y) and ventriculography (x) (y = 7.2 + 0.88 x, r = 0.98). Also, correlation between MRI right (y) and left (x) ventricular stroke volumes was satisfactory, (y = -12.8 + 1.09 x, r = 0.83). It is concluded that the multiple slice imaging technique in MRI provides an accurate noninvasive means for quantification of left ventricular ejection fraction that can be extended to the determination of left ventricular volume.

Angiocardiography↗
PubMed1988

Invasion of laryngeal cartilage by cancer: comparison of CT and MR imaging.

Forty-two patients with laryngeal carcinomas were examined with computed tomography (CT) and magnetic resonance (MR) imaging. The accuracy of both CT and MR imaging in the depiction of cartilage invasion was evaluated in 16 patients by comparing findings at CT and MR with pathologic findings. Calcified cartilage that has been invaded by cancer is frequently seen on CT scans as having an intact contour. Tumor approaching nonossified cartilage may simulate cartilage invasion. On T1-weighted MR images, invaded marrow of ossified cartilage is of intermediate signal intensity, allowing it to be differentiated from normal bone marrow. On proton-density images, tumor is of increased signal intensity, which allows it to be differentiated from nonossified cartilage. In our experience, the specificities of CT and MR imaging were approximately equal (91% and 88%, respectively), but CT had a considerably lower sensitivity than MR (46% vs. 89%). Gross movement artifacts, which resulted in nondiagnostic images, occurred in 16% of the MR examinations. MR imaging is recommended as the modality of choice in the diagnosis of cartilage invasion.

Aged↗
PubMed1986

Rates of release of GABA and catecholamines in the mediobasal hypothalamus of ovariectomized and ovariectomized estrogen-treated rats: correlation with blood prolactin levels.

Push-pull cannulae were implanted into the mediobasal hypothalamus of ovariectomized (ovx) rats. After recovery animals were treated with estradiolbenzoate (E2B) or oil and they were perfused 3 days later. Only the E2B-treated animals which exhibited prolactin surges in the afternoon without concomitant LH surges were used in this study. In ovx animals hypothalamic GABA release, measured in 5-min intervals, was pulsatile, with pulses occurring every 37 min. This pattern was profoundly affected by E2B treatment: the pulse frequency was significantly reduced to 1 pulse every 117 min in steroid-treated rats. No differences in overall mean GABA release rates and pulse amplitudes were observed in ovx vs. E2B-treated rats. Our earlier demonstration of the existence of a large number of estrogen-receptive, GABAergic neurons in the MBH of rats is suggestive that these neurons change their secretory pattern in response to estrogen treatment. Estrogen-induced prolactin surges were accompanied by increased hypothalamic NE release. Concomitant changes in DA or E release rates were not demonstrable since catecholamine concentrations were too low to be reliable. However, the daily overall release rates of these two catecholamines were lower in E2B-treated rats compared to ovx animals. It is concluded that the positive feedback action of estradiol on prolactin release involves a stimulatory noradrenergic mechanism and may also involve estrogen-receptive, GABAergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

MRI of coronary arteries: 2D breath-hold vs 3D respiratory-gated acquisition.

OBJECTIVE: Respiratory motion degrades MR images of the coronary arteries. The purpose of this study was to assess and compare two methods of reducing the effects of respiration in coronary artery MRI. Single-slice 2D imaging with breath-holding and a respiratory-gated 3D technique were used. MATERIALS AND METHODS: A comparison was made in 10 normal subjects between a 2D multiple breath-holding approach and a 3D technique with and without retrospective respiratory gating in imaging the coronary arteries. RESULTS: Respiratory gating improved the image quality in 76% of the 3D images. Both the 2D and the 3D approaches were capable of visualizing the proximal parts of the coronary arteries, with comparable vessel length and diameter. The image quality was somewhat better for images obtained by breath-holding in 83% of the vessels, probably due to less blurring by remnant respiratory motion and higher inflow contrast. CONCLUSION: The 2D breath-holding approach reveals a better image quality. However, the 3D respiratory-gated acquisition is less operator dependent, faster, and less strenuous for patients.

Adult↗