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Biomedical subjects

U Klose

Publications and source records attributed to U Klose.

At least 19 recordsLinked to original sources
PubMed1992

MR imaging of experimental meningeal melanomatosis in nude rats.

MR imaging of the rat brain has become an increasingly frequently used method in experimental neuroradiology. On a generally available 1.5 T whole body tomograph, supplemented with an individually made small coil and a special SE sequence we obtained fairly fine images of the structures of the rat brain. With gadolinium-DTPA, we were able to visualize posterior fossa and cervical leptomeningeal growth of intrathecally injected B16 melanoma in nude rats. Using MRI to follow experimental leptomeningeal metastasis, may provide a new means for diagnostic evaluation and preclinical testing of treatment modalities.

Animals↗
PubMed1992

Cerebrospinal fluid flow. I. Physiology of cardiac-related pulsation.

Cardiac-related motion of the cerebrospinal fluid (CSF) was investigated by analysis of the velocity-dependent phase of CSF protons and flow-dependent signal enhancement in magnitude images using ECG-gated FLASH sequences. In the cerebral aqueduct, CSF flow from the third to the fourth ventricle begins 200 ms after the R-wave of the ECG and simulates an arterial pulse wave pattern. It lasts about 60% of the cardiac cycle and is followed by backflow from the fourth to the third ventricle, which is slower and shorter. In the spinal canal, oscillating caudad motion precedes flow from the third to the fourth ventricle by about 50-100 ms and is superimposed on a bulk flow, which moves simultaneously in opposite directions in separate subarachnoid channels; it is directed mainly caudally in the anterior cervical subarachnoid space.

Adolescent↗
PubMed1992

Cerebrospinal fluid flow. II. Physiology of respiration-related pulsations.

Cerebrospinal fluid (CSF) flow in the cerebral aqueduct and spinal canal was analysed using real-time magnetic resonance imaging measurement techniques. Respiration-induced rhythmic modulation of the cardiac-related oscillating CSF pulsation in the cerebral aqueduct and spinal canal was found. Deep inspiration was immediately followed by a marked increase in downward CSF flow in the cervical spinal canal, whereas a delay of about two heart beats was seen before downward flow from the third to the fourth ventricle increased. This pattern was also detected during yawning and was followed by a marked increase of blood flow in the internal jugular vein.

Cerebral Aqueduct↗
PubMed1992

Cerebrospinal fluid flow. III. Pathological cerebrospinal fluid pulsations.

Cardiac- and respiration-related movements of the cerebrospinal fluid (CSF) were investigated by MRI in 71 patients. In most patients with arteriosclerotic occlusive vascular disease CSF pulsations are normal. Decreased pulsatile flow is detectable in those with arteriovenous malformations, intracranial air and following lumbar puncture and withdrawal of CSF. Increased pulsatile flow in the cerebral aqueduct was found in 2 patients with large aneurysms, idiopathic communicating syringomyelia and in most cases of normal pressure hydrocephalus (NPH). CSF flow in the cervical spinal canal is, however, reduced or normal in NPH, indicating reduction of the unfolding ability of the surface of the brain and/or inhibition of rapid CSF movements in the subarachnoid space over its convexity.

Adult↗
PubMed1992

Noninvasive blood flow measurement and quantification of shunt volume by cine magnetic resonance in congenital heart disease. Preliminary results.

Based on the phase difference method as described by Nayler et al. we developed a gradient-echo sequence, which refocuses flow related phase shifts even for infants with their higher peak velocity, higher acceleration and faster heart rates. A repetition time (TR) of 15 ms provides a high temporal resolution for dynamic studies. Modification of the flow-rephasing gradient-echo sequence in slice select direction leads to a defined phase shift and the resultant phase difference images allow blood flow measurements in the great arteries and the calculation of blood volume per heart cycle (flow volume) to assess left and right ventricular stroke volume. This can also be achieved by calculation of the ventricular volume from contiguous slices of the whole heart, but, this in excessive measuring times. Both methods were applied in 6 examinations of children with congenital heart diseases (1 pulmonary sling, 1 coarctation of the aorta, 1 ventricular septal defect, 3 atrial septal defects). The age of the patients ranged from 3 months to 13.4 years (mean age 4.9 years). The regression analyses of both methods show a high correlation for systemic flow (y = -0.98 + 1.08 x, r = 0.99, SEE = 2.59 ml) and for pulmonary flow (y = -1.40 + 0.96 x, r = 0.99, SEE = 4.70 ml). The comparison of flow calculated Qp:Qs ratio and chamber size calculated Qp:Qs ratio with data obtained by heart catheterization show also a regression line close to the line of identity (y = -0.01 + 1.04 x, r = 0.98, SEE = 0.15 and y = 0.28 + 0.96 x, r = 0.81, SEE = 0.47, respectively).

Adolescent↗
PubMed1992

[The detailed imaging of vessels in MR angiography via projections from irregularly restricted data sets].

A new method for postprocessing of three dimensional magnetic resonance angiography data sets is described. Two operations are performed with the data set prior to maximum intensity projection. First, an irregular part of interest is marked interactively within the data set. By restricting the projection algorithm to this region, a disturbing overlay by vessels of other regions is avoided. Secondly, a three dimensional interpolation of the original data set is performed. While the spatial resolution of vessel representation is unchanged, the quality of the maximum intensity projection is improved significantly. The diagnostic value of this method is demonstrated by visualisation of a carotid aneurysm and of the deep and superficial cerebral veins.

Algorithms↗
PubMed1991

Toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in vitro: H4IIEC3-derived 5L hepatoma cells as a model system.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) was investigated for its toxicity in 5L-cells, descendents of the hepatoma line H4IIEC3. TCDD reduced the proliferation of 5L-cells by about 50%, with half-maximum inhibition at 0.1-0.3 nM concentrations. As shown by flow cytometric analysis, TCDD blocked the entry of 5L-cells into the S-phase, but did not hinder their progression through S and G2/M to the G1 phase. There was a marked increase in cell volume concomitant with the inhibition of growth. Both effects became apparent as early as 4-8 h after TCDD exposure. The parental line H4IIEC3/G- and the variant lines H4IIEC3/T, p4 and H5 were insensitive to the growth-inhibitory effect of TCDD. In view of the rapid onset of effects which can readily be detected and quantitated, 5L-cells offer a highly useful system for analysing the mechanism of action of TCDD at the cellular level.

Carcinoma, Hepatocellular↗
PubMed1991

Metabolic and destructive brain disorders in children: findings with localized proton MR spectroscopy.

The diagnostic potential of volume-selective proton magnetic resonance (MR) spectroscopy in vivo was evaluated in 20 children and young adults with various neurodegenerative brain disorders. All patients were examined with MR spectroscopy in conjunction with MR imaging of the brain on a whole-body imager at 1.5 T. Comparison of spectra in our patients with those of children with normal myelination (prominent signals from N-acetylaspartate [NAA], creatine/phosphocreatine, and choline) revealed a marked decrease of NAA in 12 of 17 patients with focal or generalized demyelination. In patients with Canavan disease, NAA signal intensity was markedly increased, but no choline signal was found. Increased signal intensity from lactate occurred in patients with Leigh disease, neuroaxonal dystrophy, Schilder disease, and Cockayne disease, which indicated a disturbed energy metabolism in the examined region. These results demonstrate that proton MR spectroscopy can be applied in a clinical environment to facilitate diagnosis of hereditary and acquired brain disorders in children.

Brain↗
PubMed1990

In vivo proton spectroscopy in presence of eddy currents.

Spatially localized methods in spectroscopy often operate with magnetic field gradients for volume selection. The eddy currents induced by these gradients produce time-dependent shifts of the resonance frequency in the selected volume, which results in a distortion of the spectrum after Fourier transformation. In whole-body systems the complete compensation of eddy currents is a difficult procedure. To avoid this, a correction method is proposed for proton spectroscopy, which uses the signal of prominent water protons as a reference for the water-suppressed signal. The correction is performed in the time domain, dividing the water-suppressed signal by the phase factor of the water signal for each data point. The corrected spectra have a good resolution as shown by phantom measurements and brain and muscle spectra of volunteers.

Extracellular Space↗
PubMed1990

Morphological diagnosis of congenital and acquired heart disease by magnetic resonance imaging.

Since 1987, the authors have examined 60 patients (21 girls, 39 boys) with a variety of congenital and acquired heart diseases by means of ECG-gated magnetic resonance imaging (MRI) using a multislice spin-echo technique. The patients' ages ranged from 10 days to 20 years (mean age 3.7 years), distributed as follows: 9 patients (15%) less than or equal to 4 weeks; 26 (43.4%) greater than 4 weeks less than or equal to 1 year; 9 (15%) greater than 1 year less than or equal to 6 years; 14 (23.3%) greater than 6 years less than or equal to 15 years; and 2 (3.3%) greater than 15 years less than or equal to 20 years. In 4 cases the quality of the images on the first study were of no diagnostic value and so a second investigation took place. Thus, 60 studies could be analysed, and the findings were compared with the previous diagnoses made on the basis of echocardiography (n = 60) and angiocardiography (n = 47). The 66 anomalies of the vessels included 6 that had been misdiagnosed (2, small patent ductus arteriosus (PDA); 1, pulmonary sling; 2, palliative shunt; 1, aortopulmonary collaterals). Amendment of the previous diagnosis was achieved in 8 cases. In 1 case an aorticopulmonary window was first detected by MRI and in another, a recoarctation of the aorta. The extent of an aortic aneurysm could be defined and a dissection of the aortic wall excluded. In 5 cases MRI gave more information on the pulmonary vascular status.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Stimulation of DNA synthesis in carcinogen-induced diploid hepatocytes in vitro.

Diploid hepatocytes induced by a combination of diethylnitrosamine and 2-acetylaminofluorene were isolated and separated from polyploid hepatocytes by centrifugal elutriation. The diploid and polyploid cell fractions were approximately 90% pure and contained between 1 and 1.5 x 10(7) cells. When kept in monolayer cultures both cell populations responded to the mitogenic effect of EGF and insulin. However, the percentage of labelled nuclei was higher in predominantly diploid compared to predominantly tetraploid hepatocyte cultures at all epidermal growth factor (EGF) concentrations used in this study. At 10 ng EGF/ml and 10 mU insulin/ml the labelling index was twice as high in the diploid liver cells. Further work is required to show the relevance of the stronger response of the diploid cell fraction to mitogens in the process of carcinogenesis.

2-Acetylaminofluorene↗
PubMed1990

Variation of contrast between different brain tissues with an MR snapshot technique.

The lack of tissue contrast in gradient-echo sequences with very short repetition times can be overcome by using a single inversion pulse prior to the entire imaging sequence. The contrast can be changed by variation of the time delay between the inversion pulse and the first excitation. This snapshot technique was introduced for very fast acquisition of images, but it also provides images with a strong contrast of gray to white matter and of brain tissue to cerebrospinal fluid. The authors designed a sequence that allows sufficient spatial resolution and good image quality. The measurement time is 1.2 seconds, and the in-plane resolution is 0.8 mm. A large variation in contrast with different inversion times was demonstrated on brain images of volunteers and patients.

Brain↗
PubMed1990

Quantitative evaluation of hyaline cartilage disorders using flash sequence. I. Method and animal experiments.

A method for quantitative evaluation of hyaline cartilage signal intensities has been developed in an experimental study of 6 swine knees with different types of arthritis. A FLASH sequence with TR 50 ms, TE 10 ms and flip angles of 5, 10, 20, 25, 30, 35, 50 and 90 degrees was employed. Two parameters of the signal intensity flip angle curves proved to be useful for tissue characterisation: The initial increase (A) and the maximum (M).

Animals↗
PubMed1990

Quantitative evaluation of hyaline cartilage disorders using flash sequence. II. Clinical applications.

In a prospective clinical study 24 normal volunteers and 106 patients with acute and chronic arthritis, osteoarthritis and post-traumatic alterations of the knee joints were examined. Using the parameters A and M 98 per cent of the pathologic cartilages and 74 per cent of the normal cartilages could be identified. In addition 78.5 per cent were correctly categorized in 5 cartilage classes. The A/M classification proved to be a fast and specific method for evaluation of cartilage disorders with special promise for follow-up examinations during therapy.

Adolescent↗
PubMed1990

[Dynamic magnetic resonance tomography in pediatric cardiology: broadening of diagnostic possibilities by flow-rephasing gradient-echo sequences].

Based on the phase difference method as described by Nayler et al., we developed a gradient-echo sequence, which refocuses flow-related phase shifts. With regard to the higher peak velocity and higher acceleration in infants, we reduced the echo time (TE) to 5 ms. This is effective in rephasing the flow signals even for faster heart rates. Phase shifts are further minimized by reducing the voxel size. The slice thickness down to 2 mm also improves anatomic resolution. A repetition time (TR) of 15 ms provides high temporal resolution for dynamic studies. Modification of the flow-rephasing gradient-echo sequence allows blood flow measurements in the great arteries and the calculation of blood flow volume to assess left and right ventricular stroke volume. This can also be achieved by calculating the ventricular volume from contiguous slices of the whole heart; however, it results in excessive measuring times. Compared with conventional spin-echo techniques, anatomical analysis is improved. The size of atrial septal defects (ASD) can be measured more exactly. Small atrial or ventricular septal defects (VSD), which are not detectable on spin-echo images, are demonstrated on the gradient-echo images and semi-quantitative estimation of the pressure in the right and left ventricle can be made. Pulmonary arteries and veins are clearly differentiated from bronchial structures and are traced to subsegmental levels. Without ECG-gating, contiguous slices of interesting parts of the cardiovascular system can be obtained and successfully used for secondary angiographic reconstructions.

Child↗
PubMed1989

[NMR tomography of the shoulder joint: clinical experiences with the saturation pulse technic].

High zoom factors for MRT of the shoulder joint can lead to disturbing artifacts. The use of special saturation coils can improve longitudinal magnetisation of the central image, making it possible to produce artifact-free images of the shoulder with high resolution. Two normals and 20 patients with the rotator cuff syndrome, as well as other inflammatory and neoplastic processes, have been examined. The findings have been correlated with those of arthrography, arthro-sonography, bone scintigraphy, CT and simple radiographic examination. The MRT findings were compared with the other imaging techniques and the results are discussed. MRT proved superior to other techniques, particularly in the elucidation of soft tissue abnormalities in the rotator cuff syndrome.

Adolescent↗
PubMed1989

Centrifugal elutriation of hepatocytes from 2-acetylaminofluorene-treated rats and their characterization by flow cytometry.

Treatment of male Wistar rats with 2-acetylaminofluorene (2-AAF) markedly altered the ploidy distribution of liver cells. Small diploid hepatocytes first appeared after 4-5 weeks feeding of a diet containing 0.02% 2-AAF; after 9 weeks 65-70% of the hepatocytes were diploid. Approximately two-thirds of this new liver cell population persisted after termination of the treatment. The hepatocytes from 2-AAF treated animals were separated according to size and ploidy by centrifugal elutriation and stained for gamma-glutamyltranspeptidase (gamma-GTase). The percentage of gamma-GTase-positive hepatocytes did not significantly differ between the various elutriated cell fractions. Thus gamma-GTase-positive liver cells obtained by feeding of 2-AAF do not represent a distinct size class of hepatocytes. The significance of carcinogen-induced diploid hepatocytes in hepatocarcinogenesis is discussed.

2-Acetylaminofluorene↗