Search PubMed⌕ Search

Biomedical subjects

H Kugel

Publications and source records attributed to H Kugel.

69 records · Page 4Linked to original sources
PubMed1992

[Experimental studies on magnetic resonance tomographic and magnetic resonance angiographic imaging of poststenotic flow patterns].

A phantom has been developed, which permits the perfusion of defined stenosis with variable flow rates. The post-stenotic flow patterns were imaged by means of conventional MRI sequences and special angiographic sequences using a 1.5 total body scanner (Gyroscan S15, Philips). For conventional MRI images, spin-echo-sequences (TR 500 ms, TE 27 ms with reconstruction of the magnitude and phase images) and gradient-echo-sequences (TR 60 ms, TE 27 ms, flip angle 15 degrees with reconstruction of the magnitude images) were used. For MR angiography 2D inflow (multiple-single-slice-technique, TR 40 ms, TE 14 ms, flip angle 60 degrees) and flow-adjusted-gradient-sequences (TR 24 ms, TE 10 ms, flip angle 60 degrees) were performed. In addition to an analysis of the appearances, the length of the changed signal intensity beyond the stenosis was evaluated. For constant flow rates it increases with the severity of the stenosis. For a constant stenosis the length of the post-stenotic signal change alters with flow rate. The changes also depend on the direction of flow and the gradients of the chosen sequences. The comparison of magnitude and phase images allows the discrimination between turbulent and non-turbulent flow. It therefore appears possible to estimate the severity of arteriosclerotic occlusive disease by means of MRI in the future.

Blood Flow Velocity↗
PubMed1992

Human brain tumors: spectral patterns detected with localized H-1 MR spectroscopy.

Image-guided localized proton magnetic resonance (MR) spectroscopy of intracranial tumors was performed to correlate spectral patterns and histologic findings. Thirty-six patients were examined prior to any specific treatment. Evaluation based on signal intensity ratios showed that all tumor spectra differed from spectra of healthy brain tissue. Ratios of creatine to choline-containing compounds (Cr/Cho) and nitrogen acetyl-aspartate to Cho (NAA/Cho) were reduced significantly in all tumor spectra compared with spectra of normal tissue in contralateral brain hemispheres (P less than .005). Noncerebral tumors typically showed a vanishing or missing NAA signal, strongly reduced Cr signal, and additional signals, assigned to alanine in meningiomas and lipids in metastases. In contrast, 11 gliomas of grades 2 and 3 exhibited NAA/Cho ratios and Cr/Cho ratios that were less than normal but that were significantly larger (P less than .01) than corresponding values in eight meningiomas. Ten glioblastomas displayed spectra with various signal ratios, so no significant differences between them and other tumor types could be established. In nine gliomas a clearly detectable lactate signal was present. However, no direct correlation between lactate level and histologic tumor grading was found.

Adult↗
PubMed1990

The energy requirements of pH homoeostasis define the limits of pH regulation--a model.

The regulation of intracellular pH of Platymonas subcordiformis cells is investigated with 31P-NMR spectroscopy at various external pH values. The limits of pH homeostasis differ between respiring cells and cells solely glycolyzing. The former retain their normal cytoplasmic pH for external pH values from 5 to more than 12, while in the latter intracellular pH is less stable below external pH 6, and external pH of more than 11 causes hydrolysis of intracellular polyP. The power necessary to maintain a stable intracellular pH is calculated from the electrochemical potential and H+/OH- flux rates across the cell membrane. H+/OH- transport across the membrane by diffusion as well as through hydrogen-bonded chains is considered. Comparison of the minimal power necessary to keep intracellular pH stable at various external pH values by ATP consuming processes with the estimated power available to aerobic and anaerobic cells in the dark shows that different energy turnover may explain the different behaviour of the cells when exposed to extreme pH values.

Adenosine Diphosphate↗
PubMed1985

Genetic dependence of the electroencephalogram bispectrum.

The resting electroencephalogram of monozygotic twins and genetically unrelated controls was analyzed with the ordinary spectrum and with the bispectrum. Both the ordinary spectrum which measures linear EEG wave activity and the bispectrum which detects non-linear and correlated frequency activity had evidence for a genetic basis. It is suggested that there is a genetic basis for the process of EEG generation.

Brain↗
PubMedDate not supplied

MR imaging of poststenotic flow phenomena: experimental studies.

Poststenotic flow patterns were analyzed in a flow phantom with a 1.5-T magnetic resonance (MR) imager, with use of different MR imaging and MR angiographic pulse sequences. Spin-echo, fast field-echo, two-dimensional inflow (multiple single-section technique), and flow-adjusted-gradient sequences were applied. For the spin-echo sequences, modulus and phase images were reconstructed from each data set. The length of the region of poststenotic changes in signal amplitude and phase measured at a constant flow rate increased with stenosis grade. Likewise, the length of the region of poststenotic changes measured at a constant stenosis grade increased with flow rate. Moreover, the results depended on the alignment of the flow direction with the readout gradient. Comparison of modulus and phase images allowed discrimination of turbulent and nonturbulent flow, which yields additional information on stenosis grade in clinical MR angiography.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Phase-contrast pulsatility measurements: preliminary results in normal and arteriosclerotic iliofemoral arteries. Work in progress.

Magnetic resonance (MR) flow measurements were obtained in six healthy volunteers and 30 patients with arteriosclerotic disease with a 1.5-T imager and a pulse sequence for flow quantification based on flow-induced phase shifts. The iliac arteries were investigated in eight and the femoral arteries in 28 subjects. A trigger pulse, followed by the acquisition of 30 evenly distributed data sets, was applied every second heartbeat, thus eliminating any acquisition gap in a full heart cycle. For quantitative analysis, flow velocity was plotted as a function of time. Systolic acceleration, postsystolic deceleration, and pulsatility of flow were calculated and compared with stenosis grades determined from recent intraarterial digital subtraction angiograms. The flattening of the temporal flow patterns correlated with local severity of vascular occlusive disease.

Adult↗
PubMedDate not supplied

Quantitative measurements with localized 1H MR spectroscopy in children with Canavan's disease.

Canavan's disease is an autosomal recessive hereditary leukodystrophy resulting from deficiency of the enzyme aspartoacylase. Two children suffering from this metabolic brain disease were examined using image-guided localized proton spectroscopy. The absolute concentrations of metabolites were determined. These data demonstrate, for the first time, that the well known increase of the N-acetylaspartic acid (NAA)/Cho ratio in this disease may be not only due to a reduction of choline-containing compounds in brain tissue but, at least in specific cases, also due to an increase of the NAA concentration, which is a result of the enzyme defect.

Aspartic Acid↗
PubMedDate not supplied

Localized 31P MR spectroscopy of the transplanted human kidney in situ shows altered metabolism in rejection and acute tubular necrosis.

The purpose of this study was to investigate the function of transplant kidneys in situ, and to detect pathologic changes, using volume-selective phosphorous NMR spectroscopy (31P MRS). Localized 31P MR spectra were obtained from 37 patients using a whole-body MR scanner with a combination of surface coils, adiabatic excitation pulses, and a modified image-selected in vivo spectroscopy (ISIS) sequence. Seventeen patients with pathologic changes after renal transplant were compared with a control group of 20 patients with no evidence of transplant dysfunction. The transplant kidneys with rejection reaction showed higher ratios of inorganic phosphate (P2i) to adenosine triphosphate-alpha (ATP-alpha) than the normal control group (.4 +/- .16 compared with .22 +/- .11, P = .01) and reduced pH. The spectra of transplant kidneys with tubular necrosis had lower phosphomonoester (PME)/phosphodiester (PDE) ratios than the control group (.65 +/- .35 compared with .96 +/- .5, P = .04). The pathologies of rejection and tubular necrosis could be differentiated from each other by pH (6.93 +/- .1 in rejection versus 7.14 +/- .19 in tubular necrosis, P = .04). Preliminary results indicate that localized image-guided 31P MR spectroscopy of transplant kidneys in situ can detect rejection reactions and acute tubular necrosis noninvasively, providing an incentive for further research.

Adenosine Triphosphate↗
PubMedDate not supplied

Fast and ultrafast magnetic resonance imaging in renal lesions.

Our purpose was to analyze and compare the image quality and contrast-to-noise ratio (CNR) of different fast T1- and T2-weighted sequences with conventional spin-echo sequences in renal MRI. Twenty-three patients with focal renal lesions were examined with a T2-weighted ultrafast turbo spin-echo (UTSE) sequence with and without frequency selective fat suppression (SPIR), a combined gradient-and-spin-echo sequence (GraSE), and a conventional spin-echo sequence (SE). In addition, T1-weighted images were obtained pre- and postcontrast, using a fast spin-echo sequence (TSE) with and without SPIR and the conventional SE sequence. Among the T2-weighted images, the highest CNR and the best image quality were obtained with the UTSE sequence, followed by the fat-suppressed UTSE sequence. GraSE and conventional SE sequences showed a significantly lower CNR and image quality (p < 0.05). The T1-weighted sequences did not show significant differences, in either precontrast or postcontrast measurements. T2-weighted UTSE with and without fat suppression combined excellent image quality and high CNR for imaging and detection of renal lesions. The T1-weighted fast sequences provided no alternative to the gradient-echo or to the conventional SE sequences. The results of this systematic study suggest the use of T2-weighted fast techniques for improved diagnostic accuracy of renal MRI.

Adenoma, Oxyphilic↗
PubMedDate not supplied

Prospective comparison of fast SE and GRASE sequences and echo planar imaging with conventional SE sequences in the detection of focal liver lesions at 1.0 T.

PURPOSE: Our goal was to investigate the value of T2-weighted fast SE (FSE) sequences, FSE sequences with shortened echo spacing (UFSE), combined gradient and spin echo sequences (GRASE), and segmented T1-weighted echo planar imaging (EPI) in comparison with conventional SE sequences in the detection of focal liver lesions. METHOD: Thirty-five patients with malignant focal liver lesions underwent MRI at 1.0 T. RESULTS: All fast T2-weighted imaging techniques (FSE, UFSE, GRASE) showed fewer artifacts and overall better image quality than the conventional SE sequence. Quantitative analysis demonstrated that UFSE imaging had the highest tumor/liver contrast/noise ratio (C/N) (13.9 +/- 5.5) followed by FSE (12.7 +/- 4.5), T2 SE (10.9 +/- 4.2), and GRASE (10.0 +/- 4.8) sequences. The differences in C/N between the UFSE and T2 SE sequences was statistically significant (p < 0.05). C/N was significantly higher (p < 0.01) for the T1 SE (-7.4 +/- 3.8) than for the EPI sequence (-0.5 +/- 5.6). CONCLUSION: FSE sequences with shortened echo spacing are valuable for liver imaging at 1.0 T. In comparison with the T2 SE sequence, they yielded better image quality and comparable tumor/liver C/N.

Adult↗
PubMedDate not supplied

MR sialography: initial experience using a T2-weighted fast SE sequence.

PURPOSE: The aim of this study was to evaluate an MR technique optimized for imaging of the parotid gland ductal system. METHOD: The pulse sequence was optimized in 10 volunteers to depict static or nearly static fluid in the parotid ductal system. A heavily T2-weighted fast SE sequence (TR 3,600 ms/TE 800 ms) with a slice thickness of 30-40 mm using an 8 cm surface coil allowed depiction of the fluid-filled parotid duct. Thirteen patients with benign as well as malignant parotid gland pathologies were examined: sialadenitis (n = 2), sialadenosis (n = 3), Heerfordt syndrome (n = 1), pleomorphic adenoma (n = 2), parotid carcinoma (n = 1), lymphoepithelial carcinoma (n = 1), cystadenolymphoma (n = 2), and non-Hodgkin lymphoma (n = 1). RESULTS: The heavily T2-weighted projection image yielded good quality sialographic images. The main duct and primary branching ducts were clearly depicted in all normal cases. The main duct was visualized in all patients. Intra- and extraglandular duct widening and ductal strictures were well depicted. Sialolithiasis with a calculus in the main duct was correctly demonstrated in one case. CONCLUSION: MR sialography is noninvasive and does not depend on duct cannulation or contrast agent injection. Initial experience with a thick slice projection technique indicates that MR sialography can be successfully applied to image the parotid gland ductal system.

Adenolymphoma↗
PubMedDate not supplied

Noninvasive detection of increased glycine content by proton MR spectroscopy in the brains of two infants with nonketotic hyperglycinemia.

Using localized 1H-MR spectroscopy (1H-MRS) an inborn error of metabolism within human brain could be demonstrated, while 1H-MR imaging did not show any pathologic findings like demyelination. In two children suffering from nonketotic hyperglycinemia, the proton spectrum exhibited a large glycine signal at 3.55 ppm. In patient 1 (49-day-old girl), the pathologic signal of the inhibitory neurotransmitter glycine was of similar size in the parietooccipital white matter and in the basal ganglia region. In patient 2 (a 10-day-old girl), follow-up studies within the first 4 months of life revealed a time course of cerebral glycine content that differed from the course in plasma and cerebrospinal fluid. The continuing reduction of glycine in brain tissue corresponded more reliably with clinical findings than the stable values in plasma and cerebrospinal fluid. 1H-MRS allows the noninvasive demonstration of glycine in patients with nonketotic hyperglycinemia. This new technique may be useful to control the effect of a sodium benzoate therapy by monitoring the cerebral glycine concentration directly.

Amino Acid Metabolism, Inborn Errors↗