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Biomedical subjects

F Schick

Publications and source records attributed to F Schick.

At least 127 records · Page 7Linked to original sources
PubMed1992

Volume-selective proton MRS in vertebral bodies.

Volume-selective 1H magnetic resonance spectra of small volume elements of (13 mm)3 positioned in lumbar vertebral bodies have been investigated in 15 healthy persons of different ages and sexes and in 11 patients with leukemia using double spin-echo sequences. Signal intensities and positions of the spectral lines have been evaluated. Interindividual spectra of VOI located in the center of vertebral bodies, intraindividual spectra of central VOI in different vertebral bodies, and spectra of different localizations within the same vertebral body have been compared as well as spectra before and partly after cytostatic treatment in leukemia patients. Unexpected phenomena of the signal shapes have been found. The water signal distributions in healthy persons compared to patients after bone marrow transplantation show significant differences. The success of the cytostatic treatment in cases of leukemia is accompanied by an increase in the intensity of the lipid signals and a decrease in the water signals.

Adipose Tissue↗
PubMed1992

31P transverse relaxation times of the ATP NMR signals of human skeletal muscle in vivo.

31P MRS examinations of the calf muscles of 12 healthy volunteers were performed to determine T2 of the coupled ATP signals by using the 90 degrees-TE/2-2662-TE/2-acq selective spin-echo sequence for elimination of phase and intensity distortions. The T2 relaxation times obtained are much longer than those usually assumed: gamma-ATP, 93 ms; alpha-ATP, 74 ms; beta-ATP, 75 ms.

Adenosine Triphosphate↗
PubMed1992

Alterations of bone conducted hearing in cases of modified middle ear mechanics. Conclusions from an electrical model.

In clinical diagnosis bone conduction thresholds can be used to assess impaired hearing caused by pathological function of the inner ear. The effects of changed mechanical properties of the middle ear on bone conduction are usually not considered in patients who simultaneously suffer from middle ear and inner ear diseases. This procedure is only partially correct. An exact determination of the effects of altered middle ear mechanics on bone conduction in patients with otosclerosis or after middle ear operations is rather difficult, but such determinations can improve diagnostic validity. Therefore, a special electrical model was constructed to simulate the oscillation pattern of the basilar membrane for bone conduction and variable middle ear impedance. Results from the model and possible conclusions on bone conducted hearing in vivo are discussed. Further steps to ensure measurements of inner ear function in cases with modified middle ear mechanics are proposed.

Basilar Membrane↗
PubMed1992

Localized phosphorus NMR spectroscopy: a comparison of the FID, DRESS, CRISIS/CODEX, and STEAM methods in vitro and in vivo using a surface-coil.

The FID, DRESS, CRISIS/CODEX, and STEAM techniques for localized 31P NMR spectroscopy were compared using a Siemens Magnetom SP63 1.5 T whole-body imager and a surface-coil, 80 mm in diameter, acting as transmitter and receiver coil. The comparison was performed with phantom experiments and human in vivo investigations on the calf muscle. The phantom experiments which used the same volume size showed a comparable signal-to-noise ratio for FID and DRESS, while the two fully localized techniques showed a reduction in signal-to-noise ratio to 76% for CRISIS/CODEX and 31% for STEAM. The in vivo measurements confirm the phantom results and reveal that CRISIS/CODEX gains a 2.5 fold higher signal-to-noise ratio than STEAM under the same conditions.

Humans↗
PubMed1992

Localized in vivo 1H spectroscopy of human skeletal muscle: normal and pathologic findings.

To obtain high signal to noise ratio in small volume elements (8 cm3), in vivo 1H NMR spectroscopy of normal and diseased human skeletal muscle was performed using a double spin-echo localization method on a 1.5-T whole body system. High resolved spectra of normal calf muscle show the well known resonances of lipids (methyl, methylene, olefinic, and other fatty acid resonances), creatine/phosphocreatine, choline/carnitine, taurine, and histidine with good intraindividual reproducibility. Pronounced intraindividual differences in the lipid range were found between different upper thigh muscle groups. On pathologic conditions like myopathy, myositis or irradiation damage the spectral lipid content was increased. Three months after local irradiation of the medial vastus muscle (50 Gy), the localized 1H NMR spectrum showed a complete loss of the choline and creatine signals. In a case of M. Behçet with muscular involvement the relative reduction of the choline signal may provide an insight in the pathobiochemistry. The results of our investigations in nine healthy volunteers and three patients are presented in detail including relaxation times of the metabolites.

Adolescent↗
PubMed1991

Localized Larmor frequency-guided fat and water proton MRI of the spine: a method to emphasize pathological findings.

A measurement protocol providing a correct adjustment of the irradiation frequencies for well separated fat and water images of the lumbar spine is presented. To determine accurately the Larmor frequencies of water and fat protons within the vertebral bodies, a volume selective spectrum of a volume element (13 mm)3 located in a lumbar vertebral body was acquired with the 90 degrees-180 degrees-180 degrees double spin-echo method. These Larmor frequencies are used to adjust the frequency-selective pulse of the SENEX chemical-shift imaging sequence. This procedure provides well separated fat and water images for a large field of view even in the inhomogeneous region of the vertebral column. Their clinical importance is demonstrated by localized Larmor frequency-guided (LLFG) SENEX 1H images of the lumbar spine in healthy persons of different age and in a patient with acute myeloid leukemia.

Acute Disease↗
PubMed1984

[Metastatic differentiated thyroid cancer. Diagnostic accuracy of thyroglobulin-RIA in comparison with 131I-whole body scintigraphy].

In a retrospective analysis in patients with differentiated thyroid carcinoma, the diagnostic validities of 131I whole-body scans and radioimmunologic determinations of thyroglobulin (hTg) are compared with special regard to late metastases. Metastases were found in 83 out of 311 patients with differentiated thyroid carcinoma. In two thirds of the cases, these were primary metastases while in the remaining third of the cases, metastases developed in later follow-up with a mean time of latency of 3.3 years. While about 70% of the early metastases could bei detected by 131I scintigraphy, this percentage amounted to only 40% in late metastases. With a diagnostic sensitivity of 90%, hTg-RIA was clearly superior in the detection of early as well as of late metastases. hTg was measurable, however, only in iatrogenous hypothyroidism in 4 out of 49 cases. Based on these results and an analysis of the literature, a program for follow-up of differentiated thyroid carcinoma is proposed. The hTg-RIA is thereby used as an alternative to 131I scintigraphy in the late phase of follow-up after complete ablation of any thyroid tissue.

Adenocarcinoma↗
PubMed1983

[Direct and indirect parameters for free thyroxine. II. Diagnostic accuracy in disorders of thyroid function and binding protein anomalies].

Part II of the study concerning the clinical applicability of direct and indirect parameters for free thyroxine evaluates the diagnostic accuracy of the FT4-RIAs ImmoPhase, GammaCoat, Liquisol, Amerlex and LisoPhase in relation to FT4 index and T4/TBG ratio. This comparison of methods is done on a thoroughly classified collection (n = 640) of patients with normal and impaired thyroid function including patients with binding protein anomalies (pregnancy, estrogen-medication, phenytoin therapy, renal protein loss). FT4 normal ranges of a given kit harmonize well with data of the manufacturers and of the literature. On the other hand, the normal ranges of the various kits are not comparable. The differentiation of euthyroidism from hyper- or hypothyroidism can be made without problems using any of these methods, with the exception of the FT4-RIA GammaCoat. As expected, patients with euthyroid goiter show, on the average, slightly lower parameters for FT4. In pregnancy all direct and indirect parameters for FT4 have a tendency to lower values after the first trimester. This trend is most distinct for the T4/TBG ratio. A weak negative correlation of FT4 parameters with basal TSH, which does not exceed the upper normal range, however, can be interpreted in the sense of a relative hypothyroxinemia. Under contraceptive estrogen medication FT4 parameters do not fall outside the normal range, with the exception of the FT4-RIA ImmoPhase assay which yields a significantly increased frequency of high FT4 levels. On therapy with phenytoin FT4 values are generally lower than in controls. FT4 parameters in patients with renal protein loss of more than 2 g daily do not behave uniformly. While three of the FT4-RIAs tested (ImmoPhase, GammaCoat, Amerlex) show a tendency to lower values, the results of the remaining FT4 parameters do not differ significantly from the distribution of normals. The study leads to the conclusion that indirect FT4 parameters are still useful in the diagnosis of thyroid function; currently available FT4 radioimmunoassays may yield comparable results. With regard to the varying quality of the various commercial test kits, the choice between FT4-RIAs and indirect FT4 parameters does not depend primarily on clinical but on technical viewpoints.

Adult↗
PubMed1979

[Pre- and postoperative clearance studies in the individual kidneys in juvenile kidney surgery].

In 1978 43 patients have been operated in the Department of Pediatric Surgery, Krankenhaus München-Schwabing, because of recurrent urinary-tract infections with ureterovesical reflux or obstructive urinary-tract diseases. In all patients a split whole body clearance-study with a method modified after the method of Mühle with 131J-Hippuran was carried out pre- or postoperatively, respectively. In 78,5% of these cases the clearance-results were corresponding to the results of x-ray examination; 6 of the remaining patients had a worse clearance result and 3 had a better result than the x-ray findings would have suggested.

Child↗
PubMed1977

Discharges of superior colliculus neurons during head and eye movements of the alert cat.

452 single neurons from the superior colliculus were recorded in awake and non-paralysed cats. 75 neurons were obtained from cats with unrestrained horizontal head movements. 228 neurons remained unaffected by saccadic eye movements. Eye movement related discharge followed the onset of saccades in 156 neurons either only in the presence of a visual pattern (92 neurons) or in darkness, too (64 neurons). The latter reaction type probably depends on eye muscle afferents. In 48 neurons eye movements related activity preceded the onset of eye movements. 12 neurons eye movement related activity preceded the onset of eye movements. 12 neurons fired in synchrony with eye movements of any direction (type I). 30 neurons were excited during contralaterally directed eye versions within or into the contralateral head related hemifield. They were inhibited when the eyes moved within or into the ipsilateral head related hemifield (type II). 6 neurons with constant maintained activity during fixation were inhibited by ipsilaterally directed saccades, but remained unaffected by contralateral eye movements. Head movement related discharge followed the onset of head movements in 20 neurons only in presence of a visual pattern and also in darkness in 6 neurons. Ipsilateral head movements or postures strongly suppressed maintained activity and visual responsiveness of some neurons. 15 neurons discharged in synchrony with and prior to contralateral head movements. Ipsilateral head movements inhibited these neurons. Activation or inhibition were usually related to movement and to posture, exceptionally to movement or to posture. Electrical stimulation of recording sites of these neurons through the recording microelectrode elicits contralateral head movements.

Animals↗
PubMed1975

The effects of a spirolactone derivative on EEG and cortical single unit activity in the cat.

With systemic (60-150 mg/kg) and topical application, Aldactone exhibited strong convulsant action on the cat cerebral cortex. The most common abnormal interictal features of the surface ECoG pattern were sequences of fast waves and slow negative waves associated with positive sharp waves, negative field potentials and burst-like neuronal activation in the extracellular microelectrode record. Another abnormal pattern was a period of ECoG and neuronal inactivity subsequent to the negative transients. These series of sharp and slow waves and of inactivity were interrupted by tonic and clonic ECoG seizures characterized by regular surface positive spikes. Development of seizures, but not of interictal phenomena, could be prevented by intravenous application of Diazepam (1 mg), Nembutal (30 mg/kg) and--less effectively--by Phenhydane (20 mg/kg).

Administration, Topical↗
PubMedDate not supplied

Hematopoietic reconstitution after bone marrow transplantation: assessment with MR imaging and H-1 localized spectroscopy.

Magnetic resonance (MR) studies were performed in 14 patients as early as possible (21-110 days) after bone marrow transplantation (BMT). MR characteristics of lumbar vertebral bone marrow were studied with T1-weighted spin-echo imaging, water- and fat-selective imaging with a frequency-selective excitation technique, and point-resolved spatially localized proton spectroscopy. Signals from water and fat protons and their T1 and T2 values were analyzed. Water proton signal intensity correlated well with cellularity within bone marrow, as determined with parallel iliac crest biopsies. The fraction of signal from water in red bone marrow of patients with allogeneic transplants from siblings (four cases) was significantly higher than in four patients with autologous transplants. The latter showed very low cellularity in the period of about 4 weeks after BMT because of the cytotoxic pretreatment of the bone marrow. The MR results in six patients with allogeneic transplants from unrelated donors ranged widely, depending on the complications after BMT. Analysis of data obtained with the different techniques showed that water- and fat-selective MR imaging and spectroscopic methods are useful for noninvasive monitoring of hematopoietic reconstitution after BMT.

Adolescent↗
PubMedDate not supplied

Magnetization transfer contrast of hepatic lesions in breath-hold gradient-echo images of different T1 weighting.

Seventeen patients with hepatic lesions [six metastases from colon, breast, and gallbladder carcinoma; one gallbladder carcinoma; five hepatocellular carcinoma; three focal nodular hyperplasia (FNH); one adenoma; and one cyst] were examined by MR breath-hold two-dimensional gradient-echo imaging to assess the potential of magnetization transfer contrast (MTC) for improved conspicuity and classification. Imaging sequences were applied with and without irradiation of off-resonant radiofrequency (RF) prepulses, but other parameters were unchanged. Therefore, quantitative assessment of MTC could be performed. In contrast to former examinations of other researchers, no significant difference of MTC was found between malignant liver lesions and benign lesions as FNH or adenoma. MTC might provide differentiation between hemangioma and cysts versus solid tumors, but MTC is not capable of distinguishing benign and malignant types of solid liver tumors. Effects of unchanged MTC prepulses on signal intensity of normal liver tissue and most lesions were more pronounced for nearly proton density-weighted fast low-angle shot (FLASH) images than for T1-weighted FLASH images, obtained by using higher excitation flip angles. Liver-to-lesion contrast could not be improved clearly by MTC prepulses. The contrast between liver and lesions in the gradient-echo breath-hold images was compared with standard T1- and T2-weighted spin-echo images. Liver-to-lesion contrast in the breath-hold images was found to be inferior to T2-weighted spin-echo images in 14 of 17 cases. Lesion conspicuity in regions near the diaphragm was better in breath-hold images, because problems with marked breathing motion (as in standard imaging) could be avoided.

Adult↗
PubMedDate not supplied

Slice-selective fat saturation in MR angiography using spatial-spectral selective prepulses.

Presaturation of fat signals by frequency-selective radiofrequency (RF) pulses is often applied in MR angiography to improve the visualization of the blood vessels. Unfortunately, standard fat saturation methods might cause a considerable reduction of the blood signal in the measured slices. This effect is caused by an attenuation of blood magnetization in remote tissue regions with water protons showing a similar Larmor frequency as the fat protons in the recorded slice. The affected blood water protons subsequently flow into the recorded slice and provide low signal intensity. Suitable spatial-spectral selective methods for slice-selective fat saturation were developed to avoid this unwanted effect. A spatial-spectral fat saturation technique was compared with a corresponding only spectrally selective approach. Both saturation techniques were included in a standard two-dimensional (2D) cine sequence and applied in angiographic examinations of the thighs. The results indicate that spatial-spectral saturation (acting slice selectively) leads to a clearly higher blood signal intensity in fat-suppressed MR angiography compared with standard techniques, especially in measurements performed during the systolic phase of the cardiac cycle.

Adipose Tissue↗
PubMedDate not supplied

Improved clinical echo-planar MRI using spatial-spectral excitation.

Echo-planar imaging (EPI) is markedly susceptible to B0 field distortions and to frequency differences caused by chemical shift, because the phase of the signals is accumulating during the acquisition train. Thus, only water proton signals are usually recorded after frequency-selective suppression of the fat portions of magnetization. Otherwise, a shifted signal frequency from fat results in ghosting artifacts. In this article, a technique is presented working with spatial-spectral excitation for highly selective water or fat EPI. The proposed method allows recording in multislice operation on EPI scanners without irregular gradient or RF pulse shapes. Examples of gradient-echo and spin-echo EPI using spatial-spectral excitation by series of two to eight single slice-selective RF pulses are demonstrated. The method is not sensitive to misadjustments or inhomogeneities of the B1 field, but sufficient homogeneity of the static magnetic field B0 is required. Especially the quality of diffusion-weighted echo-planar images can be markedly improved by the new technique compared to conventional EPI, because artifacts from undesired chemical shift components are completely avoided.

Adult↗
PubMedDate not supplied

Relationship between serum adiponectin concentration and intramyocellular lipid stores in humans.

The recently identified adipocytokine adiponectin has been shown to improve insulin action and decrease triglyceride content in skeletal muscle (by stimulating lipid oxidation) in mice. In the present study, we tested the hypothesis that high serum concentrations of adiponectin are associated with lower intramyocellular (IMCL) fat content by promoting lipid oxidation in humans. IMCL-content in predominantly non-oxidative tibialis anterior muscle and oxidative soleus was determined by proton magnetic resonance spectroscopy in a cross- sectional study involving 63 healthy volunteers. In a second set of experiments, changes in IMCL in both muscles were measured after a three days dietary lipid challenge (n = 18) and after intravenous lipid challenge (n = 12) with suppressed lipid oxidation under hyperinsulinemia. Adiponectin serum concentrations were found to be negatively correlated with IMCL in the oxidative soleus muscle (IMCL [sol]) (r = - 0.46, p < 0.001) independent of measures of obesity, but not with IMCL in the non-oxidative tibialis anterior muscle (IMCL [tib]) (p = 0.40). Adiponectin serum concentrations were negatively correlated with the observed increase in IMCL load after dietary lipid challenge in the tibialis (r = 0.53, p = 0.03) but not in the soleus muscle. During suppression of lipid oxidation by hyperinsulinemia, no effect of adiponectin on IMCL was observed in either soleus or tibialis muscle. Overall, the presented findings are consistent with the hypothesis that adiponectin promotes lipid oxidation in humans resulting in lower intracellular lipid content in human muscle. These results are consistent with animal data, where adiponectin could be shown to enhance lipid oxidation and reduce muscle triglycerides.

Adiponectin↗