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Biomedical subjects

F Träber

Publications and source records attributed to F Träber.

At least 55 records · Page 3Linked to original sources
PubMed1997

Relationship between cytochrome P-450 induction by rifampicin, hepatic volume and portal blood flow in man.

OBJECTIVE: Induction of hepatic cytochrome P-450-dependent oxidative metabolism is related to an almost identical increase (30%) in both the liver weight and portal blood flow in animals. In humans by contrast, an increased liver blood flow (44%) but no significant increase in liver volume has been reported. DESIGN: Therefore, we studied prospectively the relationship between P-450 induction by rifampicin, hepatic volume and portal blood flow in 10 healthy volunteers. METHODS: After a pre-treatment phase (day 1 to 7) the 10 volunteers received 600 mg/day of rifampicin from day 7 to 12. The urinary 6-beta-hydroxycortisol output as a measure of oxidative metabolism (CYP3A4) and portal blood flow (pulsed Doppler ultrasound) were determined on days 1, 7, 11 and 13. Hepatic magnetic resonance volumetry was performed on days 1 and 13. RESULTS: Urinary 6-beta-hydroxycortisol output increased in all volunteers (P = 0.0051) from a median of 2.15 micrograms/day/kg (1.8-3.3 micrograms/day/kg) on day 1 to 9.9 micrograms/day/kg (5.7-14 micrograms/day/kg) on day 13. In 9 of 10 volunteers induction by rifampicin was related to an increase (P = 0.0218) in liver volume from a median of 1570 cm3 (1390-1830 cm3) to a median of 1690 cm3 (1420-1860 cm3). The portal flow as assessed by colour Doppler ultrasound did not change significantly between day 1 (median 22 cm/s (15-35 cm/s)) and day 13 (median 19 cm/s (16-39 cm/s)). CONCLUSION: A fourfold increase of urinary 6-beta-hydroxycortisol output after induction of cytochrome P-450 by rifampicin is associated with a significant but less than 10% increase in human liver volume. No increase of portal perfusion as assessed by Doppler ultrasound could be detected in this study.

Adult↗
PubMed1995

[1H-MR spectroscopic imaging in patients with clinically diagnosed Alzheimer's disease].

PURPOSE: To detect regional differences in accompanying metabolic changes, 1H-Magnetic Resonance Spectroscopic Imaging (MRSI) was performed in 16 patients with Alzheimer's disease (AD); the clinical diagnosis was based upon DSM-III-R and NINCDS-ADRDA guidelines. METHODS: In the hippocampal region metabolic maps of the local distribution of N-acetylaspartate (NAA), choline (Cho), creatine compounds (P(Cr)) and lactate were determined. Ratios of Cho/NAA, (P)Cr/NAA and Cho/(P)Cr calculated from selected hippocampal spectra were compared to those from healthy volunteers (n = 17). RESULTS: AD patients demonstrated an increase of Cho/NAA and (P)Cr/NAA ratios caused by increased choline compounds and decreased NAA. These alterations were observed in 11/12 cases in the hippocampal and in 7/12 in the temporo-occipital region. Hippocampal Cho/NAA ratios (0.56 +/- 0.19) were significantly elevated compared with controls (0.33 +/- 0.04; p < 0.0001). CONCLUSION: The observed elevation of choline compounds in the hippocampus supports the hypothesis that alterations in the cholinergic system play an important role in Alzheimer's disease. The observed reduction of NAA is due to neuronal degeneration.

Aged↗
PubMed1994

[Evaluation of rapid gradient-echo and turbo-spin-echo sequences in MRT of focal liver lesions using 0.5 tesla].

The value of rapid T1- and T2-weighted fast field (T1-FFE, T2-FFE) gradient-echo sequences and T2 weighted turbo-spin echo (TSE) sequences in the diagnosis of focal liver lesions using 0.5 Tesla was compared with conventional spin-echo sequences (SE). Amongst 88 liver lesions T1-SE sequences showed 98%, T2-TSE sequences showed 92%, T2-SE sequence showed 84%, T1-FFE sequence showed 78% and T2-FFE sequence showed 69%. Direct comparison has shown that TSE sequences are able to demonstrate significantly more lesions (p < 0.05) than T2-SE sequences. Quantitative assessment has shown that the tumor/liver contrast/noise ratio in the T1-SE sequence was 118% higher than in the T1-FFE sequence (p < 0.001). Comparison of T2 weighted sequences has shown that the tumour/liver contrast/noise ratio was 45% higher in the TSE sequence than in the T2-SE and 239% higher than in the T2-FFE sequence (p < 0.001). The results indicate that the TSE sequence should be used instead of the conventional T2-SE sequence because of the reduced time (about 40%), due to improved image quality and increased demonstration rate of liver lesions. Neither T1-FFE nor T2-FFE are suitable, when using moderate field strength, to replace T1-SE or TSE sequences.

Adenocarcinoma↗
PubMed1994

Mitochondrial encephalomyopathy: correlation of P-31 exercise MR spectroscopy with clinical findings.

PURPOSE: To evaluate the sensitivity of standardized exercise phosphorus-31 magnetic resonance (MR) spectroscopy in screening for subclinical muscle involvement in mitochondrial encephalomyopathy and to estimate if changes seen at biopsy have functional consequences. MATERIALS AND METHODS: Exercise MR spectroscopy was performed in 52 examinations of 18 healthy volunteers and 14 patients with defects of mitochondrial respiratory chain enzymes. Calculation and kinetic analysis of the phosphocreatine (PCr) index and pH time courses were standardized with a microcomputer program. RESULTS: PCr index scores and conventional test scores matched in 10 of 14 cases. No obvious correlation existed between pH parameters and clinical score. Muscle affection, according to pH parameter score, was rated moderate (n = 3), severe (n = 1), or maximum (n = 2) in six of 14 cases in which clinical test scores showed only mild affection. CONCLUSION: Exercise MR spectroscopic PCr index parameters provide diagnostic information on skeletal muscle involvement in patients with mitochondrial encephalopathy. The sensitivity of the PCr index parameter seems equal or superior to that of conventional diagnostic tests. The role of pH parameters, however, has yet to be defined.

Adult↗
PubMed1993

[Initial results of in vivo 31P-NMR spectroscopy of the spleen in patients with splenomegaly].

In-vivo 31P-NMR spectroscopy of the spleen was carried out in 15 patients with splenomegaly from various causes (Hodgkin's disease, non-Hodgkin lymphoma, polycythaemia vera, chronic lymphatic leukaemia, chronic myeloid leukaemia). Volume selection was with the ISIS technique, voxel size was between 3 x 5 x 5 and 8 x 6 x 7 cm3. There was a markedly elevated (PM+Pi)/beta-NTP quotient (mean 3.41 with a standard deviation of 0.37) (p < 0.001) and raised PDE/beta/NTP quotient as compared with 8 normals, who showed an (PME+Pi)/beta-NTP quotient of 2.32 and a PDE/beta/NTP quotient of 1.11. These raised quotients were interpreted as indicating increased membrane phospholipid metabolism due to increased cell turnover. The data suggest there may be some clinical value in performing 31P-NMR spectroscopy for defining splenic involvement in myeloproliferative diseases but further confirmatory studies will be necessary.

Adult↗
PubMed1993

[Magnetic resonance tomography using the fast STIR technique: optimization and a comparison with other sequences in a 0.5-Tesla system].

One disadvantage of the STIR sequence in MRI is its long acquisition time. A TR shortening for acceleration requires shortening of the inversion time depending upon the field strength. We optimized this "fast-STIR" technique at 0.5 T using calculations, phantom, volunteer, and patient measurements. This optimization procedure is transferable to other field strengths. The resulting sequence takes 4.5 minutes, fat is visualised signal-free. In the second part of our study we compared quantitatively and qualitatively the signal intensities, contrast, and sensitivity towards artifacts of this sequence with that of conventional SE and GRE sequences in 21 patients with neoplastic, inflammatory and traumatic disorders of the musculoskeletal system. The fast-STIR sequence showed similar or better lesion contrast as SE in 100% and as GRE in 88%. Decreased spatial resolution and higher sensitivity towards pulsatile artifacts of the fast-STIR sequence were only minor drawbacks.

Achilles Tendon↗
PubMed1993

[Metabolic studies of the calf musculature with 31P-MR spectroscopy in arterial obstructive disease before and after lumbar sympatholysis].

In 9 patients with arterial occlusive disease of grade IV according to Fontaine, energy metabolism was measured in the calf muscle during rest, before and after lumbar sympatholysis, by means of 31phosphorus MR spectroscopy. The concentration of inorganic phosphate (Pi) and phosphocreatine (PCr) relative to high energy phosphates, as well as the pH value in muscle cells were assessed, and the quotient Pi/PCr was calculated for estimation of energy reserves. Before sympatholysis, normal concentrations of the energy suppliers ATP and PCr were unexpectedly found in combination with reduced cellular energy reserves. After lumbar sympatholysis, in most cases no significant changes of muscle energy metabolism were detected. Independent of the muscle energy supply, a slight increase in energy supply without returning to normal values was found in only three patients. In most patients the clinical symptoms had improved at least to some extent.

Adult↗
PubMed1993

["Spectroscopic imaging." A new MR technique in the diagnosis of epilepsy?].

The technique of magnetic resonance spectroscopy fuses spectroscopic methods with the two-dimensional illustration of the metabolite concentrations by parallel acquisition of multiple single voxels from small tissue compartments. Therefore it is not necessary to define a voxel of interest before data acquisition. The interpretation of metabolite images is much easier than the analysis of single spectra, and metabolite concentrations on the right and left sides can be compared. The method has already proved reliable for brain tumors. The application of the procedure to patients suffering from epilepsy is described here in for the first time. Even in the temporal region, where most epileptogenic foci have their origin, one can obtain metabolite images of diagnostic quality without susceptibility artifacts. The epileptogenic focus is lateralized correctly, in accordance with electrophysiological and surgical evaluation, even in those cases where standard magnetic resonance imaging is normal. According to our preliminary findings the epileptogenic focus is characterized by a signal loss of N-acetyl-aspartate and creatine.

Adult↗
PubMed1993

[Intracranial ECoG electrodes. Location determination using three-dimensional reconstruction of MR data of the brain as a component of the presurgical diagnosis of epilepsy].

Subdural strip electrodes or intracerebral electrodes are required in order to precisely localize epileptic foci, which is mandatory for epilepsy surgery. The subdural electrodes are inserted via a borehole and thus precise positioning cannot be directly monitored. Therefore, the location of the electrodes in relation to the gyri and sulci has to be determined by imaging techniques. In this study, a three-dimensional magnetic resonance imaging (3D MRI) technique was used for visualization of intracranial EEG electrodes. A 3D gradient echo sequence with thin slices of 1 mm is required for the assessment of the gyral anatomy of the brain surface. Using a short repetition time of 30 ms good image quality within an acceptable acquisition time of about 15 min was possible. Post-processing with 3D surface reconstruction was performed using a Sun workstation. Three-dimensional reconstruction allows a more precise delineation of the localization of the EEG electrodes and the simultaneous display of the adjacent brain structures. Misplacement of intracranial electrodes is readily detected. 3D MRI with 3D surface reconstruction proved superior to 2D imaging and CT for the assessment of EEG electrode localization.

Electrodes↗
PubMed1992

[MR venography in deep venous thromboses of the leg and pelvis. A comparison of 2D single layer images and 3D MIP reconstructions with phlebography].

A total of 22 MR venograms were performed in 7 volunteers and 15 patients suspected of deep vein thrombosis of the lower limb and pelvis. MR findings were compared to conventional venography in all patients. MR venography is a reliable method for the exclusion of thrombosis proximal to the popliteal vein. In the calf veins, diagnosis of thrombosis is not yet reliable. For MR venography 2D-time-of-flight-inflow-technique and secondary 3D-MIP reconstructions were used and compared to each other. With both methods there were no false negative results in comparison to conventional venography. 2D single slice MR venography showed two false positive results in iliac and one in popliteal vein. MIP 3D reconstructions led to seven false positive results (three iliac, two femoral, two popliteal). The exclusive interpretation of MIP-3D reconstruction is not reliable for decision-making in deep venous thrombosis.

Adult↗
PubMed1992

[In-vivo 31P-NMR-spectroscopy in patients with dilated cardiomyopathy].

In vivo 31P-NMR spectra of heart muscle were obtained in 7 patients with dilating cardiomyopathies and in 10 normal subjects, using an ISIS technique with a 1.5 Tesla body scanner (Philips Gyroscan S15) and the results of the two groups were compared. These results were easily reproduced. In patients with cardiomyopathy there was a significant (p < 0.05) reduction of the PCr/ATP ratio as an expression of abnormal energy metabolism. Two patients with mild clinical symptoms and only slightly reduced functional measurements showed no significant changes in the 31P-NMR spectrum. The patients with the largest reduction of the PCr/ATP index also showed the most marked changes in functional measurements. The PCr/ATP ratio (as also suggested by animal experiments) appears to be a suitable non-invasive indicator for the diagnosis and staging of myocardial changes in dilating cardiomyopathies.

Adenosine Triphosphate↗
PubMed1992

MRI and MRS of the skeletal muscle.

Magnetic resonance imaging and spectroscopy were performed in several types of muscular disorders. In acute stages, 31P spectra showed remarkable changes compared with normals, and T2-weighted MR images were most sensitive in delineating the pathology. Fatty degeneration of muscle in chronic diseases yielded high contrast in T1-weighted MRI and could be quantified by 1H-MRS including the chemically selective determination of proton T1 values. In order to evaluate true abundance rations of phosphorus metabolites, 31P relaxation times T1 of muscle were measured by localized inversion recovery.

Acute Disease↗
PubMed1990

[In vivo measurement of tissue relaxation times using localized 31P and 1H MR spectroscopy].

Methods of in vivo determination of 31P longitudinal relaxation times within image-determined volume selected MRI spectroscopy have been investigated. T1 values for phosphor compounds in skeletal muscle and in brain have been measured. The 1H relaxation times of T1 and T2 of diffuse parenchymal liver disease, using inversion recovery and spin echo sequences were compared with quantitative MR tomography. Clinically, spectroscopic techniques are particularly useful where there is superimposition of water and lipid signals during MR imaging.

Brain↗
PubMed1990

[Qualitative control over quantitative MR tomography: in vitro and in vivo checks on relaxation time measurements].

In-vivo and in-vitro checks on measurements of relaxation times in MRI have been carried out as part of quality control. For the in-vitro experiments we used 13 reagents consisting of varying concentrations of copper sulphate manganese sulphate, gadolinium solutions and various oils as well as water. For in-vivo measurements we used liver parenchyma and fat in three subjects. Eight different sequences were performed; intra- and interindividual variations and comparison of three similar MRI units showed average variations of 2-3% for T1 and 3-4% variations for T2 relaxation times. This margin of error makes quantitative MRI acceptable for clinical use.

Adolescent↗
PubMed1989

[NMR tomography of the brain in patients on long-term dialysis].

24 patients on long-term dialysis, aged between 20 and 78 years, were examined by brain MRT and CT. Both methods showed equally atrophic changes in the brain; in particular, cortical atrophy appears to increase with increasing duration of dialysis. MRT shows small hyperintensive areas in the white matter which cannot be seen on CT. Hypointensive areas on MRT are not due to calcification, but pathological deposition of metals, such as iron, must be considered.

Adult↗
PubMed1989

[Relaxation time measurements in the differential magnetic resonance tomographic diagnosis of liver tumors].

T1-weighted IR sequences and T2-weighted SE sequences and combined SE/IR sequences were carried out in 62 patients with malignant and 50 patients with benign liver tumours and the T1 and T2 relaxation times were measured. IR sequences proved the most sensitive method for imaging focal liver lesions and providing good contrast between liver tissue and tumour. For lesions above 1.5 cm, quantitative MRI achieved an accuracy better than 95% in distinguishing between haemangiomas and malignant lesions. Routine quantitative measurements of relaxation times were sufficiently reproducible for clinical use.

Carcinoma, Hepatocellular↗