Biomedical subjects

O Lutz

Publications and source records attributed to O Lutz.

83 records · Page 5Linked to original sources

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

Gram-positive bacterial sepsis in rat and tissue lipolytic activity on commercial parenteral fat emulsions.

To study the influence of a gram-positive sepsis on the metabolism of circulating lipids, fasted rats were injected with saline (control group) or with a suspension of heat-killed or live Staphylococcus aureus. 18 h later, body temperature was increased, while albuminemia and ketonemia were decreased in the group injected with heat-killed bacteria, as opposed to the control group. Passing from these groups to the group injected with live bacteria, more differences appeared: increase of triglyceridemia and free cholesterolemia; decrease of esterified cholesterol levels and especially of the in vitro activity of diaphragm, heart and adipose tissue lipoprotein lipase and of hepatic lipase. The decrease of lipolytic activities occurred whether they were measured on a fat emulsion containing long-chain or medium- and long-chain triglycerides. The fact that for the latter the activity was always higher than for the former suggests that the host infected with gram-positive bacteria would clear exogenous fat more easily in the case of medium-chain triglycerides.

Animals↗

PubMedDate not supplied

[Tolerance of a new intravenously applied immunoglobulin preparation and its effect on serum globulin levels].

In a controlled prospective study, 212 patients were evaluated in 13 different hospitals with regard to the clinical tolerance of a new gammaglobulin preparation which can be administered intravenously. The age of the patients ranged from one day to 83 years. Patients with a primary or secondary immunoglobulin deficiency and patients with normal serum immunoglobulin concentrations were included in the study. In 811 infusions a total of 7128 g gammaglobulin were applied; the maximum dosage was 30 g/day. We saw a transient, recurrent and spontaneously reversible fever reaction in one patient with long-term substitution because of a primary immunodeficiency syndrome. Otherwise, no serious side-effects were seen in clinical or laboratory controls. Patients controlled for their serum gammaglobulin concentrations before and after the infusions showed a significant rise of 112.5 mg/100 ml for each infusion of 3 g gammaglobulin. The new preparation also showed an estimated half-life of 23 days, thus making it a good possibility for long-term substitution in immunodeficient patients.

Adolescent↗

PubMedDate not supplied

Subtle bone marrow edema assessed by frequency selective chemical shift MRI.

Subtle edema in yellow bone marrow from tumors (14 subjects) and osteomyelitis (9 subjects) were examined by selective nonexcitation (SENEX) water imaging using a short five pulse frequency selective excitation with lipid suppression greater than 96%. Standard spin-echo (SE) proton density-, T1- and T2-weighted images, and fat suppression methods such as short inversion time inversion recovery and also the chemical shift selective Dixon method are discussed in comparison with SENEX. Application of the SENEX method is described and images from four typical cases are demonstrated. Sensitivity to edema is obviously better using the SENEX chemical shift selective method than using other imaging techniques. Improved delineation of abnormal areas in yellow bone marrow is provided by SENEX water imaging in one slice after multislice standard imaging. After shimming, only one SE scan with frequency selective excitation is necessary to get a pure water image.

Adult↗

PubMedDate not supplied

[Examination of trabecular bone structures of the foot skeleton with MRI imaging].

AIMS: To assess trabecular density and structures at various cancellous bone sites in the foot using MR imaging. To compare the MRI findings with the bone mineral density (BMD) values obtained by quantitative computed tomography (QCT) in the lumbar vertebrae. MATERIALS AND METHODS: Bone mineral densities were measured by QCT in lumbar vertebrae 1 to 3 in ten patients with suspected osteoporosis. Sagittal images of the feet were obtained from these patients and also from seven healthy volunteers applying spin-echo and gradient-echo MR techniques. RESULTS: MR imaging revealed differences between patients with osteoporosis and individuals with healthy bones. Comparison of MR and BMD data revealed a significant dependence of MR data on the bone density measured by QCT (alpha < 0.05). In addition, a good correlation (r = 0.73) was found between the results of the different MRI techniques. CONCLUSIONS: The MR imaging techniques investigated offer an interesting tool for the non-invasive assessment of bony structures, at least at peripheral locations with yellow bone marrow. To enable reliable application in the clinical routine setting, additional studies are required to identify suitable standardized methods and establish normal ranges.

Adult↗

PubMedDate not supplied

Decreased lipolytic activity in tissues during infectious and inflammatory stress.

The clearance rate of endogenous and exogenous circulating lipids during the septic or inflammatory state remains a controversial subject. Thus, we have developed rat models of gram-negative and gram-positive sepsis and of sterile inflammation to study this problem. In addition to the febrile response, these stresses induced some of the following metabolic changes in the blood: decreased total protein, albumin, and ketone body levels and increased lactate, pyruvate, alanine, cholesterol, and triacylglycerol levels. The activities of heart, diaphragm, and adipose tissue lipoprotein lipase and of hepatic lipase decreased to differing extents depending on whether the enzyme substrate was a long-chain or a medium- and long-chain triglyceride-based emulsion. However, the latter emulsion was always hydrolyzed faster than the former. This observation suggests that, during infection/inflammation, the medium- and long-chain triglyceride-based emulsion would be cleared more quickly, would induce less hypertriglyceridemia, and would thus deliver lipid energy more rapidly than a traditional long-chain triglyceride-based emulsion.

Alanine↗

PubMedDate not supplied

In vivo and in vitro release of lipoprotein lipase and hepatic lipase by low molecular weight heparins.

The purpose of this study was to compare lipoprotein lipase (LPL) and hepatic lipase (HL) releasing activities of different low molecular weight heparins (LMWH) and of a standard heparin. In vivo, the injection of most LMWH led to a LPL and HL releasing activity inferior to that obtained with a standard heparin. The releasing of LPL by muscle in vitro and of HL by perfused liver was identical with both types of heparins, but in epididymal adipose tissue, LPL activity released by LMWH was generally higher than the activity released by unfractionated heparin. We have no explanation for this apparent contradiction between the in vivo and in vitro results.

Adipose Tissue↗

PubMedDate not supplied

Lipid selective MR imaging and localized 1H spectroscopy of bone marrow during therapy of leukemia.

In most patients with acute leukemia very low or absent lipid signals from central red bone marrow are detected using magnetic resonance (MR) techniques, in contrast to healthy persons with considerable signals from both, water and lipid protons. The proliferation of the malignant leukemic cells causes the displacement of fat cells in the marrow. This disorder is reversible during successful cytotoxic chemotherapy of acute leukemia: Lipid signals from vertebral bodies arise again due to the replacement of hypercellular leukemic marrow by fat. Different approaches for lipid selective MR imaging and spectroscopy are reported and results from typical examples are demonstrated and discussed. The report is based on examinations of 12 patients with leukemia in follow-up studies, 11 patients with other disorders of bone marrow, and 26 healthy volunteers.

Adolescent↗

PubMedDate not supplied

Lipids in bone tumors assessed by magnetic resonance: chemical shift imaging and proton spectroscopy in vivo.

The methods of fat and water selective magnetic resonance (MR) imaging and localized 1H MR spectroscopy were evaluated in the course of 37 examinations on 27 primary bone tumors. These methods are capable of demonstrating small amounts of lipids inside the tumors and subtle edema in the adacent bone marrow, in contrast to the usually applied spin-echo and gradient-echo sequences providing signals dependent on the total proton density and on the relaxation times. The tumor masses of the malignant tumors were free of signals in the fat selective images, whereas in three out of six osteochondroma fat signals could be detected. Localized MR spectroscopy was more sensitive even to very low lipid content (lipid portion < 0.5%) in the tumors and revealed signals with J-coupling from seven out of 13 malignant tumors.

Adolescent↗