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Biomedical subjects

F Kober

Publications and source records attributed to F Kober.

At least 19 recordsLinked to original sources
PubMed2004

Cine-MRI assessment of cardiac function in mice anesthetized with ketamine/xylazine and isoflurane.

Since small-animal MRI generally requires anesthesia, the effect of the anesthetic regimen on the explored organ(s) has to be taken into account for study interpretation. In this work, we assess the influence of ketamine/xylazine and isoflurane anesthesia on left-ventricular (LV) function in the mouse in vivo by cine-MRI. Three groups of animals were anesthetized with ketamine/xylazine (n = 13) and two different concentrations of isoflurane (1.25%, n = 12 and 2.00%, n = 12) delivered in O2/N2O mix. Long- and short-axis cine-MRI was performed to measure end-diastolic volume, stroke volume, ejection fraction and LV wall thickness. Ketamine/xylazine significantly reduced heart rate, cardiac output and wall thickness, but increased stroke volume and end-diastolic volume compared with both isoflurane groups. No differences across all groups were observed in ejection fraction or systolic wall thickening. Breath rate under isoflurane was significantly lower and concentration dependent, whereas heart function was independent of concentration in all measured parameters. These findings are in agreement with echocardiography and catheterization studies. Isoflurane is advantageous for MR studies because it better maintains cardiac function. Taking into account previously obtained myocardial perfusion measurements, isoflurane concentration should, however, be maintained at the minimum required for a stable sleep even if cardiac function is unaffected by higher isoflurane concentrations.

Administration, Inhalation↗
PubMed2001

Rat lung MRI using low-temperature prepolarized helium-3.

The purpose of this study was to evaluate the recently proposed technique of 3He prepolarization at low temperature and high field (Kober et al. Magn Reson Med 1999; 41:1084-1087) for fast imaging of the lung. Helium-3 was cooled to 2.4 K in a magnetic field of 8 Tesla to obtain a polarization of 0.26%. The polarized 3He was warmed up to room temperature and transferred to a rat, with a final polarization of about 0.1%, large enough for acquiring a 3D image of the rat lung in 30 s.

Animals↗
PubMed2000

In vivo 129Xe NMR in rat brain during intra-arterial injection of hyperpolarized 129Xe dissolved in a lipid emulsion.

Hyperpolarized 129Xe was dissolved in a lipid emulsion and administered to anaesthetized rats by manual injections into the carotid (approximately 1-1.5 mL in a maximum time of 30 s). During injection, 129Xe NMR brain spectra at 2.35 T were recorded over 51 s, with a repetition time of 253 ms. Two peaks assigned to dissolved 129Xe were observed (the larger at 194 +/- 1 ppm assigned to intravascular xenon and the smaller at 199 +/- 1 ppm to xenon dissolved in the brain tissue). Their kinetics revealed a rapid intensity increase, followed by a plateau (approximately 15 s duration) and then a decrease over 5 s. This behaviour was attributed to combined influences of the T1 relaxation of the tracer, of radiofrequency sampling, and of the tracer perfusion rate in rat brain. Similar kinetics were observed in experiments carried out on a simple micro-vessel phantom. An identical experimental set-up was used to acquire a series of 2D projection 129Xe images on the phantom and the rat brain.

Animals↗
PubMed1999

Low-temperature polarized helium-3 for MRI applications.

The first 3He nuclear magnetic resonance (NMR) experiments using low-temperature prepolarization are presented. 3He cells were polarized at 4.2 K and 4.7 T, transported to another magnet, heated to room temperature, and used for NMR experiments at 2.35 T. Cells with and without a rubidium coating were tested. In both cases, the NMR signal was greater than 100 times the thermal equilibrium signal. No evidence of a rubidium coating effect on the longitudinal relaxation time T1 of 3He (500 mbar) at 4.2 K could be demonstrated. NMR gradient-echo images of the cells were acquired.

Helium↗
PubMed1999

NMR imaging of thermally polarized helium-3 gas.

It is shown that thermally polarized 3He gas can be used to measure important physical parameters and to design, test, and tune imaging sequences. The bulk values of T1, T2, and the diffusion coefficient were measured in a glass cell containing a mixture of helium-3 (0.8 bar) and oxygen (0.2 bar). They were found to be T1 = 7 s, T2 = 2.4 s, and D = 1.6 cm2 s(-1). The relaxation times T2* and T1 and the apparent diffusion coefficient of thermally polarized helium-3 gas were measured in the rat lung, and these parameters were used to design a helium-3 optimized multi-spin-echo sequence which was shown to increase the signal-to-noise ratio sufficiently to obtain the first NMR-images of thermally polarized helium-3 in the rat lung.

Animals↗
PubMed1996

Radial BURST imaging.

A radial BURST approach combining BURST excitations with projection reconstruction (PR) gradients for excitation and acquisition is introduced. With the application of PR gradients during excitation, the applied RF energy is distributed more homogeneously across the sample than in the initial BURST approach. Computer simulations of the radial BURST excitation scheme are presented and experimentally verified. Actual radial BURST implementation acquiring a 64 x 64 radial BURST image in 45 ms is reported. Extensions of the radial BURST imaging technique placing a magnetization preparation experiment in front of the whole imaging sequence are also described. Furthermore, the feasibility of combining radial BURST with a multishot approach is demonstrated.

Fourier Analysis↗
PubMed1996

Diffuse and gross peritoneal carcinomatosis treated by intraperitoneal hyperthermic chemoperfusion.

Intraoperative intrapeitoneal hyperthermic chemoperfusion (IHCP) offers the following advantages: uniform distribution of heat and drugs at a high concentration in the whole intraperitoneal cavity, heat as a cytotoxic agent itself, and heat as a biomodulator of chemotherapy. Twenty-five patients suffering from diffuse and gross peritoneal carcinomatosis were enrolled into a phase II study to evaluate the feasibility and the efficacy of IHCP. IHCP was carried out with 10 micrograms mitomycin C/ml perfusate in the case of gastrointestinal malignancies or with 50 micrograms cisplatin/ml perfusate in the case of ovarian cancer with malignant ascites. Thirty-two courses of IHCP in 25 patients were eligible in for study of side effects. One patient suffered severe hematologic toxicity, WHO grade 4; two patients suffered severe impairment of renal function, WHO grade 3. Twenty-one patients were eligible for study of the response. Fifteen were classified as having a "favorable clinical response" and in three of them a pathohistologic complete remission was achieved. In only four patients was peritoneal carcinomatosis not influenced by the therapy. Ascites disappeared in 16 out of 19 patients. Tumor markers that were elevated preoperatively in 16 patients returned to normal values in 10 patients postoperatively and dropped more than 50% in three more patients. A remarkable improvement in quality of life was observed in patients who responded to the therapy.

Adult↗
PubMed1991

[Risk factors in recurrent nerve paralysis: a statistical analysis of 7566 cases of struma surgery].

Between 1979-1988, 7566 operations for benign diseases of the thyroid gland were performed. The frequency of the paresis of the recurrent nerve examined between the third and fifth postoperative day was 5.2% for patients and 3.2% for resected lobes. The incidence was correlated to performed operative procedure (enucleation, subtotal resection, lobectomy) to size (weight of specimen) and to the expansion of the goiter (substernal, intrathoracic, retrotracheal) as well as to sex. These factors influence the risk of injury with high statistic significance. The side of resection and the ligature of the thyroid inferior artery also influenced the rate of recurrent nerve pareses. Age of patient and morphology of the thyroid disease did not cause an increasing risk of nerve injury.

Adenoma↗
PubMed1990

[Chemotherapy of highly malignant thyroid tumors].

In a prospective phase II study 15 patients suffering from anaplastic thyroid carcinoma or thyroid sarcoma were treated by surgery and chemotherapy. Chemotherapy varied according to age of the patient and histological subtype of the tumour. The following regimen was used: 100 mg/m2 BSA CDDP, 20 mg/m2 mitoxantrone and 1.5 mg/m2 vincristine. 10 patients responded to chemotherapy, 4 of whom had a complete response. Responders showed a longer mean and median survival time (20.8 months versus 4.5 ms, 15.5 ms vs. 3.8 ms, respectively) than non-responders. In the group responding to chemotherapy no evidence of metachronous metastases was found. Local recurrence was absent only in the patients showing a complete response. Anaplastic carcinomas with areas of differentiated thyroid carcinoma and small cell carcinomas (after exclusion of malignant lymphoma of the thyroid) showed a higher response rate to chemotherapy than spindle or giant cell carcinoma or thyroid sarcoma.

Aged↗