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Biomedical subjects

U Hoffmann

Publications and source records attributed to U Hoffmann.

At least 127 records · Page 7Linked to original sources

Cervical carcinoma: comparison of standard and pharmacokinetic MR imaging.

PURPOSE: To stage advanced cervical carcinoma with conventional or pharmacokinetic magnetic resonance (MR) imaging by correlating imaging findings with whole-mount specimens and histopathologic findings. MATERIALS AND METHODS: Twenty-six adult patients with primary cervical cancer (stages IIB-IVA) underwent T2-weighted turbo spin-echo (SE) MR imaging; gadolinium-enhanced, T1-weighted SE MR imaging; and gadolinium-enhanced, saturation-recovery, turbo fast low-angle shot MR imaging. All imaging findings were correlated with the whole-mount specimens and histopathologic findings. Signal intensity changes versus time were analyzed by using a pharmacokinetic model and parameter values displayed as a color-coded overlay. RESULTS: Histopathologic stages were IIB (n = 9), IIIB (n = 1), and IVA (n = 16). The overall accuracy for tumor staging was 73% for T2-weighted, 81% for T1-weighted, and 92% for pharmacokinetic MR imaging. Pharmacokinetic MR imaging was accurate (90%) in the diagnosis of tumor extension into the bladder and/or rectal wall but inaccurate (69%) in that of parametrial invasion. T2-weighted images were most accurate (86%) in the assessment of parametrial tumor extension but less accurate (69%) in that of bladder or rectal invasion. CONCLUSION: T2-weighted turbo SE images are still superior to contract medium-enhanced T1-weighted SE or pharmacokinetic MR images in the diagnosis of parametrial infiltration by uterine cervical carcinoma. However, pharmacokinetic MR imaging is a promising method for demonstrating and staging IVA disease.

Adenocarcinoma↗

Flow velocity of single lymphatic capillaries in human skin.

The purpose of this study was to investigate the previously unknown flow velocity in single lymphatic capillaries of humans in the supine position. Fifteen healthy subjects (10 women and 5 men; mean age 35.8 +/- 13.1 yr) were studied. Ten microliters of fluorescein isothiocyanate-dextran (150,000 mol wt) were injected into the subepidermal layer of the foot dorsum. The filling of the microlymphatics from the resulting depot was visualized by fluorescence video microscopy and stored on videotape. Flow velocity in the microlymphatics was determined on the video screen by direct measurement of the advancement of dyed lymph during a given time. The following median velocities were obtained: 0.51 mm/s (0.27 and 0.61 mm/s for lower and upper quartiles, respectively) for velocity during initial network filling and 9.7 microns/s (6.9 and 14.2 microns/s for lower and upper quartiles, respectively) for resting velocity at the end of the filling period. Mean lymphatic capillary diameter was 54.8 +/- 8.2 microns, and mean network extension was 8.3 +/- 3.2 mm. The high filling velocities are probably due to increased interstitial pressure and volume caused by dye microinjection, whereas the values measured during the end of network filling seem to approach resting flow velocities.

Adult↗

Microvascular changes in arterial occlusive disease: target for pharmacotherapy.

The main techniques which have been used to study skin microcirculation in patients with peripheral arterial occlusive disease include intravital microscopy with and without the use of fluorescent dyes, laser Doppler fluxmetry and transcutaneous oximetry. In patients with severe ischaemia (rest pain or incipient gangrene) the number of perfused skin capillaries is reduced. Parallel to the decreased number of microvessels containing blood, transcutaneous oxygen tension is low or even approaches the zero level. The tendency to oedema formation is documented by increased leakage of intravenously injected sodium fluorescein at the capillary apex of foot skin ('candlelight phenomenon'). Laser Doppler flux at rest may still be within the normal range even in advanced disease, since the sample volume of these instruments also contains non-nutritive shunt vessels. However, reactive hyperaemia after arterial occlusion is decreased and delayed in peripheral ischaemia. Whereas rhythmic low-frequency vasomotion is significantly enhanced in patients with intermittent claudication, vasoparalysis with no flux fluctuations prevails in patients with critical ischaemia.

Arterial Occlusive Diseases↗

Pelvic lesions in patients with treated cervical carcinoma: efficacy of pharmacokinetic analysis of dynamic MR images in distinguishing recurrent tumors from benign conditions.

OBJECTIVES: Dynamic MR image series were analyzed with a pharmacokinetic two-compartment model. To preserve the spatial resolution of the dynamic MR images, the pharmacokinetic parameters were computed pixel by pixel, color coded, and superimposed on conventional MR images (pharmacokinetic mapping). The efficacies of pharmacokinetic mapping and conventional MR imaging in distinguishing between recurrent tumors and benign conditions in patients who have pelvic lesions after treatment of cervical carcinoma were compared. MATERIALS AND METHODS: Twenty-one women with 24 suspected pelvic lesions and a history of treated cervical carcinoma (stages IB-IIIA) were included in this study. Patients had been treated before MR imaging with surgery or irradiation alone (eight patients) or a combination of the two (13 patients). Patients were referred because of our findings from CT examinations and/or clinical examinations. Of 24 suspected lesions, 17 were histologically verified as tumor recurrences and seven were classified as benign masses (histologically diagnosed as fibrosis and granulation tissue). T1- and T2-weighted spin-echo images were interpreted by three observers. During and after constant-rate infusion of gadopentetate dimeglumine, the kinetics of lesion response were determined with a strongly T1-weighted saturation recovery turbo-fast low-angle shot sequence. The signal-time curves for the suspected lesions were analyzed within the framework of a pharmacokinetic two-compartment model and displayed as color-coded images. The calculated pharmacokinetic parameters (amplitude [A] and tissue distribution time [t21]) were evaluated retrospectively to obtain optimal threshold values for differentiating malignant lesions from benign lesions. RESULTS: Analysis of the pharmacokinetic mapping data showed significantly shorter (p < .005) and stronger (p < .001) contrast medium enhancement of malignant lesions (t21, 24 sec; A, 1.5 arbitrary units) than of benign lesions (t21, 65 sec; A, 0.7), resulting in a sensitivity of 100%, a specificity of 88%, and an accuracy of 96%. Interpretation of the lesions on conventional T2-weighted MR images resulted in a sensitivity of 90%, a specificity of 38%, and an accuracy of 74%. CONCLUSION: Analysis of color-coded pharmacokinetic maps is more effective than conventional MR imaging in distinguishing between malignant and benign conditions in patients who have pelvic lesions after treatment of cervical carcinoma.

Carcinoma, Squamous Cell↗

Effects of quinazoline (3H, 1H)-4-one-2-thiones with axial and central chirality on the contractile response of smooth muscle.

Quinazolines are versatile nitrogen heterocyclic compounds displaying a broad spectrum of biological and pharmacological activities. The influence of some new synthesized quinazolines with axial and central chirality was studied on the isometric muscle tension of rat ileum, rat uterus, and porcine coronary artery. While structural changes of the compounds showed only little influence on peristaltic movement of the ileum, quinazoline derivatives induced a relaxation in the uterus and in the coronary artery depending on the kind and position of the substituent. The introduction of axial chirality into the molecule of modification of the side chain caused an increase in the pharmacological action. These effects could not be inhibited by sympatholytics. So far the mechanisms and receptors causing the spasmolysis are unknown.

Animals↗

[Significance of arterial anastomoses of the distal calf and proximal foot for compensation of peripheral arterial occlusive disease].

The vascular anatomy of the distal calf and proximal foot was studied in 16 preparations obtained by corrosion. Arterial anastomoses between the different vessels are frequently observed and were also detected by digital subtraction arteriography in 14 patients with peripheral arterial occlusive disease. The comparison between anatomy and arteriography revealed that performed anastomoses in the malleolar and proximal foot region are important for compensating crural arterial occlusions. The Ramus communicans posterior, the Ramus perforans of the fibular artery and the Rete calcaneare play an important role. Whereas in other vascular territories collaterals dominate for compensation of occlusions performed anastomoses are of crucial importance at the malleolus.

Aged↗

A system for stereotactic irradiation and magnetic resonance evaluations in the rat brain.

PURPOSE: A stereotactic fixation and localization device developed for small animal stereotactic radiosurgery is described. METHODS AND MATERIALS: Irradiated volumes of spherical shape down to 1.7 mm in diameter at the 80% isodose level are attainable. The fixation device can also be used for magnetic resonance imaging (MRI) and allows target localization during magnetic resonance (MR) image content measurement. The capabilities of the entire system were investigated using a phantom that permitted measurement and localization of the three-dimensional dose distribution. Localization of target isocenter coordinates in MR images was also checked with the phantom. RESULTS: An overall spatial error of about 1 mm for subsequent stereotactic irradiation was obtained. CONCLUSIONS: The accuracy of the fixation and localization techniques is adequate to investigate radiation-induced changes in the rat brain.

Animals↗

Characterization of the cDNA and three processed pseudogenes from the murine protein kinase CK2 alpha subunit.

Seven protein kinase CK2 alpha clones were isolated from a murine genomic DNA library. They were assigned to four different genomic loci (A,B,C,D). Locus D was previously identified as a processed pseudogene (Boldyreff et al. (1992) Biochem. Biophys. Res. Commun. 186, 723-730). Here we present sequences of genomic loci B and C and the murine CK2 alpha cDNA. Loci B and C are like locus D processed pseudogenes, however, with considerable differences among each other and to the cDNA, especially with respect to the lengths of the putative gene products. Genomic locus D would code for a protein of 82 amino acids, locus B for a protein of 132 amino acids and locus C product for the full length product of 391 amino acids as the murine cDNA.

Amino Acid Sequence↗

Pharmacokinetic mapping of the breast: a new method for dynamic MR mammography.

A dynamic contrast-enhanced MRI technique for whole breast examinations is presented. The fast kinetics of tissue response during and after constant-rate intravenous infusion of gadolinium diethylenetriaminopentaacetic acid was resolved using a strongly T1-weighted saturation recovery TurboFLASH sequence that makes it possible to acquire signal-time courses sequentially from 15 adjacent slices with a temporal sampling rate of 21 s. On the basis of the mathematically established and experimentally verified linear relationship between the measured saturation recovery TurboFLASH signal variation and the gadolinium diethylenetriaminopentaacetic acid concentration in the tissue, the signal-time courses were analyzed within the framework of pharmacokinetic modeling. In our study, the tissue response was parameterized adequately using an open linear two-compartment model. With this approach, the tissue specific information contained in the signal-time course can be described using only two parameters: an amplitude A, reflecting the degree of MR signal enhancement, and an exchange parameter k21, characterizing vascular permeability and perfusion of the tissue. A clearly arranged representation of the large amount of data (480 saturation recovery TurboFLASH breast images/examination) was accomplished by means of color coding of the computed parameters, resulting in one color-coded pharmacokinetic parameter map/cross-section.

Breast↗

Simultaneous measurement of digital artery and skin perfusion pressure by the laser Doppler technique in healthy controls and patients with peripheral arterial occlusive disease.

OBJECTIVE: To assess feasibility of a new technique for simultaneous measurement of digital artery and skin perfusion pressure at the same digit using the laser Doppler method and to measure the pressure gradient between the two vessel compartments in controls and patients with peripheral arterial occlusive disease. DESIGN: A pressure cuff wrapped around the basis of the toe and connected to a Statham transducer is covered by a special plastic capsule. A hole at the distal end of the capsule permits positioning of a laser Doppler probe at the pulp. A second laser Doppler probe is placed on the skin beneath the pressure cuff. Reappearance of pulsatile flux during cuff pressure release detected by the two laser Doppler probes indicated digital artery pressure and skin perfusion pressure on the corresponding pressure curve. Results in patients with intermittent claudication were compared to results of a group of normal controls. SETTING: University Hospital, Zürich, Switzerland. MATERIALS: Eleven healthy volunteers and 14 patients with intermittent claudication due to peripheral arterial occlusive disease were studied. CHIEF OUTCOME MEASURES: Digital artery pressure (DAP), skin perfusion pressure (SPP) and pressure gradient between DAP and SPP. MAIN RESULTS: Significantly lower mean DAP (95.8 +/- 23.2 mmHg vs. 49.8 +/- 20.4 mmHg; p < 0.01) and mean SPP (81.4 +/- 18.8 mmHg vs. 38.4 +/- 21.7 mmHg; p < 0.01) were observed in the patients. Mean pressure gradients and ratios between DAP and SPP did not differ significantly between the two groups. There was a linear correlation between DAP and SPP (r = 0.82, p < 0.01). CONCLUSION: The laser Doppler method provides the possibility to measure digital artery and skin perfusion pressure simultaneously at the same digit in an easy and non-invasive way. Pressure gradients between DAP and SPP are similar in controls and patients with claudication.

Adult↗

A new therapeutic approach to popliteal artery entrapment syndrome (PAES).

OBJECTIVES: An alternative therapeutic approach to popliteal artery entrapment syndrome (PAES) with vascular complications. MATERIALS: Three male patients (16, 42 and 68 years) with thrombotic and/or embolic obstructions of popliteal or crural vessels as a consequence of popliteal entrapment syndrome. METHODS: Combined catheter treatment consisting of percutaneous transluminal thrombembolectomy (PTEE), local thrombolysis (LTL) and percutaneous transluminal dilatation (PTA) was performed for thrombotic and embolic obstructions of popliteal or crural vessels. The aberrant tendomuscular structures were surgically corrected at a later date. RESULTS: After the procedure systolic ankle/arm pressure ratios in the three patients improved from 0.66 to 1.13, 0.57 to 1.07 and 0.46 to 1.10. Twelve, 8 and 4 months later the patients were asymptomatic. None of the patients showed popliteal artery compression during plantar flexion on Duplex scanning. CONCLUSIONS: This new therapeutic approach avoids direct vascular surgery with bypass or patch implantation in patients with PAES who are often young. The long term results remain to be evaluated.

Adolescent↗

[First experiences with electron beam computed tomography of the heart:comparison with heart catheterization and echocardiographic findings].

AIM: To evaluate the diagnostic value of ultrafast CT in comparison to established methods in cardiology. MATERIAL AND METHODS: Cine and flow studies were performed in 30 patients with cardiac diseases on evolution CT. Cardiac structure and function were analysed visually and quantitatively (left ventricular ejection fraction, left ventricular myocardial mass, patency of coronary arteries, perfusion of left ventricular myocardium). The CT findings were compared with echocardiographic and angiographic findings. RESULTS: Cardiac structure, functional parameters and disorders of myocardial contraction were clearly detectable by ultrafast CT, which proved inferior in assessing cardiac valves. The patency of the first and second third of normal main coronary arteries could be estimated correctly. The estimation of the distal third, of obstructed coronary arteries and of the role of collaterals was impossible. Ten of 16 areas of myocardial infarction showed low or no enhancement. CONCLUSIONS: Ultrafast CT excellently reflects cardiac structure and function. It is an alternative to echocardiography. In view of the results of coronary artery patency one can hope that part of cardiac catheterisation would be avoidable in future.

Adult↗

Time courses of cardiac output and oxygen uptake following stepwise increases in exercise intensity.

The adjustment of pulmonary oxygen uptake (VO2) following a step increase in work rate has been characterized as consisting of an early "cardiodynamic" component with unchanged mixed-venous O2-content ("phase 1") and a subsequent "metabolic" component ("phase 2") starting when venous blood from the muscle arrives at the lungs. The aim of the present study was to investigate whether the onset of phase 2 actually indicates the arrival of blood influenced by the altered muscle metabolism. Parallel measurements of cardiac output (Doppler technique) and VO2 (breath-by-breath measurements at the mouth) were performed in eight subjects during step increases in exercise intensity (from a 20 W baseline to either 80 W, 120 W, 160 W or 200 W). To vary the absolute cardiac output values for given muscle VO2 the subjects exercised both in upright and supine position. Individual time-courses of the arterio-venous O2 difference (a-v delta O2) were computed from cardiac output and VO2 data. Independent of body position two clear-cut phases of similar duration were seen both in VO2 and in the computed a-v delta O2. The duration of the first component with unchanged a-v delta O2 was about 20 s at the lowest step amplitudes (20-80 W and 20-120 W). It decreased to about 15 s for the 20-160 W and 20-200 W steps. At the lower exercise intensities the duration of phase 1 appears too long to be entirely due to the transit time of venous blood from the exercising muscles to the lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Intravital capillaroscopy in patients with chronic venous insufficiency and lymphoedema: relevance to Daflon 500 mg.

Microangiopathy of chronic venous insufficiency is characterized by elongated, dilated and coiled skin capillaries, which are surrounded by an enlarged pericapillary space (halo). Reduction of capillary number and even areas devoid of microvessels (atrophie blanche) are common in severe chronic venous insufficiency associated with focal microvascular ischaemia (decreased transcutaneous oxygen tension). The superficial network of skin lymphatic capillaries is obliterated in part. Oedema formation results from increased permeability of blood capillaries (enhanced transcapillary diffusion of sodium fluorescein) and deficient lymphatic drainage of interstitial fluid.

Diosmin↗