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  • 1
    ISSN: 1432-1920
    Keywords: Transcranial Doppler sonography ; Duplex scanning ; Arterio-venous malformation ; Real-time sonography ; Transcranial color-coded sonography ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Transcranial color-coded real-time sonography (TCCS) is a new diagnostic method allowing the non-invasive imaging of parenchymal and vascular structures of the adult brain through the intact skull. A description of the sonographic findings in two patients presenting with a radiologically ascertained arterio-venous malformation is provided. The AVM's can be depicted in the two-dimensional B-mode image as echodense areas interspersed with zones of lower echodensity. Their extension correlated with corresponding MRI images. The color-coded illustration of intravascular flow phenomena allowed the distinct identification of the major afferent feeding vessels, the venous drainage and of the vascular convolution of both AVM's. Information on hemodynamics, as e.g. the blood supply of the angioma by the contralateral internal carotid artery, are obtained by color-coded identification of intravascular flow direction including analysis of the Doppler frequency spectrrum. All findings obtained by TCCS complied with those established by angiography. We conclude, that TCCS is a suitable method for early diagnosis and long term follow up of cerebral AVM's.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1238
    Keywords: Lung edema ; Acute respiratory distress syndrome ; Leukotrienes ; LTB4 ; Omega-oxidation products of LTB4 ; Broncho-alveolar lavage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Leukotriene (LT) generation has been implicated in the pathogenesis of the acure respiratory distress syndrome, ARDS. In the present study, we analysed broncho-alveolar lavage fluids of patients on mechanical ventilation because of ARDS (17 samples taken from 9 patients) or because of cardiogenic edema (8 samples taken from 6 patients) and of healthy volunteers (10 samples from different donors). LTs were separated as methylated and non-methylated compounds using different HPLC procedures, and were identified by chromatographic mobility, on-line UV-spectrum analysis and post HPLC immunoreactivity. In the lavage samples of the healthy volunteers and the patients with cardiogenic edema, no LTs were detected by these technicues (detection limit≃0.1–0.2 ng/ml lavage fluid). By contrast, in 15 out of 17 samples from patients with ARDS LTB4 or its metabolites 20-OH-LTB4 and 20-COOH-LTB4 were detected. The endproduct of omega-oxidation, 20-COOH-LTB4, represented the quantitatively predominant compound, detected in the range of 0.3–2.6ng/ml perfusate. We conclude that the chemotactic agent LTB4 may be involved in the amplification of inflammatory events encountered in ARDS, and that the oxidized metabolites of LTB4 are particularly suitable for monitoring lung leukotriene generation under conditions of neutrophil efflux and oxidative stress.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1619-7089
    Keywords: Key words: Liver cell hypoxia ; Nitroimidazole imaging ; Fluorine-18 fluoromisonidazole ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. Fluorine-18 labelled fluoromisonidazole ([18F]FMISO) has been shown to accumulate in hypoxic tissue in inverse proportion to tissue oxygenation. In order to evaluate the potential of [18F]FMISO as a possible positron emission tomography (PET) tracer for imaging of liver tissue hypoxia, we measured the [18F]FMISO uptake in 13 domestic pigs using dynamic PET scanning. Hypoxia was induced by segmental arterial hepatic occlusion. During the experimental procedure the fractional concentration of inspired oxygen (FiO2) was set to 0.67 in group A (n=6) and to 0.21 in group B (n=7) animals. Before and after arterial occlusion, the partial pressure of O2 in tissue (TPO2) and the arterial blood flow were determined in normal flow and flow-impaired liver segments. Standardised uptake values [SUV=kBq tissue (in g) / body weight (in kg) × injected dose (in kBq)] for [18F]FMISO were calculated from PET images obtained 3 hours after injection of about 10 MBq/kg body weight [18F]FMISO. Immediately before PET scanning, the mean arterial blood flow was significantly decreased in arterially occluded segments [group A: 0.41 (0.32–0.52); group B: 0.24 (0.16–0.33) ml min–1 g–1] compared with normal flow segments [group A: 1.05 (0.76–1.46); group B: 1.14 (0.83–1.57) ml min–1 g–1; geometric mean (95% confidence limits); P〈0.001 for both groups]. After PET scanning, the TPO2 of occluded segments (group A: 5.1 (4.1–6.4); group B: 3.5 (2.6–4.9) mmHg] was significantly decreased compared with normal flow segments [group A: 26.4 (21.2–33.0); group B: 18.2 (13.3–25.1) mmHg; P〈0.001 for both groups]. During the 3-h PET scan, the mean [18F]FMISO SUV determined in occluded segments increased significantly to 3.84 (3.12–4.72) in group A and 5.7 (4.71–6.9) in group B, while the SUV remained unchanged in corresponding normal liver tissue [group A: 1.4 (1.14–1.71); group B: 1.31 (1.09–1.57); P〈0.001 for both groups]. Regardless of ventilation conditions, a significant inverse exponential relationship was found between the TPO2 and the [18F]FMISO SUV (r 2=0.88, P〈0.001). Our results suggest that because tracer delivery to hypoxic tissues was maintained by the portal circulation, the [18F]FMISO accumulation in the liver was found to be directly related to the severity of tissue hypoxia. Thus, [18F]FMISO PET allows in vivo quantification of pig liver hypoxia using simple SUV analysis as long as tracer delivery is not critically reduced.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1619-7089
    Keywords: Key words: Fluorine-18 ; Bone graft viability ; Hip revision arthroplasty ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The biological fate of allogenic bone grafts in the acetabular cavity and their metabolic activity after acetabular augmentation is uncertain but is most important for the stability of hip implants after hip revision arthroplasty. The aim of this study was to quantify regional bone metabolism after hip replacement operations. Dynamic [18F]fluoride ion positron emission tomography (PET) was used to investigate the metabolic activity of acetabular allogenic bone grafts and genuine bone, either 3–6 weeks (short-term group, n = 9) or 5 months to 9 years (long-term group, n = 10) after hip revision arthroplasty. Applying a three-compartment model, the fluoride influx constant was calculated from individually fitted rate constants (K nlf) and by Patlak graphical analysis (K pat). The results were compared with genuine cancellous and cortical acetabular bone of contralateral hips without surgical trauma (n = 7). In genuine cortical bone, K nlf was significantly increased in short- (+140.9%) and long-term (+100.0%) groups compared with contralateral hips. Allogenic bone grafts were characterised by a significantly increased K nlf in the short-term group (+190.9%) compared with contralateral hips, but decreased almost to the baseline levels of contralateral hips (+45.5%) in the long-term. Values of K nlf cor-related with the rate constant K 1 in genuine (r = 0.89, P〈0.001) and allogenic bone regions (r = 0.79, P〈0.001), indicating a coupling between bone blood flow and bone metabolism in genuine bone as well as allogenic bone grafts. K pat values were highly correlated with K nlf measurements in all regions. In conclusion, [18F]fluoride ion PET revealed the presence of an increased host bone formation in allogenic bone grafts early after hip revision arthroplasty. In contrast to genuine cortical bone, allogenic bone graft metabolism decreased over time, possibly due to a reduced ability to respond to the same extent as genuine bone to elevated metabolic demands after surgery.
    Type of Medium: Electronic Resource
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