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  • 1
    Electronic Resource
    Electronic Resource
    Abnormalities of the airways and lung parenchyma in asthmatics: CT observations in 50 patients and inter- and intraobserver variability (1996)
    Springer
    European radiology 6 (1996), S. 199-206 
    Details
    ISSN: 1432-1084
    Keywords: Bronchiectasis ; Bronchi, CT ; Diagnostic radiology, observer performance ; Lung, diseases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of the study was to evaluate the CT abnormalities of airways and lung parenchyma in asthmatic patients and to assess inter- and intraobserver variability for these abnormalities. The CT scans of 50 asthmatic patients and 10 healthy volunteers were assessed independently by four independent chest radiologist who were masked with respect to the clinical information. Bronchiectasis involving mostly subsegmental and distal bronchi was noted in 28.5% of the asthmatic subjects and none of the non-asthmatics. Bronchial wall thickening, small centrilobular opacities and decreased lung attenuation were observed in 82%, 21% and 31% of asthmatic patients respectively, compared with 7%, 5% and 7% of healthy subjects. The intra- and inter-observer agreements for these four CT abnormalities were measured by the kappa statistic and ranged from 0.60 to 0.79 and from 0.40 to 0.60, respectively. It os concluded that asthmatic patients may exhibit bronchial wall thickening, bronchiectasis and morphological abnormalities suggestive of distal airways disease that can be assessed on CT scans with a clinically acceptable observer variability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00181147
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  • 2
    Electronic Resource
    Electronic Resource
    Different mental imagery abilities result in different regional cerebral blood flow activation patterns during cognitive tasks
    Amsterdam : Elsevier
    Neuropsychologia 30 (1992), S. 565-569+571-580 
    Details
    ISSN: 0028-3932
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Psychology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0028-3932(92)90059-U
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of tissue heterogeneity on quantification in positron emission tomography (1995)
    Springer
    European journal of nuclear medicine 22 (1995), S. 652-663 
    Details
    ISSN: 1619-7089
    Keywords: Positron emission tomography ; Tissue heterogeneity ; Tracer kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract As a result of the limited spatial resolution of positron emission tomographic scanners, the measurements of physiological parameters are compromised by tissue heterogeneity. The effect of tissue heterogeneity on a number of parameters was studied by simulation and an analytical method. Five common tracer models were assessed. The input and tissue response functions were assumed to be free from noise and systematic errors. The kinetic model was assumed to be perfect. Two components with different kinetics were mixed in different proportions and contrast with respect to the model parameters. Different experimental protocols were investigated. Of three methods investigated for the measurement of cerebral blood flow (CBF) (steady state, dynamic, integral), the second one was least sensitive to errors caused by tissue heterogeneity and the main effect was an underestimation of the distribution volume. With the steady state method, errors in oxygen extraction fraction caused by tissue heterogeneity were always found to be less than the corresponding errors in CBF. For myocardial blood flow the steady state method was found to perform better than the bolus method. The net accumulation of substrate (i.e. rCMRgjc in the case of glucose analogs) was found to be comparatively insensitive to tissue heterogeneity. Individual rate constants such ask 2 andk 3 for efflux and metabolism of the substrate in the pool of unmetabolized substrate in the tissue, respectively, were found to be more sensitive. In studies of radioligand binding, using only tracer doses, the effect of tissue heterogeneity on the parameterk on ·B max could be considerable. In studies of radioligand binding using a protocol with two experiments, one with high and one with low specific activity,B max was found to be insensitive whileK d was very sensitive to tissue heterogeneity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01254567
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Cortical region of interest definition on SPECT brain images using X-ray CT registration (1992)
    Springer
    Neuroradiology 34 (1992), S. 510-516 
    Details
    ISSN: 1432-1920
    Keywords: SPECT ; X-ray CT ; Image correlation ; rCPF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We present a method for brain single photon emission computed tomography (SPECT) analysis based on individual registration of anatomical (CT) and functional (133Xe regional cerebral blood flow) images and on the definition of three-dimensional functional regions of interest. Registration of CT and SPECT is performed through adjustment of CT-defined cortex limits to the SPECT image. Regions are defined by sectioning a cortical ribbon on the CT images, copied over the SPECT images and pooled through slices to give 3D cortical regions of interest. The proposed method shows good intra- and interobserver reproducibility (regional intraclass correlation coefficient ≈0.98), and good accuracy in terms of repositioning (≈3.5 mm) as compared to the SPECT image resolution (14 mm). The method should be particularly useful for analysing SPECT studies when variations in brain anatomy (normal or abnormal) must be accounted for.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00598963
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  • 5
    Electronic Resource
    Electronic Resource
    Rapid measurement of regional cerebral blood flow in the baboon using15O-labelled water and dynamic positron emission tomography (1993)
    Springer
    Medical & biological engineering & computing 31 (1993), S. 495-502 
    Details
    ISSN: 1741-0444
    Keywords: Baboon ; Bolus injection ; CO2 reactivity ; 15O-labelled water ; Positron emission tomography ; Regional cerebral blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The sensitivity and reproducibility of rapid measurements of regional cerebral flow (rCBF) using a bolus injection of H2 15O and dynamic positron emission tomography (PET) were investigated in anaesthetised baboons. The cerebrovascular reactivity to changes in arterial pCO2 was used as an experimental support. PET data were acquired over 4 min following a single bolus intravenous injection of H2 15O, while arterial blood was withdrawn for continuous activity counting. Images were reconstructed with a dynamic sequence of 45×2s+15×10s, including a correction for decay. Regional values of CBF were derived from non-linear least-squares fits of the time activity curves using a four-parameter two-compartment model. The results obtained with a four-parameter fitting method were compared with those obtained with two other rapid estimation methods, first fitting two parameters only, CBF and partition coefficient (p), and secondly autoradiography (with p fixed at 0·95 ml brain ml blood−1). Twelve regions of interest were analysed. The values for the basal CBF obtained from 13 measurements in two baboons were close to published values obtained with other techniques. Reproducibility checks showed a mean variation of 9·7 per cent. The CBF measurements performed in hypercapnic conditions gave results similar to published data in other animal species, showing a 4·5±0·9 per cent increase in CBF per mm Hg paCO2. The results obtained with the three estimation techniques were closely correlated. The dynamic bolus H2 15O method appeared to be suitable for high blood flow measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441985
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    Paper (German National Licenses)
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