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  • Dual-radionuclide single-photon emission tomography  (1)
  • Haemorrhage cerebral  (1)
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  • 1
    ISSN: 1619-7089
    Keywords: Key words: Pulmonary ventilation/perfusion ratio ; Dual-radionuclide single-photon emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. To date, there has been neither a good method to clarify the three-dimensional distribution of pulmonary ventilation/perfusion (V.A/Q.) ratios, nor a convenient way to assess V.A/Q. inequality. The purpose of this study was to develop a functional image of pulmonary V.A/Q. ratios based on data acquired with simultaneous dual-radionuclide single-photon emission tomography (SPET) and to assess V.A/Q. unevenness through the V.A/Q. histogram in patients with various pulmonary diseases. Dual-radionuclide SPET was performed with technetium-99m macroaggregated albumin (MAA) and krypton-81m, with the patient in the supine position. After correction for linear cross-talk, the total acquisition counts of both radionuclides were equalized. The V.A/Q. ratio, which was calculated in each pixel by dividing the 81mKr count by the 99mTc-MAA count, was expressed as a V.A/Q. image. A histogram of the pixel number plotted against the V.A/Q. ratios was then produced and its centre of weight (CW) and standard deviation (SD) determined. Ten healthy volunteers and 46 patients [seven with pulmonary vascular disease (PVD), nine with pulmonary emphysema (PE), 18 with bronchogenic carcinoma and 12 with miscellaneous diseases] participated in this study. In normal volunteers, V.A/Q. ratios were generally even, but were slightly lower in dorsal regions. Patients with PVD had lobar and/or segmental areas with a high V.A/Q. ratio. Low V.A/Q. areas extended widely in patients with PE. Bronchogenic carcinoma exceeding 3 cm in diameter was detected as a very low V.A/Q. area. The SD of V.A/Q. ratios had a significant positive correlation both with A-aDO2 (r=0.64, P〈0.001) and with cigarette smoking history (r=0.72, P〈0.001). It is concluded that the V.A/Q. ratio image produced with simultaneous dual-radionuclide SPET using 99mTc-MAA and 81mKr is a unique and simple method for demonstrating the three-dimensional distribution of V.A/Q. ratios. The unevenness of V.A/Q. distribution can be assessed through the SD of the V.A/Q. histogram.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 42 (2000), S. 499-504 
    ISSN: 1432-1920
    Keywords: Key words Magnetic resonance imaging ; Pulse sequences ; Haemorrhage cerebral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Multifocal small low-signal lesions on T2*-weighted gradient-echo (GE) MRI are reported to be common in the brain of hypertensive patients. We examined factors associated with these lesions. For one year, we routinely obtained T2*-weighted GE images (TR 1000 TE 30 ms, flip angle = 20 °) in all adult patients (314) who underwent brain MRI in our hospital, using a 1.5 T superconducting magnet. Patients with multifocal small low-signal lesions with a known or presumed pathogenesis or any condition which may cause intracerebral haemorrhage, such as brain tumours, were excluded from further analysis. Thus, 191 cases remained (104 men and 87 women; age, 62.8 ± 11.0 years, range, 30–89 years). The overall prevalence of multifocal small low-signal lesions on the GE images was 15.2 % (29/191); they were commonly in the cerebral white matter and basal ganglia. They were detected in 12 (52.2 %) of the 23 patients with prior symptomatic brain hemorrhage, 12 (20.7 %) of the 58 with prior symptomatic infarcts, and only five (4.5 %) of 110 without a prior stroke. Logistic regression analysis indicated that multifocal small low-signal lesions were significantly correlated with a symptomatic acute brain haemorrhage (odds ratio, 13.17), chronic hypertension (4.00) and a symptomatic acute infarct (3.71). The association with symptomatic acute brain haemorrhage suggests that this finding may represent subclinical microhaemorrhage. The diagnostic potential of this finding to identify individuals at risk of symptomatic intracerebral haemorrhage may require further investigation.
    Type of Medium: Electronic Resource
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