The extensive development of basal moyamoya vessels is a sign of severe hemodynamic impairment in adult patients with ischemic moyamoya disease. The results may not apply to adults with hemorrhagic onset.
Cerebral metabolic rate of oxygen (CMRO 2 ) can be assessed quantitatively using 15 O 2 and positron emission tomography. Determining the arterial input function is considered critical with regards to the separation of the metabolic product of 15 O 2 (RW) from a measured whole blood. A mathematical formula based on physiologic model has been proposed to predict RW. This study was intended to verify the adequacy of that model and a simplified procedure applying that model for wide range of species and physiologic conditions. The formula consists of four parameters, including of a production rate of RW (k) corresponding to the total body oxidative metabolism (BMRO 2 ). Experiments were performed on 6 monkeys, 3 pigs, 12 rats, and 231 clinical patients, among which the monkeys were studied at varied physiologic conditions. The formula reproduced the observed RW. Greater k values were observed in smaller animals, whereas other parameters did not differ amongst species. The simulation showed CMRO 2 sensitive only to k, but not to others, suggesting that validity of determination of only k from a single blood sample. Also, k was correlated with BMRO 2 , suggesting that k can be determined from BMRO 2 . The present model and simplified procedure can be used to assess CMRO 2 for a wide range of conditions and species.
Background and Purpose-Patients with carotid occlusive disease and stage 2 cerebral hemodynamic failure, characterized by an increased oxygen extraction fraction (OEF) as measured by positron emission tomography (PET) and otherwise known as misery perfusion, have a high risk of cerebral ischemia and subsequent stroke. In clinical practice, the detection of patients with misery perfusion through the use of widely available, noninvasive, and cost-effective modalities such as single-photon emission computed tomography (SPECT) is extremely important. Methods-We evaluated the relationships between the regional hemodynamic status of cerebral circulation, measured with split-dose [ 123 I] N-isopropyl-p-iodoamphetamine SPECT ( 123 I-IMP SPECT) and an acetazolamide challenge, and hemodynamic parameters, including OEF measured with PET, in 27 patients with both unilateral and bilateral carotid occlusive diseases. Results-A significant negative correlation was found between the SPECT-measured cerebrovascular reserve after acetazolamide administration and both the PET-measured OEF and cerebral blood volume. Neither the cerebrovascular reserve nor the cerebral blood flow index, when expressed as a SPECT-measured cerebrum-to-cerebellum ratio, was useful for detecting lesions with an elevated OEF. However, a combination of the cerebrovascular reserve and cerebral blood flow index showed high sensitivity, specificity, and positive predictive value for the detection of misery perfusion. Conclusions-Our study suggests that split-dose 123 I-IMP SPECT with an acetazolamide challenge could be useful for screening patients with misery perfusion in carotid occlusive diseases.
Because the CBF SPECT images of VaD patients showed a higher fractal dimension, these images were quantitatively more heterogeneous than those of age-matched controls. In the VaD group, cognitive function was shown to decline as the fractal dimension increased and images became more heterogeneous.
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