[Subclavian steal phenomenon induced by arteriovenous fistula for hemodialysis].
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Arteriovenous Shunt, Surgical↗
Biomedical subjects
Tsuyoshi Omae
Publications and source records attributed to Tsuyoshi Omae.
Microsphere-induced embolic stroke: an MRI study.
Despite the many studies of the middle cerebral artery occlusion (MCAO) model, efficient therapy for stroke is still lacking, emphasizing the need for further development and characterization of experimental stroke models. In the present study, the rather unexplored multifocal microsphere-induced stroke model in rats was characterized by multiparametric MRI. We induced microembolic infarction in a group of Sprague-Dawley rats by injecting a dose of about 1000 50-microm polyethylene microspheres intracranially from the external carotid artery. Diffusion-, perfusion-, and T(2)-weighted MRI were used to evaluate the infarct development during and following the first 3 hr after microsphere injection (N = 20). The animals were also imaged at 12-hr (N = 8), 24-hr (N = 17), and 48-hr (N = 5) time points. After the final imaging time point, the brains were removed and sectioned into 2-mm-thick slices, and infarct volumes were measured by 2,3,4-triphenyltetrazolium chloride (TTC) staining. From calculated apparent diffusion coefficient (ADC) maps, a volume of reduced ADC appeared 0.5-1.0 hr postinjection, and by the 3-hr time point the volume of ADC reduction had increased to a size of 5% +/- 1% (mean +/- SEM) of the brain hemisphere. The lesion volume increased significantly (P < 0.01) to 16% +/- 2% of the hemisphere volume at the 12-hr time point, while at 24 hr the lesion (15% +/- 2% of the hemisphere) was also significantly larger (P < 0.001) than at 3 hr. The perfusion deficit resulting from the microsphere injection was immediate, going from a cerebral blood flow index (CBF(i)) of 74% +/- 3% at the time of microsphere injection to 68% +/- 2% of the contralateral mean at 3 hr (P < 0.05), to 55% +/- 4% of the contralateral values at 12 hr (P < 0.05), and to 57% +/- 2% of the contralateral mean at 24 hr (P < 0.001). The lesion development in the microsphere-induced stroke model was found to be slower than in the MCAO model, and continued up to the 24-48-hr time point.
Animals↗
Ultrasonographically predicting the extent of collateral flow through superficial temporal artery-to-middle cerebral artery anastomosis.
BACKGROUND AND PURPOSE: This study was performed to elucidate whether the extent of bypass flow through superficial temporal artery-to-middle cerebral artery (STA-MCA) anastomosis could be indirectly estimated by measuring the blood flow velocity in the superficial temporal artery (STA) by using duplex ultrasonography. METHODS: We analyzed 29 patients (31 sides) who underwent STA-MCA bypass surgery for occlusive cerebrovascular disease (28 sides) or unclippable cerebral aneurysm that required therapeutic occlusion of the internal carotid artery (three sides). The flow velocities of the STA were measured by using ultrasonography. For patients who underwent the surgery unilaterally, the flow velocity ratios of the operated side to the contralateral side for the individual arteries were calculated. The correlation between these flow velocity parameters and the extent of bypass flow, which was graded based on the findings of cerebral angiography, was investigated. RESULTS: Both the affected STA flow velocity and the STA flow velocity ratio, particularly those in the end diastole, increased in patients with more extensive bypass flow. In patients with extensive, moderate, and poor bypass flow, the end diastolic flow velocities of the operated STA were 27.4 +/- 8.8, 23.0 +/- 7.8, and 13.5 +/- 7.5 cm/s, respectively and the end diastolic flow velocity ratios of the STA were 3.4 +/- 0.8, 2.1 +/- 0.5 and 1.3 +/- 0.4, respectively. The pulsatility index and resistance index of the affected STA were significantly lower in the patients with more extensive bypass flow. The optimal threshold value of the end diastolic flow velocity ratio of STA for the group with extensive bypass flow was 2.75, whereas that for the group with poor bypass flow was 1.60. With the obtained values, the sensitivity and specificity were 87.5% and 93.9% for the group with extensive bypass flow and 95.2% and 95.0% for the group with poor bypass flow, respectively. CONCLUSION: The blood flow velocity in the operated STA seems to be a highly sensitive parameter for predicting the extent of bypass flow in patients undergoing STA-MCA anastomosis.
Angiography, Digital Subtraction↗
Separating changes in the intra- and extracellular water apparent diffusion coefficient following focal cerebral ischemia in the rat brain.
Selective intracellular (IC) and extracellular (EC) brain water apparent diffusion coefficient (ADC) values were measured in normal and ischemic rat brain. Selective T(1)-relaxation enhancement of the EC water, using intracerebroventricular (ICV) infusion of an NMR contrast reagent (CR), was used to separate the IC and EC signal contributions. In the CR-infused, normal brain (n = 4), T(1) = 235 +/- 10 ms and T(2) = 46 +/- 2 ms for IC water (85%) and T(1) = 48 +/- 8 ms and T(2) = 6 +/- 2 ms for EC water (15%). Volume-localized ADC(z) (z-gradient axis) values were 0.90 +/- 0.02 (EC+IC), 0.81 +/- 0.05 (IC), 0.51 +/- 0.02 (EC+IC), and 0.53 +/- 0.07 (IC), for normal, CR-infused, ischemic, and ischemic/CR-infused groups, respectively (ADC values are x10(-3) mm(2)/s; n = 5 for each group). Imaging ADC(z) values were 0.81 +/- 0.03 (EC+IC), 0.75 +/- 0.05 (IC), 0.51 +/- 0.04 (EC+IC), and 0.52 +/- 0.05 (IC), respectively, for the same groups. Imaging ADC(av) (average diffusivity) values for the same groups were 0.70 +/- 0.05 (EC+IC), 0.69 +/- 0.06 (IC), 0.45 +/- 0.06 (EC+IC), and 0.44 +/- 0.06 (IC), respectively. These results suggest that the IC water ADC determines the overall water ADC value in normal and ischemic rat brain.
Animals↗