Minute changes in thickness of less than 100 μm in the arterial wall cannot be measured by conventional B-mode or M-mode imaging. This paper describes a novel noninvasive method (phased tracking) for measuring such minute changes in arterial wall thickness during one cardiac cycle. A method for evaluation of the regional elastic modulus in the circumference direction, Eθ, from the resulting change in wall thickness is also described. The method was used for two in vivo studies: (1) Eθ was determined in two groups consisting of 31 healthy subjects and 95 subclinical subjects with normal wall thickness of the carotid arteries, and the value in the subclinical group was found to be larger than that in the healthy group. (2) For subjects with hyperlipemia, the spatial distribution of Eθ was evaluated for carotid atherosclerotic plaque. Soft inclusions were found in every plaque, and there were differences in elasticity from the surrounding hard tissues. This novel method is a potentially useful diagnostic technique for analysis of both early-stage atherosclerosis and plaque vulnerability.

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We investigated the characteristics (velocity and frequency) of microembolic signals (MES) detected by transcranial Doppler (TCD) . The subjects were 22 patients (69 ± 9 years old) with cardioembolic stroke (CE), 28 (65 ± 11 years old) with atherothrombotic stroke (stenosis of the internal carotid or middle cerebral arteries) (AS), 36 (63 ± 10 years old) with lacunar stroke (LS), and 9 (57 ± 16 years old) with mechanical valve replacement (MVR) . Using a Multi-Dop X4 (DWL Co., Germany), a 20-min TCD recording was made over the middle cerebral artery. Signals with an intensity of 6 dB or more above the background Doppler spectrum and associated with harmonic sound were defined as MESS. MESs were detected in 23% of patients with CE (17 signals), 71% (144) of patients with AS, 0% (0) of patients with LS, and 100% (88) of patients with MVR. There was a significant positive correlation (p<0.01) between MES velocity and frequency in all types of disease: AS (r=0.84), CE (r=0.80) and MVR (r=0.91) . The ratio of the velocity of MES (M) to that of background blood flow (B) (MB ratio) in AS (0.65 ± 0.21) was significantly smaller (p<0.05) than that in CE (0.77 ± 0.10) or MVR (0.72 ± 0.14) .
These findings suggest that the frequency of the harmonic sound is related to the velocity of microemboli that traverse the ultrasound beam, and that the velocity of microemboli and duration of MESs are inversely correlated. Most microemboli detected in patients with AS flow close to the vascular walls.

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We evaluate the effectiveness of TCD monitoring for detection of distal embolism just after Interventional treatment for cerebrovascular disease. Material and methods : Thirteen cases of cerebrovascular disease undergoing Interventional treatment were subjected to TCD monitoring just after intervention to detect distal embolization. Seven cases of internal carotid artery (ICA) stenting, 1 PTA of middle cerebral artery (MCA), and 5 GDC embolization of intracranial aneurysm were assessed by 30 minutes of TCD monitoring by transtemporal insonation and countered HITS. Antithrombin and antiplatelet therapy were administered after intervention in all cases. Results : HITS was detected in 3 of 13 cases, and 1 of the 3 cases had an embolic event (RIND) . The number of HITS in symptomatic case were 36 per 30 minutes and in asymptomatic case were 2 and 4 per 30 minutes. On post-therapeutic DWI of MRI, 3 of 13 cases had procedure-related infarctions and 1 of the 3 cases was symptomatic with a high number HITS. Conclusion : TCD monitoring during the early postoperative phase of intervention is effective in predicting embolic events.

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Purpose: The present study using duplex Doppler sonography (DDS) was conducted to assess collateral flow by the vertebral artery in consecutive patients with cardioembolic stroke without acute severe brain swelling: 9 cases of internal carotid artery occlusion (CES-I group), 7 cases of middle cerebral artery occlusion (CES-M group), 11 cases of atherothrombotic stroke (ATS group) and 21 normal volunteers (control group) . Methods: DDS using an SSD-1700 (Aloka) with a 7.5-MHz linear-type probe in the carotid and vertebral artery was performed in all cases. DDS data, mean flow velocity (MFV) and Gosling' s pulsatility index (PI) were analyzed using 7.5-MHz pulsed wave Doppler on the common carotid artery (CCA) and vertebral artery (VA) . Results: 1) MFV-CCA was significantly greater than MFV-VA in the ATS and control groups. In the CES-I group, MFV-VA was elevated, but there was no significant correlation between MFV-CCA and MFV-VA. In the CES-M group, there was no significant correlation between MFV-CCA and MFV-VA. 2) MFV-VA in the CES-I group was significantly greater than that in the control or ATS group. 3) PI-CCA was significantly greater than PI-VA only in the ATS group. Conclusion: A high MFV of VA in patients with cardioembolic stroke without acute severe brain swelling might be an indicator of good collateral circulation.
Key words : duplex Doppler sonography, vertebral artery, cardioembolic stroke, cerebral blood flow

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We hypothesized that microemboli in the basilar artery can be one of the major causes of isolated episodes of vertigo in patients with prosthetic heart valves. In this study, five patients were evaluated for recurrent vertigo after receiving prosthetic heart valves. Vertiginous symptoms associated with vertebrobasilar emboli were characterized by their short duration (within 5 to 30 min), recurrent onset and immediate resolution. HITS were detected in both the middle cerebral artery (MCA) and basilar artery (BA) with a TC-2 64B device (EME Ltd.) or Multi-Dop P (DWL Ltd.) during a 20-min period. Thirty-two patients (control subjects) without vertigo after prosthetic heart valve implantation were also examined by TCD. In the patients with vertigo, the mean HITS rate in the BA was 49.6 ± 18.5/h (range 28 to 72), whereas that in control subjects was 9.8 ± 10.7/h (range 0 to 40, p<0.05) . The mean HITS rate in the MCA was 52.8 ± 29.7/h (range 32 to 104: control; 17.1 ± 14.4, 0 to 56, p<0.05) . The vertiginous patients were then administered aspirin at 60 to 81 mg/day orally in combination with warfarin. In all patients, the vertigo attacks disappeared within 2 to 6 days, and the mean HITS rate in the BA decreased significantly to 8.4 ± 7.3/h (range 0 to 20, p<0.05) . In the MCA, the mean HITS rate was also decreased to 10.4 ± 4.6/h (range 4 to 16, p<0.05) .
In patients with vertigo attacks, who undergo mechanical heart valve placement, TCD examinations could detect HITS in the BA. This may be helpful for the diagnosis and prevention of cerebrovascular accidents in the posterior circulation.

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The mortality from and/or incidence of neurological sequelae of childhood acute encephalopathies, including Reye's syndrome, influenza encephalopathy and acute necrotizing encephalopathy, are still high. We have already reported that mild hypothermia therapy facilitates excellent recovery from acute encephalopathy. The purpose of this study was to investigate the usefulness of transcranial Doppler sonography (TCD) as a nonintensive care technique for severe acute encephalopathy during mild hypothermia therapy. The subjects comprised 12 children with acute encephalopathy: nine boys and three girls. The mean age of the patients was 4.6±4.56 (mean±standard deviation), ranging from 1 year 8 months to 15 years 3 months. The etiologies of acute encephalopathy were thought to be influenza-related in 8 patients, varicella in one, and unknown in the remaining three. They were evaluated and treated at Nihon University Itabashi Hospital during a 7-year period (1993 to 1999) . We used TCD (TC2-64, EME) for bedside monitoring, and evaluated the PI (pulsatility index, Gosling 1974) of the MCA and ACA at three points during therapy (before, during and after hypothermia) . The PI of the MCA and ACA was significantly higher before hypothermia than during and after hypothermia (p<0.01) . There were no significant changes in the PI during and after hypothermia. In the group showing excellent recovery, the PI fell on the day after the start of hypothermia therapy. On the other hand, in the poor outcome group, the PI rose on the day after the start of hypothermia therapy. Thus we were able to decide the timing of the rewarming point using TCD. TCD is useful for bedside monitoring in children with severe acute encephalopathies.

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