Recently, it has become possible to measure blood flow velocity by MRI flow mapping. This study was designed to evaluate the accuracy of MRI flow mapping for measuring blood flow velocity in the common carotid artery (CCA), in comparison with a conventional ultrasonic quantitative flow measurement system (QFM) . We studied 58 patients aged 19-74 years (mean age, 40 years; 20 males, 38 females) without cerebrovascular disorders, essential hypertension, diabetes mellitus, or hyperlipidemia. The maximum and mean blood flow velocity of the CCA were determined by QFM 2000 XA (Nippon Koden Co.) and MRI (Siemens Co. 1.0T) based on MRI phase-contrast measurement. Technical parameters of MRI were: TR/TE/FA=31 ms/6 ms/25, slice=6 mm, matrix=256 × 256, field of view = 200 × 200 mm. The maximum blood flow velocity was 55.2 ± 16.8 cm/s by QFM, and 56.8 ± 15.5 cm/s by MRI. The maximum flow velocity in the CCA determined by MRI was significantly correlated with that determined by QFM (r=0.69, p<0.001), and the two methods were in good agreement. The mean flow velocity in the CCA was 22.6±5.6cm/s by QFM, and 25.3±7.3 cm/s by MRI. The mean flow velocity measured by MRI was higher than that measured by QFM, but the two values were significantly correlated (r=0.59, p<0.001) . These results indicate that the maximum blood flow velocity in the CCA as measured by MRI is in good agreement with that determined by QFM.
Recently, high-intensity transient signals (HITS) obtained by transcranial Doppler ultrasonography (TCD) were reported to reflect micro-emboli in cerebral arteries. Frequent detection of HITS in patients with mechanical valve replacement has been reported for many years. However, the mechanism and significance of these signals has remained unclear. We attempted to elucidate whether HITS indicate a risk of cerebral infarction in patients with mechanical valve (St. Jude Medical valve: SJM) replacement, and also carried out an animal experimental study to clarity the mechanism of HITS formation. HITS was frequently detected in patients with SJM valves. The HITS count after surgery in patients with cerebral infarction (83 ± 66/15 min) was significantly higher than that in patients without a history of stroke (7 ± 7/15 min) (p<0.001) . The HITS count in patients with mechanical valve replacement appeared to increase with time after surgery. Thus, the HITS count appeared to indicate the risk of cerebral infarction after mechanical valve replacement. In the experimental study, injection of clotted blood into the aorta produced low-frequency and small-intensity HITS. Introduction of micro-bubbles into the aorta produced high-frequency and large-signal-intensity HITS. These two kinds of HITS were detected in patients with SJM valves. Thus, HITS in patients with SJM valves may be produced by both gaseous and solid micro-emboli.
A 52-year-old man with aortic regurgitation (AR) presented with a subarachnoid hemorrhage (SAH) due to a ruptured mycotic aneurysm. Transcranial Doppler sonography (TCD) of the left middle cerebral artery demonstrated an increased peak systolic flow velocity (FVmax) of 95 cm/s and no flow during the end-diastolic phase. Management of cerebral vasospasm giving consideration to cardiac function was successful, and no further increase of FVmax was observed. After replacement of the aortic valve, TCD showed normalization of the wave contour compared with that before replacement. As AR patients are prone to cerebral vasospasm due to end-diastolic cerebral hypoperfusion, serial observation by TCD is helpful for management.
We evaluated the clinical usefulness of three-dimensional (3-D) echoencephalography in infants. The transducer was placed on the anterior fontanel and all the sections were serially and automatically scanned in a few seconds. A 3-D image was constructed by an internal computer in a few seconds. We could produce B-mode images at any direction, including those which could not be achieved via conventional methods. By using 3-D imaging, we could easily grasp the three-dimensional structure of the central nervous system. Further, we could measure ventricular volumes. We concluded that 3-D echoencephalography in infants is very useful.
Background and Purpose: To assess the influence of the skull on blood flow signals detected by transcranial Doppler, we measured bone density in the skull using dual energy X-ray absorptimetry. Methods: Bone mineral density (BMD) was studied in 219 normal volunteers (mean age±SD 53.5±17.9 years, 80 men, 139 women) . In 37 of the subjects (mean age ±SD 56.4±15.8 years, 17 men, 20 women), blood flow signals were also measured using a 2-MHz range-gated pulsed-wave Doppler. Results: BMD in women was lower than that in men over 60 years of age (p<0.05) . The rate of unsuccessfully recorded flow signals increased with age, especially in women (14 of 17 women aged 60 years or over) . BMD in the unsuccessful recording group (1.482 ± 0.123 g/cm2, mean ± SD) was significantly lower than that in the successful recording group (1.835±0.058 g/cm2) (p<0.05) . Conclusion: The rate of unsuccessfully recorded blood flow signals increased with advancing age, especially in women, and with lower BMD in the skull.
From the viewpoint of safety, it is necessary for the diagnostic ultrasonic equipment used in clinical practice to satisfy the FDA 510 (k) requirement track III. The new requirement requires medical doctors and staff to have a greater understanding of ultrasonic bioeffects as indicated by the mechanical index (MI) and the thermal index (TI), on the real-time display of recently developed diagnostic ultrasonic devices. This article describes the significance of MI and TI and the variables in clinical use. Also it is noted that the ultrasonic examiner should uphold the principle of ALARA (as low as reasonably achievable) in clinical use.