Efficacy of Transcranial Color Flow Imaging in Patients with Abnormal Blood Flow Velocity of the Middle Cerebral Artery

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Purpose We used TC-CFI to delineate the abnormal blood flow in the middle cerebral artery (MCA), a segment of which had been found by TCD to be associated with an abnormal blood flow velocity. Our purpose was to find whether or not the procedure is useful in excluding false positive sign. Method The subjects were assigned to one of the following two groups: a high velocity group-those who had a maximum systolic flow velocity in the MCA (determined by TCD) that exceeded the mean +2 SD of the normal controls (126 cm/s) ; and a low velocity group-those with a velocity below the mean -2SD (52 cm/s) . In both group, the segmental image of the MCA (where a high or low flow velocity was recorded by TCD) was studied by TC-CFI to elucidate the cause of the flow abnormalities. Results and Conclusion 1. The stenotic lesion was easily detected with TC-CFI, because the flow signal changed from red to yellow or a mosaic pattern. The section where the maximum systolic flow velocity (determined after angle correction) exceeded 170 cm/s is indeed stenotic. 2. Two explanations are offered for the segment that showed a low flow velocity by TCD: the actual flow velocity was also low; and the existence of a so-called false-positive phenomenon (i.e., the corrected flow velocity is normal because the angle between the MCA and the Doppler beam is large) . 3. TC-CFI is very useful in elucidating the relationship between the Doppler beam and the flow through the MCA.