CHANGES IN BLOOD-FLOW VELOCITY AND DIAMETER OF THE MIDDLE CEREBRAL-ARTERY DURING HYPERVENTILATION - ASSESSMENT WITH MR AND TRANSCRANIAL DOPPLER SONOGRAPHY

PURPOSE: To compare blood flow velocity changes within the middle cere bral artery (MCA) during hyperventilation, as measured with by both tr anscranial Doppler sonography and MR imaging, with the diameter of the MCA as measured with MR imaging alone. METHODS: The studies were perf ormed in six healthy Volunteers ranging in age-from 22 to 31 years (me an, 27 years), Transcranial Doppler sonography was carried out with a range-gated 2-MHz transducer. MR examinations were done on a 1.5-T ima ging unit. MR angiography was performed using the time-of-flight techn ique. MR flow measurements were carried out by using the phase-mapping technique with an EGG-triggered phase-contrast sequence. RESULTS: Dur ing hyperventilation, the mean blood flow velocity of the proximal MCA declined by 49.6% +/- 5.7 (mean +/- standard deviation) as measured w ith Doppler sonography, and by 47% +/- 4.6 as measured with MR flow ca lculation, The diameter of the MCA (3.4 +/- 0.3 mm) remained unchanged on MR imaging studies (3.3 +/- 0.3 mm), CONCLUSION: We found a good c orrelation between relative flow velocity changes measured by transcra nial Doppler sonography and MR techniques. MR imaging revealed no sign ificant changes in the diameter of the proximal MCA during normal Vers us hyperventilation. Relative changes in flow velocity in the MCA woul d thereby reflect relative changes in cerebral blood flow, at least du ring hyperventilation.