Reliability of semiquantitative ultrasonic perfusion imaging of the brain

Background and Purpose. Contrast burst depletion imaging (CODIM) visualizes cerebral perfusion by destruction of microbubbles and observation of image intensity course. Because of its complexity, artifacts occur. Criteria of reliability to improve diagnostic significance were created and validated. Methods and Results. Eighteeen healthy volunteers were examined with 2 echo contrast agents (ECAs) and 3 frame rates in 3 regions of interest (ROIs). Perfusion coefficient (PC), T,,in (time to decrease intensity to 10% of its max), and relative error (RE) (deviation of measured data from fitted model) were determined. PC differed significantly neither between CA nor between frame rates (overall mean = 1.60 +/- 0.21 X 10(-2) s(-1)). T-min differed significantly between frame rate groups (P < .001, 33.4 +/- 11.2 s/0.5 Hz; 3.6 +/- 2.5 s/5 Hz) since it is related to destruction of microbubbles that occurs with each frame and to the perfusion rate. RE was higher in the Optison group and tended to decrease in ROIs closer to the probe. Conclusions. PC was independent of frame rate and ECA. T-min was shorter with higher frame rates. Due to a very rapid decay at 5 Hz, the ideal frame rate should be about 1 Hz, that is, because the number of frames acquired within T-min and therefore signal-to-noise ratio is higher at 1 Hz. Since the algorithm is complex (high RE) and more artifacts should occur in patients (insufficient bone window, etc), a triggering of the insonations by, for example, heart rate could decrease artifacts and increase diagnostic power of CODIM.