Quantification of flow rates using harmonic grey-scale imaging and an ultrasound contrast agent: an in vitro and in vivo study

It is unclear if the dye-dilution theory and its corresponding parameters a re capable of measuring brain perfusion using harmonic grey-scale imaging. We performed a study on a flow phantom using a SONGS 5500 (1.83.6-MHz harmo nic imaging);and Levovist(TM) as the ultrasound (US) contrast agent (UCA). We applied the UCA in six different doses (0.1 to 3.0 mL) and used eight di fferent flow-rates (180 to 540 mL/min). Additionally, we performed a study on dog brain using Levovist(TM) boluses of 1.5 mL and 3 mL. We evaluated th e influence of dose and flow-rate on the parameters of the time-intensity c urve: peak signal intensity (PST), area under the curve (AUC) and mean tran sit time (MTT). Along with an increase of the Levovist(TM) dose, the AUC an d the PSI increased only in the dose range between 0.1 and 0.5 mL Levovist( TM); further increase led to no change of parameters. Flow-rate showed no i nfluence on AUC, MTT or PSI. The dye-dilution theory is not a useful theore tical model for the analysis of perfusion using harmonic grey-scale imaging . A possible explanation for this effect is the bubble saturation. (E-mail: seide_g@neuro.mu-luebeck.de) (C) 2001 World Federation for Ultrasound in M edicine & Biology.