The quantification of absolute myocardial perfusion in humans by contrast echocardiography: algorithm and validation

We sought to test whether myocardial blood flow (MBF) can be quantified by myocardial contrast echocardiography (MCE) using a volumetric model of ultrasound contrast agent (UCA) kinetics for the description of refill curves after ultrasound-induced microsphere destruction.

Absolute myocardial perfusion or MBF (ml.min(-1).g(-1)) is the gold standard to assess myocardial blood supply, and so far it could not be obtained by ultrasound.

The volumetric model yielded MBF = rBV.beta/rho(T), where rho(T) equals tissue density. The relative myocardial blood volume rBV and its exchange frequency beta were derived from UCA refill sequences. Healthy volunteers underwent MCE and positron emission tomography (PET) at rest (group I: n = 15; group II: n = 5) and during adenosine-induced hyperemia (group II). Fifteen patients with coronary artery disease underwent simultaneous MCE and intracoronary Doppler measurements before and during intracoronary adenosine injection.

In vitro experiments confirmed the volumetric model and the reliable determination of rBV and beta for physiologic flow velocities. In group I, 187 of 240 segments were analyzable by MCE, and a linear relation was found between MCE and PET perfusion data (y = 0.899x + 0.079; r(2) = 0.88). In group II, resting and hyperemic perfusion data showed good agreement between MCE and PET (y = 1.011x + 0.124; r(2) = 0.92). In patients, coronary stenosis varied between 0% to 89%, and myocardial perfusion reserve was in good agreement with coronary flow velocity reserve (y = 0.92x + 0.14; r(2) = 0.73).

The volumetric model of UCA kinetics allows the quantification of MBF in humans using MCE and provides the basis for the noninvasive and quantitative assessment of coronary artery disease.