DOPPLER MYOCARDIAL IMAGING VS B-MODE GRAY-SCALE IMAGING - A COMPARATIVE IN-VITRO AND IN-VIVO STUDY INTO THEIR RELATIVE EFFICACY IN ENDOCARDIAL BOUNDARY DETECTION

Doppler myocardial imaging (DMI) is a new ultrasound imaging modality in which colour Doppler algorithms are adapted to visualise the myocar dium. It allows measurement of regional intramyocardial velocities and quantification of intramural left ventricular function. However promi sing the technique is, to date the accuracy of endocardial boundary de tection by DMI has not been validated. As Doppler velocity estimation is based on measurement of phase shift rather than signal strength, th e technique is relatively independent of chest wall attenuation. In th e current study, a series of in vitro and in vivo studies was performe d to compare standard B-mode grey-scale imaging (GSI) and DMI techniqu es in endocardial boundary detection. In vitro, the minimum and maximu m volumes of a single-chamber tissue-mimicking phantom were calculated using both imaging techniques. In vivo,left ventricular end-diastolic (ED) volume and end-systolic (ES) volume indices were measured from G SI and DMI images in a group of 40 volunteers. All images were obtaine d in the freeze-frame mode with the Doppler display turned on and off so that simultaneous DMI and GSI information was obtained. In vitro, t he limits of agreement between the minimum volume of the phantom and t he minimum volume measured by GSI and DMI was 4% and 3%, respectively. For maximum volumes, limits of agreement were 3% for GSI and 2% for D MI. In vivo, the limits of agreement between the two imaging technique s in volume measurements were 6 mL (9%) for ED and 4 mL (11%) for ES. The comparison of the endocardial boundary detection by GSI vs. DMI sh owed DMI to be significantly superior: ED (72+/-16% vs. 85+/-8%, respe ctively; p <0.05) and ES (71+/-13% vs. 88+/-7%, respectively; p <0.05) . The results of the study show that: (1) in vitro, based on two-dimen sional algorithms, DMI provides as accurate volume measurements as GSI ; and (2) in vivo, there is a very good agreement of left ventricular volume measurements between GSI and DMI. However, the endocardial boun dary is more reliably displayed and visually easier to detect using DM I than GSI. Copyright (C) 1997 World Federation for Ultrasound in Medi cine & Biology.