Answer #59

The correct answer is A: Filters exclude high velocities and low intensity reflectors

Tissue Doppler imaging is commonly performed when assessing diastolic function. In this setting, the goal to assess the movment of the mitral annulus in diastole.

The ultrasound machine filters needed for tissue Doppler imaging are opposite that of standard spectral Doppler imaging. Standard spectral Doppler (Pulsed Wave and Continuous Wave Doppler) imaging focuses on blow flow which has relatively high velocities ( 1-5 meters/second) compared to tissue (5-20 cm/second). Thus filters are needed to exclude high velocities (large Doppler shift) signals returning to the probe. Red blood cells are also very weak reflectors as opposed to tissue which is a very strong reflector. Thus during spectral Doppler, filters are set to exclude high intensity reflectors. With Tissue Doppler you want to instead exclude these low intensity reflectors to focus on the tissue. This is why one some machines because of the filters, the gain needs to be turned down significantly to get good images for tissue Doppler. Hence only answer A is correct as with Tissue Doppler the filters exclude high velocity signals and low intensity reflectors.