<unk>  <unk>  is a medical ultrasound technology, specifically a form of echocardiography that measures the velocity of the heart muscle (myocardium) through the phases of one or more heartbeats by the<unk>  effect (frequency shift) of the reflected ultrasound. The technique is the same as for flow<unk>  echocardiography measuring flow velocities.<unk>  signals, however, have higher amplitude and lower velocities, and the signals are extracted by using different filter and gain settings. The terms<unk><unk>  imaging (TDI) and<unk>  velocity imaging (TVI) are usually synonymous with<unk>  because echocardiography is the main use of<unk><unk> . Like<unk>  flow,<unk><unk>  can be acquired both by spectral analysis (spectral density estimation) as pulsed<unk>  and by the autocorrelation technique as colour<unk><unk>  (duplex ultrasonography). While pulsed<unk>  only acquires the velocity at one point at a time, colour<unk>  can acquire simultaneous pixel velocity values across the whole imaging field. Pulsed<unk>  on the other hand, is more robust against noise, as peak values are measured on top of the spectrum, and are unaffected of the presence of clutter (stationary reverberation noise).
Tissue Doppler echocardiography
Doppler ultrasonography
Speckle tracking echocardiography
Intracoronary optical coherence tomography
Magnetocardiography
Phonocardiogram
Fractional flow reserve
Strain rate imaging