Doppler is traditionally used for examination of blood flow velocity.  Alteration of filters and scales permits use of the modality to measure high amplitude, low velocity data from moving muscle - these adjustments permit tissue Doppler imaging (TDI), Figure 1. 

Figure 1: Example of Tissue Doppler Imaging (TDI)

The main applications of TDI have related to its use in the evaluation of long axis function-color TDI (Figure 2) enables simultaneous assessment of all segments in the view, and post-processing of the data is used to demonstrate the velocity wave-form.

Ischemia limits the velocity increment with stress, and a close correlation has been reported between Doppler velocity and ischemia evidenced by independent visual evaluation of wall motion or thallium SPECT defects.  Although a fully quantitative approach to stress echo interpretation (see stress echocardiography section) may be feasible using tissue Doppler, we believe this is more accurately obtained using deformation imaging (see strain section), which is more site-specific.

Figure 2: Example of colour TDI

Although not site-specific, tissue velocity is a robust measure that is more independent of loading conditions than are conventional measures. TDI provides a useful marker of subclinical myocardial dysfunction. The Cardiovascular Imaging Research Group has had a longstanding interest in tissue characterization using TDI, strain parameters (Figure 3) and indices of backscatter (Figure 4).

Figure 3: Example of Strain Characterizations

Figure 4: Example of Myocardial Backscatter

The interrogation of long axis function using TDI is also a valuable technique for assessing the timing of contraction. In addition to implications for cardiac resynchronization therapy, dyssynchrony (Figure 5) is itself an important pathophysiologic signal, which has prognostic significance and may be an important contributor to the progression of heart failure.

Figure 5: Example of Left Ventricular Dyssynchrony Assessment

Personnel

• Rodel Leano (sonographer)
• Carly Jenkins (sonographer)
• Malcolm Burgess (Postdoctoral scholar)
• Professor Tom Marwick