Tissue harmonic imaging for standard left ventricular measurements: Fundamentally flawed?

Tissue harmonic imaging (THI) is a B mode imaging technique that improves echocardiographic image quality by reducing superficial artefact. The modality increases image signal-to-noise ratio at the expense of reduced axial resolution. While the qualitative improvements of harmonic echocardiographic imaging are widely accepted, the degree to which this is translated into improved quantitative measurements and whether THI-derived measurements result in systematic bias continue to be areas of uncertainty. This review examines differences between THI and fundamental imaging-derived measurements from a theoretical, tissue phantom and clinical perspective.