US Tissue Harmonic and Spatial Compound Imaging: What Are They and How Do They Change the Image?

Tissue harmonic and spatial compound imaging are advanced US settings that were commercialized in the 1990s and became commonplace in the early 2000s. Tissue harmonic imaging uses endogenously produced high frequency components to construct the image. Harmonic images mitigate clutter and accentuate useful artifacts, such as shadowing. Spatial compound imaging combines images taken at several angles to reduce noise and speckle and mitigate artifacts. These settings can also be used together to improve image quality in complementary ways and alter artifact appearance. Although the settings have been used clinically for more than 20 years, there is still uncertainty about what tissue harmonic and spatial compound imaging are and how they can improve clinical images, both individually and when combined.