Adaptive imaging and spatial compounding in the presence of aberration.

Spatial compounding reduces speckle and increases image contrast by incoherently averaging images acquired at different viewing angles. Adaptive imaging improves contrast and resolution by compensating for tissue-induced phase errors. Aberrator strength and spatial frequency content markedly impact the desirable operating characteristics and performance of these methods for improving image quality. Adaptive imaging, receive-spatial compounding, and a combination of these two methods are presented in contrast and resolution tasks under various aberration characteristics. All three imaging methods yield increases in the contrast-to-noise ratio (CNR) of anechoic cysts; however, the improvements vary depending on the properties of the aberrating layer. Phase correction restores image spatial frequencies, and the addition of compounding opposes the restoration of image spatial frequencies. Lesion signal-to-noise ratio (SNR), an image quality metric for predicting lesion detectability, shows that combining spatial compounding with phase correction yields the maximum detectability when the aberrator strength or spatial frequency content is high. Examples of these modes are presented in thyroid tissue.