Digital adaptive TVG control for grey‐scale ultrasonic echocardiography

In echocardiography wide‐dynamic‐range (∼90 dB) ultrasonic signals must be compressed for display to ∼15 dB with minimum image distortion. Large dynamic range is caused by absorption, scattering, dispersion, and by reflection from cardiac interfaces at varying angles of incidence. Echo levels in sector‐scanning echocardiography differ with look angle, precluding operator adjustment. Thus, sector scanners need adaptive TVG profiles, or AGC. A digital, real‐time, adaptive TVG for sector‐scanning echocardiography is described herein. This technique is not subject to analog realizability constraints. The described adaptive TVG uses image data stored in a minicomputer to calculate a slowly varying TVG profile which commands a voltage controlled amplifier. The gain‐profile algorithm is basic to the adaptive TVG. The grey‐scale display quality of the echo output of the voltage controlled amplifier is examined and discussed. Alternatively, the technique permits the TVG input to be numerically recovered off‐line and normalized relative to the average level in the neighborhood of each image point. Preliminary echocardiographic tests are discussed using one‐dimensional data. The multidimensional adaptive TVG technique is currently being implemented in a scanning echocardiographic camera. [Work partially supported by NIH Grant 1 R01 HL20872‐01.]