Optimization of angular and frequency compounding in ultrasonic attenuation estimations

Previous reports have shown that the variance in ultrasound attenuation measurements is reduced when spatial and frequency compounding were applied in data acquisition and analysis. This paper investigates factors affecting the efficiency of compound attenuation imaging methods. A theoretical expression is derived that predicts the correlation between attenuation versus frequency slope (β) estimates as a function of the increment between measurement frequencies (Δf) and the angular separation between beam lines (Δθ). Theoretical results are compared with those from attenuation measurements on tissue-mimicking phantoms and from simulation data. Both predictions and measurement results show that the correlation between β estimates as a function of (Δf) is independent of the length of the radio frequency (rf) data segment over which β is derived. However, it decreases with an increase in the length of the data segment used in power spectra estimates. In contrast, the correlation between β estimates as a function of Δθ decreases when the rf data segment length is longer or the frequency of the signal is higher.