Improved parametric imaging of scatterer size estimates using angular compounding

Abstract

The feasibility of estimating and imaging scatterer size using backscattered ultrasound signals and spectral analysis techniques was demonstrated previously. In many cases, size estimation, although computationally intensive, has proven to be useful for monitoring, diagnosing, and studying disease. However, a difficulty that is encountered in imaging scatterer size is the large estimator variance caused by statistical fluctuations in echo signals from random media. This paper presents an approach for reducing these statistical uncertainties. Multiple scatterer size estimates are generated for each image pixel using data acquired from several different directions. These estimates are subsequently compounded to yield a single estimate that has a reduced variance. In this feasibility study, compounding was achieved by translating a sectored-array transducer in a direction parallel to the acquired image plane. Angular compounding improved the signal-to-noise ratio (SNR) in scatterer size images. The improvement is proportional to the square root of the effective number of statistically independent views available for each image pixel.

Experimental Application of Ultrafast Imaging to Spectral Tissue Characterization

“…Likewise, the measurement of BSC is affected by electronic noise, which is also stochastic by nature. Thus, to obtain a robust estimate of the BSC, coherent image compounding was implemented by averaging decorrelated spectra from multiple locations of the investigated tissue (Chen et al 2005) or from the same location in multiple frames with different angles of observation (Gerig et al 2004). Another approach consisted of deforming the tissue by applying an external pressure to obtain different signatures (Herd et al 2011).…”

Review of Quantitative Ultrasound: Envelope Statistics and Backscatter Coefficient Imaging and Contributions to Diagnostic Ultrasound

“…Smoothing techniques involving multi-taper methods and Welch’s technique have also been explored in the context of BSC estimation further expanding the tradeoffs between QUS spatial resolution and the quality of scatterer property estimates [23–27]. Another method for improving spectral-based estimates is angular compounding [28–29]. …”

Spatial Angular Compounding ofPhotoacoustic Images

“…The concept is similar to spatial compounding methods for improving the quality of US B-mode [10], [34]–[36], quantitative US [37], [38] and US strain [11], [39], [40] images. The success of spatial compounding of US images relies on the combination of fully decorrelated speckle patterns, which may be achieved with large relative translations [10] or rotations [41], deformation [26], or variations in transmit parameters, such as frequency [42] and beem steering [43].…”