Improvements in elastographic contrast-to-noise ratio using spatial-angular compounding

Abstract

Spatial-angular compounding is a new technique developed for improving the signal-to-noise ratio (SNR) in elastography. Under this method, elastograms of a region-of-interest (ROI) are obtained from a spatially weighted average of local strain estimated along different insonification angles. In this article, we investigate the improvements in the strain contrast and contrast-to-noise ratio (CNR) of the spatially compounded elastograms. Spatial angular compounding is also applied and evaluated in conjunction with global temporal stretching. Quantitative experimental results obtained using a single-inclusion tissue-mimicking phantom demonstrate that the strain contrast reduces slightly but the CNR improves by around 8 to 13 dB. We also present experimental spatial angular compounding results obtained from an in vitro thermal lesion in canine liver tissue embedded in a gelatin phantom that demonstrate the improved visual characteristics (due to the improved CNR) of the compound elastogram. The experimental results provide guidelines for the practical range of maximum insonification angles and estimates of the optimum angular increment.

Spatial‐angular compounding for elastography using beam steering on linear array transducers

“…Results obtained using the phased-array transducer also demonstrate a similar trend. 22,23 In this article, we therefore select the maximum angle to be around 10° beyond which no appreciable increases in the SNR e or CNR e are obtained. This can be explained by the significant increase in the decorrelation of the pre-and postcompression rf echo signals at larger angles.…”

Correlation Analysis for Angular Compounding in Strain Imaging

“…So the center of the aperture for the precompression signals is positioned at A 1 (b/2, 0), and the center of the aperture for postcompression signals is positioned at A 2 (-b/2, 0). The cross correlation between the signals acquired before and after compression are modeled as follows (similar to that described in (14) in our previous work [5]): (1) where s 1 and s 2 denote ultrasonic RF echo signals before and after compression. The subscripts 1 and 2 refer to the pre-and postcompression signals, respectively.…”

“…SPATIAL-ANGULAR compounding for strain imaging or elastography was recently introduced by our group [1]- [3] as a method of reducing noise artifacts in elastograms. Here, pre-and postcompression radio-frequency (RF) echo signals are acquired at multiple insonification angles for a unidirectional, quasistatic compression.…”

Full Angle Spatial Compound of ARFI images for breast cancer detection

“…Angular and spatial composition of strain images in a process similar to MACI has been previously proposed for static elastography [32][33][34], showing that image quality improves when averaging images generated from different angles and positions. Although the force generation principle is different in static elastography than in ARFI, it could also be expected that contrast-to-noise ratio (CNR) improves when ARFI strain images are averaged.…”