Optimization of Transmit Parameters in Cardiac Strain Imaging With Full and Partial Aperture Coherent Compounding

Abstract

Coherent compounding methods using the full or partial transmit aperture have been investigated as a possible means of increasing strain measurement accuracy in cardiac strain imaging; however, the optimal transmit parameters in either compounding approach have yet to be determined. The relationship between strain estimation accuracy and transmit parameters-specifically the subaperture, angular aperture, tilt angle, number of virtual sources, and frame rate-in partial aperture (subaperture compounding) and full aperture (steered compounding) fundamental mode cardiac imaging was thus investigated and compared. Field II simulation of a 3-D cylindrical annulus undergoing deformation and twist was developed to evaluate accuracy of 2-D strain estimation in cross-sectional views. The tradeoff between frame rate and number of virtual sources was then investigated via transthoracic imaging in the parasternal short-axis view of five healthy human subjects, using the strain filter to quantify estimation precision. Finally, the optimized subaperture compounding sequence (25-element subperture, 90° angular aperture, 10 virtual sources, 300-Hz frame rate) was compared to the optimized steered compounding sequence (60° angular aperture, 15° tilt, 10 virtual sources, 300-Hz frame rate) via transthoracic imaging of five healthy subjects. Both approaches were determined to estimate cumulative radial strain with statistically equivalent precision (subaperture compounding E(SNRe %) = 3.56, and steered compounding E(SNRe %) = 4.26).

Monitoring Canine Myocardial Infarction Formation and Recovery via Transthoracic Cardiac Strain Imaging

“…An ATL P4-2 phased array probe (20-mm 64-element aperture, 2.5 MHz, 0.32 mm pitch) was used with a research ultrasound system (Verasonics Vantage, Redmond, WA, USA). A compounding sequence employing 15 transmits, 60° angular aperture, 15° tilt, 300 Hz frame rate, and 14 mm depth was implemented (Sayseng et al 2018). Two seconds of RF and ECG data were recorded to ensure at least one systolic event was captured.…”

“…Displacement and strain estimation were performed as previously described (Sayseng et al 2018). Briefly, RF data was beamformed using delay-and-sum.…”

Spatiotemporal Bayesian Regularization for Cardiac Strain Imaging: Simulation and In Vivo Results

“…To compare the algorithm performance in vivo, strain filters [67] were derived for the accumulated radial and longitudinal strains at all time points for each method by performing  values for radial and longitudinal strains at 46 % and -17.69 % strains were compared by one-way analysis of variance (ANOVA) with the Bonferroni multiple comparison test following an approach reported in [35].…”

“…Typically, RF-based CSI involves performing BM either with 2-D [23,31] or 1-D kernels in a 2-D search region [32][33][34][35][36][37]. For BM displacement estimation algorithms, 1-D or 2-D kernels from pre-deformation RF data are matched with postdeformation kernels in a pre-defined search range using a similarity metric (e.g., sum of absolute difference, sum of squared difference, mutual information, phase correlation, normalized cross-correlation (NCC) [38][39][40]).…”

A comparison between unfocused and focused transmit strategies in cardiac strain imaging

“…This study aimed to determine the optimal transmit approach for transthoracic parasternal short-axis strain imaging by comparing the radial strain estimation accuracy and precision of three transmit strategies, all previously employed by our group: composite focused imaging with narrow beams (Pernot et al 2007), focused imaging with wide beams (Provost et al 2011), and coherently compounded diverging wave imaging (Sayseng et al 2018). The transmit sequences were investigated in simulation to compare strain estimation accuracy, and in transthoracic imaging of healthy human subjects to compare strain estimation precision via the Strain Filter.…”