Plane-Wave Compounding in Automated Breast Volume Scanning: A Phantom-Based Study.

The goal of this study was to assess whether it is viable to implement plane-wave imaging in the Automated Breast Volume Scanner (ABVS) to speed up the acquisition process. This would allow breath-hold examinations, thus reducing breathing artifacts without loss of imaging quality. A calibration phantom was scanned in an Automated Breast Volume Scanner-mimicking setup using both dynamic receive focusing with a fixed transmit focus and unfocused plane-wave compounding. Contrast-to-noise ratio and lateral resolution were compared using two beamforming schemes, delay-and-sum and Stolt's f-k algorithm. Plane-wave compounding using only 11 compounding angles and Stolt's f-k algorithm provided image quality similar to that of focused transmission with dynamic receive focusing (contrast-to-noise ratios = 10.3 and 10.8 dB for Stolt's f-k migration with Hann apodization and focused transmission, respectively; full width at half-maximum = 0.38 and 0.4 mm, respectively; all at 30-mm depth with transmit focus at 30 mm) with a higher signal-to-noise ratio at all depths. Furthermore, a full 3-D volume of a breast-mimicking phantom was scanned using this optimal set of compounding angles and different speeds (10, 20 and 50 mm/s) to assess the impact of scanning time on image quality. Only minor differences in contrast-to-noise ratio were found (cyst 1: 6.0 ± 0.3 dB, cyst 2: 5.5 ± 0.2 dB, cyst 3: 5.7 ± 0.5 dB). These differences could not be correlated to the movement speeds, indicating that acquisition speed does not significantly affect image quality. Our results suggest that plane-wave imaging will enable breath-hold automated breast volume scanning examinations, eliminating breathing artifacts while otherwise preserving similar image quality.

Automated 3D ultrasound elastography of the breast: a phantom validation study.

In breast cancer screening, the automated breast volume scanner (ABVS) was introduced as an alternative for mammography since the latter technique is less suitable for women with dense breasts. Although clinical studies show promising results, clinicians report two disadvantages: long acquisition times (>90 s) introducing breathing artefacts, and high recall rates due to detection of many small lesions of uncertain malignant potential. Technical improvements for faster image acquisition and better discrimination between benign and malignant lesions are thus required. Therefore, the aim of this study was to investigate if 3D ultrasound elastography using plane-wave imaging is feasible. Strain images of a breast elastography phantom were acquired by an ABVS-mimicking device that allowed axial and elevational movement of the attached transducer. Pre- and post-deformation volumes were acquired with different constant speeds (between 1.25 and 40.0 mm s(-1)) and by three protocols: Go-Go (pre- and post-volumes with identical start and end positions), Go-Return (similar to Go-Go with opposite scanning directions) and Control (pre- and post-volumes acquired per position, this protocol can be seen as reference). Afterwards, 2D and 3D cross-correlation and strain algorithms were applied to the acquired volumes and the results were compared. The Go-Go protocol was shown to be superior with better strain image quality (CNRe and SNRe) than Go-Return and to be similar as Control. This can be attributed to applying opposite mechanical forces to the phantom during the Go-Return protocol, leading to out-of-plane motion. This motion was partly compensated by using 3D cross-correlation. However, the quality was still inferior to Go-Go. Since these results were obtained in a phantom study with controlled deformations, the effect of possible uncontrolled in vivo tissue motion artefacts has to be addressed in future studies. In conclusion, it seems feasible to implement 3D ultrasound quasi-static elastography on an ABVS-like system and to reduce scan times within one breath-hold (~10 s) by plane-wave acquisitions.