Implementation of tissue harmonic synthetic aperture imaging on a commercial ultrasound system

Abstract

This paper presents an imaging technique for synthetic aperture (SAI) tissue harmonic imaging (THI) on a commercial ultrasound system. Synthetic aperture sequential beamforming (SASB) is combined with a pulse inversion (PI) technique on a commercial BK 2202 UltraView system. An interleaved scan sequence that performs dynamic receive focused (DRF) imaging and SASB, both using PI, is implemented. From each acquisition four images can be created: DRF image, SASB image, tissue harmonic DRF image (DRF-THI), and tissue harmonic SASB image (SASB-THI). For SASB imaging, a fixed transmit and receive focus at 80 mm and an F# of 3 is applied. For DRF imaging, default scanner settings are used, which are a focus at 85 mm and F# of 5.7 in transmit and a dynamic receive aperture with an F# of 0.8. In all cases a 2.14 MHz one-and-ahalf cycle excitation transmit waveform is used. A BK 8820e 192 element convex array transducer is used to conduct scans of wire phantoms. The-6 dB and-20 dB lateral resolution is measured for each wire in the phantom. Results show that the-6 dB lateral resolution for SASB-THI is as good as for DRF-THI except at the point of the virtual source. SASB-THI even shows 7% reduction in-6 dB lateral resolution for the deepest wire at 100 mm. The-20 dB resolution for SASB-THI at [25, 50, 75, 100] mm was reduced by [5, 0-34, 11] % compared to DRF-THI, which shows, that except for the point of the virtual source, the lateral resolution was improved by SASB-THI. A successful implementation of SASB-THI was achieved on a commercial system, which can be used for future pre-clinical trials.

Clinical Evaluation of Synthetic Aperture Harmonic Imaging for Scanning Focal Malignant Liver Lesions

“…SASB can generate an acoustic field intense enough to create harmonics for THI, and it has been suggested that these techniques be combined to improve the image quality of SASB even further. The pulse inversion technique was used to generate THI, and the beamforming steps for the final SASB-THI image are illustrated in Figure 1 (Hemmsen et al 2014b;Rasmussen et al 2012;Yigang et al 2011). In a preliminary study in which healthy volunteers were scanned, two radiologists evaluated the image quality of SASB-THI as equal to that of a conventional imaging technique combined with THI (DRF-THI), indicating that SASB-THI can be used for medical imaging (Rasmussen et al 2013).…”

Tissue harmonic synthetic aperture ultrasound imaging

“…The advantage of SASB, besides the reduction in computational load, is that the lateral resolution remains higher and more uniform over depth compared to regular dynamic receive focusing (DRF) 19 . The use of virtual sources in SASB has been shown to create an acoustic field intense enough to generate harmonics 21,22 .…”

Clinical evaluation of Synthetic Aperture Sequential Beamforming and Tissue Harmonic Imaging

“…The default imaging technique in many modern ultrasound scanners is the combination of Dynamic Received Focusing (DRF) and Tissue Harmonic Imaging (THI) [1]. Tissue harmonic imaging (THI) enhances image quality through improvement in contrast, resolution and fewer artifacts in gray scale ultrasonography [2][3].…”

“…Then, the image data are beamformed using the fixed focus points as a virtual source to obtain the final synthetic aperture [4,[8][9]. SASB use of virtual sources creates an acoustic field intense enough to create harmonics for THI [1,9]. To attain the improvement of THI and SASB, this combination was suggested as a new imaging technique [1,10].…”

“…SASB use of virtual sources creates an acoustic field intense enough to create harmonics for THI [1,9]. To attain the improvement of THI and SASB, this combination was suggested as a new imaging technique [1,10]. In a previous preliminary evaluation study with the combination of SASB and THI, SASB-THI attained equally good image quality as DRF-THI [10].…”