Preliminary study of synthetic aperture tissue harmonic imaging on in-vivo data

Abstract

A method for synthetic aperture tissue harmonic imaging is investigated. It combines synthetic aperture sequential beamforming (SASB) with tissue harmonic imaging (THI) to produce an increased and more uniform spatial resolution and improved side lobe reduction compared to conventional B-mode imaging. Synthetic aperture sequential beamforming tissue harmonic imaging (SASB-THI) was implemented on a commercially available BK 2202 Pro Focus UltraView ultrasound system and compared to dynamic receive focused tissue harmonic imaging (DRF-THI) in clinical scans. The scan sequence that was implemented on the UltraView system acquires both SASB-THI and DRF-THI simultaneously. Twenty-four simultaneously acquired video sequences of in-vivo abdominal SASB-THI and DRF-THI scans on 3 volunteers of 4 different sections of liver and kidney tissues were created. Videos of the in-vivo scans were presented in double blinded studies to two radiologists for image quality performance scoring. Limitations to the systems transmit stage prevented user defined transmit apodization to be applied. Field II simulations showed that side lobes in SASB could be improved by using Hanning transmit apodization. Results from the image quality study show, that in the current configuration on the UltraView system, where no transmit apodization was applied, SASB-THI and DRF-THI produced equally good images. It is expected that given the use of transmit apodization, SASB-THI could be further improved.

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

“…Eight radiologists evaluated SASB-THI and DRF-THI sequences of livers with and without focal malignant liver lesions to assess diagnostic sensitivity and specificity, as well as image quality. The findings from this study, together with previous theoretical and experimental reports (Hemmsen et al 2014a;Rasmussen et al 2013), suggest that SASB-THI can be used for medical imaging.…”

“…In a previous pre-clinical study with SASB-THI as the imaging technique, only healthy slim volunteers were scanned (Rasmussen et al 2013). Scanning heavy or obese patients is more difficult, because of the thicker abdominal fat layers and higher heart rates (Hansen et al 2014).…”

“…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).…”

Clinical evaluation of Synthetic Aperture Sequential Beamforming and Tissue Harmonic Imaging

“…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].…”

“…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]. However, this study was only performed with healthy volunteers, so the true clinical relevance could not be clarified.…”