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Session: Ultrasound
Session starts: Thursday 26 January, 10:30
Presentation starts: 10:45
Room: Room 559

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Vera van Hal (Eindhoven University of Technology)
Hein de Hoop (Eindhoven University of Technology)
Jan-Willem Muller (Eindhoven University of Technology)
Hans-Martin Schwab (Eindhoven University of Technology)
Richard Lopata (Eindhoven University of Technology)

Abstract:
Abdominal ultrasound (US) imaging is used to monitor rupture risk of abdominal aortic aneurysms. However, assessment of aortic geometry and wall deformation using conventional US is limited by the lateral lumen-wall contrast and resolution. We therefore introduce high frame rate multi-perspective (MP) bistatic imaging to improve aortic US. In MP bistatic imaging, two curved array transducers receive simultaneously on each transmit event. The advantage of such bistatic US imaging was investigated in US simulations and in an experimental study on ex vivo porcine aortas. Using MP bistatic imaging, the wall-lumen contrast-to-noise ratio was improved by up to 8 dB in vessel wall regions between transducers. This improved the accuracy of strain estimates in US simulations by 41-84% and resulted in more homogeneous strain results in ex vivo experiments. In vivo, MP image fusion is hampered by wavefront aberrations, caused by the strong speed-of-sound variations between muscle and fat in the abdominal wall. This limits abdominal US image quality by introducing distortions of the imaged structures, especially at deep imaging locations, such as the aorta. In MP US, these aberrations can be even more crucial, because image features from different probes can misalign severely. We developed a generic algorithm for aberration correction in US image reconstruction to improve image quality for both single-perspective (SP) and MP US. Its accuracy for abdominal imaging was evaluated in acoustic simulations and phantom experiments involving tissue-mimicking and ex vivo porcine material with large speed-of-sound contrast (~100 m/s). The lateral resolution was improved by up to 90% in US simulations and up to 65% in experiments compared to standard US image reconstruction. Moreover, geometric distortions were resolved in MP imaging, leading to a reduction in position error of around 80%. In conclusion, a more complete understanding of aortic geometry and wall motion can be retrieved by using high frame rate MP bistatic imaging with two curved array transducers. Moreover, results show that in vivo MP image fusion can be enabled by aberration correction using modelled arrival times in US image reconstruction. An in vivo study on bistatic MP aortic US imaging in healthy volunteers is ongoing.