Combined perfusion and doppler imaging using plane-wave nonlinear detection and microbubble contrast agents

Abstract

Plane-wave imaging offers image acquisition rates at the pulse repetition frequency, effectively increasing the imaging frame rates by up to two orders of magnitude over conventional line-by-line imaging. This form of acquisition can be used to achieve very long ensemble lengths in nonlinear modes such as pulse inversion Doppler, which enables new imaging trade-offs that were previously unattainable. We first demonstrate in this paper that the coherence of microbubble signals under repeated exposure to acoustic pulses of low mechanical index can be as high as 204 ± 5 pulses, which is long enough to allow an accurate power Doppler measurement. We then show that external factors, such as tissue acceleration, restrict the detection of perfusion at the capillary level with linear Doppler, even if long Doppler ensembles are considered. Hence, perfusion at the capillary level can only be detected with ultrasound through combined microbubbles and Doppler imaging. Finally, plane-wave contrast-enhanced power and color Doppler are performed on a rabbit kidney in vivo as a proof of principle. We establish that long pulse-inversion Doppler sequences and conventional wall-filters can create an image that simultaneously resolves both the vascular morphology of veins and arteries, and perfusion at the capillary level with frame rates above 100 Hz.

Fast Vascular Ultrasound Imaging With Enhanced Spatial Resolution and Background Rejection

“…The kidney scan processed in this work included 150 frames compared to the 1000 frame long tumor scan. In color and power Doppler modes frame rates higher than 6 Hz are used in order to ensure smooth image update [3]. Even with ensembles of 1000 frames, this rate can be achieved in plane-wave imaging by processing partially overlapping timeseries.…”

“…wall-filter) was used to separate the echoes of flowing microbubbles from the weak harmonic tissue clutter and stationary microbubbles. Following [3] and [23], a sixth order high pass Butterworth filter with a projection initialization was used. The cut-off frequency was chosen as 0.03•PRF and used for both kidney and tumor models.…”

“…Bar-Zion (e-mail: barz@tx.technion.ac.il) and D. Adam (e-mail: dan@biomed.technion.ac.il) are with the Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa 32000, (arterioles) by applying Doppler processing [3], [4]. However, the resolution of these scans is limited by the point spread function (PSF) of the system, reducing the clinical usability of CEUS.…”

Phase-transition Perfluorocarbon Nanoparticles for Ultrasound Molecular Imaging and Therapy

“…As a result, microbubbles have not only been used as contrast agents for ultrasound molecular imaging [73,74], but also as carriers to enhance genes and drugs delivery [75][76][77][78].…”

Multi-frame rate plane wave contrast-enhanced ultrasound imaging for tumour vascular imaging and perfusion quantification

“…Recent development of plane wave high frame-rate (HFR) CEUS has offered new opportunities many applications such as vascular flow imaging [6]- [8], elastography [9], cardiac imaging [10], and brain functional imaging [11]. The high temporal resolution from plane wave imaging and the high sensitivity from CEUS can be used not only for imaging fast moving targets, but also to improve visualisation of the slow blood flow in small vessels such as those associate in the kidney or tumour angiogenesis [12].…”