Search

Implementation of a high-frequency ultrasound (HFUS) beamformer is computationally challenging because of its high sampling rate. This article introduces an efficient beamformer with sub-Nyquist sampling (or bandpass sampling) that is suitable for HFUS imaging. Our approach used channel radio frequency data sampled at bandpass sampling rate (i.e., 4/ $3\textbf {f}_{\textbf {c}}$) and postfiltering-based interpolation to reduce the computational complexity. A polyphase structure for interpolation was used to further reduce the computational burden while maintaining an adequate delay resolution ($\boldsymbol {\delta }$). The performance of the proposed beamformer (i.e., 4/ $3\textbf {f}_{\textbf {c}}$ sampling with sixfold interpolation, $\boldsymbol {\delta } = 8\textbf {f}_{\textbf {c}}$) was compared with that of the conventional method (i.e., $4\textbf {f}_{\textbf {c}}$ sampling with fourfold interpolation, $\boldsymbol {\delta }= 16\textbf {f}_{\textbf {c}}$). Ultrafast coherent compounding imaging was used in simulation, in vitro and in vivo imaging experiments. Axial/lateral resolution and contrast-to-noise ratio (CNR) values were measured for quantitative evaluation. The number of transmit pulse cycles was varied from 1 to 3 using two transducers with different fractional bandwidths (67% and 98%). In the simulation, the proposed and conventional methods showed the similar −6-dB axial beam widths (63.5 and $61.5~ \boldsymbol {\mu }\textbf {m}$ , respectively) from the two-cycle transmit pulse using the transducer with a bandwidth of 67%. In vitro and in vivo imaging experiments were performed using a Verasonics ultrasound research platform equipped with a high-frequency array transducer (20–46 MHz). The in vitro imaging results using a wire target showed consistent results with the simulation study (i.e., disparity $< 5~ \boldsymbol {\mu }\textbf {m}$ at −6-dB axial resolution). The in vivo feasibility study with a murine mouse model with breast cancer was also performed, and the proposed method yielded a similar image quality compared with the conventional method. From these studies, it was demonstrated that the proposed HFUS beamformer based on the bandpass sampling can substantially reduce the computational complexity while minimizing the loss of spatial resolution for HFUS imaging. [ABSTRACT FROM AUTHOR]

Ultrasound imaging using a matrix array allows real-time multi-planar volumetric imaging. To enhance image quality, the matrix array should provide fast volumetric ultrasound imaging with spatially consistent focusing in the lateral and elevational directions. However, because of the significantly increased data size, dealing with massive and continuous data acquisition is a significant challenge. We have designed an imaging acquisition sequence that handles volumetric data efficiently using a single 256-channel Verasonics ultrasound research platform multiplexed with a 1024-element matrix array. The developed sequence has been applied for building an ultrasonic pupilometer. Our results demonstrate the capability of the developed approach for structural visualization of an ex vivo porcine eye and the temporal response of the modeled eye pupil with moving iris at the volume rate of 30 Hz. Our study provides a fundamental ground for researchers to establish their own volumetric ultrasound imaging platform and could stimulate the development of new volumetric ultrasound approaches and applications. [ABSTRACT FROM AUTHOR]

Combined ultrasound and photoacoustic imaging systems are being developed for biomedical and clinical applications. One common probe configuration is to use a linear transducer array with external light delivery to produce coregistered ultrasound and photoacoustic images. The diagnostic capability of these systems is dependent on the effectiveness of light delivery to the imaging target. We use Monte Carlo modeling to investigate the optimal design geometry of an integrated probe. Simulations are conducted with multiple tissue compositions and wavelengths. The effect of a skin layer with the thickness of a mouse or a human is also considered. The model was validated using a tissue-mimicking gelatin phantom and corresponding Monte Carlo simulations. The optimal illumination angle is shallower with human skin thickness, whereas intermediate angles are ideal with mouse skin thickness. The effect of skin thickness explains differences in the results of prior work. The simulations also indicate that even with identical hardware and imaging parameters, light delivery will be up to 3 × smaller in humans than in mice, due to the increased scattering from thicker skin. Our findings have clear implications for the many researchers using mice to test and develop imaging methods for clinical translation. [ABSTRACT FROM AUTHOR]