Real-time delay-multiply-and-sum beamforming with coherence factor for in vivo clinical photoacoustic imaging of humans

Abstract

In the clinical photoacoustic (PA) imaging, ultrasound (US) array transducers are typically used to provide B-mode images in real-time. To form a B-mode image, delay-and-sum (DAS) beamforming algorithm is the most commonly used algorithm because of its ease of implementation. However, this algorithm suffers from low image resolution and low contrast drawbacks. To address this issue, delay-multiply-and-sum (DMAS) beamforming algorithm has been developed to provide enhanced image quality with higher contrast, and narrower main lobe compared but has limitations on the imaging speed for clinical applications. In this paper, we present an enhanced real-time DMAS algorithm with modified coherence factor (CF) for clinical PA imaging of humans in vivo . Our algorithm improves the lateral resolution and signal-to-noise ratio (SNR) of original DMAS beamformer by suppressing the background noise and side lobes using the coherence of received signals. We optimized the computations of the proposed DMAS with CF (DMAS-CF) to achieve real-time frame rate imaging on a graphics processing unit (GPU). To evaluate the proposed algorithm, we implemented DAS and DMAS with/without CF on a clinical US/PA imaging system and quantitatively assessed their processing speed and image quality. The processing time to reconstruct one B-mode image using DAS, DAS with CF (DAS-CF), DMAS, and DMAS-CF algorithms was 7.5, 7.6, 11.1, and 11.3 ms, respectively, all achieving the real-time imaging frame rate. In terms of the image quality, the proposed DMAS-CF algorithm improved the lateral resolution and SNR by 55.4% and 93.6 dB, respectively, compared to the DAS algorithm in the phantom imaging experiments. We believe the proposed DMAS-CF algorithm and its real-time implementation contributes significantly to the improvement of imaging quality of clinical US/PA imaging system.

Two-Dimensional Spatial Coherence for Ultrasonic DMAS Beamforming in Multi-Angle Plane-Wave Imaging

“…Consequently, the side-lobe clutter and ghost artifact can be suppressed in the beamforming output due to their lower coherence relative to the main-lobe signal. DMAS beamforming in combination with adaptive weighting has been adopted not only in medical ultrasound but also in photoacoustic imaging [19]. Note that, though the original form of DMAS beamforming is computationally demanding due to the multiplication between every possible channel pair, a low computational cost formulation has been exploited and implemented in real time on a research scanner [20].…”

GPU implementation of photoacoustic short-lag spatial coherence imaging for improved image-guided interventions

“…For example, real-time, 4-cm-deep DAS, delay-multiply-and-sum (DMAS), DAS + CF, or DMAS + CF imaging was achieved with processing times of 7.5, 7.6, 11.1, or 11.3 ms, respectively (with the exclusion of memory transfer times between the GPU and CPU). 43 A variation of DMAS, namely the multiple DAS with enveloping beamformer, was implemented on a Quadro P5000 GPU to reconstruct images in 41.62 ms. 74 Another version of DMAS, proposed by Miri Rostami et al., 75 reported a 12-ms processing time for images of size . The reported GPU-SLSC frame rate is better than that achieved with these beamformers and with a parallel backprojection algorithm reporting 17-Hz frame rates when reconstructing duplex images.…”

“…40 However, these techniques require a combination of delay sequences for each pixel in the reconstructed image, 41 which increases computational burden. Additional beamforming alternatives include coherence factor (CF) weighting 42 or a combination of beamforming methods (e.g., DAS + CF, 43 SAF + CF, 44 and MV + CF 37 ), and these options suffer from challenges similar to those stated above.…”

Versatile Single-Element Ultrasound Imaging Platform using a Water-Proofed MEMS Scanner for Animals and Humans

“…Thus, unlike mechanical sector scanning, the mirror scanning does not highly depend on the physical dimensions and weight of the single-element transducer. To steer the acoustic path, we employed a water-proofed microelectromechanical system (MEMS), a design which has been recently employed in photoacoustic microscopy and optical coherent tomography [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] . Some studies have been performed US imaging on phantoms in vitro, but not in vivo 25,26 .…”