Optoacoustic imaging with synthetic aperture focusing and coherence weighting

Liao, Chao-Kang; Li, M L; Li, P C

doi:10.1364/ol.29.002506

Cited by 120 publications

(88 citation statements)

References 10 publications

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“…Liao et al presented the idea of using a synthetic-aperture focusing technique (SAFT) to improve the resolution and the signal-to-noise ratio (SNR) in photoacoustic imaging, in which a point detector (e.g., a needle hydrophone) is required. 9 Here, we investigate a virtual-point-detector-based SAFT combined with coherence weighting to extend the depth of focus. The virtual-point-detector concept enables the SAFT to be applied to a large-NA transducer.…”

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confidence: 99%

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Improved in vivo photoacoustic microscopy based on a virtual-detector concept

et al. 2006

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(Doc. ID 63562) Recently an in vivo high-resolution backward-mode photoacoustic microscope was developed that shows potential for applications in dermatology and related cancer research. However, the limited depth of focus of the large-numerical-aperture (NA) ultrasonic lens employed in this system causes the image quality to deteriorate significantly in the out-of-focus region. To solve this problem, we devised and explored, for the first time to our knowledge, a virtual-detector-based synthetic-aperture focusing technique, combined with coherence weighting, for photoacoustic microscopy with such a large-NA transducer. Images of phantoms show that the proposed technique improves the −6 dB lateral resolution from 49-379 to 46-53 m and increases the signal-to-noise ratio by up to 29 dB, depending on the distance from the ultrasonic focal point. In vivo experiments show that the technique also provides a clearer representation of the vascular distribution in the rat's scalp.

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“…9 The idea of CF weighting is illustrated in Fig. 1(b), where the vertical axis is the depth and the horizontal axis denotes the lateral position.…”

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Improved in vivo photoacoustic microscopy based on a virtual-detector concept

et al. 2006

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“…When the near-IR window ͑700 to 800 nm͒ is used for deep penetration, the photoacoustic signal from the microvasculature is compromised and typically requires averaging to enhance the SNR and contrast. 21 Current strategies, such as the synthetic aperture focusing technique 77,132 ͑SAFT͒, the virtual point detection mechanism, 133,134 the adaptive beam forming method, 135 and the exogenous vascular contrast agent [136][137][138] have made remarkable progress. However, further exploration is required to escape from this dilemma.…”

Section: Snr and Contrast Enhancementmentioning

confidence: 99%

Photoacoustic imaging and characterization of the microvasculature

2010

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Abstract. Photoacoustic ͑optoacoustic͒ tomography, combining optical absorption contrast and highly scalable spatial resolution ͑from micrometer optical resolution to millimeter acoustic resolution͒, has broken through the fundamental penetration limit of optical ballistic imaging modalities-including confocal microscopy, two-photon microscopy, and optical coherence tomography-and has achieved high spatial resolution at depths down to the diffusive regime. Optical absorption contrast is highly desirable for microvascular imaging and characterization because of the presence of endogenous strongly light-absorbing hemoglobin. We focus on the current state of microvascular imaging and characterization based on photoacoustics. We first review the three major embodiments of photoacoustic tomography: microscopy, computed tomography, and endoscopy. We then discuss the methods used to characterize important functional parameters, such as total hemoglobin concentration, hemoglobin oxygen saturation, and blood flow. Next, we highlight a few representative applications in microvascular-related physiological and pathophysiological research, including hemodynamic monitoring, chronic imaging, tumor-vascular interaction, and neurovascular coupling. Finally, several potential technical advances toward clinical applications are suggested, and a few technical challenges in contrast enhancement and fluence compensation are summarized.

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“…In order to construct a PA image, it is necessary to receive signals from different locations through scanning. While various scanning strategies are considered, the ultrasound array transducer can be regarded as the most accessible receiver because it is widely used in the clinic for ultrasound imaging [2][3][4]. In addition, receiving PA signals from the same ultrasound imaging array simplifies fusion of PA and ultrasound images [5].…”

Section: Introductionmentioning

confidence: 99%

Synthetic-aperture based photoacoustic re-beamforming (SPARE) approach using beamformed ultrasound data

Zhang

Bell

Guo

et al. 2016

Biomed. Opt. Express

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Photoacoustic (PA) imaging has been developed for various clinical and preclinical applications, and acquiring pre-beamformed channel data is necessary to reconstruct these images. However, accessing these pre-beamformed channel data requires custom hardware to enable parallel beamforming, and is available for a limited number of research ultrasound platforms. To broaden the impact of clinical PA imaging, our goal is to devise a new PA reconstruction approach that uses ultrasound post-beamformed radio frequency (RF) data rather than raw channel data, because this type of data is readily available in both clinical and research ultrasound systems. In our proposed Synthetic-aperture based photoacoustic rebeamforming (SPARE) approach, post-beamformed RF data from a clinical ultrasound scanner are considered as input data for an adaptive synthetic aperture beamforming algorithm. When receive focusing is applied prior to obtaining these data, the focal point is considered as a virtual element, and synthetic aperture beamforming is implemented assuming that the photoacoustic signals are received at the virtual element. The resolution and SNR obtained with the proposed method were compared to that obtained with conventional delayand-sum beamforming with 99.87% and 91.56% agreement, respectively. In addition, we experimentally demonstrated feasibility with a pulsed laser diode setup. Results indicate that the post-beamformed RF data from any commercially available ultrasound platform can potentially be used to create PA images.

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Optoacoustic imaging with synthetic aperture focusing and coherence weighting

Cited by 120 publications

References 10 publications

Improved in vivo photoacoustic microscopy based on a virtual-detector concept

Improved in vivo photoacoustic microscopy based on a virtual-detector concept

Photoacoustic imaging and characterization of the microvasculature

Synthetic-aperture based photoacoustic re-beamforming (SPARE) approach using beamformed ultrasound data

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