Near-infrared optical-resolution photoacoustic microscopy

et al. 2016

J. Biomed. Opt

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Abstract. Grueneisen relaxation photoacoustic microscopy (GR-PAM) can achieve optically defined axial resolution, but it has been limited to ex vivo demonstrations so far. Here, we present the first in vivo image of a mouse brain acquired with GR-PAM. To induce the GR effect, an intensity-modulated continuous-wave laser was employed to heat absorbing objects. In phantom experiments, an axial resolution of 12.5 μm was achieved, which is sixfold better than the value achieved by conventional optical-resolution PAM. This axial-resolution improvement was further demonstrated by imaging a mouse brain in vivo, where significantly narrower axial profiles of blood vessels were observed. The in vivo demonstration of GR-PAM shows the potential of this modality for label-free and high-resolution anatomical and functional imaging of biological tissues.

Section: Resultsmentioning

confidence: 99%

Grueneisen relaxation photoacoustic microscopyin vivo

Shi

et al. 2016

J. Biomed. Opt

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“…PAT has been demonstrated capable of providing structural, functional, and metabolic information [12][13][14][15][16] . PAT has also successfully measured the elastic properties of biological tissue, including strain 5 , the viscosity-elasticity ratio 17 , and vascular compliance 18 .…”

Section: Introductionmentioning

confidence: 99%

Quantitative photoacoustic elastography of Young’s modulus in humans

Photons Plus Ultrasound: Imaging and Sensing 2017

Zhou

Gong

et al. 2017

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Elastography can noninvasively map the elasticity distribution of biological tissue, which is often altered in pathological states. In this work, we report quantitative photoacoustic elastography (QPAE), capable of measuring Young's modulus of human tissue in vivo. By combining photoacoustic elastography with a stress sensor having known stress-strain behavior, QPAE can simultaneously measure strain and stress, from which Young's modulus is calculated. We first applied QPAE to quantify the Young's modulus of tissue-mimicking agar phantoms with different concentrations. The measured values fitted well with both the empirical expectations based on the agar concentrations and those measured in independent standard compression tests. We then demonstrated the feasibility of QPAE by measuring the Young's modulus of human skeletal muscle in vivo. The data showed a linear relationship between muscle stiffness and loading. The results proved that QPAE can noninvasively quantify the absolute elasticity of biological tissue, thus enabling longitudinal imaging of tissue elasticity. QPAE can be exploited for both preclinical biomechanics studies and clinical applications.

“…By integrating optical excitation with acoustic detection, photoacoustic tomography (PAT) combines rich optical absorption contrasts with high ultrasonic spatial resolution at depths 12 . With 100% relative sensitivity to optical absorption, i.e., a given percentage change in the optical absorption yields the same percentage change in the photoacoustic signal, PAT achieves structural, functional, metabolic, and mechanical imaging of biological tissue [13][14][15][16][17] . Taking advantage of the strong optical absorption of melanin, photoacoustic techniques have been successfully used for imaging and sensing melanoma CTCs.…”

Section: Introductionmentioning

confidence: 99%

Linear-array-based photoacoustic tomography for label-free high-throughput detection and quantification of circulating melanoma tumor cell clusters

Photons Plus Ultrasound: Imaging and Sensing 2017

Zhou

Zhang

et al. 2017

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Circulating tumor cell (CTC) clusters arise from multicellular grouping in the primary tumor and elevate the metastatic potential by 23 to 50 fold compared to single CTCs. High throughout detection and quantification of CTC clusters is critical for understanding the tumor metastasis process and improving cancer therapy. In this work, we report a lineararray-based photoacoustic tomography (LA-PAT) system capable of label-free high-throughput CTC cluster detection and quantification in vivo. LA-PAT detects CTC clusters and quantifies the number of cells in them based on the contrast-to-noise ratios (CNRs) of photoacoustic signals. The feasibility of LA-PAT was first demonstrated by imaging CTC clusters ex vivo. LA-PAT detected CTC clusters in the blood-filled microtubes and computed the number of cells in the clusters. The size distribution of the CTC clusters measured by LA-PAT agreed well with that obtained by optical microscopy. We demonstrated the ability of LA-PAT to detect and quantify CTC clusters in vivo by imaging injected CTC clusters in rat tail veins. LA-PAT detected CTC clusters immediately after injection as well as when they were circulating in the rat bloodstreams. Similarly, the numbers of cells in the clusters were computed based on the CNRs of the photoacoustic signals. The data showed that larger CTC clusters disappear faster than the smaller ones. The results prove the potential of LA-PAT as a promising tool for both preclinical tumor metastasis studies and clinical cancer therapy evaluation.