Label-free high-throughput photoacoustic tomography of suspected circulating melanoma tumor cells in patients in vivo.

SIGNIFICANCE: Detection and characterization of circulating tumor cells (CTCs), a key determinant of metastasis, are critical for determining risk of disease progression, understanding metastatic pathways, and facilitating early clinical intervention. AIM: We aim to demonstrate label-free imaging of suspected melanoma CTCs. APPROACH: We use a linear-array-based photoacoustic tomography system (LA-PAT) to detect melanoma CTCs, quantify their contrast-to-noise ratios (CNRs), and measure their flow velocities in most of the superficial veins in humans. RESULTS: With LA-PAT, we successfully imaged suspected melanoma CTCs in patients in vivo, with a CNR >9. CTCs were detected in 3 of 16 patients with stage III or IV melanoma. Among the three CTC-positive patients, two had disease progression; among the 13 CTC-negative patients, 4 showed disease progression. CONCLUSIONS: We suggest that LA-PAT can detect suspected melanoma CTCs in patients in vivo and has potential clinical applications for disease monitoring in melanoma.

Snapshot Photoacoustic Topography Through an Ergodic Relay for High-throughput Imaging of Optical Absorption.

Current embodiments of photoacoustic imaging require either serial detection with a single-element ultrasonic transducer or parallel detection with an ultrasonic array, necessitating a trade-off between cost and throughput. Here, we present photoacoustic topography through an ergodic relay (PATER) for low-cost high-throughput snapshot widefield imaging. Encoding spatial information with randomized temporal signatures through ergodicity, PATER requires only a single-element ultrasonic transducer to capture a widefield image with a single laser shot. We applied PATER to demonstrate both functional imaging of hemodynamic responses and high-speed imaging of blood pulse wave propagation in mice in vivo. Leveraging the high frame rate of 2 kHz, PATER tracked and localized moving melanoma tumor cells in the mouse brain in vivo, which enabled flow velocity quantification and super-resolution imaging. Among the potential biomedical applications of PATER, wearable monitoring of human vital signs in particular is envisaged.

Small near-infrared photochromic protein for photoacoustic multi-contrast imaging and detection of protein interactions in vivo.

Photoacoustic (PA) computed tomography (PACT) benefits from genetically encoded probes with photochromic behavior, which dramatically increase detection sensitivity and specificity through photoswitching and differential imaging. Starting with a DrBphP bacterial phytochrome, we have engineered a near-infrared photochromic probe, DrBphP-PCM, which is superior to the full-length RpBphP1 phytochrome previously used in differential PACT. DrBphP-PCM has a smaller size, better folding, and higher photoswitching contrast. We have imaged both DrBphP-PCM and RpBphP1 simultaneously on the basis of their unique signal decay characteristics, using a reversibly switchable single-impulse panoramic PACT (RS-SIP-PACT) with a single wavelength excitation. The simple structural organization of DrBphP-PCM allows engineering a bimolecular PA complementation reporter, a split version of DrBphP-PCM, termed DrSplit. DrSplit enables PA detection of protein-protein interactions in deep-seated mouse tumors and livers, achieving 125-µm spatial resolution and 530-cell sensitivity in vivo. The combination of RS-SIP-PACT with DrBphP-PCM and DrSplit holds great potential for noninvasive multi-contrast deep-tissue functional imaging.

High-throughput ultraviolet photoacoustic microscopy with multifocal excitation.

Ultraviolet photoacoustic microscopy (UV-PAM) is a promising intraoperative tool for surgical margin assessment (SMA), one that can provide label-free histology-like images with high resolution. In this study, using a microlens array and a one-dimensional (1-D) array ultrasonic transducer, we developed a high-throughput multifocal UV-PAM (MF-UV-PAM). Our new system achieved a 1.6 ± 0.2 µm lateral resolution and produced images 40 times faster than the previously developed point-by-point scanning UV-PAM. MF-UV-PAM provided a readily comprehensible photoacoustic image of a mouse brain slice with specific absorption contrast in ∼16 min, highlighting cell nuclei. Individual cell nuclei could be clearly resolved, showing its practical potential for intraoperative SMA.

Single-impulse Panoramic Photoacoustic Computed Tomography of Small-animal Whole-body Dynamics at High Spatiotemporal Resolution.

Imaging of small animals has played an indispensable role in preclinical research by providing high dimensional physiological, pathological, and phenotypic insights with clinical relevance. Yet pure optical imaging suffers from either shallow penetration (up to ~1-2 mm) or a poor depth-to-resolution ratio (~1/3), and non-optical techniques for whole-body imaging of small animals lack either spatiotemporal resolution or functional contrast. Here, we demonstrate that standalone single-impulse photoacoustic computed tomography (SIP-PACT) mitigates these limitations by combining high spatiotemporal resolution (125-µm in-plane resolution, 50 µs / frame data acquisition and 50-Hz frame rate), deep penetration (48-mm cross-sectional width in vivo), anatomical, dynamical and functional contrasts, and full-view fidelity. By using SIP-PACT, we imaged in vivo whole-body dynamics of small animals in real time and obtained clear sub-organ anatomical and functional details. We tracked unlabeled circulating melanoma cells and imaged the vasculature and functional connectivity of whole rat brains. SIP-PACT holds great potential for both pre-clinical imaging and clinical translation.

Plasma lipoprotein(a) levels are associated with the severity of coronaryheart disease in Han Chinese people.

BACKGROUND/AIM: The aim of this study was to investigate the association of lipoprotein(a) [Lp(a)] with the severity of coronary heart disease (CHD) in Han Chinese people. MATERIALS AND METHODS: Six hundred and seventy-nine patients with angiographically defined CHD were enrolled in this cross-sectional study. Fasting lipids were measured, and the severity of CHD was quantitatively assessed for each patient according to the number of stenotic coronary branches and the Gensini scoring system. RESULTS: The levels of Lp(a), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), and apolipoprotein (apo) B100 increased, while high-density lipoprotein cholesterol (HDL-C) and apoAI decreased significantly with the number of stenotic vessels. The levels of Lp(a) increased and HDL-C and apoAI decreased significantly with the Gensini scores. The logistic regression analyses showed that Lp(a) and HDL-C were independently associated with the number of stenotic coronary vessels after adjusting for age, weight, body mass index, sex, smoking, alcohol consumption, hypertension, diabetes, triglycerides, TC, LDL-C, VLDL-C, apoAI, and apoB100. However, only Lp(a) was independently associated with the Gensini scores after adjustment. CONCLUSION: Our data indicate that Lp(a) might be a useful marker in predicting the severity of coronary heart disease.

Lipoprotein ratios are better than conventional lipid parameters in predicting coronary heart disease in Chinese Han people.

BACKGROUND AND AIM: Dyslipidaemia is the main risk factor for coronary heart disease (CHD). Plasma lipid levels are conven-tionally used to predict coronary risk globally, but further studies are required to investigate whether the lipoprotein ratios are superior to conventional lipid parameters as predictors for CHD. METHODS: A hospital-based case-control study consisting of 738 CHD patients and 157 control subjects was conducted in a Chinese Han population. Demographic characteristics and plasma lipid or apolipoprotein data were collected. Univariate and multivariate logistic regression analyses were carried out to examine the relationship between the lipoprotein ratios and CHD risk. RESULTS: The CHD group had significantly higher age, non-high-density lipoprotein cholesterol (non-HDL-C), lipoprotein (a) [Lp(a)], triglyceride (TG)/HDL-C, total cholesterol (TC)/HDL-C, low-density lipoprotein cholesterol (LDL-C)/HDL-C, non-HDL-C/HDL-C, very low-density lipoprotein cholesterol (VLDL-C)/HDL-C, and apolipoprotein B100/apolipoprotein AI (apoB100/apoAI) than the control group (p < 0.05 for all). Moreover, the prevalence of male sex, smoking, and hypertension in the CHD group was significantly higher than in the control group. The results from univariate logistic regression analysis showed that the ratios of TC/HDL-C (OR 1.135, 95% CI 1.019-1.265), LDL-C/HDL-C (OR 1.216, 95% CI 1.033-1.431), non-HDL-C/HDL-C (OR 1.135, 95% CI 1.019-1.265), and apoB100/apoAI (OR 1.966, 95% CI 1.013-3.817) significantly increased the risk for CHD. By multivariate logistic regression analysis, the results were not materially altered and each of the four ratios was independently associated with CHD after adjustment for non-lipid coronary risk factors. ApoB100/apoAI showed the strongest association with CHD in both the univariate and multivariate logistic regression analyses. CONCLUSIONS: Our data indicate that the lipoprotein ratios are superior to conventional lipid parameters as predictors for CHD. Of the ratios, apoB100/apoAI is the best to predict CHD risk.

Handheld photoacoustic probe to detect both melanoma depth and volume at high speed in vivo.

We applied a linear-array-based photoacoustic probe to detect melanin-containing melanoma tumor depth and volume in nude mice in vivo. This system can image melanomas at five frames per second (fps), which is much faster than our previous handheld single transducer system (0.1 fps). We first theoretically show that, in addition to the higher frame rate, almost the entire boundary of the melanoma can be detected by the linear-array-based probe, while only the horizontal boundary could be detected by the previous system. Then we demonstrate the ability of this linear-array-based system in measuring both the depth and volume of melanoma through phantom, ex vivo, and in vivo experiments. The volume detection ability also enables us to accurately calculate the rate of growth of the tumor, which is an important parameter in quantifying the tumor activity. Our results show that this system can be used for clinical melanoma diagnosis and treatment in humans at the bedside. Linear-array-based PA images of melanoma acquired in vivo on day 3 (a) and day 6 (b).

Urogenital photoacoustic endoscope.

Photoacoustic (PA) endoscopy for human urogenital imaging has the potential to diagnose many important diseases, such as endometrial and prostate cancers. We have specifically developed a 12.7 mm diameter, rigid, side-scanning PA endoscopic probe for such applications. The key features of this endoscope are the streamlined structure for smooth cavity introduction and the proximal actuation mechanism for fast scanning. Here we describe the probe's composition and scanning mechanism and present in vivo experimental results suggesting its potential for comprehensive clinical applications.