Multifocal optical-resolution photoacoustic microscopy in vivo

Optical Imaging Laboratory, Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
Optics Letters (Impact Factor: 3.29). 04/2011; 36(7):1236-8. DOI: 10.1364/OL.36.001236
Source: PubMed


Although ultrasound arrays have been exploited in photoacoustic imaging to improve imaging speed, ultrasound-array-based optical-resolution photoacoustic microscopy (OR-PAM) has never been achieved previously to our knowledge. Here we present our development of multifocal OR-PAM using a microlens array for optical illumination and an ultrasound array for photoacoustic detection. Our system is capable of imaging hemoglobin concentration and oxygenation in individual microvessels in vivo at high speed. Compared with a single focus, multiple foci reduce the scanning load and increase the imaging speed significantly. The current multifocal system can acquire 1000 × 500 × 200 voxels at ~10 μm lateral resolution within 4 min.

Download full-text


Available from: Konstantin Maslov,
  • Source
    • "The final output laser energy from the catheter tip was maintained to be ∼500 nJ/pulse. Following the widely used method to estimate the surface laser fluence in optical-resolution photoacoustic imaging [12], [14], we assume the laser was focused at ∼1 mm below the tissue surface; this energy corresponds to an optical fluence of only ∼7 mJ/cm2 per pulse at the tissue surface, below the 20-mJ/cm2 ANSI safety limit for skin surface at this wavelength. A custom-made electric slip ring, which also includes a stationary and a rotary part, was assembled co-axially with the fiber optic rotary joint to form an optical-electric rotary joint (Fig. 1(b)) that can rotate as fast as 1800 revolutions per minute (RPM). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Photoacoustic imaging is an emerging technology that can provide anatomic, functional, and molecular information about biological tissue. Intravascular spectroscopic and molecular photoacoustic imaging can potentially improve the identification of atherosclerotic plaque composition, the detection of inflammation, and ultimately the risk stratification of atherosclerosis. In this study, a first-of-its-kind intravascular optical-resolution photoacoustic tomography (OR-PAT) system with a 1.1 mm diameter catheter is developed, offering optical-diffraction limited transverse resolution as fine as 19.6 μm, ∼10-fold finer than that of conventional intravascular photoacoustic and ultrasonic imaging. To offer complementary imaging information and depth, the system also acquires co-registered intravascular ultrasound images in parallel. Imaging of an iliac stent and a lipid phantom shows that the high resolution and contrast of OR-PAT can enable improved stent implantation guidance and lipid identification. In the future, these capabilities may ultimately improve the diagnosis and interventional treatment of vulnerable atherosclerotic plaques, which are prone to cause thrombotic complications such as myocardial infarction and stroke.
    PLoS ONE 03/2014; 9(3):e92463. DOI:10.1371/journal.pone.0092463 · 3.23 Impact Factor
  • Source
    • "By performing beamforming the desired signals will be enhanced and the noise will be suppressed simultaneously, thereby the SNR will be improved. Ultrasonic array transducer has been successfully used in mechanical scanning PAM system with multifocal optical illumination to improve the imaging speed significantly [11]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we report our latest progress on proving the concept that ultrasonic phased array can improve the detection sensitivity and field of view (FOV) in laser-scanning photoacoustic microscopy (LS-PAM). A LS-PAM system with a one-dimensional (1D) ultrasonic phased array was built for the experiments. The 1D phased array transducer consists of 64 active elements with an overall active dimension of 3.2 mm × 2 mm. The system was tested on imaging phantom and mouse ear in vivo. Experiments showed a 15 dB increase of the signal-to-noise ratio (SNR) when beamforming was employed compared to the images acquired with each single element. The experimental results demonstrated that ultrasonic phased array can be a better candidate for LS-PAM in high sensitivity applications like ophthalmic imaging.
    Biomedical Optics Express 11/2012; 3(11):2694-9. DOI:10.1364/BOE.3.002694 · 3.65 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Optical-resolution photoacoustic microscopy (OR-PAM) is capable of achieving optical-absorption-contrast images with micron-scale spatial resolution. Previous OR-PAM systems have been frame-rate limited by mechanical scanning speeds and laser pulse repetition rate (PRR). We demonstrate OR-PAM imaging using a diode-pumped nanosecond-pulsed Ytterbium-doped 532-nm fiber laser with PRR up to 600 kHz. Combined with fast-scanning mirrors, our proposed system provides C-scan and 3D images with acquisition frame rate of 4 frames per second (fps) or higher, two orders of magnitude faster than previously published systems. High-contrast images of capillary-scale microvasculature in a live Swiss Webster mouse ear with ~6-µm optical lateral spatial resolution are demonstrated.
    Optics Express 08/2011; 19(18):17143-50. DOI:10.1364/OE.19.017143 · 3.49 Impact Factor
Show more