Photoacoustic imaging is a promising method for visualizing biological tissues with optical absorbers. This article provides an overview of the rapidly developing field of photoacoustic imaging. Photoacoustics, the physical basis of photoacoustic imaging, is analyzed briefly. The merits of photoacoustic technology, compared with optical imaging and ultrasonic imaging, are described. Various imaging techniques are also discussed, including scanning tomography, computed tomography and original detection of photoacoustic imaging. Finally, some biomedical applications of photoacoustic imaging are summarized.

Photoacoustic imaging in biomedicine

This page shows some examples of multimedia files. It is also available at: http://www.ieee-uffc.org/tr/mexample.pdf. For submission of multimedia manuscripts to TUFFC, please follow “Information for Contributors” at: http://www.ieeeuffc.org/tr/contrib.pdf. Multimedia Example Created by Jian-yu Lu, Editor-in-Chief, 07/07/03 IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society 1. Color Figure: The IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (TUFFC) now accepts color figures online with corresponding grayscale figures in print without additional charges if authors follow the multimedia manuscript submission procedure in the “Information for Contributors”. The “color figures” icon below indicates in the print that a color version of the figure is available online. It also links to the color figure submitted originally by the authors for viewing details. Because of the sizes of color figures and the additional editorial work such as making two sets of PostScript files in which they remain identical after replacing grayscale with color, authors should request color figures online only when it is necessary. The color figure must be in JPEG (Joint Photographic Expert Group) or GIF (Graphics Interchange Format) format to reduce file size and to decrease the bandwidth usage on the TUFFC server. Fig. 1. An eight-layer printed circuit board (PCB) used primarily for multi-channel ultrasound signal reception and storage. The board was designed in the Ultrasound Lab at The University of Toledo, led by Dr. Jian-yu Lu. It is one of the many PCBs designed for a high-frame rate medical ultrasound imaging system [1], which consists of 128 linear, ±144V peak, 0.05-10MHz, and 12-bit arbitrary waveform generators for the production of ultrasound signals or for other research purposes. 2. Movies: Please click on the movie icon to see a movie. The two movies below give you an idea on the file size versus movie quality. “VCD quality” here means 1150kbits/s for video and 224kbits/s for 16-bit MP2 stereo audio at 44.1KHz sampling rate. Fig. 2. An introduction to the Ultrasound Lab at The University of Toledo. 3. Movies and Animations: Please click on the movie icons to see movies or animations. Fig. 3. Circuit design and construction of the imaging system. 4. Movies and Animation: Please click on the movie icons to see movies or animation. Movie [File size: 785KB; Format: MPEG1; Resolution: 320X240; Duration: 9 seconds]

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control

A finite element model of an ear stored on a computer readable medium having logic representing a three-dimensional geometric model of the ear; logic for meshing individual anatomical structures of the ear accounting for whether the anatomical structures include at least one of air, liquid material and solid material; logic for assigning material properties for each anatomical structure based on at least one physical property of each anatomical structure; logic for assigning boundary conditions for some of the anatomical structures indicative of interaction between such anatomical structures; and logic for employing acoustic-structural coupled analysis to the anatomical structures of the ear to generate data indicative of the acoustic effect on mechanical vibration transmission in the ear. Various embodiments of 'one-chamber' and 'two-chamber' analyses and models are described.

3-dimensional finite element modeling of human ear for sound transmission

Disclosed is a laser radar device having a wide two-dimensional field of view, a large receiving aperture, and responsivity to short pulse light. Specifically disclosed is a laser radar device provided with a laser light source which generates pulse laser light, a scanner which transmits a transmission pulse to a target while two-dimensionally scanning a pencil-shaped transmission beam and outputs scan angle information, a reception lens which receives reception light that has arrived, a long light-receiving element array which converts the reception light to reception signals and outputs the reception signals, a transimpedance amplifier array which amplifies the reception signals, an adder circuit which adds the reception signals from respective elements of the transimpedance amplifier array, a distance detection circuit which measures the light round-trip time to the target of an output signal from the adder circuit, and a signal processing unit which obtains the distances to multiple points on the target on the basis of the light round-trip time and the light speed by causing the scanner to perform a two-dimensional scan operation while associating the two-dimensional scan operation with the scan angle information to thereby measure the three-dimensional shape of the target.

Laser radar device

The estimation of material properties is important for scene understanding, with many applications in vision, robotics, and structural engineering. This paper connects fundamentals of vibration mechanics with computer vision techniques in order to infer material properties from small, often imperceptible motions in video. Objects tend to vibrate in a set of preferred modes. The frequencies of these modes depend on the structure and material properties of an object. We show that by extracting these frequencies from video of a vibrating object, we can often make inferences about that object's material properties. We demonstrate our approach by estimating material properties for a variety of objects by observing their motion in high-speed and regular frame rate video.

Visual Vibrometry: Estimating Material Properties from Small Motions in Video

Full noncontact laser ultrasound (LUS) imaging has several distinct advantages over current medical ultrasound (US) technologies: elimination of the coupling mediums (gel/water), operator-independent image quality, improved repeatability, and volumetric imaging. Current light-based ultrasound utilizing tissue-penetrating photoacoustics (PA) generally uses traditional piezoelectric transducers in contact with the imaged tissue or carries an optical fiber detector close to the imaging site. Unlike PA, the LUS design presented here minimizes the optical penetration and specifically restricts optical-to-acoustic energy transduction at the tissue surface, maximizing the generated acoustic source amplitude. With an appropriate optical design and interferometry, any exposed tissue surfaces can become viable acoustic sources and detectors. LUS operates analogously to conventional ultrasound but uses light instead of piezoelectric elements. Here, we present full noncontact LUS results, imaging targets at ~5 cm depths and at a meter-scale standoff from the target surface. Experimental results demonstrating volumetric imaging and the first LUS images on humans are presented, all at eye- and skin-safe optical exposure levels. The progression of LUS imaging from tissue-mimicking phantoms, to excised animal tissue, to humans in vivo is shown, with validation from conventional ultrasound images. The LUS system design insights and results presented here inspire further LUS development and are a significant step toward the clinical implementation of LUS. A technology that delivers ultrasound images of living tissue without directly touching the target has undergone successful human testing for the first time. The need to contact a patient’s skin with conventional sound-sensitive piezoelectric devices can cause errors in ultrasound imaging when operators apply different amounts of pressure. Xiang Zhang and Brian Anthony from the Massachusetts Institute of Technology, in Cambridge, United States, and colleagues have designed a system that overcomes these limitations by using lasers to create and listen to ultrasound. The new method uses pulsed light to excite a thin upper portion of skin, producing acoustic waves that penetrates deeply into tissue. The ultrasound that scatters back to the surface is then detected with a laser interferometer. Noncontact imaging of 3D objects, animal tissue, and human volunteers detected features comparable to conventional ultrasound.

/pdf/full-noncontact-laser-ultrasound-first-human-data-2c1pdnk31i.pdf

Full noncontact laser ultrasound: first human data.

Sonic excitation is used to locate, without contact, an object or defect beneath a surface. Defects may include, for example, damage and flaws in load bearing concrete structures wrapped in plastic, fiberglass or composite sheathing, while buried objects amenable to detection include landmines or above-ground mines.

Acoustic detection of hidden objects and material discontinuities

■ The worldwide proliferation of land mines leads to thousands of civilian casualties each year and threatens military forces who patrol hostile territories. To reduce these casualties, military and humanitarian organizations seek methods to detect the large variety of mines being deployed. Many mine detection systems currently under development can detect only metal or a specific mine feature, have limited standoff range, or are impractical for field operations. A promising approach uses acoustic waves to induce mechanical vibrations in both plastic and metal mines. The vibration field above these mines can then be measured remotely with a laser Doppler vibrometer. This article describes a method to advance acoustic land-mine detection by increasing standoff range from the minefield and by developing a more practical lightweight system. We take a novel approach to excite mines by using a parametric acoustic array (PAA) source to transmit a highly directive sound beam from a safe distance. We discuss the standoff system concept, the process of PAA wave generation, and the coupling of acoustic waves to the ground to excite mines. A proof-of-concept system, built at Lincoln Laboratory, deploys a commercial PAA and a commercial laser vibrometer. We tested the system at a land-mine facility and measured distinct vibration signatures from buried anti-personnel mines. The overall concept shows promise. The PAA tested in these experiments, however, was developed for home entertainment and has marginal power for land-mine detection, even at close range. A system suitable for standoff detection requires more acoustic power and substantial modification. We estimate that power gains up to 50 dB may be achievable, and we discuss alternatives to the commercial PAA design.

Standoff Acoustic Laser Technique to Locate Buried Land Mines

We investigated the fundamental limits to the performance of a laser vibrometer that is mounted on a moving ground vehicle. The noise floor of a moving laser vibrometer consists of speckle noise, shot noise, and platform vibrations. We showed that speckle noise can be reduced by increasing the laser spot size and that the noise floor is dominated by shot noise at high frequencies (typically greater than a few kilohertz for our system). We built a five-channel, vehicle-mounted, 1.55 μm wavelength laser vibrometer to measure its noise floor at 10 m horizontal range while driving on dirt roads. The measured noise floor agreed with our theoretical estimates. We showed that, by subtracting the response of an accelerometer and an optical reference channel, we could reduce the excess noise (in units of micrometers per second per Hz1/2) from vehicle vibrations by a factor of up to 33, to obtain nearly speckle-and-shot-noise-limited performance from 0.3 to 47 kHz.

/pdf/laser-vibrometry-from-a-moving-ground-vehicle-3rgsi1bbz0.pdf

Laser vibrometry from a moving ground vehicle

Acoustic-laser vibrometry, a non-contact method for nondestructive testing, was studied by altering operational and defect parameters to determine their effects on measured signatures and system performance. The method detects delamination and voids in fiber-reinforced polymer reinforced concrete by vibrating the material with an acoustic excitation and measuring the vibration signature with a laser vibrometer. The operational parameters studied were excitation sound pressure level, laser signal, angle of incidence, and dwell time. The defect parameters studied were aspect ratio, size, and curvature. This study was undertaken to understand the method׳s phenomenology and to provide fundamental knowledge for an operational field system.

http://people.csail.mit.edu/ju21743/docs/chen_NDTE_2015.pdf

Robert W. Haupt

Papers

Full noncontact laser ultrasound: first human data.

Acoustic detection of hidden objects and material discontinuities

Standoff Acoustic Laser Technique to Locate Buried Land Mines

Laser vibrometry from a moving ground vehicle

Operational and defect parameters concerning the acoustic-laser vibrometry method for FRP-reinforced concrete