Feasibility of noncontact piezoelectric detection of photoacoustic signals in tissue-mimicking phantoms.

The feasibility of air-coupled ultrasound transducers to detect laser-induced ultrasound from artificial blood vessels embedded in an optically scattering phantom is demonstrated. These air-coupled transducers allow new applications in biomedical photoacoustic imaging where contact with tissue is not preferred. One promising application of such transducers is the addition of photoacoustic imaging to the regular x-ray mammographic screening procedure.

Imaging of tumor vasculature using Twente photoacoustic systems.

Photoacoustic imaging is a hybrid imaging modality based on the detection of acoustic waves generated by the absorption of short laser pulses in biological tissue. It combines the advantages of excellent contrast achieved in optical techniques with the high resolution of ultrasound imaging. In this article we present a review of the work done at the University of Twente to image tumor angiogenesis in vivo using this technique.

Real-time in vivo photoacoustic and ultrasound imaging.

A real-time photoacoustic imaging system is designed and built. This system is based on a commercially available ultrasound imaging system. It can achieve a frame rate of 8 frames/sec.

Photoacoustic imaging of port-wine stains.

Background And Objective: To optimize laser therapy of port-wine stains (PWSs), information about the vasculature as well as lesion depth is valuable. In this study we investigated the use of photoacoustic imaging (PAI) to obtain this information.

Study Design/materials And Methods: PAI uses pulsed light to generate ultrasound upon absorption of short light pulses by blood.

Photoacoustic imaging of valves in superficial veins.

Background And Objectives: In intravenous access to veins there is a risk of puncturing venous valves or blocking of the catheter by the valves. Therefore, we have investigated whether and how photoacoustic imaging (PAI), which visualizes the lumen of blood vessels, can be used to detect these valves.

Study Design/materials And Methods: Venous valves in superficial veins on the dorsal side of the hand of human volunteers were located by palpation and visual inspection.

In vivo photoacoustic imaging of blood vessels with a pulsed laser diode.

Photoacoustic imaging is a hybrid imaging modality that is based on the detection of acoustic waves generated by absorption of pulsed light by tissue chromophores such as hemoglobin in blood. For this technique, usually large and costly Q-switched Nd:YAG lasers are used. These lasers provide a pulse energy of at least several milliJoules.

Imaging of small vessels using photoacoustics: an in vivo study.

Background And Objectives: The ability to correctly visualize the architectural arrangement of microvasculature is valuable to many diverse fields in medicine. In this study, we applied photoacoustics (PA) to obtain high-resolution images of submillimeter blood vessels.

Study Design/materials And Methods: Short laser pulses are used to generate ultrasound from superficial blood vessels in several animal models.

Photoacoustic imaging of blood vessels with a double-ring sensor featuring a narrow angular aperture.

A photoacoustic double-ring sensor, featuring a narrow angular aperture, is developed for laser-induced photoacoustic imaging of blood vessels. An integrated optical fiber enables reflection-mode detection of ultrasonic waves. By using the cross-correlation between the signals detected by the two rings, the angular aperture of the sensor is reduced by a factor of 1.

Photoacoustic determination of blood vessel diameter.

A double-ring sensor was applied in photoacoustic tomographic imaging of artificial blood vessels as well as blood vessels in a rabbit ear. The peak-to-peak time (tau(pp)) of the laser (1064 nm) induced pressure transient was used to estimate the axial vessel diameter. Comparison with the actual vessel diameter showed that the diameter could be approximated by 2ctau(pp), with c the speed of sound in blood.

Poly(vinyl alcohol) gels for use as tissue phantoms in photoacoustic mammography.

Materials for solid photoacoustic breast phantoms, based on poly(vinyl alcohol) hydrogels, are presented. Phantoms intended for use in photoacoustics must possess both optical and acoustic properties of tissue. To realize the optical properties of tissue, one approach was to optimize the number of freezing and thawing cycles of aqueous poly(vinyl alcohol) solutions, a procedure which increases the turbidity of the gel while rigidifying it.