Optoacoustic imaging


Optoacoustic imaging

Optoacoustic imaging (Photoacoustic Imaging) is an imaging technology based on the photoacoustic effect, and can be used for obtaining images of structures in turbid environments. The optoacoustic technique combines the accuracy of spectroscopy with the depth resolution of ultrasound.

Contents

Background

The oldest technical application of the photothermal effect is believed to be the photophone, a communication device invented by Bell (1880). Bell observed the emanation of audible sounds from a transparent tube containing material in suspension, when a modulated light source is focused on the tube. Modulation of the light impinging on an absorbing substance will produce a similar modulation in temperature via the photothermal effect.

Optoacoustic wave generation

When a short laser pulse irradiates an absorbing medium there is local absorption →local heating → local expansion. This local expansion leads to ultrasonic pressure waves that travel through the medium at the speed of sound, and can be recorded using high frequency pressure sensors (such as piezoelectric sensors or optical sensors). The slow speed of sound in tissue (~1500 m/s) in comparison to the speed of light allows for the time resolved detection of these pressure waves and the determination of depth from where these pressure waves originated. By using an array of sensors the temporal delay of these incoming pressure wavefronts can be combined into an ultrasound image.

Proposed applications

Although the technology is still in its infancy, optoacoustic imaging is being employed in the development of various devices. Such devices include breast cancer detection equipment, as well as equipment used for measuring blood oxygenation levels. In both cases, the change in the optical properties of blood in respect to oxygen saturation and the strong optical contrast between hemoglobin and surrounding tissue is utilized.

External links

See also



Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Medical imaging — This article is about imaging techniques and modalities for the human body. For imaging of animals in research, see Preclinical imaging. Medical imaging Diagnostics A CT scan image showing a ruptured abdominal aortic aneurysm …   Wikipedia

  • Biological imaging — may refer to any imaging technique used in biology.Typical examples include: * Bioluminescence imaging, a technique for studying laboratory animals using luminescent protein * Calcium imaging, determining the calcium status of a tissue using… …   Wikipedia

  • Near-field scanning optical microscope — Near field scanning optical microscopy (NSOM/SNOM) is a microscopic technique for nanostructure investigation that breaks the far field resolution limit by exploiting the properties of evanescent waves. This is done by placing the detector very… …   Wikipedia

  • Photoacoustic tomography — (PAT), or photoacoustic computed tomography (PACT), is a materials analysis technique based on the reconstruction of an internal photoacoustic source distribution from measurements acquired by scanning ultrasound detectors over a surface that… …   Wikipedia