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Photoacoustic Imaging

When a laser beam is shined into tissue, the absorption of light causes a thermal expansion of the surrounding tissue, which in turn generates a shock wave. This phenomenon is known as the photoacoustic effect. The resulting shock waves can be measured with an ultrasound probe, allowing insights into the tissue composition. Due to their high absorption coefficient, hemoglobin and melanin distributions are popular targets for this imaging modality. Facilitated by differences in absorption spectra between the oxygenated and deoxygenated states of hemoglobin, blood oxygenation detection is one of the most popular applications of photoacoustic imaging.

There are two major imaging methods making use of the photoacoustic effect. In photoacoustic computed tomography, an unfocused detector is used and the image must be reconstructed by inversely solving photoacoustic equations. In photoacoustic tomography, a focused ultrasound detector is used which uses point-by-point rasterization.

Resources used

Wikipedia on Photoacoustic Imaging

Visual Sonics: What is Photoacoustic Imaging?


Publications

A review of clinical photoacoustic imaging: Current and future trends

Attia A, Balasundaram G, Moothanchery M, Dinish U, Bi R, Ntziachristos V, Olivo M - Photoacoustics - 2019


Photoacoustic Imaging

Zhang Y, Hong H, Cai W - Cold Spring Harbor Protocols - 2011


Biomedical photoacoustic imaging

Beard P - Interface Focus - 2011


Photoacoustic imaging and characterization of the microvasculature

Hu S, Wang L - Journal of Biomedical Optics - 2010


DATA OUTPUT
image
MEASURED QUANTITY
ultrasound generated by photoacoustic effect

Photoacoustic Imaging Image

Helmholtz Imaging spinning wheel

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