Photoacoustics is the imaging of ultrasound backscatter originating from a laser's flash into tissue where chromophores (usually haemaglobin, melanin or customized nano-particles) absorb the light energy, and thus heat up during the laser pulse (~5 nano seconds, <0.1 degree centigrade), expand and create an acoustic wave which can be detected by a standard piezoelectric transducer.
Our system uses the location of the elements in the transducer to estimate the origin of the wave and thus forms a two dimensional map or image of the chromophores. The frequency of the photoacoustic wave is determined by the transit time of sound across the vessel or size of the vessel.
Tissue is relatively transparent in the infra red (700 to 969 nanometers) so the laser's light can be mapped over several centimeters , for example, in blood vessels where the acoustic waves are generated.
As the vessel expands, a pressure wave is generated on the side closest to the transducer, and a rarefaction wave is generated from the far side of the vessel, so the frequencies are dependent on vessel sizes. Thus the bandwidth of the transducer determines what size vessels can be imaged so a wide bandwidth single crystal transducer is optimal.
A 10 to 30 millijoule laser pulse is optimal for imaging and this can be generated by a NdYag laser with an OPO wavelength converter. This type of laser can usually only fire 10 to 20 times a second leaving time for the UltraVision to generate several regular ultrasound images of the same tissue and fuse the ultrasound and photo acoustic images for identification of the morphology.
Nano-particals can be attached to antibodies and once injected they can be captured at the specific disease location and then imaged by photoacoustic methods.
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WinProbe Corporation is an accredited ISO13485:2003 / ISO 9001: 2008 manufacturer