Being somewhat new to the optics fields, I only recently learned about photoacoustic imaging and how it works. In short, light can provide great tissue contrast, but the scattering of photons means they do not travel in a straight line. This makes imaging that relies solely on photons limited to depths within the optical diffusion limit (roughly 1 mm in the skin). Conversely, ultrasound imaging can penetrate tissue more deeply, but has poor contrast and speckle artifacts. Thus, investigators such as Lihong Wang use an imaging method that optimizes the photoacoustic effect where pulsed laser light can generate a rapid rise in temperature deep within tissue, inducing emission of ultrasound waves from the subsequent thermoelastic expansion. This combination of optical and ultrasound technology gives new meaning to the term "multi-modality imaging" and has a variety of applications, including the ability to define the boundaries in skin cancer. Dr. Wang's plenary at BioMed 2012 on how photoacoustic tomography uses ultrasound to break through the optical diffusion limit will take place on Sunday, April 29th, from 8-9:30am in room Symphony I & II.
My third grade gifted students are looking for a way to make sure all pin bones have been removed from fish. Does this laser application have potential for solving their problem? They are currently looking into spectroscopy to identify calcium and magnesium which is found in fish bones.
ReplyDeleteHi Karen. Firstly, thank you for being a teacher and motivating your students to learn more about optics. You have an very important job and I hope you can instill an enthusiasm for science and math in your third graders.
ReplyDeleteJust so I understand, you and your students are trying to find a way to confirm that all the small pin bones have been removed from a fish, correct? While I am not an expert in photoacoustic tomography, I don't know if this would be the best technique. The photoacoustic effect relies on absorption of laser light (something I have not aware of with bones). I would think high frequency ultrasound would be a better approach to detect these small bones since the interface between soft tissue and hard bone would reflect many of the ultrasound waves. There are several very high frequency ultrasound systems that have high resolution that should produce a large signal if any bones do remain in the tissue. The only question would be the thickness of the fish, since the high frequency US will not be able to penetrate very deeply. I also don't know how practical this is cost wise, but it would be an interesting proof of concept experiment.
Hope this helps and best of luck with the science project for your students!
Thanks for the feedback, Craig. I guess we will have to stick with spectroscopy, although I'm not sure how deep the bone can be and still be protected.
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