| Popis: |
The interaction of ultrasound with diffusive optical waves holds the promise of improved resolution and depth of penetration for non-ionizing, non-invasive medical imaging. Light offers the ability to make spectroscopic measurements, which can monitor metabolism but, while it can propagate deeply into the body at near infrared wavelengths, it is so strongly scattered in most tissues that imaging is achieved only with measures such as time-resolved or frequency-domain techniques. On the other hand ultrasound has the ability to penetrate deeply with considerably less scattering. We have proposed a mechanism for imaging through the body by mixing diffusive optical waves with focussed ultrasound to produce new, so-called virtual diffusive sources. In the present work, we consider various mechanisms of interaction and report some results suggesting that the interaction in a laboratory phantom is predominantly the result of particle motion rather than variations in the index of refraction of the background medium. This result may be important in development of techniques to maximize the strengths of the virtual sources. |
