Optical Imaging  

Thermoacoustic Tomography

Radiofrequency-induced thermoacoustic tomography has been explored to image biological tissue. Short radiofrequency pulses irradiate tissue to generate acoustic waves by thermoelastic expansion. The radiofrequency-induced thermoacoustic waves are detected with a focused ultrasonic transducer. The time-domain signal from the ultrasonic transducer represents a one-dimensional image along the acoustic axis of the ultrasonic transducer, similar to an ultrasonic A-scan. Scanning the system perpendicularly to the acoustic axis of the ultrasonic transducer generates multi-dimensional images. Ultrasonic arrays can be used for high-speed imaging (see PAT section).

This imaging technique furnishes a new contrast mechanism. It is capable of providing deep penetration (several centimeters) into biological tissues with finer than mm spatial resolution. Because cancer tissue and normal tissue exhibit different responses to radiofrequency signals, this technique has great potential in early breast cancer diagnosis.

Selected publications:

  • Pramanik, M.; Swierczewska, M.; Green, D.; Sitharaman, B.; Wang, L. V.; "Single-walled carbon nanotubes as a multimodal—thermoacoustic and photoacoustic—contrast agent," Journal of Biomedical Optics 14(3) 034018 (2009) [PDF]

  • Pramanik, M.; Ku, G.; Li, C. H.; Wang, L. V.; "Design and evaluation of a novel breast cancer detection system combining both thermoacoustic (TA) and photoacoustic (PA) tomography," Medical Physics 35(6) 2218-2223 (2008) [PDF]

  • Ku, G.; Fornage, B. D.; Jin, X.; Xu, M. H.; Hunt, K. K.; Wang, L. V.; "Thermoacoustic and photoacoustic tomography of thick biological tissues toward breast imaging," Technology in Cancer Research & Treatment 4(5) 559-565 (2005) [PDF]

  • Xu, M. H.; Wang, L. V.; "Universal back-projection algorithm for photoacoustic computed tomography," Physical Review E 71(1) 016706-(1-7) (2005) [PDF]

  • Xu, Y.; Wang, L. V.; Ambartsoumian, G.; Kuchment, P.; "Reconstructions in limited-view thermoacoustic tomography," Medical Physics 31(4) 724-733 (2004) [PDF]

  • Xu, M. H.; Wang, L. V.; "Analytic explanation of spatial resolution related to bandwidth and detector aperture size in thermoacoustic or photoacoustic reconstruction," Physical Review E 67(5) 056605 (2003) [PDF]

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