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Published January 2001 | Published
Journal Article Open

Scanning microwave-induced thermoacoustic tomography: Signal, resolution, and contrast


Scanning thermoacoustic tomography was explored in the microwave region of the electromagnetic spectrum. Short microwave pulses were used to induce acoustic waves by thermoelastic expansion in biological tissues. Cross sections of tissue samples were imaged by a linear scan of the samples while a focused ultrasonic transducer detected the time-resolved thermoacoustic signals. Based on the microwave-absorption properties of normal and cancerous breast tissues, the piezoelectric signals in response to the thermoacoustic contrast were investigated over a wide range of electromagnetic frequencies and depths of tumor locations. The axial resolution is related to the temporal profile of the microwave pulses and to the impulse response of the ultrasonic transducer. The lateral resolution is related to the numerical aperture of the ultrasonic transducer as well as to the frequency spectra of the piezoelectric signals in the time window corresponding to the axial resolution. Gain compensation, counteracting the microwave attenuation, was applied to enhance the image contrast.

Additional Information

© 2001 American Association of Physicists in Medicine. Received 12 July 2000; accepted for publication 25 October 2000. We thank Dr. K. Chang for a helpful discussion. This project was sponsored in part by National Institutes of Health Grants No. R29 CA68562, No. R01 CA71980, and No. R21 CA83760, National Science Foudation Grant No. BES-9734491, and Texas Higher Education Coordinating Board Grant No. ARP 000512-0123-1999.

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