Signal processing in scanning thermoacoustic tomography in biological tissues

Microwave-induced thermoacoustic tomography was explored to image biologica l tissues. Short microwave pulses irradiated tissues to generate acoustic w aves by thermoelastic expansion. The microwave-induced thermoacoustic waves were detected with a focused ultrasonic transducer to obtain two-dimension al tomographic images of biological tissues. The dependence of the axial an d the lateral resolutions on the spectra of the signals was studied. A resh aping filter was applied to the temporal piezoelectric signals from the tra nsducer to increase the weight of the high-frequency components, which impr oved the lateral resolution, and to broaden the spectrum of the signal, whi ch enhanced the axial resolution. A numerical simulation validated our sign al-processing approach. (C) 2001 American Association of Physicists in Medi cine.