Index of content:
Volume 28, Issue 1, January 2001
- NON-IONIZING RADIATION IMAGING
28(2001); http://dx.doi.org/10.1118/1.1335500View Description Hide Description
28(2001); http://dx.doi.org/10.1118/1.1333409View Description Hide Description
Scanning thermoacoustictomography 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 thermoacousticcontrast 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 imagecontrast.