Attenuation Coefficient Measurement Technique at 100 MHz with the Scanning Laser Acoustic Microscope

Absrmcf-There has been a lack of an accurate procedure for the measurement of an attenuation coefficient for biological tissues at 100 MHz with the scanning laser acoustic microscope (SLAM). The solution to this problem has been approached with two general schemes. One involved a calibrated look-up table, and the other utilized the measurement of insertion loss. For the latter a procedure has been developed and verified using known biological solutions. The insertion loss procedure yields an attenuation coefficient uncertainty to within five percent, a dynamic range from 4 to 28 dB/mm. and an insertion loss sensitivity of 0.2 dB. N IMPORTANT tissue characterization property is the ultrasonic attenuation coefficient, which is the decrease in energy of the sound wave when it propagates through a material. The attenuation includes absorption and scattering. Absorption represents the loss of energy into heat within the specimen. Scattering is a redirection of the energy due to the inhomogeneities of the specimen and includes reflection, refraction, and diffraction. The scanning laser acoustic microscope (SLAM) is a useful tool for providing at 100 MHz, the ultrasonic attenuation coefficient of tissue. A number of techniques have been developed to perform this measurement with the SLAM, and this report details and evaluates these techniques. Details of ultrasonic velocity measurements are found in companion papers [l], [2].