Ultrasonic attenuation and propagation speed in normal human brain

Attenuation and propagation speed in the 1‐ to 5‐MHz frequency range were measured in vitro in 22 tissue samples from six anatomic sites in five normal human brains obtained unfixed at autopsy. Two methods were used to measure attenuation: (1) received amplitude reduction resulting from insertion of tissue sample between a pair of transducers, and (2) radiation force reduction resulting from insertion of tissue sample between a transducer and a reflector. The piezoelectric transducer method gave attenuation values −10% to +90% higher than the radiation force method. Attenuation (by transducer method) was a function of frequency to the 1.08 power with a value of 0.87 dB ⋅ cm−1 at 1 MHz. Propagation speed was measured by observing signal arrival time change resulting from insertion of the tissue sample between the transducer pair. Propagation speed was 1562 m ⋅ s−1 at 1 MHz with a dispersion of 1.2 m ⋅ s−1  ⋅  MHz−1 over the 1‐ to 5‐MHz frequency range. Ages at death were 3 days, 20, 21, 42, and 72 years. R...