The temperature elevation in tissues generated by an ultrasonic beam of plane sawtooth wave tone bursts along its axis is calculated based on a solution of an extended Burgers’ equation for a medium with loss due to various relaxation processes. The absorption coefficient of the medium is assumed to be proportional to frequency to the bth power (1≤b≤1.4). The results show that when the power generated by a transducer is kept constant, an enhancement of temperature rise in the medium due to narrow- and high-amplitude bursts of ultrasound is evident. For example, if spatial-peak temporal-average intensity, ISPTA=0.1 W/cm2=const, the temperature rise generated by sawtooth wave tone bursts with a duty factor of 10−4 (ISPPA=1000 W/cm2 at the low-loss fluid and tissue interface where the sawtooth wave just forms) is about twice that generated by its corresponding linear continuous wave counterpart.
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Wu et al. (1990) studied this question.