Sonographic heat generation in vivo in the gravid long-tailed macaque (Macaca fascicularis)

Temperature elevations that occur during diagnostic ultrasonic exposure were assessed in vivo in gravid macaques after 10, 20, or 30 min (scan mode; N = 30) or 5, 10, or 15 min (pulsed Doppler; N = 32). Five time points were assessed during the second and third trimesters (gestational days 70 to 150 ± 2; term, ~ 165 days) using a transient thermocouple technique. Measurements were obtained intracranially or at the muscle-bone interface using a commercial sector scanner (ATL MK 600, 7.5 MHz scanhead; scan mode, I(SPTA) = 27 mW/cm², I(SPPA) = 85 W/cm², pulse repetition frequency (PRF) = 1 kHz; pulsed Doppler - I(SPTA) = 54 mW/cm², I(SPPA) = 1.5 W/cm², PRF = 18.5 kHz). Overall, the greatest temperature elevation achieved with either modality or location was 0.6°C.