Akademik Veri Yönetim Sistemi
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, cilt.125, sa.6, ss.3601-3610, 2009 (SCI-Expanded)
It is widely accepted that diagnostic ultrasound has the potential to elevate the temperature of tissue being scanned. Because both the maximum value of the temperature rise and the temporal profile of that rise are necessary to estimate the risk correctly, the temperature rise (Delta T(t)] at an observation point for an exposure condition is presumed to have two components, that is, Delta T(t) = Delta T(max)X(t). The amplitude component Delta T(max) is the maximum value of Delta T(t), and the exposure time component X(t) represents the time dependency of that Delta T(t). Ninety-six cases were investigated to obtain the proposed Delta T(t) model at six frequencies, four source diameters, and four f-numbers. Then, using the relative change in the rate of induction of a thermal effect due to ultrasound exposure that produces Delta T(t) different from a threshold exposure, the safe use time (SUT) model was constructed. SUT informs the user of the maximum duration of exposure in a region at a particular output level that would be no more hazardous than scanning at the threshold exposure. Using the SUT model, high power ultrasound can be applied for a short time so that the user can improve imaging performance while staying within safe limits. (C) 2009 Acoustical Society of America. [DOI: 10.1121/1.3126525]