Question

A patient is having a procedure known as extracorporeal shock wave lithotripsy (ESWL) done. This procedure uses sound waves to disrupt kidney stones. Assume that the sound enters one side of the body from water in a direction perpendicular to the body’s surface. The sound waves then enter the kidney perpendicularly as well. Assume that the cross sectional area of the kidney is 50 cm².

The density of the tissue between the body’s surface and the kidney is 0.950 g/cm³, and the speed of sound in this tissue is 1.440 X 10⁵ cm/s.

The density of the kidney is 1.04 g/cm³, and the speed of sound in the kidney is 1.557 X 10⁵ cm/s.

150 J of energy is to be passed through the kidney.

What total time should the sound waves be allowed to pass through the kidney if the logarithmic intensity of the wave is 150 dB?

Answer 1

13) The relati on between intensity in dB and intensity in WIm 2 1 (dB) = 10log 150-1010g( )-15-loge-1-10, W/m2 fn The relati on between intensity and power is, tA IA (150 J) 103 W/m2) 50x104 m2 fn fn - 30 s