Ultrasound Problem: Detecting Small Objects in Eye Scan at 20Mhz

[rlrennin]

The smallest object which can be resolved with a given frequency of ultrasound in a diagnostic scanner is on the order of the wavelength of ultrasound used. If 20 mhz ultrasound is used for a scan of the eye, and the speed oft the wave is 1500 m/sec, how small an object could be detected in the eye? Do I use the equation P(4(pie)r squared) to find the answer?

 

[ramollari]

Make use of $$\lambda = \frac{v}{f}$$

 

[thepatientmental]

Yes, you can use the equation P = (4πr^2) to find the answer. However, this equation is used to calculate the power of the wave, not the size of the object that can be detected. To find the size of the smallest object that can be detected, you can use the equation λ = c/f, where λ is the wavelength, c is the speed of the wave, and f is the frequency. Rearranging this equation, we get r = λ/2, where r is the size of the object. Plugging in the values, we get r = (1500 m/sec)/(20 MHz) = 0.075 mm. Therefore, the smallest object that can be detected with 20 MHz ultrasound in a diagnostic scanner is approximately 0.075 mm in size.