How is the IRC calculated?

The Impedance Reflection Coefficient (IRC) is a measure used in ultrasound to quantify how much of the ultrasound wave is reflected back when encountering different tissue interfaces, based on their acoustic impedances. The formula for calculating the IRC involves the acoustic impedances (z1 and z2) of the two media.

In this specific context, the formula for IRC is given as IRC (%) = (z2 - z1) / (z1 + z2) x 100. This formula illustrates how the difference in acoustic impedance between the two media (z2 - z1) is compared to the total impedance (z1 + z2). The calculation effectively measures the proportion of the wave that is reflected at the interface, with the resulting percentage providing insight into how much energy is lost versus transmitted.

The reasoning behind this calculation is rooted in the principles of wave behavior at interfaces; when an ultrasound wave passes from one medium to another, not all of the wave continues through the second medium. This formula allows for a clear understanding of how changes in the impedance values affect the behavior of the ultrasound wave, which is crucial for interpreting sonographic images.

Other choices do not conform to the correct definition of IRC in medical physics. Some may calculate different ratios or