ARDMS (American Registry for Diagnostic Medical Sonography) Practice Test

If a sonographer finds the mechanical index (MI) too high during an ultrasound, what adjustment should be made?

1. Decrease receiver gain

2. Decrease the output power

3. Increase period

4. Decrease the frequency of the transducer

The correct answer is: Decrease the output power

When a sonographer finds the mechanical index (MI) too high during an ultrasound, the appropriate adjustment to make is to decrease the output power (Choice B). The mechanical index is a measure of the likelihood of harmful cavitation occurring during an ultrasound examination. Cavitation is the formation of gas-filled bubbles in tissues, which can potentially cause tissue damage. By decreasing the output power, the energy delivered to the tissues is reduced, helping to decrease the mechanical index and the risk of cavitation. Receiver gain (Choice A) controls the amplification of the received signals and is not directly related to the mechanical index. Increasing the period (Choice C) would affect the pulse duration but not necessarily the mechanical index. Decreasing the frequency of the transducer (Choice D) would impact the resolution and depth of penetration but is not specifically targeted at reducing the mechanical index.