ARDMS (American Registry for Diagnostic Medical Sonography) Practice Test

During a carotid duplex ultrasound, the most significant amount of Doppler shift to measure the peak velocity is obtained when using scanning angles of 0 or 180 degrees. This is because a Doppler ultrasound measures the change in frequency of the sound waves reflected by moving red blood cells. When the Doppler angle is 0 degrees (parallel to blood flow) or 180 degrees (antiparallel to blood flow), it results in the greatest sensitivity to detect the maximum velocity of blood flow accurately.

Options A, B, and C are not the best choices because angles other than 0 or 180 degrees reduce the accuracy of peak velocity measurement due to decreased sensitivity to the Doppler shift of blood flow velocity.