Which noninvasive instrument assesses arterial blood flow by emitting sound waves reflected off moving blood cells?

• A. Doppler ultrasonography
• B. Electrocardiogram
• C. Radiography
• D. Nerve conduction velocity testing

Answer: (A)

Doppler ultrasonography uses ultrasound energy emitted toward the body and listens for the frequency shift that occurs when waves bounce off moving red blood cells. That Doppler shift is translated into information about the speed and direction of blood flow, making this method ideal for assessing arterial perfusion noninvasively. It can detect areas of reduced flow from narrowing or blockages and is commonly used in vascular evaluations. Often, color Doppler adds a visual map of flow, reinforcing the assessment.

The other options don’t measure blood flow: an electrocardiogram records the heart’s electrical activity, radiography uses X-rays to image structures, and nerve conduction velocity testing evaluates how fast nerves transmit impulses.