Which clinical modality has the lowest output intensity?

Which clinical modality has the lowest output intensity?

• A. Pulsed Doppler
• B. Gray scale imaging
• C. Continuous wave Doppler
• D. Power Doppler

Answer: (B)

Output intensity is the amount of acoustic energy delivered to tissue. Gray-scale imaging (B-mode) aims to show structure with minimal exposure, using short pulses and a low duty cycle so the average power remains low while still producing a clear image. Doppler modalities need stronger signals to detect motion or flow: pulsed Doppler uses discrete bursts, continuous wave Doppler transmits without interruption, and power Doppler sums Doppler energy over time to boost sensitivity. Each of these requires more energy than gray-scale imaging, with power Doppler typically demanding the most. So gray-scale imaging has the lowest output intensity.

Output intensity is the amount of acoustic energy delivered to tissue. Gray-scale imaging (B-mode) aims to show structure with minimal exposure, using short pulses and a low duty cycle so the average power remains low while still producing a clear image. Doppler modalities need stronger signals to detect motion or flow: pulsed Doppler uses discrete bursts, continuous wave Doppler transmits without interruption, and power Doppler sums Doppler energy over time to boost sensitivity. Each of these requires more energy than gray-scale imaging, with power Doppler typically demanding the most. So gray-scale imaging has the lowest output intensity.