Answer #20

The correct answer is B: M mode. This form of ultrasound has the highest temporal resolution since there is a just one scan line along which information is gathered. An easy way to conceptualize temporal resolution is as frame rate. How many frames per second are being generated. For M mode this can be up to 1800 frames/second .For 2 D Doppler (Choice C) the ultrasound machine has to scan over a plan, one scan line at a time to generate an image frame; this takes time so the temporal resolution is not as good and may be on the order of 30-75 frames/second. By the same principals, 3D Doppler (Choice D) is worse since the machine has to scan in two different plane orthogonal to each other. Finally color Doppler (Choice A) also has poor temporal resolution since along each line of scanning, the ultrasound machine has to send a whole packet of scan lines to get information needed for color Doppler. Thus temporal resolution is worse than 2D Doppler.