Frame Rate

Frame rate was first tested by photographer Edward James Muygridge in 1872. He photographed a horse in gallop to settle a commonly debated question if all four hooves of a horse were off the ground at the same time while in gallop. What he confirmed was something the naked human eye could not perceive; in gallop all four feet did indeed lift off the ground.

Frame rate refers to how many times per second an image is updated. There are four ways that affect frame rate: sector size, depth, the number of line densities, and the number of focal zones. To increase frame rate, narrowing the imaging sector will decrease the time it takes to scan one frame. In M-mode imaging, the ultrasound beam width is minimized, and acquisition frame rates increase. This results in an increase in spatial and temporal resolution as compared with 2-D imaging. Second is decreasing the depth which decreases the Pulse Repetition Period (PRP). Third is decreasing the line density which requires fewer lines to scan one frame (at the cost of spatial resolution). Last is the use of a single focal zone which decreases the number of pulses needed per line.

Frame rate can be calculated by taking one divided by the time to scan one frame. The answer will be in units of Hertz. Having a higher frame rate will allow you to produce an image that is easier to visualize. In turn, the more frames you have the less lag there will be between each frame. This is what improves the temporal resolution of the image allowing better visualization of structures.

Key Words for Frame Rate

1. Frame
2. Rate
3. Temporal Resolution
4. Edward Muybridge
5. Frames per Second
6. Hertz
7. Image Sector
8. Pulse Repetition Time
9. Line Density
10. Focal Zone