Clinical and experimental investigation of a smoothed CT reconstruction algorithm.

The usefulness of a smoothed reconstruction CT algorithm was studied using raw data from the EMI Mark I head scanner. The reconstruction algorithm operated on an off-line computer, independent of the EMI algorithm. This technique greatly reduces image noise and improves the visibility of very low-contrast structures, but at the cost of reduced spatial resolution. Phantom tests with contrasts as low as 0.14% demonstrated the validity of the images. Clinical results showed greatly improved visualization of gray and white matter with no increase in dose. It was necessary to expand the CT density scale so that the range from air to water was divided into 2,000 parts.