Study Of The Testing Of Stair-Step Artifacts And Some Other Performance Of Spiral Computed Tomography Scanners And The Remote Performance Testing Software

The development and clinic application of the spiral CT technique has brought new challenges on CT quality assurance study. Compared with conventional CT scanners, spiral CT scanners have many advantages such as high scanning-speed and high z-axis resolution, and which characterize with some new image parameters such as longitudinal resolution, artifacts and the z-axis uniformity and noise. The remote performance testing of CT is a trend with the development of PACS and network. The purpose of this study is to solve the problems as stated above, to promote the CT quality assurance program in China.Starting with analysis on the fundamentals of spiral scanning and conventional scanning, the main performance parameters such as uniformity, noise, stair-step artifacts and spatial resolution had been studied. The testing and evaluating methods were proposed as follows:1. Testing of stair-step artifacts from spiral CT. Stair-step artifacts is a special phenomena due to spiral CT. A mathematics model of the quantity of stair-step artifacts was deduced. A simple but useful testing phantom was devised and used. The origin, the characteristics and the relation with scanning parameters of stair-step artifacts were investigated.2. Auto-testing of the spatial resolution. By using Catphan500, a new way to differentiate the CT spatial resolution was brought forward.3. Testing and evaluation of the z-axis uniformity and noise of MSCT. The definition of the z-axis uniformity and noise of MSCT has been brought forward. The parameters have been measured and evaluated. That met the increased demands of conducting QA for spiral Multi-Slice CT.4. Development the software for the remote CT performances testing, the result is objective and accurate.The main innovations in the study are below:1. A mathematics model of stair-step artifacts was deduced.2. A new method of measurement of artifacts was brought forward.3. A new way to differentiate CT spatial resolution was brought forward.4. The definition of the z-axis uniformity and noise of MSCT was brought forward.