SOFTWARE UPGRADING IN A CT SCANNER - INFLUENCE ON QUANTITATIVE CT

Purpose: In an attempt to improve field uniformity and CT number stabi lity, the software in a CT scanner was replaced with a new version. Th e purpose of the present study was to investigate the influence of the software upgrading on density measurements. Material and Methods: The upgrading influence was investigated by means of a torso phantom (Eur opean spinal). The phantom simulates a torso which contains 3 vertebra e of different densities. Results: Despite the use of a reference stan dard under the phantom, the software change resulted in: a) improved s hort-term precision; b) increased density values at 80 and 100 kVp, de creased at 130 kVp; and c) increased influence of the kVp on the value s. Conclusion: The results of the present study suggest that conversio n factors have to be used in density values for reference populations as well as in the values of patients undergoing follow-up studies.