Evaluation of an automated system for temporal subtraction of thin-section thoracic CT.

The purpose of this study was to objectively evaluate the registration accuracy of an automated temporal subtraction system of thin-section thoracic CT. The automated subtraction system was applied to data from 20 subjects with lung diseases. The registration accuracy was evaluated based on the concept of target registration error using 19 landmarks chosen at the bifurcations of segmental bronchi. The landmarks were identified, and the displacements of the landmarks were measured. The average displacements of the landmarks in x, y and z directions were 0.56 pixels+/-0.64 (SD), 0.56 pixels+/-0.62 (SD, standard deviation) and 0.28 sections+/-0.40 (SD), respectively. Differences in average displacements between the landmarks were not statistically significant. Our computer system demonstrated promising results. The average displacements of the landmarks were less than the dimensions of a voxel. Further study is necessary to determine whether such a computer system can improve the diagnostic performance of radiologists.