Theoretical limitations in CT picture quality and recognition capability

So far as only the physical evaluation of CT (computed tomography) is performed, number of problems remain both practically and theoretically. Two of such are as follows. (1) The meaning of the problems values obtained by the physical evaluation in clinical field are not known definitely. (2) In order to properly evaluate CT scanners of different types from the physical standpoint, it is insufficient to know only physical picture quality. It is necessary to know the relations with mechanical parameters. The contrast-detail-dose curve has been proposed, which indicates the limit of finding the small losses in contrast, clinically important. In the present report it is explained how the contrast-detail-dose curve is determined by physical values (noise and MTF) in the above problem (1). Then in the problem (2), it is considered how the high contrast resolving power is influenced by mechanical parameters in actual CT scanners. (J.P.N.)