Physical Problems Associated with Data Collection in CT

The main topic of this book is a discussion of the algorithms by which the distribution of the relative linear attenuation at an effective energy ē, namely µ_ē(x, y), is calculated from estimates of its line integrals along a finite number of lines. The measurements in CT are taken in order to estimate these line integrals. In this chapter we discuss the physical limitations and problems that arise in estimating the line integrals from the calibration and actual measurements. Except for the problems of photon statistics and beam hardening, our discussion will be limited to a summary of the problems with some indication on how their effects may be reduced. We also discuss the different scanner configurations that are used in computerized tomography. In Chapter 5 we illustrate the effects on the quality of the reconstruction of the different sources of error in the data collection.