New Construction Technologies for CT imaging

New reconstruction technologies are becoming popular in CT imaging. A theoretical limit on the potential of new reconstruction algorithms is developed.

Dose (or radiation exposure) reduction is a topic of continual interest in CT imaging. CT scanners take x-rays from multiple angles around the patient, and the cumulative radiation dose delivered has the potential to cause harm. The increase in computational power has led to the emergence of new reconstruction algorithms (often called iterative reconstruction algorithms) in CT imaging. Iterative reconstruction algorithms present images that are more pleasing to view, especially at low radiation dose. However, the exact amount of dose reduction has been the subject of some controversy, with some reports claiming large dose reductions of a factor of 4 or more. 

In this work, we derive an information theoretic upper bound on the possible dose reduction from iterative reconstruction for a specific task, the quantification of a circular lesion embedded into a scan. The dose reduction varies according to the anatomy being scanned, but for a typical scan is approximately 50%. Dose reductions above this limit may be possible if a priori knowledge is used or larger effective slice thickness is being realized, but these are associated with bias or other side effects.