A super resolution technique for clinical multislice CT

Abstract

Increasing the spatial resolution of current multislice clinical CT system is always desirable. However, further resolution improvement by reducing the pixel pitch or the aperture of the detector elements is difficult because of the tradeoff between the pixel size and dose level. In this paper, we demonstrate a methodology for improving spatial resolution of a clinical multislice CT without reducing the detector element size. The flying focal spot (i.e. electron beam wobbling) technique is used to increase the data sampling rate for in-plane (x-y) and z-axis scan acquisitions. In order to reduce the number of focal spot positions to achieve a certain spatial resolution, a super resolution technique using projections onto convex sets (POCS) is applied here to improve projection raw data sampling with reduced number of focal spot positions. The results indicate that it is possible to significantly increase spatial resolution on current multislice clinical CT systems without reducing the detector element size. In absence of noise, super resolution algorithms employing iterative regularization, such as POCS, can reduce the required number of focal spot positions. Thus, technical requirements on the multislice CT systems, such as rotation time and number of projections per rotation, can be much relaxed. However, noise reduction methods and methods of reducing projections per rotation, such as compressed sensing, are needed to work with super resolution technique to keep the radiation exposure from exceeding the current limit of clinical multislice CT.