Many-view under-sampling (MVUS) technique for low-dose CT: Dose versus image quality

In computed tomography (CT) imaging, radiation dose delivered to the patient is one of the major concerns. Among many technical solutions to lowering radiation dose while preserving clinical utilities of the images, sparse-view CT is a promising technique. However, a fast power switching of an x-ray tube, which is needed for the sparse-view sampling, can be challenging in many CT systems. We have recently proposed a novel alternative approach to sparse-view circular CT that can be readily incorporated in the existing CT systems, and have successfully shown its feasibility. Instead of switching the x-ray tube power, one can place an oscillating multi-slit collimator between the x-ray tube and the patient to partially block the x-ray beam thereby reducing the radiation. In this study, we performed a preliminary study on the effects of dose reduction via using multi-slit collimators of varying sizes of slit-openings on the reconstructed image quality. MicroCT projection data of a mouse were used and a numerical collimation was applied in the form of multi-slits. We used a sinusoidal motion of the collimator to the perpendicular direction of the rotation axis for the purpose of obtaining more uniform spatial sampling of the image. For image reconstruction, we used a total-variation minimization (TV) algorithm which has shown its out-performance in many sparse-view CT applications. This study UQI value was calculated to investigate the dependence of image quality on slit-opening size. Additionally, a visual image quality assessment was made.