Development of a low-dose CT by use of moving beam-blocker

Abstract

X-ray computed tomography (CT) has been widely used for clinical applications such as screening and diagnosis of diseases, interventional imaging for therapy, and prognostic evaluation. With its increased use in clinics, dose reduction is the most important feature people seek in new CT techniques or equipment’s. Much efforts have been directed towards better utilizing the existing CT systems and towards bringing new engineering for dose reduction. These clinical or engineering approaches, most intuitive and straightforward methods of reducing radiation dose to the patients are either decreasing the tube current during a scan or taking less projections for image reconstruction, or both. A host of algorithms have been developed to improve the quality of images reconstructed from the data acquired at low tube-current condition. Another good number of algorithms inspired by a compressive sensing (CS) theory have been developed to reconstruct images from sparse-view projections or from incomplete data. In spite of potential usefulness of the sparse-view technique, however, its implementation in clinical diagnostic CT systems is hardly found yet. It is perhaps due to the fact that a fast tube switching is challenging if not impossible particularly for the systems that operate with a very fast gantry rotation. In this work, we propose novel method of sparse data-sampling that uses an oscillating or rotating multi-slit collimator. By using the multi-slit collimator, one can effectively achieve a sparse-view imaging without switching the X-ray tube. A multi-slit collimator is mode of radio-opaque material to block the X-ray beam outside the slit openings. At a given source location, projection data is therefore acquired only through the slit-openings. Since substantial part of the collimator blocks the X-ray radiation, the collimation can help reducing radiation dose greatly. We name this type of scan many-view under-sampling (MVUS) technique. We proposed a novel scanning method for low-dose CT that can be potentially applicable to the existing CT systems with an addition of a collimator, and performed a simulation and experimental study to demonstrate.