A preliminary study of intensity-weighted ROI imaging in cone-beam CT

Some of the recently developed image reconstruction algorithms for cone-beam computed tomography (CBCT) involve the computation of the finite Hilbert transform. We have previously studied noise property of the finite Hilbert transform and observed that it can be used for potentially improving the image noise property within a region of interest (ROI) in IGRT. Imaging radiation dose is one of the critical issues in IGRT, and in addition to existing dose-reduction schemes by use of ROI imaging, it is possible to achieve further patient dose reduction through modulating beam intensity so that a sub-ROI in the ROI be exposed by high flux of x-ray photons and the rest of the ROI be exposed by low flux of them. In this work, we investigate the technique for obtaining sub-ROI images, which is supposed to include the target under treatment, with high contrast-to-noise ratio (CNR) and the images within the rest of the ROI with low CNR. Numerical studies have been conducted as a preliminary in this work.