Exact image reconstruction in a helical cone-beam scan with a variable pitch

In most applications of helical cone-beam computed tomography (CT), the ratio, which is referred to as the pitch, between the translation distance of the subject and the rotation angle of the source-detector per unit time remains constant. However, situations do exist where it may be more desirable to use a helical scan with a variable pitch. One of such applications could arise in helical cone-beam CT fluoroscopy for the determination of vascular structures through real-time imaging of contrast bolus arrival. Most of th existing reconstruction algorithms have been developed only for helical cone-beam CT with a constant pitch. In this work, we extend our general formula for constant pitch to address the reconstruction from data acquired in helical cone-beam CT with a variable pitch. The condition, under which our formula remains valid, is also presented. The preliminary numerical studies confirm that our generalized algorithm can yield exact reconstruction in helical cone-beam CT with a variable pitch