Computed tomography imaging

A computed tomography method, comprising:

• generating an X-ray beam travelling in a beam direction z from an X-ray source having a focal spot;
• using a mask having a plurality of block regions and a plurality of apertures having a period p in a first orthogonal direction x, orthogonal to the beam direction z to divide the beam into a plurality of X-ray beamlets;
• passing the X-ray beam through a subject;
• capturing an image on an X-ray detector having an array of pixels extending in the x direction, the plurality of pixels having a period a in the x direction;
• moving the subject with respect to an imaging system comprising the X-ray source, mask and the X-ray detector;
• capturing a plurality of images as the subject is moved with respect to the imaging system, each image corresponding to a rotation angle θ and being in a form of a plurality of measured datapoints as a function of x, and storing the measured datapoints;
• and
• reconstructing a three-dimensional computed tomography image from the plurality of measured datapoints;
• wherein the mask is structured such that each of the beamlets defines a region in the subject which when geometrically scaled to a detector mask is less than F, wherein F is a full width half maximum (FWHM) of an overall spread function caused by the combination of a finite size of the focal spot and a finite pixel resolution at a plane of the detector, in the x-direction;
• and
• the step of reconstructing reconstructs the three-dimensional computed tomography image at a finer pitch than the period p of the mask.