Apparatus and method for providing a near-parallel projection from helical scan data

Abstract

An apparatus and method for providing a projection image directly from data acquired by a CT scanner, the method comprising: acquiring an amount of data corresponding to an object that is scanned by the CT scanner, wherein the amount of data is generated by an x-ray source that projects a fan beam of x-rays toward a detector array on an opposite side of a gantry of the CT scanner as the object is passed through an opening in the gantry, the acquired amount of data comprising a reconstruction volume; selecting a viewing direction of the object; selecting a portion of a surface intersecting the reconstruction volume, wherein the selected portion comprises an imaging surface inside the reconstruction volume and corresponding to the viewing direction of the object; dividing the imaging surface into a plurality of rows and columns, thus creating a grid of points corresponding to the imaging surface; determining, for each point in the grid, a data point in the acquired amount of data corresponding to an x-ray source position wherein a ray from the x-ray source to the grid point is closest an orientation parallel to the view direction, and a detector position where the ray intersects the detector array; and presenting a projection image corresponding to the selected imaging surface, wherein the projection image comprises a plurality of projection points and each projection point in the projection image is a converted value of the data points of the acquired data.