A method and apparatus for imaging a body by exposing the body to radiation transmitted through the body via successive angular portions from a radiation source on one side of the body to a radiation detector in alignment with the radiation source on the opposite side of the body; the radiation detector including a two-dimensional matrix of detector elements producing electrical outputs corresponding to the magnitudes of the radiation received by each detector element; the radiation source producing a conical beam sufficiently large such that each exposure covers all the detector elements in the two-dimensional array after traversing the body. Also described are a method and apparatus for producing angiographical images having an enhanced contrast-to-noise ratio (CNR) by subtracting, from each contrast image produced after injecting a contrast material, a masking image produced before injecting the contrast material, starting with the masking image determined to have a minimum change over its immediately preceding masking image in the respective sequence.