| 摘要 |
A tomographic apparatus for constructing a two-dimensional image of a cut (35) through an object comprises a source (3) for providing a planar beam of radiation so that the beam passes through said object, and thus defines said cut; a detector (9) positioned opposite said source and aligned therewith for detecting the radiation not absorbed or scattered by said object; an arrangement for causing relative movement, between said object and said source and detector combination about an axis of rotation (44) that is perpendicular to said cut through said object; a reconstruction device (39) coupled to said detector for performing a reconstruction process based upon non-absorbed and non-scattered radiation detected by said detector at a plurality of different relative positions between said object and said source and detector combination as reached by said movement causing arrangement, wherein said reconstruction device converts values of non-absorbed and non-scattered radiation into values of absorbed radiation in each of an arbitrarily large number of voxels selected within said cut; and a display (41) coupled to said reconstruction device for projecting a two-dimensional image of said amounts of absorbed radiation. The detector comprises a chamber (13) filled with an ionizable substance, and including a first (17, 18) and a second (27, 29) electrode arrangement, substantially in parallel with each other; a radiation entrance (33) arranged such that the planar radiation beam (1) can enter the chamber between and substantially in parallel with the first and second electrode arrangements and ionize the ionizable substance; an electron avalanche amplification arrangement (15) for avalanche amplification of electrons created during ionization; and a read-out arrangement (27) for detection of the electron avalanches and/or correspondingly produced ions.
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