Patent ID: 6477223
Filing Date: 2002-11-05
Classification: A61B,G01T,H01J

Abstract:
A tomographic apparatus for constructing a two-dimensional image of a cut through an object comprising:a radiation source for providing a planar beam of radiation so that the beam passes through said object, and thus defines said cut; a detector 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 that is perpendicular to said cut through said object; a reconstruction device 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 coupled to said reconstruction device for projecting a two-dimensional image of said amounts of absorbed radiation; said detector further comprising: a chamber filled with an ionizable substance; a first and a second substantially planar electrode arrangement, located substantially in parallel with each other to at least partially form two oppositely located sidewalls of said chamber; a radiation entrance arranged such that the planar radiation beam 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 for avalanche amplification of electrons created during ionization; a read-out arrangement for detection of the electron avalanches and/or correspondingly produced ions and wherein the electron avalanche amplification arrangement comprises a plurality of avalanche amplification regions and said avalanche amplification arrangement comprises an avalanche cathode arranged between the first and the second electrode arrangement; and wherein â€ƒa dielectric substrate arranged between the avalanche cathode and the second electrode arrangement such that the avalanche cathode, the dielectric substrate, and the second electrode constitute a laminated structure, the dielectric substrate comprising a plurality of openings or holes aligned with openings or holes of said avalanche cathode, and wherein the read-out arrangement includes a plurality of separated read-out elements, each being adapted to detect electron avalanches, and/or correspondingly produced ions, created in or around a respective one of the plurality of avalanche amplification regions.