Patent ID: 6180949
Filing Date: 2001-01-30
Classification: C09K,G01T,G21K

Abstract:
A method for dual energy recording of an X-ray pattern containing X-rays of different energy level the consecutive steps of:(1) exposing a single sheet phosphor screen to an X-ray pattern of different energy level passing through an object, said phosphor screen containing in consecutive order a support, a first continuous phosphor-containing layer with a phosphor having a first X-ray absorption capacity with respect to different energy levels of X-ray radiation, and permanently and contiguously united therewith a second phosphor-containing layer having a grid structure, with parallel rows of phosphor-containing stripes or dots with a phosphor having a second X-ray absorption capacity, said second X-ray absorption capacity being different from said first X-ray absorption capacity, wherein said first phosphor first X-ray absorption capacity with respect to different energy levels of X-ray radiation mainly contains barium as host metal and said second phosphor with said second X-ray absorption capacity with respect to different energy levels of X-ray radiation mainly contains strontium as host metal, and wherein said phosphor containing strontium as host metal corresponds to the following empirical formula (I):Sr.sub.(1-x-y) Mg.sub.x Ca.sub.y F.sub.(2-a-b) BraCl.sub.b :zA (I)wherein:x is in the range 0.ltoreq.x.ltoreq.0.10,y is in the range 0.ltoreq.x.ltoreq.0.10,a is in the range 0.ltoreq.a.ltoreq.1.30,b is in the range 0.ltoreq.b.ltoreq.1;z is in the range 10.sup.-7.ltoreq.z.ltoreq.0.15, andA is Eu.sup.2+ or Eu.sup.2+ together with one or more of the co-dopants selected from the group consisting of Eu.sup.3+, Y, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, La, Gd and Lu,(2) separately scanning-wise photo-stimulating said phosphors in said single sheet phosphor screen,(3) separately photo-electronically detecting fluorescent light emitted by said different phosphors and providing two sets of digital image signals corresponding with said detected fluorescent light levels, and optionally and(4) extracting an image of specific structure by subtraction processing of said sets of signals.