Radiation image conversion panel

Details Radiation image conversion panel Radiation image conversion panel

2001-10-09

2003-11-25

Kelly, Cynthia H. (Department: 1774)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S212000, C428S917000, C250S284000, C313S506000

Reexamination Certificate

active

06652994

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a radiation image conversion panel employing stimulable phosphors, and specifically to a radiation image conversion panel which results in excellent balance between the emission luminance and the sharpness of said stimulable phosphors.
BACKGROUND OF THE INVENTION
Radiation images such as X-ray images are widely employed for medical diagnoses. Utilized as a method for obtaining X-ray images is so-called radiography in which X-rays, which have passed through an object, are subjected to irradiation onto a phosphor layer (being a fluorescent screen) to result in visible light, which is irradiated onto a silver salt bearing film, in the same manner as conventional photography, and the resulting film is subjected to photographic processing. In recent years, however, a method has been invented in which images are formed directly from a phosphor layer without employing silver salt coated films.
Said method is described, for example, in U.S. Pat. No. 3,859,527 and Japanese Patent Publication Open to Public Inspection No. 55-12144. Specifically, a radiation image conversion panel comprised of stimulable phosphors is utilized, and the stimulable phosphor layer of said radiation image conversion panel is subjected to radiation exposure which has passed through the object being diagnosed so that radiation energy is stored corresponding to the radiation transmittance of each portion of said object. Subsequently, the resulting stimulable phosphor layer is sequentially subjected to stimulation employing electromagnetic waves (stimulating light), such as visible light and infrared rays, so that radiation energy stored in said stimulable phosphor layer is released as stimulated luminescence. Signals of the intensity variation of said stimulated luminescence are subjected, for example, to photoelectric conversion to obtain electrical signals. The resulting electrical signals are employed to reproduce visible images on recording materials such as light-sensitive films or display devices such as a CRT.
The radiation image conversion panel, employing said stimulable phosphors, stores radiation image information and releases stored energy through stimulating light scanning. Therefore, after scanning, it is possible to repeatedly store radiation images so as to be capable of being repeatedly used. Accordingly, compared to radiography in which a combination of conventional radiographic films and intensifying screens is used, it is possible to obtain radiation images with ample information, while utilizing much less radiation exposure. Further, contrary to the fact that in the conventional radiography, radiographic film is consumed for every exposure, said radiation image conversion method is more advantageous from the viewpoint of resource conservation as well as economic efficiency, because it is possible to repeatedly utilize said radiation image conversion panel.
The stimulable phosphors employed in said radiation image conversion panel are those which result in stimulated luminescence after having been subjected to irradiation of stimulating light after said radiation. In practice, phosphors are commonly employed which result in stimulated luminescence in the wavelength range of 300 to 500 nm utilizing stimulating light in the wavelength region of 400 to 900 nm. Herein, examples of stimulable phosphors, which have conventionally been employed in said radiation image conversion panel, are described in Sections (1) through (14) below.
(1) Rare earth element activated alkaline earth metal fluorinated halogen phosphors represented by the composition formula of (Ba
1-x
, M
II+
x
)FX:yA, described in Japanese Patent Publication Open to Public Inspection No. 55-12145, wherein M
II+
represents at least one of Mg, Ca, Sr, Zn, and Cd; X represents at least one of Cl, Br, and I; A represents at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, and Er; “x” and “y” each represent figures satisfying the relationship of 0≦x≦0.6 and 0≦y≦0.2, respectively.
Further, said phosphors may comprise additives as described (a) through (n).
(a) X′, BeX″, M
III
X
3
′″, described in Japanese Patent Publication Open to Public Inspection No. 56-74175, (wherein X′, X″ and X′″ each represent at least one of CL, Br and I; and M
III
represents a trivalent metal);
(b) metal oxides described in Japanese Patent Publication Open to Public Inspection No. 55-160078, such as BeO, BgO, CaO, SrO, BaO, ZnO, Al
2
O
3
, Y
2
O
3
, La
2
O
3
, In
2
O
3
, SiO
2
, TiO
2
, ZrO
2
, GeO
2
, SnO
2
, Nb
2
O
5
, and ThO
2
;
(c) Zr and Sc described in Japanese Patent Publication Open to Public Inspection No. 56-116777;
(d) B described in Japanese Patent Publication Open to Public Inspection No. 57-23673;
(e) As and Si described in Japanese Patent Publication Open to Public Inspection No. 57-23675;
(f) M·L (wherein M represents at least one alkali metal selected from the group of Li, Na, K, Rb, and Cs; L represents at least one trivalent metal selected from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In, and Tl) described in Japanese Patent Publication Open to Public Inspection No. 58-206678;
(g) calcined tetrafluoroboric acid compounds described in Japanese Patent Publication Open to Public Inspection No. 59-27980;
(h) calcined, univalent or divalent metal salt of hexafluorosilic acid, hexafluorotitanic acid or hexafluorozirconic acid, described in Japanese Patent Publication Open to Public Inspection No. 59-27289;
(i) NaX′ (wherein X′ represents at least one of Cl, Br and I), described in Japanese Patent Publication Open to Public Inspection No. 59-56479;
(j) transition metals such as V, Cr, Mn, Fe, Co, and Ni, described in Japanese Patent Publication Open to Public Inspection No. 59-56479;
(k) M
I
X ′, M′
II
X″, M
III
X′″ and A, (wherein M
I
represents at least one alkali metal selected from the group of Li, Na, K, Rb, and Cs; M′
II
represents at least one divalent metal selected from the group of Be and Mg; M
III
represents at least one trivalent metal selected from the group of Al, Ga, In, and Tl; A represents a metal oxide; X′, X″ and X′″ each represents at least one halogen atom selected from the group of F, Cl, Br, and I), described in Japanese Patent Publication Open to Public Inspection No. 59-75200;
(l) M
I
X′ (wherein M
I
represents at least one alkali metal selected from the group of Rb or Cs; and X′ represents at least one halogen atom selected from the group of F, Cl, Br, and I), described in Japanese Patent Publication Open to Public Inspection No. 60-101173;
(m) M
II
′X′
2
,M
II
′X″
2
, (wherein M
II
′ represents at least an alkaline earth metal selected from the group Ba, Sr, or Ca; X′ and X″ each represents at least one halogen atom selected from the group of Cl, Br, or I, and X′≠X″), described in Japanese Patent Publication Open to Public Inspection No. 61-23679; and
(n) LnX″
3
(wherein Ln represents at least one rare earth metal selected from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; X″ represents at least one halogen atom selected from the group of F, Cl, Br, and I), described in Japanese Patent Publication Open to Public Inspection No. 61-264084.
(2) Divalent europium activated alkaline earth metal halide phosphor represented by the composition formula of M
II
X
2
·aM
II
′
2
:xEu
2+
(wherein M
II
represents at least one alkaline earth metal selected from the group of Ba, Sr, and Ca; X and X′ each represent at least one halogen atom selected from the group of Cl, Br, and I; and X≠X′; “a” represents a figure satisfying the relationship of 0≦a≦0.1 and “x” represents a figure satisfying the relationship and 0≦x≦0.2), described in Japanese Patent Publication Open to Public Inspection No. 60-84381.
Further, said phosphors may comprise additiv

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