X-ray or gamma ray systems or devices – Beam control – Window
Reexamination Certificate
1998-11-19
2001-02-06
Church, Craig E. (Department: 2876)
X-ray or gamma ray systems or devices
Beam control
Window
C378S140000, C378S160000, C378S150000
Reexamination Certificate
active
06185279
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a casing for an electromagnetic radiation source, in particular an X-ray source, which includes a window making it possible to eliminate extrafocal radiation.
The invention is quite particularly applicable, in the medical field, to X-ray imaging devices.
As shown in
FIG. 1
, which represents the part of the window of an X-ray source of the prior art, the X-ray source comprises a cathode
10
and an anode
11
which are contained in a casing
12
that is transparent to X-rays. The assembly comprising of the cathode
10
, the anode
11
and the casing
12
is in turn contained in a casing
13
that is opaque to X-rays, with the exception of a part located facing the X-ray beam emitted by the anode
11
, which comprises of a window
15
made of material that is transparent to X-rays. The gap between the transparent casing
12
and the opaque casing
13
is filled by oil
16
used for insulation and for cooling the X-ray source.
As is well-known, the cathode
10
emits electron radiation which strikes the rotating anode
11
which re-emits an X-ray beam from a focal surface. The X-ray beam emitted by the anode
11
comprises radiation output by this focal surface, and also extrafocal parasitic radiation. This extrafocal parasitic radiation must be eliminated, preferably as close as possible to the emission source.
Conventionally, in order to eliminate this extrafocal radiation, as shown in
FIG. 1
, a conical element
30
or diaphragm made of material that is opaque to X-rays, for example made of lead, and provided with a central opening
31
for passage of the X-ray beam was provided. The diameter of the opening
31
is a compromise between obtaining a wide field and eliminating extrafocal radiation. However, in some cases, it was desirable to obtain smaller fields, for example by using a smaller focal surface. However, in this case, the diameter of the opening
31
is no longer adapted to the emitted X-ray beam and, in particular, no longer eliminates the extrafocal radiation. Conventionally, use was then made, in order to eliminate the extrafocal radiation, of extrafocal fingers
32
, made of material that is opaque to X-rays, for example made of lead, which were brought into position both laterally and longitudinally by a rod system
33
, in accordance with the desired field. Such a system is mechanically complex, expensive and furthermore does not make it possible to collimate the X-ray beam as close as possible to the focus.
BRIEF SUMMARY OF THE INVENTION
It is therefore desirable to provide a casing for an electromagnetic radiation source, in particular an X-ray source, which makes it possible to do without the conical element or diaphragm and the extrafocal fingers for eliminating the extrafocal radiation.
In an embodiment of the invention a casing for an electromagnetic radiation source, in particular an X-ray source, comprises a window made of a material that is transparent to electromagnetic radiation, the window comprising at least one chamber in which a material that is opaque to electromagnetic radiation can move, this chamber being designed in such a way that the opaque material can be introduced from the exterior of the chamber and that, inside the chamber, this opaque material surrounds a region for passage of an electromagnetic radiation beam in such a way that the area of the radiation passage region varies as a function of the volume of opaque material in the chamber, by virtue of which parasitic extrafocal radiation is eliminated from the beam.
The present invention also relates to a method for eliminating the extrafocal radiation from an electromagnetic radiation beam by using a window in a casing of an electromagnetic radiation source as defined above.
REFERENCES:
patent: 4541107 (1985-09-01), Rossi
patent: 4856042 (1989-08-01), Staron et al.
patent: 056552 (1982-07-01), None
patent: 239882 (1987-10-01), None
patent: 438147 (1935-11-01), None
patent: 2005911 (1979-04-01), None
Chaskin Jay L.
Church Craig E.
GE Medical Systems SA
LandOfFree
Casing for electromagnetic radiation source and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Casing for electromagnetic radiation source and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Casing for electromagnetic radiation source and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2613760