X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Reexamination Certificate
1997-02-10
2002-11-12
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
C378S098200
Reexamination Certificate
active
06480570
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray image display apparatus for exposing a subject to an X-ray and thereby performing fluoroscopy and radiography on a subject region, and in particular to an X-ray image display apparatus in which a compensation filter and a collimator can be controlled so as to display an image satisfactorily on an image display device.
As shown in
FIG. 1
, a conventional X-ray image display apparatus of this kind includes a bed
2
for placing a subject
1
thereon, an X-ray tube
3
for exposing the subject
1
to an X-ray, an X-ray detector
4
disposed on the opposite side of the bed
2
from the X-ray tube
3
to convert an image of the X-ray transmitted through the subject
1
to a visible light image, a support
5
for supporting the X-ray tube
3
and the X-ray detector
4
, a television camera
6
for scanning the visible light image supplied from the X-ray detector
4
and outputting a video signal, an A/D converter
7
for converting the video signal supplied from the television camera
6
to a digital signal, a display processor
8
for processing the digital signal supplied from the A/D converter
7
and converting the processed image data to a video signal, an image display device
9
for displaying the video signal inputted from the display processor
8
as an image, a compensation filter
10
disposed between the X-ray tube
3
and the subject
1
to partially an X-ray exposure dose, a filter control circuit
11
for manually adjusting the position of the compensation filter
10
, a collimator
12
disposed on an output face of the X-ray tube
3
to partially interrupt the X-ray, and a collimator control circuit
13
for manually adjusting the collimator
12
. The display processor
8
includes an image processor
14
for conducting processing such as frequency emphasis and subtraction on the digital signal supplied from the A/D converter
7
, and a display circuit
15
for converting image data supplied from the image processor
14
to a video signal. In
FIG. 1
, numeral
16
denotes an X-ray controller for controlling the operation of the X-ray tube
3
, and numeral
17
denotes a support controller for controlling driving of the bed
2
and the support
5
.
In such an X-ray image display apparatus, an unnecessary part near the X-ray emitted from the X-ray tube
3
or a part where severe halation has occurred is interrupted by manually adjusting the collimator control circuit
13
while observing the image displayed on the image display device
9
. As for a part having brightness close to that of halation, the brightness is lowered by adjusting the filter control circuit
11
.
As an improvement to the conventional technique as shown in
FIG. 1
, a circuit for automatically controlling the filter control circuit
11
and the collimator control circuit
13
by using image data generated by the display processor
8
may occur to those skilled in the art. The circuit shown in
FIG. 2
is a development of the conventional technique, and corresponds to an intermediate technique located between the conventional technique and the present invention.
In the X-ray image display apparatus shown in
FIG. 2
with such an improvement added thereto, automatic control of the compensation filter
10
for removing unnecessary parts of the X-ray emitted from the X-ray tube
3
is exercised on the basis of a suitable control position calculated by the filter control circuit
11
by using image data taken in from the image processor included in the display processor
8
. Representive examples of such calculation and control will now be described by referring to FIG.
3
.
FIG. 3
shows an output image region of the X-ray detector
4
including an X-ray image intensifier. The output image region is included in the scanning region of the television camera
6
. The output image region is circular in shape. Therefore, the inside of a circle denoted by numeral
4
becomes an effective image region. The circular region is divided into a plurality of region blocks a, b, c, . . . , u. A representative value included in each region block is compared with a reference value. On the basis thereof, the filter control circuit
11
makes a calculation to determine whether the compensation filter
10
should be used or not. In general, it is desirable to conduct weighting in the central part and the peripheral part in the circular region and exercise control so as to form a satisfactory image in the central part. In case the X-ray passes outside the subject
1
, i.e., the X-ray is directly incident upon the peripheral part of the X-ray detector
4
, or in case a large quantity of contrast medium gathers in one place in subject
1
and hence the place can be judged to be a dark portion, it is also possible to exercise such control as to disregard the representative value of the region block of that part. A control signal based upon calculation in the filter control circuit
11
is sent to the compensation filter
10
to control the position of the compensation filter
10
. By exercising such feedback control, a satisfactory image having reduced halation is obtained in fluoroscopy of a target part of the subject
1
.
In recent years, advancements in image processing techniques have made it possible to expand and display moving pictures in real time and perform filtering on images in a video processing circuit. Expansion display been conventionally performed by changing the size of the image intensifier functioning as the X-ray detector
4
. In angiography of the subject
1
, however, a catheter and a guide wire have become very thin. In case expansion is performed only by stepwise changing the pickup range of the display screen of the image intensifier, the display area becomes narrower as the expansion ratio is increased. When the image is expanded, therefore, the catheter or wire might depart from the display range and be lost. Or even if the subject moves or the bed is slightly moved during display of an expanded image, the catheter or wire might depart from the display range and be lost. Thus, such expansion display has become uncapable of coping with such disadvantages. Therefore, expansion display using the display circuit
15
shown in FIG.
2
and digital processing has been put to use. In this case, an arbitrary area can be expanded or compressed at an arbitrary magnification owing to digital processing. In
FIG. 4
, the picked-up image area is represented by a square region E.
FIG. 5
shows the display image area of the image display device
9
. If, as an example, region blocks e, f, g, j, k,
1
, o, p and q in the area included in the square region E shown in
FIG. 4
are expanded by the display circuit
15
, only the portion including the region blocks e, f, g, j, k, l, o, p and q is expanded and displayed on the screen of the image display device
9
as shown in FIG.
5
. By using the image thus expanded and displayed, even a fine cathether can be easily manipulated.
In case expansion display using the display circuit
15
and digital processing is made in the image display in such an X-ray image diagnostic apparatus, the image in the area included in the square region E shown in
FIG. 4
is taken in and the compensation filter
10
is controlled by the filter control circuit
11
by using representative values of respective region blocks e, f, g, j, k, l, o, p and q. Therefore, a satisfactory image is obtained as the entire image in the region
4
. As for the expanded and displayed image portion shown in
FIG. 5
, however, a satisfactory display image is not obtained. The peripheral region shown in
FIG. 4
is an area which is not observed. In the portion including the region blocks a, b, c, h, m, r, d, i, n, s, t and u, the subject
1
is thus subjected to unnecessary X-ray exposure. Therefore, the subject
1
is subjected to unnecessary exposure to the X-ray.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an X-ray image display apparatus in which the position of a compensation filter or a collimator is
Antonelli, Terry Stout & Kraus, LLP.
Church Craig E.
Hitachi Medical Corporation
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