Title: X-ray radiographic apparatus, X-ray restrictor, and X-ray radiographic method
Abstract: A switching mechanism is configured such that a lower limb radiographic filter 11a is moved inside a radiation field of the X-rays that is an opening portion of an X-ray movable restriction only when radiographing a region of a subject from the groin to the toe, or the filter is moved outside the radiation field when radiographing the lumber region of the subject. With this switching mechanism thus constituted, it is possible to lighten a burden of the operator, and realize the X-ray radiographic apparatus having high universality.
Patent Number: 6,898,271 Issued on 05/24/2005 to Akutsu, et al.
| Inventors:
|
Akutsu; Kouji (Nara, JP);
Miyamoto; Wataru (Kusatsu, JP);
Yasumi; Masayuki (Kyoto, JP);
Nakayama; Tetsu (Kyoto, JP);
Nakata; Isao (Kyoto, JP);
Umeda; Mitsuru (Kyoto, JP)
|
| Assignee:
|
Shimadzu Corporation (Kyoto, JP)
|
| Appl. No.:
|
404475 |
| Filed:
|
April 1, 2003 |
Foreign Application Priority Data
| May 29, 2002[JP] | 2002-155635 |
| Current U.S. Class: |
378/157; 378/159 |
| Intern'l Class: |
G21K 003/00 |
| Field of Search: |
378/156-159
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Church; Craig E.
Assistant Examiner: Yun; Jurie
Attorney, Agent or Firm: Rankin, Hill, Porter & Clark LLP
Claims
1. An X-ray radiographic apparatus comprising:
an X-ray tube for radiating X-rays to a subject;
an X-ray detector for detecting an X-ray applied to the subject;
a holding member for holding said X-ray tube and said X-ray detector;
a table top board for laying the subject thereon;
a filter for extracting X-ray components radiated from said X-ray tube; and
a movement mechanism for moving said filter outside or inside a radiation field
of the X-rays radiated from said X-ray tube so that said filter is moved inside
said radiation field only when the relative position between said holding member
and said table top board is at a predetermined position, and said filter is moved
outside said radiation field when said relative position is other than said predetermined
position.
2. The X-ray radiographic apparatus according to claim 1, wherein said filter
restricts an X-ray flux radiated from said X-ray tube in a predetermined shape.
3. The X-ray radiographic apparatus according to claim 1, wherein said filter
is a currently used filter and is one of a plurality of available filters and wherein
said movement mechanism includes a switching member for switching said currently
used filter with another of said plurality of available filters.
4. The X-ray radiographic apparatus according to claim 2, wherein said filter
is a currently used filter and is one of a plurality of available filters and wherein
said movement mechanism includes a switching member for switching said currently
used filter with another of said plurality of filters.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an X-ray radiographic apparatus and an X-ray
radiographic method for radiographing a subject by detecting an X-ray applied from
an X-ray tube to the subject, and more particularly to a technique for performing
an X-ray radiography of the subject, employing a filter for extracting the X-ray
components, and also relates to an X-ray restrictor used in the X-ray radiographic apparatus.
2. Description of the Related Art
In related art, when the X-ray radiographic apparatus is employed to make the
angiography for the lower limb, simultaneously for both legs, a contrast medium
is injected into the blood vessel of the subject, and the contrast medium flowing
within the blood vessel from the lumber region to the toe is radiographed with
the X-ray radiographic apparatus. During this radiography, a holding member (e.g.,
C-type arm) for holding an X-ray tube and an X-ray detector (image intensifier)
for the X-ray radiographic apparatus, or a table top board for laying the subject
thereon is being moved continuously or stepwise from the lumber region to the toe.
However, the related-art X-ray radiographic apparatus had a problem that
when the radiography is performed using a filter for extracting the X-ray components,
the operator had a burden with the operation of the filter and the radiography
becomes difficult. For example, when the angiography for the lower limb is made
simultaneously for both legs, some halation occurs in the radiographed image because
the transmission factor of X-rays is different between a leg portion and a portion
between both legs. To prevent the halation, if a specific mat is placed between
both legs of the subject, the operator has more burden with the mat. Also, the
halation may be prevented by placing the filter near a bulb of the X-ray tube,
in which the center of the radiographed image of the lumber region is hidden by
the filter, making the radiography difficult.
SUMMARY OF THE INVENTION
This invention has been achieved in the light of these affairs, and it is an
object of the invention to provide an X-ray radiographic apparatus and X-ray radiographic
method with high universality in which a burden of the operator is lightened, and
also provide an X-ray restrictor used in the X-ray radiographic apparatus.
In order to achieve the above object, this invention has the following constitution.
An X-ray radiographic apparatus, according to a first aspect of the invention, comprising:
an X-ray tube for radiating X-rays to a subject;
an X-ray detector for detecting an X-ray applied to the subject;
a holding member for holding the X-ray tube and the X-ray detector;
a table top board for laying the subject thereon;
a filter for extracting X-ray components radiated from the X-ray tube; and
a movement mechanism for moving the filter outside or inside a radiation field
of the X-rays radiated from the X-ray tube so that the filter is moved inside the
radiation field, only when the relative position between the holding member and
the table top board is at a predetermined position, and the filter is moved outside
the radiation field, when the relative position is other than the predetermined position.
With the invention of the first aspect, the movement mechanism moves the filter
outside or inside the radiation field of the X-rays radiated from the X-ray tube,
wherein the movement mechanism is configured such that the filter is moved inside
the radiation field, only when the relative position between the holding member
and the table top board is at a predetermined position, or the filter is moved
outside the radiation field, when the relative position is other than the predetermined
position. Accordingly, to acquire the radiographed image at the predetermined position
employing the filter, the movement mechanism moves the filter inside the radiation
field only at the predetermined position, thereby performing an X-ray radiography
of the subject at the predetermined position through the filter. Further, to acquire
the radiographed image other than at the predetermined position without employing
the filter, the movement mechanism moves the filter outside the radiation field
other than at the predetermined position, thereby performing an X-ray radiography
of the subject other than at the predetermined position without the filter. Consequently,
it is possible to lighten a burden of the operator who places a mat on the subject
as performed in the related art, and further to select whether or not to use the
filter depending on the radiographing position, thereby facilitating the radiography,
whereby the X-ray radiographic apparatus has a higher universality.
The filter is not specifically limited, as long as the X-rays having a specific
energy, or the X-ray components, can be extracted from the X-ray flux that is different
for each wavelength of the X-rays. For example, the filter may restrict the X-ray
flux radiated from the X-ray tube in a predetermined shape. The "restrict in a
predetermined shape" may involve setting a higher transmission factor of the X-rays
within the predetermined shape and a lower or null transmission factor of the X-ray
outside the predetermined shape, or setting a higher transmission factor of the
X-rays outside the predetermined shape and a lower or null transmission factor
of the X-ray within the predetermined shape.
Further, the movement mechanism may include a switching member for selectively
switching a plurality of filters into a certain filter to move the filter inside
or outside the radiation field of the X-rays. In this manner, various filters may
be employed to perform the X-ray radiography.
In this specification, the inventions regarding an X-ray radiographic method,
the X-ray tube for use in the X-ray radiographic apparatus, and the X-ray restrictor
are also disclosed.
(1) An X-ray radiographic method for performing an X-ray radiography of a subject, comprising:
radiating X-rays from an X-ray tube to the subject;
detecting an X-ray applied to the subject with an X-ray detector;
moving at least one of a holding member for holding the X-ray tube and the
X-ray detector and a table top board for laying the subject thereon;
moving a filter, which extracts X-ray components radiated from the X-ray tube,
outside or inside a radiation field of the X-rays radiated from the X-ray tube
so that the filter is moved inside the radiation field, only when the relative
position between the holding member and the table top board is at a predetermined
position, or the filter is moved outside the radiation field, when the relative
position is other than the predetermined position.
With the invention (1), to acquire the radiographed image at the predetermined
position employing the filter, the filter is moved inside the radiation field only
at the predetermined position, thereby performing an X-ray radiography of the subject
at the predetermined position through the filter, or to acquire the radiographed
image other than at the predetermined position without employing the filter, the
filter is moved outside the radiation field other than at the predetermined position,
thereby performing an X-ray radiography of the subject other than at the predetermined
position without the filter. Consequently, it is possible to lighten a burden of
the operator who places a mat on the subject as performed in the related art, and
further to select whether or not to use the filter depending on the radiographing
position, thereby facilitating the radiography.
(2) The X-ray radiographic method as defined in (1), may comprise selectively
switching a plurality of filters into a certain filter to move the filter inside
or outside the radiation field of the X-rays.
With the invention (2), since the method includes selectively switching a plurality
of filters into a certain filter to move the filter inside or outside the radiation
field of the X-rays, various filters may be employed to perform the X-ray radiography.
(3) An X-ray tube for use in an X-ray radiographic apparatus comprising an X-ray
detector, a holding member for holding the X-ray tube and the X-ray detector and
a table top board for laying a subject thereon, the X-ray tube comprising:
an X-ray source for radiating X-rays to the subject;
a filter for extracting X-ray components radiated from an X-ray source; and
a movement mechanism for moving the filter outside or inside a radiation field
of the X-rays radiated from the X-ray source so that the filter is moved inside
the radiation field, only when the relative position between the holding member
and the table top board is at a predetermined position, and the filter is moved
outside the radiation field, when the relative position is other than the predetermined position.
(4) An X-ray restrictor for controlling a radiation field of X-rays radiated
from an X-ray tube of an X-ray radiographic apparatus, the X-ray radiographic apparatus
comprising the X-ray tube, an X-ray detector, a holding member for holding the
X-ray tube and the X-ray detector and a table top board for laying a subject thereon,
the X-ray restrictor comprising:
a filter for extracting X-ray components radiated from the X-ray tube; and
a movement mechanism for moving the filter outside or inside the radiation field
of the X-rays radiated from the X-ray tube so that the filter is moved inside the
radiation field, only when the relative position between the holding member and
the table top board is at a predetermined position, and the filter is moved outside
the radiation field, when the relative position is other than the predetermined position.
With the inventions (3) and (4), the movement mechanism is configured such that
the filter is moved inside the radiation field, only when the relative position
between the holding member and the table top board is at a predetermined position,
or the filter is moved outside the radiation field, when the relative position
is other than the predetermined position. Consequently, it is possible to lighten
a burden of the operator, and realize the X-ray tube and the X-ray restrictor having
a higher universality.
(5) The X-ray tube as defined in (3), wherein the filter may restrict an X-ray
flux radiated from the X-ray tube in a predetermined shape.
(6) The X-ray restrictor as defined in (4), wherein the filter may restrict an
X-ray flux radiated from the X-ray tube in a predetermined shape.
The filter as defined in (3) and (4) is not specifically limited, like the filter
of the first aspect of the invention, but may restrict the X-ray flux radiated
from the X-ray tube in a predetermined shape, like the inventions (5) and (6).
(7) The X-ray tube as defined in (3) or (5), wherein the movement mechanism may
include a switching member for selectively switching a plurality of filters into
a certain filter.
(8) The X-ray restrictor as defined in (4) or (6), wherein the movement mechanism
may include a switching member for selectively switching a plurality of filters
into a certain filter.
With the inventions (7) and (8), the movement mechanism is constituted of a
switching member for selectively switching a plurality of filters into a certain
filter to move the filter inside or outside the radiation field of the X-rays.
In this manner, various filters may be employed to perform the X-ray radiography.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view showing the schematic constitution of an X-ray radiographic
apparatus according to an embodiment of the invention;
FIG. 2 is a front view showing the schematic constitution of the X-ray radiographic
apparatus according to the embodiment of the invention;
FIG. 3 is a view, partially broken away, of an X-ray tube and a collimator for
use in the X-ray radiographic apparatus according to the embodiment of the invention;
FIG. 4 is a plan view of the X-ray tube and the collimator according to the embodiment;
FIG. 5A is a plan view of a switching mechanism equipped within the collimator
according to the embodiment in a state before the filter is switched;
FIG. 5B is a plan view of a switching mechanism equipped within the collimator
according to the embodiment in a state when the filter is switched;
FIG. 6 is a flowchart showing a series of the X-ray radiography involved in
the angiography of the lower limb;
FIG. 7 is a cross-sectional view of one variation of the switching mechanism; and
FIG. 8 is a plan view of another variation of the switching mechanism.
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of the present invention will be described below with reference
to the accompanying drawings.
FIG. 1 is a side view showing the schematic constitution of an X-ray radiographic
apparatus according to an embodiment of the invention, and FIG. 2 is a front view
thereof. FIG. 3 is a view, partially broken away, of an x-ray tube and a collimator
for use in the X-ray radiographic apparatus according to the embodiment of the
invention, and FIG. 4 is a plan view thereof. FIGS. 5A and 5B are plan views of
a switching mechanism equipped within the collimator. In this embodiment, an X-ray
radiographic apparatus will be exemplified in which a blood vessel image is radiographed
by injecting a contrast medium into the subject via a catheter for injecting the
contrast medium. This X-ray radiographic apparatus comprises a table top board
1 for laying the subject thereon for medical examination, a strut portion
2, and a C-type arm
3, as shown in FIGS. 1 and 2. This strut portion
2 is attached to a ceiling plane and fixed except for rotation around the
axial center of a vertical axis (z-axis in FIGS.
1 and
2). The C-type
arm
3 corresponds to a holding member of the invention.
The table top board
1 can be moved up and down and also moved along the
body axis of the subject M. A table top board driving control section
4
is connected to the table top board
1 to control the driving of the table
top board
1. The table top board driving control section
4 controls
a driving mechanism for driving the table top board
1, a brake mechanism
for stopping the movement of the table top board
1 in the body axis direction,
a brake releasing mechanism for releasing the movement of the table top board
1
in the body axis direction, and a detection mechanism for detecting the position
of the table top board
1 (not shown).
The X-ray tube
5 is supported at one end of the C-type arm
3 to
radiate the X-rays to the subject M. An image intensifier
6 (hereinafter
appropriately abbreviated as "I.I") is supported at the other end of the C-type
arm
3 to detect the X-rays radiated on the subject M and convert them into
an optical image. The C-type arm
3 can be rotated around the axial center
of the body axis (x-axis in the FIGS. 1 and 2) of the subject M and also around
the axial center of an axis (y-axis in FIGS. 1 and 2) in a perpendicular direction
to the body axis of the subject M on the horizontal plane. The strut portion
2
can be rotated around the axial center of the vertical axis (z-axis in FIGS.
1
and
2). I.I
6 corresponds to an X-ray detector in this invention.
A C-type arm driving control section
7 is connected to the strut portion
2 and the C-type arm
3, respectively to control the driving of the
strut portion
2 and the C-type arm
3. The C-type arm driving control
section
7 controls a drive mechanism for driving the strut portion
2
and the C-type arm
3 and a detection mechanism for detecting the position
of the strut portion
2 and the C-type arm
3 (not shown).
A high voltage generating section
8 is connected to the X-ray tube
5
to apply a bulb voltage and a bulb current to the X-ray tube
5. As shown
in FIGS. 3 and 4, the X-ray tube
5 has a collimator
9 mounted on
a plane in a direction for radiating the X-rays, in which this collimator
9
controls a radiation field of the X-rays. The collimator
9 comprises an
X-ray movable restriction
10 having four plate-like members
10a
and a switching mechanism
12 having a plurality of filters
11.
The collimator
9 corresponds to an X-ray restrictor in this invention.
Four plate-like members
10a constituting the X-ray movable restriction
10 are disposed orthogonal to each other to have an opening portion
10b,
each plate-like member
10a being movable in the direction of the
arrow a in FIGS. 3 and 4. The X-rays passing through the opening portion
10b
become the radiation field of the X-rays, each plate-like member
10a
being movable to adjust the size of the opening portion
10b and
thereby the radiation field of the X-rays.
As shown in FIGS. 1 and 2, a collimator drive control section
13 are connected
to the plate-like members
10a and the switching mechanism
12,
respectively to control the driving of the plate-like members
10a for
the collimator
9 and the switching mechanism
12 (see FIGS.
3
and
4). The collimator drive control section
13 controls a drive
mechanism (not shown) for driving the plate-like members
10a, a motor
22 for driving a base gear
16 of the switching mechanism
12,
and a revolution counter
23 for detecting the position of the filter
11.
A specific constitution of the switching mechanism
12 will be described later.
The data converted into an optical image by I.I
6 is passed via a control
section
14 to an arithmetical operation section
15 for performing
various arithmetical operations, and outputting as a radiographed image. The control
section
14 totally controls the table top board driving control section
4, the C-type arm driving control section
7, the high voltage generating
section
8, and the collimator driving control section
13. The arithmetical
operation section
15 has a function of calculating the relative position
between the C-type arm
3 and the table top board
1, on the basis
of the positions of the C-type arm
3 and the table top board
1, besides
the arithmetical operations.
Referring to FIGS. 3 to
5B, a specific constitution of the switching
mechanism
12 will be described below. The switching mechanism
12
comprises the base gear
16 with a plurality of filters
11 disposed,
a drive gear
17 and a position detecting gear
18 which are fitted
with the base gear
16, a base shaft
19 passing through a central
part of the base gear
16, a drive shaft
20 passing through a central
part of the drive gear
17, a detection shaft
21 passing through a
central part of the position detecting gear
18, a motor
22 for revolving
the drive shaft
20 around the axial center, and the revolution counter
23
linked to the bottom of the detection shaft
21.
In this embodiment, the filter
11 disposed in the base gear
16
has
a lower limb radiographic filter
11a and three additional filters
11b, as shown in FIG.
4. The lower limb radiographic filter
11a restrict an X-ray flux radiated from the X-ray tube
5
to the quadrilateral shape with a quadrilaterally-shaped hole near the center thereof.
The three additional filters
11b regulate the degree of transmission
of X-rays. In this embodiment, the lower limb radiographic filter
11a
is provided with a rectangular filter
11c with lower transmission
factor of X-ray near the center, so that the X-ray flux transmitted through the
lower limb radiographic filter
11a is restricted to the square shape
with the rectangular hole near center thereof. In this embodiment, the filter
11c
has the rectangular shape, but the filter
11c is not limited
to the rectangular filter
11c. For example, the filter
11c
may have an oval shape, which is disposed in the vicinity of the center in
the lower limb radiographic filter
11a, corresponding to the portion
between both legs.
When the motor
22 revolves the drive shaft
20 around the axial
center, the drive gear
17 is revolved, and the base gear
16 fitted
with the drive gear
17 is also revolved. Each filter
11a,
11b disposed in the base gear
16 is revolved in the direction
of the arrow b in FIG. 4 around the axial center of the base shaft
19 by
the revolution of the base gear
16. Further, the revolution counter
23
measures the number of revolutions of the position detecting gear
18 fitted
with the base gear
16 via the detection shaft
21, whereby the position
of each filter
11a,
11b revolved in the direction of
the arrow b in FIG. 4 is detected.
Each filter
11a, 11b is moved outside or inside
the opening portion
10b of the X-ray movable restriction
10,
namely, outside or inside the radiation field of the X-rays by revolving the base
gear
16, as shown in FIG. 4. A certain filter
11 is selected from
among the four filters (lower limb radiographic filter
11a, additional
filters
11b) by revolving the base gear
16 every 90°
and switched. Accordingly, the switching mechanism
12 corresponds to a movement
mechanism in this invention, as well as switching member in this invention.
Referring now to a flowchart of FIG. 6, an X-ray radiographic method involving
the angiography for lower limb will be described below. In this embodiment, an
X-ray radiography is performed in the order from the lumber region to the toe with
the contrast medium flowing inside the blood vessel.
(Step S
1) Movement of the Table Top Board
After the subject M is laid on the table top board
1, the table top
board is moved up or down with the subject M laid thereon, so that the table top
board
1 is positioned at a predetermined height. Then, the table top board
1 is moved along the direction of the body axis of the subject M, so that
the lumber region of the subject M is located between the X-ray tube
5 and
I.I
6 for the C-type arm
3.
(Step S
2) Radiography of the Lumber Region
If the lumber region of the subject M is located between the X-ray tube
5
and I.I
6 for the C-type arm
3, it is started to radiograph the lumber
region. Then, the additional filters
11b other then the lower limb
radiographic filter
11a are located within the radiation field of
X-rays, namely, the lower limb radiographic filter
11a is located
outside the radiation field, whereby the lumber region is radiographed by transmitting
the X-rays through the additional filters
11b inside the radiation
field, as shown in FIG.
5A. More specifically, the X-rays are radiated from
the X-ray tube
5, and via the additional filters
11b and the
X-ray movable restriction
10 to the subject M. The X-rays applied to the
subject M are detected and converted into an optical image by I.I
6. The
converted data is transferred via the control section
14 to the arithmetical
operation section
15 for performing various arithmetical operations to acquire
a radiographed image of the lumber region. In this embodiment, since it is intended
to examine how the contrast medium flows inside the blood vessel, an output result
of the radiographed image is displayed on a TV monitor (not shown) and examined
without actually acquiring the radiographed image.
The table top board
1 is moved in a direction of the head of the subject
M, to acquire the radiographed image from the lumber region to the toe, while examining
the radiographed image of the lumber region. The radiographed image is acquired
in the order while the table top board
1 is being moved.
(Step S
3) Switch of the Filter
If the groin (crotch of the thigh) of the subject M reaches the position between
the X-ray tube
5 and I.I
6, the switching mechanism
12 switches
the filter
11. That is, the relative position between the holding member
and the table top board in this invention means the relative position between the
C-type arm
3 and the table top board
1 where a region of the subject
M on the toe side from the groin is located between the X-ray tube
5 and
I.I
6 for the C-type arm
3.
In switching, the additional filters
11b inside the radiation field
are revolved in a direction of the arrow in FIG. 5B, and moved outside the radiation
field as shown in FIG.
5B. Instead, the lower limb radiographic filter
11a,
which is located outside the radiation filed, is revolved in the same direction
and moved inside the radiation field as shown in FIG.
5B. Thereby, the lower
limb radiographic filter
1a is selected and switched. The revolution
counter
23 detects the position of the filter
11, whereby the lower
limb radiographic filter
11a is controlled to be located inside the
radiation field.
(Step S
4) Radiography of Both Legs
After the lower limb radiographic filter
11a is switched, it
is started to radiograph both legs. In radiographing both legs, the X-rays are
passed through the lower limb radiographic filter
11a inside the
radiation field. More specifically, of an X-ray flux radiated from the X-ray tube
5, the X-rays near the center are hardly transmitted by the rectangular
filter
11c near the center of the lower limb radiographic filter
11a, and the X-rays in other portions are transmitted. Thereby, the
X-ray flux transmitted through the lower limb radiographic filter
11a
is applied to the subject M in a restricted state of square shape with the
rectangular hole near the center thereof. Accordingly, the X-rays are applied to
a portion of the leg of the subject M corresponding to the position of square shape
of the lower limb radiographic filter
11a, but hardly applied to
a portion between both legs corresponding to the vicinity of the center of the
lower limb radiographic filter
11a, or the rectangular filter
11c.
The radiographed image of both legs is displayed on the TV monitor and examined,
on the basis of the data of the X-rays applied to both legs of the subject M in
the same manner as radiography of the lumber region in step S
2.
The table top board
1 is moved in a direction of the head of the subject
M, to acquire the radiographed image from the groin to the toe, while examining
the radiographed image of both legs. The radiographed image is acquired in the
order while the table top board
1 is being moved.
If the radiographed image is acquired up to the toe, the table top board
1
with the subject M laid thereon is moved along the body axis of the subject M to
avoid the C-type arm
3. After the table top board
1 is moved up or
down, the subject M is let off the table top board
1, whereby the series
of X-ray radiography is ended.
In the series of X-ray radiography according to the steps S
1 to S
4,
to acquire the radiographed image of both legs using the lower limb radiographic
filter
11a in step S
4, the lower limb radiographic filter
11a is moved inside the radiation field in step S
3, only when
both legs are radiographed, thereby performing an X-ray radiography of both legs
of the subject M through the filter
11a. To acquire the radiographed
image of the lumber region in step S
2, other than both legs, without employing
the filter
11a, the filter
11a is moved outside the
radiation field, thereby performing an X-ray radiography of the lumber region of
the subject M without the filter
11a.
In the apparatus of this embodiment, the switching mechanism
12 is configured
to move the filter
11 outside or inside the radiation field of X-rays radiated
from the X-ray tube
5. Also, when the relative position between the C-type
arm
3 and the table top board
1 is at the predetermined position,
where a region of the subject M on the toe side from the groin is located between
the X-ray tube
5 and I.I
6 for the C-type arm
3 in this embodiment,
the lower limb radiographic filter
11a of the four filters is moved
inside the radiation field, while the relative position is not at the predetermined
position, the filter
11a is moved outside the radiation field.
In this embodiment, when radiographing both legs, the X-rays are applied to a
portion of the leg of the subject M corresponding to the position of square shape
of the lower limb radiographic filter
11a, but hardly applied to
a portion between both legs corresponding to the vicinity of the center of the
lower limb radiographic filter
11a, or the rectangular filter
11c,
reducing a difference in the transmission factor between the leg portion and the
portion between both legs. Consequently, no halation occurs, whereby there is no
need for placing a mat over the subject M to prevent the halation, and it is possible
to lighten a burden on the operator.
Further, when radiographing the lumber region of the subject M, for example,
other than both legs, the additional filters
11b are employed in
place of the lower limb radiographic filter
11a, so that the center
of the radiographed image of the lumber region is not hidden by the rectangular
filter
11c in the lower limb radiographic filter
11a.
Consequently, it is possible to select whether or not to employ the lower limb
radiographic filter
11a depending on the radiographing position,
facilitating the radiography, whereby the X-ray radiographic apparatus with high
universality is realized.
In this embodiment, the switching mechanism
12 has means for selecting
and switching the lower limb radiographic filter
11a from among the
four filters
11, whereby the X-ray radiography is made using various filters.
This invention is not limited to the above embodiment, but may be modified or
varied in the following manner.
(1) In the above embodiment, a contrast medium is injected via a contrast medium
injecting catheter, and it is examined how the contrast medium flows inside the
blood vessel. However, this invention is also applicable to a digital subtraction
angiography in which the radiographed images before and after catheter injection
are subject to a subtraction operation. Also, this invention is applicable to an
X-ray radiographic apparatus for simply performing the X-ray radiography for medical
examination without catheter injection, and an X-ray CT apparatus.
(2) In the above embodiment, the filters
11 to be switched are the lower
limb radiographic filter
11a and the additional filters
11b,
but not limited to those filters
11a and
11b. Also,
the lower limb radiographic filter
11a is only provided in the base
gear
16, but when the filter
11a is not employed, the X-ray
radiography may be made without any use of other filters.
(3) In the above embodiment, the switching mechanism
12 is employed as
movement mechanism of this invention, and has the function of the switching member
in this invention, but the switching member is not limited to the switching mechanism
12 in this embodiment. For example, a plurality of filters
31 are
disposed on the belt
30, as shown in a cross-sectional view of FIG. 7, and
the filters
31 are selected and switched by moving the belt
30 in
a direction of the arrow in FIG.
7.
Also, it does not necessarily follow that the function of switching member
is provided. The lower limb radiographic filter
11a may be moved
outside or inside the radiation field by providing the lower limb radiographic
filter
11a alone in the base gear
16 as described in the variation
example (2). Alternatively, a single filter
41 may be disposed on a base
board
40 movable in the horizontal direction, in place of the base gear
16 of this embodiment, whereby the filter
41 may be moved outside
or inside the radiation field by moving the base board
40 in the horizontal
direction, as shown in a plan view of FIG.
8.
(4) In the above embodiment, the switching mechanism
12 as the movement
mechanism in this invention is provided in the collimator
9 that is the
X-ray restrictor in this invention, but the movement mechanism in this invention
may be provided in the X-ray tube
5.
(5) In the above embodiment, the holding member in this invention uses the C-type
holding member
3 with the C-type arm
8, but is not specifically limited
as long as the holding member holds the X-ray tube and the X-ray detector.
As will be apparent from the above description, with the invention of the first
aspect, the movement mechanism is configured such that the filter is moved inside
the radiation field, only when the relative position between the holding member
and the table top board is at a predetermined position, or the filter is moved
outside the radiation field, when the relative position is other than the predetermined
position. Consequently, it is possible to lighten a burden of the operator, whereby
the X-ray radiographic apparatus has a higher universality.
*
