Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Reexamination Certificate
2001-06-04
2003-10-07
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
C250S370070
Reexamination Certificate
active
06630676
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The invention relates to an X-ray image taking apparatus, more specifically, a mechanism for attaching a plane type radiation detector unit to a C-arm type diagnostic apparatus or fluoroscopic radiographing stand, and input/output (hereinafter referred to as “I/O”) cables of a signal and a power source thereof.
With a spread of a digital radiographing (hereinafter referred to as “DR”) apparatus, its clinical use has been extended on various fields from an alimentary canal examination to an interventional radiology (hereinafter referred to as “IVR”) for a non-blood vessel system and a simple digital subtraction angiography (hereinafter referred to as “DSA”).
In addition to the general fluoroscopic radiographing stand, there is an IVR-digital correspondence type fluoroscopic radiographing stand equipped with a C-arm, wherein a digital image processing device is made small in size and high in performance; an operation ability with an X-ray high voltage device is improved; an image intensifier (hereinafter referred to as “I.I.”) has a high image quality and a lower distortion; and transfer and preservation of a full digital image are contrived by employing a 4 million pixel CCD camera of a high density resolving power.
FIG. 3
shows a C-arm type X-ray image taking apparatus wherein a TV camera
19
using CCD and an I.I.
18
are provided on a C-arm
14
rotated around a body axis of an object or patient
9
to face an X-ray tube
12
sandwiching therebetween a top board
10
, on which the object
9
to be tested is received. In order to provide fluoroscopy or radiograph with X-rays from various angles with respect to the whole body of the object
9
, the I.I.
18
and the X-ray tube
12
are rotated in the C directions around the body axis of the object
9
by the C-arm
14
, and moved parallel in the A directions, i.e. head-feet directions of the object
9
along a height direction moving guide
15
. The I.I.
18
is moved in the D directions on the supporting plate
17
so that the I.I.
18
can be moved to and from the object
9
. Also, the I.I.
18
and the X-ray tube
12
can be rotated around the supporting point of the C-arm
14
in the directions of the head-feet of the object
9
. The top board
10
can be rotated in the B directions by a rising-falling C-arm
13
. As described above, the fluoroscopic radiographing positions can be taken with various angles without moving the object
9
.
In the X-ray image taking apparatus using the I.I.
18
, since the I.I.
18
is large, when an operator operates the apparatus in the vicinity of the object
9
and when the evacuation is required, the I.I.
18
is moved in a vertical direction.
Recently, in place of the I.I.
18
, a plane type radiation detector has been applied to the X-ray image taking device. The plane type radiation detector is normally formed of an X-ray converting film for converting X-rays into light, photo diode arrays arranged in a matrix shape right under the X-ray converting film; and TFT switches connected to the respective photo diode arrays. The plane type radiation detector has two types. In one type, after X-rays are irradiated, the respective TFT switches are sequentially turned on, so that signal charges accumulated in the respective pixels are read out to form an X-ray image. In the other type, there are provided radiation sensor arrays formed of a converting layer for directly outputting charge signals sensitive to radiation and corresponding to incident amount, and the TFT switches are connected to electrodes arranged in a matrix shape right under the radiation sensor arrays. In use, the respective TFT switches are sequentially turned on, so that signal charges accumulated in the respective pixels are read to form an X-ray image. The latter is explained in the following.
FIG. 4
shows a detector cassette
21
, wherein a plane type detecting portion
22
, power source
26
, control circuit portion
25
, gate circuit portion
23
, reading circuit portion
24
and image memory
27
are built in, and a connecting terminal
28
for external connection is provided. The gate circuit portion
23
and the reading circuit portion
24
are controlled from an outside at the control circuit portion
25
through the connecting terminal
28
, and charge signals accumulated in the condensers of the pixels formed of semiconductors in the detecting portion
22
are read in the reading circuit portion
24
and stored in the image memory
27
. Then, the data is transferred outside through the connecting terminal
28
. The detector cassette
21
is attached to a detecting portion attaching frame of the X-ray image taking apparatus, and a signal cable is connected to the connecting terminal
28
.
FIG. 5
shows a detector cassette
21
, wherein a plane type detecting portion
22
, power source
26
, control circuit portion
25
, gate circuit portion
23
, reading circuit portion
24
, image memory
27
and a communication circuit
29
are built in, and input/output of signals with an outer portion are carried out by a communication circuit through radio signals. The gate circuit portion
23
and reading circuit portion
24
are controlled from the control circuit portion
25
through the communication circuit
29
by radio signals from the outside, and charge signals accumulated in the condensers of the pixels formed of the semiconductors at the detecting portion
22
are read in the reading circuit portion
24
and stored in the image memory
27
. Then, if necessary, the data is transferred outside from the communication circuit
29
. The detector cassette
21
is simply attached to the detecting portion attaching frame of the X-ray image taking apparatus, and output and input of the signals are carried out by radio signals through the communication circuit
29
, so that a connecting cable is not required.
FIG. 6
is a sectional view showing a structure of a pixel
30
for constituting the detecting portion
22
of the plane type radiation detector. The pixel
30
includes an active matrix board, wherein electrode wirings, such as gate line and reading signal line, a thin film transistor TFT
32
and a condenser
38
are formed in an X-Y matrix shape on a glass base board; an X-ray converting layer
37
extending over the substantially whole surface above the active matrix board; a pixel electrode
31
positioned thereunder; and an upper electrode
36
located thereabove.
The X-ray converting layer
37
has good photoconducting characteristics according to the irradiation intensity of X-rays to generate a charge signal. For example, a film having a large area can be formed easily by vapor deposition, and amorphous selenium (hereinafter referred to as “a-Se”) or the like formed in a film having a thickness of 300 to 1,200 &mgr;m can be used. The upper electrode
36
of the X-ray converting layer
37
is formed on a surface at the X-ray incident side, and the pixel electrode
31
is formed at a position corresponding to each pixel
30
on a side opposite to the X-ray incident side.
The condenser
38
is connected between the pixel electrode
31
and the ground. Also, a bias voltage is applied to the X-ray converting layer
37
from a bias applying portion, and a charge generated at the X-ray converting layer
37
according to an X-ray irradiation intensity is accumulated in the condenser
38
.
The TFT
32
has a signal reading switch function and is arranged in two dimensions every pixel
30
. And, the charge signal of the condenser
38
is read out by a switch pulse from a gate line terminal
33
a
to the reading circuit portion
24
through a reading signal line terminal
34
a.
FIG. 7
shows a circuit diagram for explaining operations of the plane type radiation detector. The respective pixels
30
are regularly arranged in the length and width directions on the active matrix board
35
. The gate circuit portion
23
is driven by the signal from the control circuit portion
25
, and pulse signals G
1
, G
2
, G
3
, . . . are sequentially sent to the gate electrodes of
Gabor Otilia
Kanesaka & Takeuchi
Shimadzu Corporation
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