Image analysis – Applications – Biomedical applications
Reexamination Certificate
1999-07-26
2001-03-13
Johns, Andrew W. (Department: 2621)
Image analysis
Applications
Biomedical applications
Reexamination Certificate
active
06201891
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray imaging apparatus using a CCD sensor, and particularly to an X-ray imaging apparatus which displays an image on a CRT or the like by means of digital processing and without using a film, and a recording medium constituting the apparatus. The X-ray imaging apparatus of the present invention is useful for a medical or dental diagnostic apparatus or an industrial nondestructive inspection apparatus.
A conventional X-ray imaging apparatus uses an X-ray film in order to recognize the internal state of an object of diagnosis, inspection, or the like in the form of an image. Recently, an X-ray imaging apparatus using a CCD sensor has been developed for the purposes such as those of shortening the development time, facilitating the data storage, and preventing data from deteriorating. Such an X-ray imaging apparatus uses a method in which the CCD sensor directly receives X-rays and digitized data are displayed on a CRT. The conventional X-ray imaging apparatus is configured so that the CCD sensor receives light from a material which converts X-rays transmitted through an object part e.g. a diseased part to be examined into light, and image data which are digitized pixel by pixel are displayed on an image display device.
In a conventional X-ray imaging apparatus which uses a CCD sensor in this way, the trouble of development can be decreased as compared with the method used in a former apparatus in which an image is formed by exposing an X-ray film to X-rays, thereby shortening the time required for diagnosis of a diseased part.
The conventional X-ray imaging apparatus using a CCD sensor has advantages that image data are digitized and hence the data are not deteriorated, and that the image data can be collectively stored into a recording medium and hence the space for storing the data can be reduced.
In such a conventional X-ray imaging apparatus, the brightness, the contrast, and the magnification degree of the diseased part on the screen of the image display device can be freely adjusted. Consequently, the apparatus serves as effective auxiliary means for diagnosis or inspection. In the medical and dental fields, particularly, digitization of image data allows such an X-ray imaging apparatus to be useful as an auxiliary to diagnosis. When used in an industrial nondestructive inspection apparatus, such a conventional X-ray imaging apparatus can improve the inspection efficiency and enhance the inspection accuracy.
A CCD sensor used in a conventional X-ray imaging apparatus is configured in the same manner as that used in a video camera or the like, or has a configuration in which the CCD sensor receives visible light, the visible light is converted in real time into an analog signal, and the analog signal is then output. Unlike the conventional CCD sensor used in the video camera or the like, however, a CCD sensor used in an X-ray imaging apparatus is provided with a fluorescent member (a scintillator made of, for example, Gd
2
O
2
S) which converts X-rays into visible light, on the surface of the CCD. Also an X-ray imaging apparatus of another kind in which, in place of such a fluorescent member, a cadmium telluride detecting element (CdTe detecting element) for converting X-rays into electric charges is connected to the surface of the CCD for each pixel is used.
Usually, the inspector observes a still X-ray image obtained by an X-ray imaging apparatus. In a conventional X-ray imaging apparatus, therefore, an analog signal from a CCD sensor is converted into a digital signal by an A/D converter at the timing when X-rays are irradiated, and the digital signal is once accumulated in a memory. Furthermore, an image display device is configured so that the digitized image data are displayed as a still image on a CRT or the like.
In order to know the timing when X-rays are irradiated, a conventional X-ray imaging apparatus which uses a CCD sensor as described above must receive trigger signals notifying the start and end of exposure from an X-ray exposure apparatus.
Next, an example of a conventional X-ray imaging apparatus using a CCD sensor will be described with reference to the accompanying drawings.
FIG. 23
is a block diagram showing the whole configuration of a conventional X-ray imaging apparatus using a CCD sensor, and
FIG. 24
shows a flow of a procedure conducted from the start of exposure to the display of an image in the conventional X-ray imaging apparatus.
Referring to
FIG. 23
, an X-ray exposure apparatus
210
irradiates a diseased part which is an exposure object, and an X-ray detection unit
201
receives X-rays
211
which have been transmitted through the exposure object. The X-ray detection unit
201
comprises a CCD element
212
, an A/D converter
215
, and a CCD driver
216
, and supplies a digital image signal
217
corresponding to the X-rays
211
, to an accumulation unit
205
. The accumulation unit
205
to which the digital image signal
217
is supplied comprises an accumulation value calculation circuit
223
and a frame memory
225
.
At the same time when the X-rays
211
are irradiated, the X-ray detection unit
201
outputs an X-ray exposure start trigger signal
241
to an accumulation start circuit
221
of an accumulation start unit
204
. Simultaneously with the end of exposure of the X-rays
211
, the X-ray detection unit
201
outputs an X-ray exposure end trigger signal
242
to an accumulation stop circuit
230
of an accumulation stop unit
208
. At this time, the accumulation stop circuit
230
supplies an accumulation stop instruction signal
231
to the accumulation value calculation circuit
223
, and at the same time a display instruction flag
232
to a display instruction circuit
233
of a display instruction unit
209
. Upon receiving the display instruction flag
232
, the display instruction circuit
233
outputs a display instruction signal
234
to a CPU
235
of an image display unit
238
. Upon receiving the display instruction signal
234
, the CPU
235
acquires digital image data for display
226
from the frame memory
225
, and displays the data on an image display device
237
such as a CRT. As required, digital image data for storage
239
output from the CPU
235
are stored as image data into a storage medium
240
.
In
FIG. 23
, the arrows indicate the X-rays and the flows of the signals, the numeral
213
indicates an analog image signal, the numeral
214
indicates a CCD driving signal, the numeral
222
indicates an accumulation start instruction signal, the numeral
224
indicates an accumulated digital image signal, and the numeral
236
indicates an image display signal.
Referring to
FIG. 23
, when the X-ray exposure apparatus
210
irradiates the CCD element
212
with the X-rays
211
, the CCD element
212
outputs the analog image signal
213
corresponding to an image of the exposure object, to the A/D converter
215
. The A/D converter
215
to which the analog image signal
213
is supplied outputs the digital image signal
217
.
Simultaneously with exposure of the X-rays
211
, the X-ray exposure apparatus
210
outputs the X-ray exposure start trigger signal
241
to the accumulation start circuit
221
. The accumulation start circuit
221
always monitors the input state of the X-ray exposure trigger signal
241
.
FIG. 24
shows the flow of the procedure conducted from the start of exposure of X-rays to the display of an image in the thus configured X-ray imaging apparatus of the prior art. The accumulation start circuit
221
conducts the process of STEP
2
of the flow shown in FIG.
24
. When the X-ray exposure start trigger signal
241
is not input, the accumulation start circuit
221
does not conduct accumulation of image data in STEP
3
.
By contrast, when the X-ray exposure start trigger signal
241
is supplied to the accumulation start circuit
221
of the accumulation start unit
204
, accumulation of the image data is started in STEP
4
. At this time, the accumulation start circuit
221
of the accumulation start uni
Ino Yoshihiro
Ohmori Koichi
Shinkaji Yasuhiko
Yamamoto Toshiyoshi
Johns Andrew W.
Matsushita Electric - Industrial Co., Ltd.
Sheridan & Ross P.C.
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