JPH01147445A - X-ray energy differential image photographing device - Google Patents

Abstract

PURPOSE:To take enough time for image accumulation by performing the image accumulation and image reading alternately at every scanning frame of a TV camera and fixing X-ray energy during the period of an image accumulating frame. CONSTITUTION:In case of photographing the output image of an X-ray image intensifier 7 by the TV camera 12, a frame for accumulating an image in a TV camera image picked up surface and a frame for reading an image signal from the TV camera are separated. In the image accumulating frame, an optical shutter 9 is opened and the X-ray energy is fixed. In a reading frame, the optical shutter is kept closed, and only in this frame, the change of the X-ray energy is performed. Thus enough time can be spent for the image accumulation without taking special consideration into the electron beam scanning period of the TV camera.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for measuring X-ray absorption of a subject, and in particular, a method for measuring the distribution of trace elements in a moving subject in a short time. The present invention relates to an X-ray energy difference imaging device suitable for obtaining an X-ray energy difference image with little influence.

[Conventional technology]

For diagnosis of ischemic heart disease represented by myocardial infarction,
Techniques for imaging the site and extent of coronary artery stenosis are extremely important, and the development of a minimally invasive intravenous contrast method is desired. For intravenous contrast imaging of coronary arteries, it is necessary to be able to detect a dilute iodine contrast agent with high sensitivity, and to be able to capture images in a short time to eliminate blurring due to pulsation.

Traditionally, as a method to achieve the above objectives, Nuclear
Instruments and Methods in Physics Research 246 (1986) No. 713
Pages 718 to 718 (Nuclear Instru
mentS and Met, hods 1nPh
ysics Re5each, A-246, (198
6) pρ, 713-718).

This method uses synchrotron radiation suitable for obtaining an intense m-color X-ray beam as an X-ray source for high-sensitivity detection of contrast agents. An energy difference method is used based on the large difference in the amount of X-ray absorption. In addition, for short-term image capture, an X-ray image intensifier and a color TV camera are used as X-ray image detectors, using phosphors that emit red and blue colors in the output fluorescent film. During imaging, the red light transmission filter and the blue light transmission filter are exchanged at high speed in synchronization with the X-ray energy switching, and the two images of the red and blue images of the output phosphor screen of the X-ray image intensifier are converted into two energy images. This method uses a color TV camera to take pictures.

[Problem that the invention seeks to solve]

The above conventional technology modifies the output fluorescent film of the X-ray image intensifier to give it red and blue emission colors, and further,
There are problems associated with the development of X-ray image intensifiers, such as the need to use a phosphor with a very short afterglow time in continuous imaging at short intervals.

An object of the present invention is to provide a highly practical device using a conventionally used X-ray image intensifier and TV left camera.

[Means for solving problems]

The above purpose is to separate the image accumulation on the TV left camera image plane and the readout of image signals from the TV left camera when capturing output images of the X-ray image intensifier (hereinafter abbreviated as X-ray II) using the TV left camera. However, this is achieved by changing the X-ray energy during image signal readout. Also, while changing the X-ray energy, images with different X-ray energies are mixed in the TV left camera readout signal, so the X-ray shutter and optical shutter are
Closed while reading the left camera image signal.

[Effect]

The method of the present invention will be explained based on the time chart shown in FIG.

From time t1 to time t12, the spectrometer energy is not changed and the X-ray energy is E1. During this time, the X-ray shutter is opened and the subject is irradiated with X-rays.

The output of X-ray II remains afterglow even after the X-ray shutter is closed at t2. For this reason, the optical shutter is opened only from time t to time t2 to transmit the TV left camera image. During this time, TV
Electron beam scanning of the left camera imaging tube is not performed, and images are stored on the imaging surface.

Next, for one hour from t2 to t3, the X-ray shutter is closed and the energy of the spectrometer is changed. During this time, the image pickup tube is scanned with an electron beam, and the image signals accumulated on the image pickup surface are read out. Note that while reading the image signal,
X-ray II of the TV left camera because the optical shutter is closed
There is no image input due to afterglow, and the intensity level of the image does not change during readout.

In this way, image capturing and image signal reading performed between time t1 and t3 are performed after t3.

By repeating this, it becomes possible to continuously capture images with different energies.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. In the figure, 1 is the X-ray source, 2 is the xi ray shutter, and 3 is the continuous
line, 6 shows continuous X-rays as monochromatic or narrow energy band width
4 is a monochromatic or narrow energy bandwidth X-ray spectrometer; 5 is an object; Next, in the detector system, 7
11 is an optical device containing an optical lens 8 and an optical shutter 9. 12 is a TV left camera 13 is a controller that drives the X-ray shutter 2, spectrometer 6, and optical shutter 9 according to the synchronization signal of the TV camera. , 14 is a data collection processing device that records and processes the image signal of the TV camera;
15 is a display device that displays the image processing results.

In this embodiment, high-intensity synchrotron radiation is used as the X-ray source 1, and a crystal spectrometer using a single crystal of silicon, germanium, or the like is used as the spectrometer 6. For example, when performing angiography of the subject 5 using an iodine contrast agent using this spectrometer, monochromatic X-rays around the absorption edge of iodine are generated, and the subject is exposed to pulsed X-rays using an X-ray shutter. Irradiate as a line.

The process of obtaining an X-ray energy difference image using the apparatus of this embodiment will be explained based on the time chart shown in FIG. In the figure, times t1 to 18 correspond to the TV camera vertical synchronization signal shown in (1), and each time interval equally corresponds to one frame of the TV camera. In (1) to (8), the driving states of each device constituting the apparatus of this embodiment are shown.

The time from t1 to t2 is the first frame, during which the energy of the spectrometer is not changed, and the X-ray energy is kept at an energy E, which is lower than the absorption edge energy of iodine.
The X-ray shutter is opened and the subject is irradiated with El monochromatic X-rays. At this time, the output of X-ray II has the time characteristic shown in (4) due to the rise and afterglow of the X-ray TI output fluorescent film, and the afterglow remains even after the X-ray shutter is closed at t2.

Therefore, in order to block the input light to the TV camera at t2, the optical shutter is opened only from tl to 12 as shown in (3). The TV camera does not perform electron beam scanning of the image pickup tube in the first frame.

This is a state in which images are accumulated on the imaging surface (photoelectric film).

An image of energy E1 is accumulated.

Next, in the second frame from time t2 to t3,
The X-ray shutter and the optical shutter are closed, and the spectrometer energy is changed so that monochromatic X-rays with an energy higher than the absorption edge energy are emitted to iodine with energy E2. At the same time, in this frame, the image pickup tube is scanned by the electron beam, and an image of the energy E accumulated in the first frame is read out and recorded by the data acquisition processing device.

In the next third frame, an image using monochromatic X-rays of energy E2 is accumulated in the same manner as in the first frame.

Then, in the fourth frame, similarly to the second frame, the monochromatic X of energy E is changed by changing the spectrometer energy.
The line is returned to the state where it is emitted, and at the same time the energy E2
The image is read out and recorded in the data collection processing device.

As a result, the time difference in capturing images of energies E1 and E2 is (ta ti), and images of two energies can be captured at a time interval of two frames. Furthermore, there are four frames between time t1 and time t5, and continuous shooting is possible with these four frames as one cycle.

X-ray energy E recorded in the data acquisition processing device
, and E2, the desired energy difference image can be obtained.

The X-ray energies E1 and E2 are close to each other with the absorption edge energy of iodine in between, and therefore the X-ray absorption rate of living tissues other than the contrast agent hardly changes between El and E2, so the contrast of the living tissue are almost the same for images E and E2. However, regarding contrast agents, since El and E2 have an absorption edge between them and iodine, E
, and E2 images are significantly different in contrast.

As a result, in the energy difference image, the image of the living tissue is erased, and a high contrast image of only the blood vessel image can be obtained. In addition, the image capturing time interval between X-ray energies E1 and E2 is 2 frames, and if the electron beam scanning time of the TV camera is shortened, two images can be captured in a short time when the movement of the living body can be ignored. Therefore, false images due to the movement of the living body do not occur in the energy difference image.

In the device of this embodiment, since the optical shutter requires high-speed response, it is preferable to use a shutter using PLZT or liquid crystal.

Note that in this example, synchrotron radiation was used as the X-ray source 1, and a crystal spectrometer using a single crystal was used as the spectrometer 6, but an X-ray tube could also be used as the X-ray source 1. , a bandpass filter or a multilayer film spectrometer can also be used as the spectrometer 6.

Next, another embodiment of the present invention will be explained according to the time chart shown in FIG.
corresponds to the TV camera vertical synchronization signal shown in (1), and t
1 to t2 is the first frame, and t2 to t3 is the second frame. In (1) to (8), the driving states of each device constituting the apparatus of this embodiment are shown.

In the first frame, the energy of the spectrometer is not changed from time t1 to 11/, and the X-ray energy is kept at energy E1 lower than the termination energy for iodine.
The X-ray shutter is opened and the subject is irradiated with El monochromatic X-rays. At this time, the output of X-ray II has the time characteristic shown in (4) due to the rise and afterglow of the X-ray technician 1 output fluorescent film.

Afterglow remains even after closing the X-ray shutter at 11/.

Therefore, in order to block the input light to the TV camera at t11, the optical shutter is moved from tl to t1 as shown in (3).
Open only between '. The TV camera is in a state in which the electron beam of the imaging tube is not scanned from 11 to t1' in the first frame, and images are accumulated on the imaging surface (photoelectric film), and images of energy E1 are accumulated.

Next, in the first frame, the X-ray shutter and the optical shutter are closed from t□' to 12, and the spectrometer energy is changed so that energy higher than the absorption edge energy is emitted to iodine of energy E2. At the same time, during this period, the electron beam of the image pickup tube is scanned, from tl to t.
1' is read out and recorded in the data acquisition processing device.

In the next second frame, similarly to the first frame, the energy of the spectrometer is not changed from time t2 to 127, and the electron beam scanning of the image pickup tube is stopped.
Images by monochromatic X-rays of energy E2 are accumulated. Then, between time t2' and t3, the spectrometer energy is changed by one to return to a state in which monochromatic X-rays of energy E1 are emitted, and at the same time, an image of energy E2 is read out and recorded in the data acquisition processing device.

As a result, the time difference in capturing images of energies E1 and E2 is (t2 tt).

Images with two energies can be captured at a time interval of one frame. Here, the part corresponding to 11 to t□' in the first frame and the part corresponding to 1, / from t2 in the second frame are not read out as one image, but this image If the time required for accumulation is short enough, there will be no interlayer.

〔Effect of the invention〕

According to the invention, using a conventional X-ray image intensifier and a TV camera.

Since it is possible to capture energy images around the absorption edge energy of the contrast agent in a short time when the movement of the living body is negligible, it has the effect of being able to obtain high-contrast energy difference images with a highly practical device.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of one embodiment of the present invention, FIG. 2 is a time chart showing the operation of component equipment in one embodiment of the present invention, and FIG. 3 is a configuration diagram of another embodiment of the present invention. It is a time chart showing the operation of the device.

Claims (1)

[Scope of Claims] 1. In an apparatus for sequentially irradiating a subject with X-rays having different energies and obtaining an energy difference image from the obtained X-ray image, an X-ray shutter for blocking the irradiation of the X-rays to the subject; , a means for changing the energy of the X-rays, an X-ray image intensifier for converting the X-ray image of the subject into a light image, a TV camera for capturing the light image, and a means for transmitting the light image to the TV camera. An optical shutter that blocks the incidence of light, and an optical shutter that closes the X-ray shutter and the optical shutter so that the readout scanning of the image of the TV camera and the energy change of the X-rays are performed in parallel while the X-ray shutter and the optical shutter are closed. An X-ray energy difference imaging apparatus comprising: control means for controlling opening and closing of a shutter, readout scanning of the TV camera, and timing of the energy changing means. 2. Claim 1, characterized in that synchrotron radiation emitted from a high-energy electron storage ring is used as the source of the X-rays, and a crystal spectrometer is used as the means for changing the X-ray energy. The X-ray energy difference imaging device described in . 3. An X-ray energy difference imaging apparatus characterized in that an X-ray tube is used as the X-ray source, and a bandpass filter or a multilayer spectrometer is used as a means for changing the X-ray energy.