JP4161578B2 - X-ray equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray imaging apparatus, and more particularly to an X-ray imaging apparatus that filters an X-ray energy spectrum distribution due to an X-ray tube voltage with an additional filter and images a region of interest in an X-ray image with an appropriate contrast.
[0002]
[Prior art]
A conventional X-ray imaging apparatus includes an X-ray tube that irradiates a subject with X-rays, a high-voltage generator that supplies a tube voltage and a tube current to the X-ray tube, and an X-ray tube facing the subject. An imaging means (for example, a film) that captures the difference in the X-ray transmission distribution of the subject from the transmitted X-rays as an X-ray image.
As the X-ray tube, a rotary anode X-ray tube is generally used. The rotary anode X-ray tube includes a cathode having a filament and an anode having a target made of tungsten or the like, and the cathode and the anode are arranged between the cathode and the anode. The high voltage output from the high voltage generator is applied to the filament, and a current that causes thermionic electrons to flow is applied to the filament.
The thermoelectrons emitted from the filament are accelerated by a high voltage between the cathode and the anode, collide with the target of the anode, and generate X-rays. The X-rays generated at this time have characteristics in which characteristic X-rays are added to continuous X-rays, and have an X-ray energy spectrum corresponding to a high voltage applied between the cathode and the anode.
[0003]
FIG. 5 shows an X-ray spectrum distribution of typical chest X-ray imaging in general imaging. FIG. 5 shows X-ray energy (keV) on the horizontal axis and the X-ray spectrum of the relative X-ray quantum number on the vertical axis using an additional filter with a thickness of Cu 1.0 mm under X-ray conditions of 140 kV and 100 mAs. The low energy X-ray component of 20 to 55 keV that appears when the additional filter is not used is attenuated, and only the high energy component of 55 keV or higher including the characteristic X-ray is radiated by the additional filter Cu 1.0 mm. Thus, the X-ray spectrum emitted from the X-ray tube sealed in the X-ray tube container is considerably reduced in the number of low energy quanta by the additional filter of the X-ray tube, and the number of high energy quanta. There are many X-ray distributions.
This is because if the energy of incident X-rays is made too low, the following adverse effects occur due to the relationship with the effective density region of a light receiving system such as an imaging means (for example, a film). In previous chest X-rays, contrast was emphasized and X-rays taken at a low tube voltage of about 50 kV were used. Therefore, lesions that overlap the ribs and mediastinum were not expressed because they were outside the effective density region. It was. In order to eliminate such drawbacks, in recent years, high energy X-rays have been used by using a relatively high tube voltage of 140 kV and an additional filter Cu 1.0 (mm).
[0004]
[Problems to be solved by the invention]
The conventional X-ray imaging apparatus is configured as described above, and imaging is performed using an additional filter. However, an attempt is made to show more X-ray absorption different portions of the subject in a limited concentration range. Then, it becomes difficult to show a part with a small absorption difference. On the other hand, if an attempt is made to express a portion having a small absorption difference, the range of absorption difference and thickness that can be expressed is limited.
In conventional imaging techniques, high-energy X-rays have a higher transmission capability than low-energy X-rays, and are suitable for imaging lesions that overlap the ribs and mediastinum. When a part having a small difference in line absorption is to be imaged, there is a problem that high-contrast X-ray transmission increases X-ray transmission, and imaging with good contrast cannot be performed.
As a method for solving this problem, by selecting different tube voltages and types of additional filters for a portion where the X-ray absorption difference is small and a portion where the X-ray absorption difference is large, an X-ray having a large transmission ability is selected from a portion where a minute contrast is required. A method can be considered that corresponds to the part that needs to be used.
However, in the conventional X-ray imaging apparatus, in order to replace the additional filter in the middle of X-ray imaging, the generation of X-rays must be stopped and then the additional filter must be replaced. Since it is interrupted, there is a problem that the subject moves during that time.
[0005]
The present invention has been made in view of such circumstances, and performs X-ray imaging with high-energy X-rays and low-energy X-rays without interrupting X-ray imaging. An object of the present invention is to provide an X-ray imaging apparatus capable of improving the visibility from a small part to a large part.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an X-ray imaging apparatus of the present invention irradiates a subject with X-rays emitted from an X-ray source via an additional filter, and transmits transmitted X-rays that have passed through the subject to X-rays. In an X-ray imaging apparatus for imaging by imaging means, means for sequentially inserting at least two different additional filters between the X-ray source and the subject in one imaging, and imaging different depending on the additional filters An imaging condition memory for storing imaging conditions and an imaging condition setting for setting the imaging conditions so that the combined density of the imaging conditions by means of emitting X-rays under conditions and two or more different additional filters becomes an appropriate value It is characterized by having a vessel.
[0008]
The X-ray imaging apparatus of the present invention is configured as described above, and an additional filter is arranged on the radiation surface side of the X-ray tube that is an X-ray source, and at least two kinds of different additional filters can be obtained by one imaging. Sequentially inserted by means such as rotation of the motor, the X-ray energy spectrum is filtered, the position of the additional filter is detected by the position detector, and different imaging is performed according to the additional filter set in the X-ray controller. Under the condition, different high voltages are sequentially applied from the high voltage generator to the X-ray tube, and the X-rays are controlled to be radiated.
Therefore, the X-ray spectrum of the X-rays that pass through the additional filter from the X-ray source and are irradiated on the subject is controlled, and an X-ray image of the subject is captured by X-rays having a plurality of energy distributions.
The shooting conditions are set by the shooting condition setting unit from the shooting condition memory storing the data of the past shooting conditions so that the combined density shot under two or more different shooting conditions becomes an appropriate value. Then, control is performed so that the density of a composite image such as a photographed film becomes an easily viewable value.
Therefore, when performing general radiography of the lung field or the like as an imaging target, a lesion portion overlapping the ribs and the mediastinum portion has a small X-ray absorption difference while ensuring a sufficient gradation of the image of the imaging site. Can also be obtained.
In addition, X-ray transmission images of low-energy X-rays and high-energy X-rays can be obtained with a single imaging without interrupting the imaging operation. It is possible to improve the visibility from a small part to a large part.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the X-ray imaging apparatus of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing the configuration of the X-ray imaging apparatus of the present invention. FIG. 2 is a view showing the additional filter disc 4 of the X-ray imaging apparatus.
The X-ray imaging apparatus includes an X-ray tube 3, an additional filter disk 4 provided between the X-ray tube 3 and the subject 7, provided with two different additional filters 4 a and 4 b, and rotated by a motor 5; An imaging condition memory in which data of imaging conditions photographed at an appropriate density is set and stored by a position detector 6 that detects the rotational position of the additional filters 4a and 4b of the additional filter disk 4 and different additional filters 4a and 4b. 16 and an imaging condition setting unit 11 that sets an imaging part of the subject 7 and selects an imaging condition from the data stored in the imaging condition memory 16 and sets the imaging condition in the X-ray controller 10, according to different additional filters 4 a and 4 b. The high voltage generator 2 that sequentially applies and supplies the tube voltage and tube current to the X-ray tube 3 in one imaging under the imaging conditions set in the X-ray controller 10 and the X-ray tube with different tube voltage and tube current. Radiated from 3 That X-rays are different additional filters 4a correspondingly, and a film 8 which X-rays transmitted through 4b different X-ray energy spectrum is to shoot the X-ray image transmitted through the patient 7.
[0010]
Next, the mechanism of the X-ray imaging apparatus will be described. The X-ray output from the X-ray tube 3 passes through the additional filter disc 4, passes through the subject 7, and is detected by the film 8. An additional filter disk 4 shown in FIG. 2 is inserted between the X-ray tube 3 and the subject 7, and when an X-ray switch (not shown) is pressed, the X-ray signal 12 is X-ray controlled. The additional filter disc 4 is rotated at a high speed by the motor 5 in response to the motor drive signal 13 from the X-ray controller 10. The additional filter disc 4 is composed of two types of additional filters 4a and 4b that are different from a circular substrate made of a material transparent to X-rays. The additional filters 4a and 4b are attached. The additional filter disc 4 is driven by a motor 5 and rotates at high speed, and the rotational position of the additional filter disc 4 is detected by a position detector 6. The filter detection signal 14 at the detected position is input to the X-ray controller 10, and the X-ray condition set in the imaging condition memory 16 of the X-ray controller 10 is read out by the filter detection signal 14, After a time, an X-ray radiation signal 15 is output, and a high voltage corresponding to the rotating additional filters 4a and 4b is applied to the X-ray tube 3 in response to the filter detection signal 14 from the position detector 6, and once. X-rays are emitted in sequence.
Further, the X-ray controller 10 is provided with an imaging condition memory 16 and an operation panel is provided with an imaging condition setting unit 11. The imaging condition memory 16 uses the additional filters 4 a and 4 b that are appropriate for each diagnostic region of the subject 7. Data on photographing conditions that can be photographed at various densities are stored. When the diagnostic condition setting unit 11 inputs the diagnostic part of the subject 7, the imaging condition data corresponding to the diagnostic part stored in the imaging condition memory 16 is selected, and the imaging condition is sent to the X-ray controller 10. Is set. Then, according to the filter detection signals 14 of the different additional filters 4 a and 4 b from the position detector 6, imaging is sequentially performed for one imaging under the imaging conditions set in the X-ray controller 10.
[0011]
Next, the imaging operation of the X-ray imaging apparatus will be described with reference to FIG. FIG. 3 is a diagram illustrating a timing chart of the imaging operation of the X-ray imaging apparatus.
First, when an X-ray switch (not shown) is pressed, the X-ray signal 12 is input to the X-ray controller 10. (Time point a in FIG. 3)
A motor drive signal 13 is sent from the X-ray controller 10 to the motor 5, and the additional filter disc 4 attached to the rotary shaft begins to rotate as the motor 5 begins to rotate. (Time point b in FIG. 3)
When the position detector 6 receives the filter detection signal 14 and detects the filter position “additional filter 4a” (no filter), the first imaging condition (60 kV) having the X-ray spectral distribution shown in FIG. , 300 mAs) is read from the imaging condition memory 16 of the X-ray controller 10. (Time point c in FIG. 3)
Then, after a predetermined time, an X-ray radiation signal 15 is output, and a high voltage of 60 kV of the first imaging condition is applied from the high voltage generator 2 to the X-ray tube 3. (Time point d in FIG. 3)
Then, it is applied only during the tube current time product of 300 mAs in the first imaging condition, the X-ray radiation signal 15 is stopped, and the first X-ray radiation is terminated. (Time point e in FIG. 3)
Subsequently, when the filter position “additional filter 4b” (Cu, 2 mm) is detected, the second imaging condition (140 kV, 100 mAs) having the X-ray spectrum distribution shown in FIG. It is. (Time point f in FIG. 3)
Similarly, after a predetermined time, the X-ray radiation signal 15 is output, and a high voltage of 140 kV of the second imaging condition is applied from the high voltage generator 2 to the X-ray tube 3. (Time point g in FIG. 3) Then, the X-ray radiation signal 15 is stopped and the second X-ray radiation is terminated by applying the tube current time product of 100 mAs in the second imaging condition. (Time point h in FIG. 3)
Then, the motor operation signal 13 stops and the motor stops. (Time point i in FIG. 3) Finally, the X-ray signal 12 is turned OFF. (Time point j in FIG. 3)
[0012]
The X-ray photograph obtained by the above-described series of first and second X-ray radiation imaging operations has an X-ray spectral distribution of FIG. 4C, which is a combination of FIGS. 4A and 4B. It was taken with a line. Thus, X-ray imaging having both high-energy X-rays and low-energy X-rays can be performed by performing imaging while changing the type of additional filter member and imaging conditions accordingly. And it becomes possible to improve the visibility from a site | part with a small X-ray absorption difference to a big site | part.
Furthermore, the combined density can be maintained at an appropriate value by combining the tube current time products of the photographing conditions. Therefore, when performing general radiography of the lung field or the like as an imaging target, imaging of other portions with small differences in X-ray absorption while securing sufficient radiographic images of lesions overlapping the ribs and mediastinum Images can also be obtained.
[0013]
The data of the first imaging condition and the second imaging condition stored in the imaging condition memory 16 are the material of the additional filters 4a and 4b, the tube voltage and the tube in the combination of the actual apparatus and the X-ray tube 3 using the chest phantom. The spectral distribution can be measured and obtained using the current-time product value as a parameter.
[0014]
In the above embodiment, the two types of additional filters are arranged on the additional filter disc 4. However, the present invention is not limited to this. For example, two or more different additional filters are arranged and X-rays are arranged. It is good also as composition which performs photography.
In this embodiment, the film 8 is used as the X-ray imaging means. I. -It can be similarly applied even when a TV system or an FPD (Flat Panel Detector) system is used.
[0015]
【The invention's effect】
The X-ray imaging apparatus of the present invention is configured as described above. At least two or more different additional filters are sequentially inserted between the X-ray source and the subject in one imaging operation, and accordingly Further, by emitting X-rays under different imaging conditions, a composite image of two or more different X-ray spectra can be obtained by one imaging. As a result, X-ray images can be captured by high-energy X-rays and low-energy X-rays in a single imaging.
Even in a composite image of two or more types of different X-ray spectra, the imaging data stored in the imaging condition memory is selected by the imaging condition setting device, and irradiation is performed under appropriate X-ray imaging conditions. X-ray images can be obtained, and the visibility from a portion having a small X-ray absorption difference to a portion having a large X-ray absorption can be improved, and the diagnostic efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an X-ray imaging apparatus according to the present invention.
FIG. 2 is a view showing an additional filter disk of the X-ray imaging apparatus of the present invention.
FIG. 3 is a timing chart illustrating the operation of the X-ray imaging apparatus of the present invention.
FIG. 4 is a diagram showing a transmission spectrum distribution imaged using an additional filter of the X-ray imaging apparatus of the present invention.
FIG. 5 is a diagram showing a transmission spectrum distribution at the time of conventional chest imaging.
[Explanation of symbols]
2 ... high pressure generator 3 ... X-ray tube 4 ... addition filter disks 4a, 4b ... addition filter 5 ... motor 6 ... position detector 7 ... subject 8 ... film 10 ... X-ray controller 11 ... imaging condition setting device 12 ... X-ray signal 13 ... Motor drive signal 14 ... Filter detection signal 15 ... X-ray radiation signal 16 ... Imaging condition memory

Claims (1)

In an X-ray imaging apparatus that irradiates a subject with X-rays emitted from an X-ray source through an additional filter and images transmitted X-rays that have passed through the subject with an X-ray imaging unit, the X-ray source and the subject Means for sequentially inserting at least two or more different additional filters between the specimens in one imaging, means for emitting X-rays under different imaging conditions according to the additional filters, and the two or more different additions An X-ray imaging apparatus comprising: an imaging condition memory for storing imaging conditions, and an imaging condition setting unit for setting the imaging conditions so that a combined density of imaging conditions by a filter becomes an appropriate value .

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