JP2012217596A - X-ray diagnostic imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray diagnostic imaging apparatus for attaining an imaging method to be required in a clinical site at a high degree of freedom and with exposure accuracy.SOLUTION: The X-ray diagnostic imaging apparatus includes an X-ray tube 01, a radiation quality filter 02, an X-ray restricting device 03, a table 04, an X-ray detection means 05, a grid 06, a display means 07, and an X-ray control means 08. The apparatus also includes: an X-ray detector information storage means 09 for storing a sensitivity characteristic; a fluoroscopic information storage means 10 for storing four parameters, i.e., the fluoroscopic tube voltage, fluoroscopic tube current, fluoroscopic irradiation time, and intensity of an output signal to be output from the X-ray detection means as digital values; a setting means 11 for setting two parameters, i.e., the photographing tube voltage and tube current; a photographing information storage means 12 for storing the set two parameters and target output signal intensity in photographing; and a photographing X-ray condition calculation means 13 for calculating the parameter of photographing irradiation time, based on the four parameters stored in the fluoroscopic information storage means, the two stored parameters, and the target output signal intensity in photographing.

Description

  The present invention relates to an X-ray diagnostic imaging apparatus having both fluoroscopic and radiographic functions, and more particularly to a technique of an exposure control method that appropriately controls X-ray conditions during radiography.

  In recent years, flat panel detectors (hereinafter abbreviated as FPD) in which a large number of X-ray detection elements using semiconductors are arranged vertically and horizontally are widely used as X-ray detection means. FPD has advantages in that it is lighter and more compact than image intensifiers (hereinafter abbreviated as I.I.), has no image distortion, and has a wide effective field of view. The use of an auxiliary detector for controlling the X-ray exposure time is difficult, and if the use of the auxiliary detector is considered, there is a possibility of sacrificing the compactness that was an advantage of FPD.

  For example, Patent Document 1 has been proposed as a technique for performing X-ray exposure control without using an auxiliary detector.

  Patent Document 1 proposes an X-ray photography apparatus that determines an imaging X-ray condition from a fluoroscopic X-ray condition. Specifically, the fluoroscopic tube voltage obtained by the fluoroscopic brightness automatic adjustment mechanism reflects the subject thickness when the fluoroscopic tube current is assumed to be constant. Therefore, the subject thickness is obtained from the fluoroscopic tube voltage, and the preset subject thickness is obtained. The photographing is performed by the product (hereinafter abbreviated as mAs) of the photographing tube voltage, photographing tube current and photographing irradiation time corresponding to the above.

JP 58-116530 A

  Patent Document 1 described above has the following problems.

  That is, even when the brightness is appropriately maintained by the fluoroscopic brightness automatic adjustment mechanism, the scattered X-rays increase when the subject is thick, and the contrast of the image is lost as compared to when the subject is thin. For this reason, there is a case where brightness and contrast are appropriately maintained by lowering the tube voltage and increasing the tube current by an operator's manual operation, and the imaging method required in the clinical field cannot be realized with high flexibility and exposure accuracy. .

  The present invention has been made in view of the circumstances as described above, and an object thereof is to provide an X-ray diagnostic imaging apparatus that realizes an imaging method required in a clinical field with a high degree of freedom and exposure accuracy.

  In order to achieve the above object, the present invention provides the X-ray detection means to obtain an X-ray dose incident on the X-ray detection means in a final fluoroscopic frame and a target output signal intensity of imaging performed after the fluoroscopy. The ratio of X-ray dose that needs to be incident is the fluoroscopic X-ray condition required to give the X-ray dose incident on the X-ray detection means in the final frame of fluoroscopy, and the target output signal of imaging performed after the fluoroscopy An X-ray diagnostic imaging apparatus that utilizes a fact that a ratio with a radiographic X-ray condition required to give an X-ray dose that needs to be incident on the X-ray detection means in order to obtain intensity has a predetermined relationship . However, the imaging target of the final fluoroscopic frame and the imaging target of the imaging performed after the fluoroscopy are the same.

  Fig. 1 (a) shows that the X dose of d was incident on the FPD when imaging was performed under the X-ray conditions of α [kV], β [mA], and γ [ms] on the imaging target (subject). Show. Therefore, we will give a solution for how the X-ray conditions should be used in order to make 2 * d X-rays incident on the FPD ((b) in the figure).

  That is, in the present invention, for the same imaging target, the relationship between the X-ray dose incident on the FPD and the X-ray conditions (tube voltage, tube current, irradiation time) is clarified, and when shifting from fluoroscopy to imaging, a predetermined The imaging X-ray condition is calculated by calculation.

  The specific configuration of the present invention is as follows.

The X-ray diagnostic imaging apparatus of the present invention outputs an X-ray tube that generates X-rays to be irradiated to a subject, and an X-ray intensity distribution that is disposed opposite to the X-ray tube and transmits the subject as a digital value. An X-ray image comprising: a ray detection means; a display means for displaying an X-ray image detected by the X-ray detection means; and an X-ray control means for performing fluoroscopic X-ray control used for determining an imaging region. In the diagnostic apparatus, X-ray detector information storage means for storing sensitivity characteristics of imaging and fluoroscopy modes of the X-ray detection means, and fluoroscopy information storage means for storing fluoroscopy information in the last fluoroscopic frame when shifting from fluoroscopy to radiography And setting information for setting the imaging tube voltage and imaging tube current of the imaging X-ray conditions, and imaging information for storing the imaging X-ray conditions set in the setting means and the target output signal intensity of the imaging X-ray detection means Storage means and the perspective information storage means X-ray imaging condition calculation means for calculating imaging irradiation time from the stored fluoroscopic information, the imaging X-ray conditions stored in the imaging information storage means, and the target output signal intensity of imaging of the X-ray detection means, It is characterized by comprising.

  As described above, it is possible to provide an X-ray diagnostic imaging apparatus having a high degree of freedom and exposure accuracy to a clinical site.

The figure for demonstrating the problem which this invention solves. The figure for demonstrating the "centroid" in a histogram. Schematic which shows the sensitivity characteristic of FPD. FPD output signal intensity ratio (Figure explaining the case where the tube voltage is changed under the condition that the subject and mAs are constant. A graph that summarizes the coefficients of each order in the polynomial for each tube voltage by approximating the output signal strength ratio of FPD by polynomial approximation. A graph that summarizes the coefficients of each order in the polynomial for each tube voltage by approximating the output signal strength ratio of FPD by polynomial approximation. A graph that summarizes the coefficients of each order in the polynomial for each tube voltage by approximating the output signal strength ratio of FPD by polynomial approximation. A graph that summarizes the coefficients of each order in the polynomial for each tube voltage by approximating the output signal strength ratio of FPD by polynomial approximation. Schematic which shows the structure of the X-ray image diagnostic apparatus which concerns on embodiment. 5 is a flowchart for explaining the operation of the first embodiment. The enlarged view of the setting means 11 part. 6 is a setting example of a tube voltage and tube current set on a maintenance screen (not shown) of the setting means 11. An example of the relationship between the fluoroscopic tube voltage and the imaging tube current set in Embodiment 4 (mAs Auto).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the embodiment, functions that can be considered as system specifications will be described by dividing them into the following eight types.

1) When setting the fluoroscopic X-ray conditions manually and automatically setting the radiographic X-ray conditions
2) When setting both the fluoroscopic X-ray conditions and radiographic X-ray conditions automatically (hereinafter abbreviated as Full Auto)
3) When the fluoroscopic X-ray conditions are set automatically, and in shooting, the tube voltage and tube current are set manually, and the irradiation time is set automatically (hereinafter abbreviated as Timer Auto)
4) When the fluoroscopic X-ray conditions are set automatically, and when shooting, tube voltage is set manually, tube current, and irradiation time are set automatically (hereinafter abbreviated as mAs Auto)
5) When changing from fluoroscopy to shooting, SID changes
6) Changing the quality filter when moving from fluoroscopy to shooting
7) When changing the irradiation size when moving from fluoroscopy to shooting
8) When substantially setting Density with the target output signal intensity In Embodiments 1 to 4, the SID when shifting from fluoroscopy to imaging is fixed, the quality filter, the irradiation size, the grid, and the subject are Identical. Further, it is assumed that fluoroscopy is used for positioning of the part of the subject and that the transition from fluoroscopy to imaging is instantaneous.

  Here, the predetermined calculation used when shifting from fluoroscopy to photographing will be described in detail.

  To secure 2 * d X-ray dose by changing the settings of β [mA] and γ [ms] under the condition that α [kV] is fixed, set the other one twice while fixing one It can be realized by changing. In other words, this can be realized by changing the setting to a combination of β [mA] and γ [ms] that doubles mAs under a condition where the tube voltage is fixed.

  Next, consider securing a 2 * d X-ray dose by changing the tube voltage setting instead of changing the mAs setting. The relationship between the incident X-ray dose to FPD and mAs is directly proportional, such that when one is doubled, the other is doubled, and when one is tripled, the other is tripled. In addition, since the relationship between the incident X-ray dose to the FPD and the output signal intensity from the FPD is also directly proportional, the relationship between the mAs and the output signal intensity from the FPD is also directly proportional.

  However, in the case of tube voltage, there is no such relationship, so it is clear about the incident X-ray dose to the FPD or the change in the output signal intensity from the FPD when changing from one tube voltage to another tube voltage. There is a need to. At that time, it is necessary to consider the tube voltage dependence of the sensitivity of the FPD (the slope of the sensitivity characteristic in FIG. 3). The tube voltage dependency is that the sensitivity changes depending on the tube voltage.

  In the following, in order to simplify the explanation, it is assumed that the sensitivity characteristic of the FPD does not depend on the tube voltage.

  The change in the incident X-ray dose to the FPD when changing from a certain tube voltage to a different tube voltage can be calculated from the output signal strength from the FPD using the sensitivity characteristics of the FPD (see Fig. 3). . Here, for the sake of simplicity, the discussion assumes that the sensitivity characteristics of the FPD do not depend on the tube voltage, so the output signal intensity ratio from the FPD when the tube voltage is changed should be considered as the incident X-dose ratio to the FPD. Fig. 4 shows the output signal intensity ratio obtained. This figure shows the output signal intensity when changing from a certain tube voltage (tube voltage shown in the legend) to a different tube voltage (tube voltage shown on the horizontal axis of the graph) under the condition that the subject and mAs are fixed. The ratio is obtained. For example, the output signal intensity ratio when the tube voltage is changed from 40 [kV] to 110 [kV] is about 28 (28 times the output signal intensity) when calculated from FIG.

  These characteristic curves can be accurately approximated by polynomials of the third order, and the four coefficients of the polynomial (coefficients related to the 1st to 3rd order terms and constant terms) are specific to each tube voltage (the tube voltage shown in the legend). It is. Accordingly, as shown in FIGS. 5A to 5D, if each coefficient is plotted for each tube voltage, each coefficient can be defined as a function of the tube voltage. However, the formulas in the graphs shown in FIGS. 5A to 5D indicate the third-order approximation polynomial of each curve. In addition, we conduct experiments, obtain the above approximate polynomials from finite data measured in advance, and use these approximate polynomials to accurately output even in unmeasured data areas different from the finite data measured in advance. It has been confirmed that the signal intensity ratio can be calculated. Therefore, by calculating and using the approximate polynomial calculated based on the above idea from finite measurement data, the output signal intensity ratio due to tube voltage fluctuation, that is, the ratio of incident X dose to the FPD due to tube voltage fluctuation can be obtained. Can do.

  For example, the procedure for obtaining the output signal intensity ratio due to the fluctuation from the tube voltage A to the tube voltage B is as follows.

(step 1)
Under the condition that the subject and mAs are fixed, the output signal intensity at that time is measured while changing the tube voltage, and a characteristic curve as shown in FIG. 4 is obtained. At the same time, a cubic approximation polynomial of the characteristic curve is obtained for each tube voltage (legend shown in the figure).

(Step 2)
From the third-order approximation polynomial for each tube voltage obtained in step 1, four coefficients of the polynomial are plotted for each tube voltage as shown in FIGS. 5A to 5D, and each coefficient is defined as a function of the tube voltage. The four coefficients mean the third-order term, second-order term, first-order term, and constant term. Although the third-order approximation polynomial is described here, the order may be increased in order to increase accuracy. The same applies to the approximation of the characteristic curve in Procedure 1.

(Step 3)
Each coefficient at tube voltage A is obtained from the approximate polynomial of each coefficient defined in step 2. Thereby, the characteristic curve of the tube voltage A is obtained.

(Step 4)
From the characteristic curve obtained in step 3, the output signal intensity ratio corresponding to the tube voltage B is obtained.

  In the above, the discussion proceeded on the assumption that the sensitivity characteristic of FPD does not depend on the tube voltage, but the sensitivity characteristic of FPD etc. that uses CsI (TI) as a scintillator has tube voltage dependence, strictly speaking, that It is necessary to clarify the relationship between the ratio of the incident X-ray dose to the FPD due to the fluctuation of the tube voltage after considering the dependence. The following summarizes the differences when FPD tube voltage dependence is not taken into account, and shows the discussion up to this point in relation to the FPD incident X-ray dose, tube voltage, tube current, and irradiation time. .

  When considering the tube voltage dependence of FPD, the incident X-ray dose is obtained from the measured value of the output signal intensity in step 1 above, using the sensitivity characteristics at each tube voltage of FPD. The incident X-ray dose when changing from a certain tube voltage (tube voltage shown in the legend) to a different tube voltage (tube voltage shown on the horizontal axis of the graph) with the vertical axis in FIG. 4 as the “incident X-ray dose ratio” Find the ratio relationship. Compared with the case where the tube voltage dependence of the FPD is not taken into consideration, only this point is different.

(i) When FPD tube voltage dependence is not taken into consideration Since the output signal intensity ratio and the incident X-dose ratio are equivalent, the ratio of output signal intensity can be used when calculating the incident X-dose ratio to the FPD . (Adopt {Equation 1})
(ii) When considering tube voltage dependence of FPD
The incident X-ray dose is obtained from the measured values of the sensitivity characteristics and output signal intensity at each tube voltage of the FPD, and the relationship of the incident X-ray dose ratio to the FPD due to tube voltage fluctuation is obtained. (Adopt {number 2})

但し、
i₁ FPDへの入射X線量1
mA₁ FPDへの入射X線量1を与えた際の管電流
ms₁ FPDへの入射X線量1を与えた際の照射時間
i₂ FPDへの入射X線量2
mA₂ FPDへの入射X線量2を与えた際の管電流
ms₂ FPDへの入射X線量2を与えた際の照射時間
ratio_signal 管電圧変動によるFPDの出力信号強度比(FPDの管電圧依存性を考慮しない場合)
(FPDへの入射X線量2を与えた際の管電圧から入射X線量1を与えた際の管電圧へ変えた際の出力信号強度比)
ratio_dose 管電圧変動によるFPDの入射X線量比(FPDの管電圧依存性を考慮する場合)
(FPDへの入射X線量2を与えた際の管電圧から入射X線量1を与えた際の管電圧へ変えた際の入射X線量比)
である。

However,
i ₁ X-ray dose to FPD 1
mA ₁ Tube current when the incident X-ray dose to the FPD is ₁
ms ₁ Irradiation time when an incident X-ray dose of 1 is given to the FPD
i ₂ FPD incident X-ray dose 2
mA ₂ Tube current when the incident X-ray dose to the FPD is ₂
ms ₂ Irradiation time when an incident X-ray dose of 2 is given to the FPD
ratio _signal FPD output signal strength ratio due to tube voltage fluctuation (when FPD tube voltage dependency is not considered)
(Output signal intensity ratio when the tube voltage when the incident X-ray dose 2 is given to the FPD is changed to the tube voltage when the incident X-ray dose 1 is given)
ratio _dose Incident X-ray dose ratio of FPD due to tube voltage fluctuation (when considering tube voltage dependence of FPD)
(The ratio of incident X-ray dose when changing the tube voltage when supplying incident X-ray dose 2 to the tube voltage when applying incident X-ray dose 1)
It is.

<Embodiment 1>
In the first embodiment, a case will be described in which the fluoroscopic X-ray conditions that are difficult in Patent Document 1 are set manually and the imaging X-ray conditions are set automatically.

  FIG. 6 is a schematic diagram showing the configuration of the X-ray image diagnostic apparatus according to the embodiment of the present invention.

  The X-ray diagnostic imaging apparatus according to the embodiment includes an X-ray tube 01 that generates X-rays for irradiating the subject M with X-rays, and a quality filter that changes the energy distribution of the X-rays, as shown in FIG. 02, an X-ray diaphragm 03 for controlling the X-ray irradiation area, a table 04 placed opposite to the X-ray tube for placing the subject M, and an X-ray from the X-ray tube 01 to the subject M Is installed between the table 04 and the X-ray detection means 05, and outputs the X-ray intensity distribution transmitted through the subject M as a digital value. A grid 06 that removes scattered X-rays generated when passing through the screen, a SID adjustment means (not shown) that can change the SID within a certain range, and an X-ray image detected by the X-ray detection means 05 are displayed. Display means 07 to perform X-ray control for taking an image used for definitive diagnosis, and used for definitive diagnosis X-ray control means 08 for performing fluoroscopic X-ray control used for determining the imaging region, etc., and imaging X-ray conditions, that is, 1) imaging tube voltage, 2) imaging tube current, 3 ) Among the three parameters of the photographing irradiation time, there are setting means 11 for presetting two parameters of the photographing tube voltage and the tube current or setting them during the procedure.

  Further, the X-ray control means 08 includes an X-ray detector information storage means 09 for storing sensitivity characteristics of the imaging and fluoroscopic modes of the X-ray detection means 05, and 1) in the final fluoroscopic frame when shifting from fluoroscopy to radiography. The fluoroscopy information storage means 10 for storing four parameters of fluoroscopic tube voltage, 2) fluoroscopic tube current, 3) fluoroscopic irradiation time, 4) output signal intensity output as a digital value from the X-ray detection means 05, and the setting Two parameters related to the imaging X-ray condition set in the means 11, imaging information storage means 12 for storing the target output signal intensity of imaging, four parameters stored in the fluoroscopy information storage means 10, and From the two parameters related to the imaging X-ray conditions stored in the imaging information storage means 12 and the target output signal intensity of imaging, the imaging X-ray condition calculation means 13 for calculating the imaging irradiation time parameter by a predetermined calculation, and more Constitution It has been.

  Furthermore, an image processing apparatus P that performs various image processing such as noise reduction processing, sharpening processing, gradation processing, etc. on the digital X-ray image detected by the X-ray detection means 05, and the image processing device And a D / A converter C for digital / analog conversion of the digital data subjected to various processes in P.

  Next, the operation and principle of the X-ray diagnostic imaging apparatus according to the present invention will be described with reference to FIG.

  FIG. 7 is a flowchart for explaining the operation of the first embodiment.

(Step S1)
Prior to inspection
1) Sensitivity characteristics of the imaging and fluoroscopic mode of the X-ray detection means 05 are stored in the X-ray detector information storage means 09.
2) On the maintenance screen (not shown) of the setting means 11 for the tube voltage and tube current as shown in FIGS.
3) The target output signal intensity of shooting is stored in the shooting information storage means 12,
4) The output signal intensity ratio according to claim 4 or the incident X-ray dose ratio in the imaging X-ray condition calculation means 13,
Remember. Regarding 1), when considering the tube voltage dependence of FPD, the sensitivity characteristics for each tube voltage are stored. For 3), the average value, the center of gravity ^{(Note 1)} , or the median value of all output signal strengths in the region of interest is used as the target output signal strength. For 4), it is defined as a function for each tube voltage that does not store all the finite data measured in advance, but obtains each coefficient of the output signal intensity ratio or the third-order approximation polynomial of the incident X-dose ratio. Only the coefficients (4 × 4 = 16) of the third-order approximation polynomial are stored. The output signal intensity ratio or the incident X-dose ratio can be obtained from the above procedures (procedure 1) to (procedure 4) only from these coefficients.
^{(Note 1) The} center of gravity means the pixel value that becomes a delimiter when considering dividing the area of the histogram (horizontal axis: pixel value, vertical axis: frequency of pixel value) into two equal parts (see Fig. 2) .

  As shown in FIG. 9, the photographing tube voltage is determined by the fluoroscopic tube voltage, and the photographing tube current is determined by the photographing tube voltage determined by the fluoroscopic tube voltage. In the figure, the fluoroscopic tube voltage and the photographing tube voltage, and the photographing tube voltage and the photographing tube current are defined by a simple linear relationship, but other relationships may be defined within a controllable range. Further, in the setting means 11, as shown in FIG. 8, a region of interest (hereinafter abbreviated as ROI (Region Of Interest)) for calculating the output signal intensity in the final fluoroscopic frame output from the X-ray detection means 05 is displayed. Set. For the setting, set the coordinate position to be used as ROI in the field of view.

(Step S2)
Enter inspection. Positioning of the image by fluoroscopy. In the fluoroscopy here, the combination of the fluoroscopy tube voltage, fluoroscopy tube current, and fluoroscopy irradiation time can be arbitrarily changed on the operator side by the setting means 11 (see FIG. 8). That is, the cursor is placed on an item to be changed among the fluoroscopic tube voltage, the fluoroscopic tube current, and the fluoroscopic irradiation time, and the adjustment is performed using the “+” button and the “−” button.

(Step S3)
When the fluoroscopy is completed and the subsequent radiographing is performed, in the final fluoroscopy frame, 1) fluoroscopy tube voltage, 2) fluoroscopy tube current, 3) fluoroscopy irradiation time, and 4) output signal output as a digital value from the X-ray detection means 05 The four parameters of intensity are stored in the perspective information storage means 10. Information on the fluoroscopic tube voltage, fluoroscopic tube current, and fluoroscopic irradiation time is obtained from the X-ray control means 11, and information on the output signal intensity in the final fluoroscopic frame is obtained from the X-ray detection means 05.

(Step S4)
From the output signal strength of the final fluoroscopic frame stored in the fluoroscopic information storage means 10 and the sensitivity characteristics of the fluoroscopic mode stored in the X-ray detector information storage means 09, the light enters the X-ray detection means 05 in the final fluoroscopic frame. Find the dose you had. When considering the tube voltage dependence of FPD, the incident dose is obtained using the sensitivity characteristics of the fluoroscopic mode corresponding to the fluoroscopic tube voltage in the final fluoroscopic frame.

(Step S5)
From the fluoroscopic tube voltage in the final fluoroscopic frame stored in the fluoroscopic information storage means 10 and the photographing tube voltage and photographing tube current set on the maintenance screen of the setting means 11, the photographing tube voltage and the photographing tube current are obtained.

(Step S6)
X-ray detection means for obtaining imaging target output signal intensity from the imaging target output signal intensity stored in the imaging information storage means 12 and the sensitivity characteristics of the imaging mode stored in the X-ray detector information storage means 09 Find the dose that needs to be incident on 05. When the tube voltage dependence of FPD is taken into consideration, the dose that needs to be incident is obtained using the sensitivity characteristic of the imaging mode corresponding to the imaging tube voltage obtained in (Step S5).

(Step S7)
The imaging X-ray condition calculation means 13 calculates the imaging irradiation time based on {Equation 1} or {Equation 2}. In addition, the following values are used in the calculation for each variable.

  Steps S4 to S7 are performed by the imaging X-ray condition calculation means 13.

Dose that needs to be incident on the X-ray detection means 05 in order to obtain the target output signal intensity of imaging obtained in i ₁ (step S5)
Tube current obtained in mA ₁ (step S6)
ms ₁ Variable to be calculated based on {Equation ₁ } or {Equation 2}
Dose incident on X-ray detection means 05 during the final fluoroscopic frame obtained in i ₂ (step S4)
mA ₂ fluoroscopic tube current stored in fluoroscopic information storage means 10
ms ₂ fluoroscopy irradiation time stored in fluoroscopy information storage means 10
ratio _signal Output signal intensity ratio when changing from fluoroscopy tube voltage to tube voltage (when FPD tube voltage dependency is not considered)
ratio _dose Incident X-ray dose ratio when changing from fluoroscopy tube voltage to tube voltage (when considering FPD tube voltage dependence)

However, if the imaging irradiation time (ms ₁ ) calculated by the imaging X-ray condition calculation means 13 exceeds the allowable X-ray reading time of the X-ray detection means 05, or the calculated imaging tube current and imaging irradiation If the product of time exceeds Back up mAs ^{(Note 2)} , a signal is sent from the imaging X-ray condition calculation means 13 to the setting means 11, and the X-ray irradiation condition warning lamp is turned on or blinking as shown in FIG. , Prevent image loss. In this embodiment, the case where a lamp is used for the warning has been described. However, any means such as a warning message may be used as long as the object of prompting the operator to be alerted can be achieved.
^{(Note 2) For} clinical operation, the maximum mAs that can be output from the X-ray tube is preset before the examination, and X-rays are not irradiated with more mAs. Generally, the mAs are referred to as “Back up mAs”.

(Step S8)
The X-ray control unit 08 controls the X-ray tube 01 so that X-rays can be irradiated with 1) imaging tube voltage, 2) imaging tube current, and 3) imaging irradiation time calculated by the imaging X-ray condition calculation unit 13. To do.

(Step S9)
Imaging is performed by irradiating the subject M with X-rays from the X-ray tube 01. The obtained photographed image is displayed on the display means 07.

  In the above, the case where the ROI set in (Step S1) is performed has been described, but as described in claim 9, the ROI is arbitrarily set by the setting means 11 (see FIG. 8) during the procedure. Is possible. At that time, the imaging X-ray condition calculation means 13 calculates so that the imaging target output signal intensity can be obtained for the changed ROI.

<Embodiment 2>
In the second embodiment, Full Auto will be described.

  The difference between the second embodiment and the first embodiment is only whether or not the fluoroscopic X-ray condition is automatically set.In the first embodiment, the operator arbitrarily selects a combination of the fluoroscopic tube voltage, the fluoroscopic tube current, and the fluoroscopic irradiation time. In contrast, in the second embodiment, the fluoroscopic tube voltage, the fluoroscopic tube current, and the fluoroscopic irradiation time are all automatically set so that the luminance of the fluoroscopic image is always constant.

  Accordingly, the steps from (Step S1) to (Step S9) in Embodiment 1 are the same as those in Embodiment 1 except for (Step S2) .In the case of Embodiment 2, the fluoroscopic X in (Step S2) of Embodiment 1 is the same. Line conditions are automatically set.

<Embodiment 3>
In the third embodiment, Time Auto will be described.

  The differences between the third embodiment and the first embodiment are 1) whether or not the fluoroscopic X-ray condition is automatically set, and 2) the method of setting the radiographic X-ray condition, that is, among the parameters in the radiographic X-ray condition. The tube voltage and the tube current can be arbitrarily changed by the operator. In the first embodiment, the operator can arbitrarily change the combination of the fluoroscopic tube voltage, the fluoroscopic tube current, and the fluoroscopic irradiation time.In the third embodiment, the fluoroscopic tube voltage, the fluoroscopic tube current, and the fluoroscopic irradiation time are all fluoroscopic images. Is automatically set so that its brightness is always constant.

  In general, even if the subject thickness is the same, the X-ray quality is changed depending on the part, that is, the tube voltage is mostly changed. In addition, when the subject to be photographed is an infant, there is a possibility that the subject may move at the time of photographing. Therefore, there is a demand from the clinical site that photographing is performed with the shortest possible photographing irradiation time to prevent blur due to body movement on the photographed image. This function responds to such clinical requirements. For the latter, the imaging irradiation time can be shortened by setting the imaging tube voltage or imaging tube current higher. The tube voltage and tube current are manually set by setting means 11 as shown in FIG.

  Therefore, among (Step S1) to (Step S9) of Embodiment 1, except for (Step S1), (Step S2) and (Step S6), it is the same as Embodiment 1, and in the case of Embodiment 3, The setting of item 2) in (Step S1) of Embodiment 1 is unnecessary, the fluoroscopic X-ray condition is automatically set in (Step S2), and the tube voltage and tube current are arbitrarily set in setting means 11 in (Step S6). It becomes the procedure of.

<Embodiment 4>
In the fourth embodiment, mAs Auto will be described.

  The fourth embodiment is similar to the third embodiment, and differs from the third embodiment only in whether or not the tube current is automatically set. In the case of the third embodiment, it is a concern that the imaging irradiation time calculated by the imaging X-ray condition calculation means 13 is read by the X-ray detection means 05 by setting the imaging tube voltage and tube current low. When the transition from fluoroscopy to radiography is exceeded, a warning lamp or message is issued to the operator and the radiographing is temporarily interrupted. It is a point that cannot move to shooting.

  In such a case, the imaging tube current and the imaging tube current are adjusted as shown in FIG. 10 in consideration of the subject thickness so that the imaging irradiation time does not exceed the allowable X-ray reading time of the X-ray detection means 05 before the inspection. The above problem can be avoided by defining the relationship and automatically setting the tube current.

  Therefore, (Step S1) to (Step S9) of Embodiment 1 is the same as Embodiment 1 except for (Step S1), (Step S2) and (Step S6), and in the case of Embodiment 4, Instead of the setting of the item 2) in (Step S1) of the first embodiment, the relationship between the fluoroscopic tube voltage and the imaging tube current as shown in FIG. 10 is defined, and the fluoroscopic X-ray condition is automatically set in (Step S2). ) Is a procedure for arbitrarily setting the tube voltage in the setting means 11.

<Embodiment 5>
In the fifth embodiment, a case where the SID changes when shifting from fluoroscopy to shooting will be described.

In the fifth embodiment, the procedure itself is the same as in the first to fourth embodiments, but in each embodiment, the imaging irradiation time calculated by the imaging X-ray condition calculation means 13 in (Step S7) is taken from fluoroscopy. If the SID changes when moving to, make corrections based on the distance square law ^{(Note 3)} . Specifically, the photographing irradiation time is corrected based on {Equation 3}. However, T _Correct is a photographing irradiation time corrected based on the distance square law, T _Pre is a photographing irradiation time before correction, SID _Rad is a SID at the time of photographing, and SID _Fluoro is a SID at the time of fluoroscopy. The correction is performed by the X-ray condition calculation means 13 when the X-ray control means 08 receives the SID information from the SID adjustment means (not shown).

^(注3)X線の点線源から放射される放射の強度は、距離の二乗に反比例する。

^{(Note 3)} The intensity of the radiation emitted from the X-ray point source is inversely proportional to the square of the distance.

<Embodiment 6>
In the sixth embodiment, a case where the quality filter is changed between fluoroscopy and photographing will be described.

In Embodiment 6, the procedure itself is the same as in Embodiments 1 to 4, but in each embodiment, the output signal intensity ratio or incidence used in the calculation based on {Equation 1} or {Equation 2} in (Step S7). When obtaining the relationship of X dose ratio (ratio _signal or ratio _dose in the same formula), as described in claim 6, the output signal obtained by changing the tube voltage and changing the quality filter while keeping mAs fixed When calculating the intensity ratio or the ratio of the incident X-ray dose to the FPD and changing the quality filter for fluoroscopy and radiography, use the output signal intensity ratio or the ratio of the incident X-ray dose measured in advance in the actual calculation. Correspond with.

<Embodiment 7>
In the seventh embodiment, a case where the irradiation size is changed when shifting from fluoroscopy to photographing will be described.

  In Embodiment 7, the procedure itself is the same as in Embodiments 1 to 4, but in each embodiment, imaging is performed from fluoroscopy with respect to the imaging irradiation time calculated by imaging X-ray condition calculation means 13 in (Step S7). Correction is performed in the case of changing the irradiation size at the time of shifting to (1).

  When the irradiation size is changed by opening / closing the X-ray diaphragm, the scattered X-ray dose generated around the irradiation region and detected by the X-ray detection means 05 changes. As a result, since the output signal intensity changes, it is necessary to correct the change in the scattered X-ray dose that changes depending on the degree of opening / closing of the X-ray diaphragm according to the irradiation size.

This can be corrected based on the output signal intensity ratio from the FPD obtained when the X-ray diaphragm is opened and closed according to the irradiation size under certain X-ray conditions. For example, the apparatus has four irradiation sizes of 7 × 7, 9 × 9, 12 × 12, and 16 × 16 inches, and the output signal intensity ratio under the above conditions is 7 × 7: 9 × 9: 12 × 12: 16 × 16 = a: b: c: d. Based on {Equation 4} with respect to the photographing irradiation time calculated by the photographing X-ray condition calculation means 13 when the photographing is actually changed from the perspective at 12x12 inches to the photographing when it is changed to 9x9 inches. Shooting exposure time is corrected. However, T _Correct is a photographing irradiation time corrected based on { _Equation 4}, and T _Pre is a photographing irradiation time before correction. The X-ray control means 08 receives the irradiation size information from the X-ray stop 03, and correction is performed by the imaging X-ray condition calculation means 13. Further, correction can be performed in the same way for other irradiation sizes, and in the above, 7 × 7, 9 × 9, 12 × 12, and 16 × 16 inches are used, but the irradiation size is not limited.
^{(Note 4)} 1 inch = 2.54 [cm]

<実施形態8>
実施形態8では、Densityのような役割を目標出力信号強度で設定する場合について説明する。

<Embodiment 8>
In the eighth embodiment, a case where a role such as Density is set by the target output signal intensity will be described.

  The role of Density here is explained. In the case of Full Auto, the lower and upper limits of the fluoroscopy and radiography X-ray conditions that are automatically set are fixed. However, when an object thickness that cannot be covered by the upper limit is an object to be imaged, a function is provided that allows the operator to arbitrarily change the voltage in order to prevent image loss due to insufficient X-ray conditions. The touch buttons -3 to +3 shown at the bottom of FIG. 8 indicate the function, and prior to the inspection, the voltage step width corresponding to each touch button is stored in the maintenance screen (not shown) of the setting unit 11. . The 0 button corresponds to a tube voltage controlled by Full Auto. For example, +1 is set and stored in a maintenance screen (not shown) prior to inspection with an interpretation of how many kV tube voltage is increased with respect to 0.

  In the eighth embodiment, the role of Density is set not by the tube voltage but by the target output signal intensity. The advantage of setting the target output signal intensity instead of the tube voltage is effective when there are many scattered X-rays, that is, when the subject tube thickness is large and the tube voltage increases accordingly. By increasing the target output signal strength, the imaging irradiation time calculated by the imaging X-ray condition calculation means 13 is lengthened, and it is possible to prevent insufficient contrast of the image due to an increase in image loss and tube voltage. it can.

  M subject, P image processor, CD / A converter, 01 X-ray tube, 02 X-ray filter, 03 X-ray diaphragm, 04 table, 05 X-ray detection means, 06 grid, 07 display means, 08 X-ray control Means, 09 X-ray detector information storage means, 10 fluoroscopy information storage means, 11 setting means, 12 imaging information storage means, 13 imaging X-ray condition calculation means

Claims (13)

An X-ray tube for generating X-rays for irradiating the subject;
X-ray detection means that outputs an X-ray intensity distribution that is disposed opposite to the X-ray tube and passes through the subject as a digital value;
Display means for displaying an X-ray image detected by the X-ray detection means;
An X-ray diagnostic imaging apparatus having X-ray control means for performing fluoroscopic X-ray control used for determining an imaging region,
X-ray detector information storage means for storing sensitivity characteristics of imaging and fluoroscopic modes of the X-ray detection means;
Fluoroscopy information storage means for storing fluoroscopy information in the final fluoroscopy frame when shifting from fluoroscopy to shooting;
Setting means for setting the tube voltage and tube current of the imaging X-ray condition;
Imaging information storage means for storing imaging X-ray conditions set in the setting means and target output signal intensity of the imaging X-ray detection means;
Imaging X-ray for calculating imaging irradiation time from fluoroscopy information stored in the fluoroscopy information storage means, imaging X-ray conditions stored in the imaging information storage means, and target output signal intensity of imaging of the X-ray detection means An X-ray diagnostic imaging apparatus comprising: a condition calculation unit. The imaging X-ray condition calculation means calculates the final fluoroscopy from the fluoroscopy tube voltage and output signal intensity stored in the fluoroscopy information storage means and the sensitivity characteristics of the fluoroscopy mode stored in the X-ray detector information storage means. Calculating the X-ray dose incident on the X-ray detection means of the frame;
From the imaging tube voltage and imaging target output signal intensity stored in the imaging information storage means and the sensitivity characteristics of the imaging mode stored in the X-ray detector information storage means, the imaging target output signal intensity is determined. The X-ray diagnostic imaging apparatus according to claim 1, wherein an X-ray dose that needs to be incident on the X-ray detection unit to obtain the X-ray image is calculated. The imaging X-ray condition calculation means includes an X-ray dose incident on the X-ray detection means during the final fluoroscopic frame, and an X-ray dose that needs to be incident on the X-ray detection means in order to obtain a target output signal intensity of imaging, The X-ray diagnostic imaging apparatus according to claim 2, wherein a relational expression between the fluoroscopic X-ray condition and the imaging X-ray condition is used. The relational expression is a function indicating the relationship between the ratios of the output signal intensities output from the X-ray detection means when the tube voltage is changed in a state where the product of the tube current and the irradiation time is constant, or their output signals. The function indicating the relationship between the intensity and the ratio of the incident X-ray dose incident on the X-ray detection means obtained from the sensitivity characteristics stored in the X-ray detector information storage means is used. Line image diagnostic device. A function indicating the relationship between the ratios of the output signal intensities output from the X-ray detection means when the tube voltage is changed with the product made constant, or the output signal intensity and X-ray detector information storage means The function indicating the relationship of the ratio of the incident X-ray dose incident on the X-ray detection means obtained from the sensitivity characteristic stored in the above is an approximate expression approximated from finite data measured in advance, and an unmeasured data area 5. The X-ray diagnostic imaging apparatus according to claim 4, wherein the output signal intensity or the ratio of the incident X-ray dose is derived using the approximate expression. A function indicating the relationship between the ratios of the output signal intensities output from the X-ray detection means when the tube voltage is changed with the product made constant, or the output signal intensity and X-ray detector information storage means The function indicating the relationship of the ratio of the incident X-ray dose incident on the X-ray detection means obtained from the sensitivity characteristics stored in is defined in accordance with the type of the quality filter while changing the tube voltage. The X-ray diagnostic imaging apparatus according to claim 4 or 5. The imaging X-ray condition calculation means calculates imaging X-rays calculated from the formulated relational expression when the distance between the focal point of the X-ray tube and the X-ray detection means changes when shifting from fluoroscopy to imaging. The X-ray image diagnostic apparatus according to claim 3, wherein distance correction is performed for the condition. When the X-ray irradiation area changes during the transition from fluoroscopy to imaging, the imaging X-ray condition calculating means changes the irradiation area with respect to the imaging X-ray condition calculated from the formulated relational expression. The X-ray diagnostic imaging apparatus according to claim 3, wherein correction that reflects minutes is performed. The output signal intensity in the final fluoroscopic frame output from the X-ray detection means and the target output signal intensity of imaging stored in the imaging information storage means are calculated or set for the same region of interest in the imaging area. The X-ray diagnostic imaging apparatus according to claim 1, wherein the region of interest can be set in advance in a region to be imaged or set during a procedure.   The output signal intensity in the final fluoroscopic frame output from the X-ray detection means and the target output signal intensity of imaging stored in the imaging information storage means are the average value of the output signal intensity in the region of interest, or the center of gravity or 10. The X-ray diagnostic imaging apparatus according to claim 9, wherein a median value is used. The imaging X-ray condition calculation means is configured to determine whether the imaging X-ray condition obtained from the relational expression exceeds an X-ray condition that can be output by the X-ray tube, or within the obtained imaging X-ray condition. 4. The X-ray according to claim 3, wherein a trigger signal such as a message, a lamp, or the like for warning the operator is issued when the irradiation time of imaging exceeds the allowable X-ray capture time of the X-ray detection means. Line image diagnostic device.   The X-ray diagnostic imaging apparatus according to claim 11, further comprising warning means such as a message, a lamp, and the like that prompts an operator based on a trigger signal of the imaging X-ray condition calculation means. The fluoroscopy information storage means includes four parameters: a fluoroscopic tube voltage, a fluoroscopic tube current, a fluoroscopic irradiation time, and a digital signal value output from the X-ray detection means in the final fluoroscopic frame when shifting from fluoroscopy to imaging. Store
Of the three parameters of the setting means imaging X-ray conditions, imaging tube voltage, imaging tube current, and imaging irradiation time, two parameters of imaging tube voltage and imaging tube current are set in advance or set during the procedure,
The imaging information storage means stores two parameters of the imaging X-ray condition set in the setting means, and a target output signal intensity of the imaging X-ray detection means,
The imaging X-ray condition calculation means includes four parameters stored in the fluoroscopy information storage means, two parameters related to the imaging X-ray conditions stored in the imaging information storage means, and imaging parameters of the X-ray detection means. The X-ray image diagnosis apparatus according to any one of claims 1 to 12, wherein a parameter of an imaging irradiation time is calculated from a target output signal intensity.

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