CN110987979A - X-ray imaging apparatus - Google Patents
X-ray imaging apparatus Download PDFInfo
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- CN110987979A CN110987979A CN201910422739.4A CN201910422739A CN110987979A CN 110987979 A CN110987979 A CN 110987979A CN 201910422739 A CN201910422739 A CN 201910422739A CN 110987979 A CN110987979 A CN 110987979A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
- G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/54—Control of apparatus or devices for radiation diagnosis
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/44—Constructional features of apparatus for radiation diagnosis
- A61B6/4429—Constructional features of apparatus for radiation diagnosis related to the mounting of source units and detector units
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
- A61B6/5205—Devices using data or image processing specially adapted for radiation diagnosis involving processing of raw data to produce diagnostic data
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
- A61B6/56—Details of data transmission or power supply, e.g. use of slip rings
Abstract
An X-ray imaging apparatus is obtained which automatically adjusts the tube current value in accordance with the change in the 1-pixel size of the acquired image and the tube voltage value v. In the position setting unit (9c), the geometrical positional relationship among the X-ray generator (1), the subject (4), and the X-ray detector (3) is set. A tube current calculation unit (9e) calculates a tube current value i by acquiring a variation characteristic of the 1 pixel size of an image and the focal size of the anode power with respect to the X-ray generator (1) and a tube voltage value v according to the subject (4) based on the geometric positions of the X-ray generator (1), the subject (4), and the X-ray detector (3) acquired from the position setting unit (9 c). An X-ray control unit (12) determines the anode power of the X-ray generator (1) on the basis of the tube current value i and the tube voltage value v, and controls the output of the X-ray generator (1) on the basis of the determined anode power.
Description
Technical Field
An embodiment of the present invention relates to an X-ray imaging apparatus that automatically sets radiation conditions according to the 1-pixel size of an acquired image.
Background
In an X-ray imaging apparatus such as an X-ray fluoroscopy apparatus or an X-ray Computed Tomography (CT) apparatus, for example, as shown in patent documents 1 to 3, a projection condition of X-rays is controlled using two parameters, i.e., a tube voltage value v and a tube current value i. When the anode power (tube voltage value v × tube current value i) is increased in most X-ray generators, the focal spot size of the X-ray becomes large, resulting in blurring of the acquired image.
In the conventional apparatus, an operator must input values of a tube voltage and a tube current to the apparatus to adjust a focal size while observing a blur of an image. In this case, if the focus size is kept small to avoid blurring of the image, the anode power is reduced, and as a result, the amount of X-rays output from the X-ray generator is insufficient, resulting in an image having a poor Signal to Noise (SN) ratio. In this way, the optimum values of the tube voltage and the tube current must be considered to be both resolution and SN ratio which cause blurring, and therefore it is difficult for an operator who lacks knowledge about X-rays to input the optimum values.
[ Prior art documents ]
[ patent document ]
Patent document 1: japanese patent laid-open No. 2003-173895
Patent document 2: japanese patent laid-open No. 2004-317368
Patent document 3: japanese patent laid-open No. 2005-149762
Disclosure of Invention
[ problems to be solved by the invention ]
As described above, when the projection conditions of X-rays are determined in the X-ray imaging apparatus, if the anode power is increased, the focal point size increases and the acquired image may be blurred, that is, the resolution may decrease.
Therefore, in order to efficiently acquire an image in a short imaging time, it is necessary to perform imaging with a maximum anode power at which blurring is not significant for a 1-pixel size of the acquired image. However, in the conventional technique, such a problem cannot be solved, and an operator determines an appropriate tube voltage value v and an appropriate tube current value i while determining the blur of an image by visual observation.
The present embodiment is proposed to solve the problems of the conventional techniques described above. An object of the present embodiment is to provide an X-ray imaging apparatus capable of acquiring an image with high resolution and good SN ratio by a simple operation by automatically adjusting a tube current value in accordance with a change in a 1-pixel size of an acquired image and a tube voltage value v.
[ means for solving problems ]
The X-ray imaging apparatus according to the embodiment of the present invention has the following configuration.
(1) And a position setting unit for setting a geometrical positional relationship among the X-ray generator, the subject, and the X-ray detector.
(2) And a tube current calculation unit that calculates a tube current value i based on the geometric positions of the X-ray generator, the subject, and the X-ray detector acquired from the position setting unit, the calculated change characteristics of the 1-pixel size of the acquired image and the focal size of the anode power with respect to the X-ray generator, and a tube voltage value v according to the subject.
(3) And an X-ray control unit which obtains anode power of the X-ray generator based on the tube current value i and the tube voltage value v, and controls the output of the X-ray generator based on the anode power.
The embodiments of the present invention may have the following configurations.
(1) The method comprises the following steps: an image processing unit that corrects the resolution or SN ratio of the captured image; and a tube current correction unit for adjusting the tube current value based on the resolution or signal-to-noise ratio correction value of the image processing unit.
(2) The method comprises the following steps: a moving mechanism that moves at least one of the X-ray generator, the subject, and the X-ray detector; a mechanism control unit that controls the amount of movement of the movement mechanism; a position setting unit that sets a change in the geometric position of each portion of the imaging apparatus after correction due to movement of at least one of the X-ray generator, the subject, and the X-ray detector; and the tube current calculation unit that calculates the tube current value i based on the geometric positions of the respective portions of the imaging apparatus corrected by the position setting unit.
(3) The method comprises the following steps: a thumbnail (thumbnail) generation unit which generates thumbnails of the images before and after correction; a thumbnail arrangement unit that displays the thumbnails in a predetermined format; and an input device that selects a prescribed thumbnail from the thumbnails arranged by the thumbnail arrangement section, and selects a correction value for obtaining a focal size and/or a tube current value i of a captured image based on the thumbnail selected by the input device.
Drawings
Fig. 1 is a block diagram of an X-ray imaging apparatus according to embodiment 1.
Fig. 2 is a block diagram showing the configuration of a data processing unit according to embodiment 1.
Fig. 3 is a flowchart showing the operation of the X-ray imaging apparatus according to embodiment 1.
Fig. 4 is a flowchart showing the operation of the X-ray imaging apparatus according to embodiment 2.
Fig. 5 is a flowchart showing the operation of the X-ray imaging apparatus according to embodiment 3.
Fig. 6 is a diagram showing an example of a display screen when processing for improving the SN ratio and improving the resolution is selected in embodiment 2.
Fig. 7 is a diagram showing an example of a display screen when the contour emphasis correction and the noise removal correction processing are selected in embodiment 3.
Fig. 8 is a diagram showing another example of a display screen when the contour emphasis correction and the noise removal correction processing are selected in embodiment 3.
Fig. 9 is a graph showing a relationship between the focal size F and the 1-pixel size p of the acquired image.
Description of the symbols
1: x-ray tube
2: x-ray beam
3: detector
4: subject
5: rotary platform
6: rotating/lifting mechanism
7: displacement mechanism
8: XY mechanism
9: data processing unit
9 a: scanning control unit
9 b: reconstruction unit
9 c: position setting unit
9 d: position calculating part
9 e: tube current calculating part
9 f: image processing unit
9 g: thumbnail generation unit
9 h: thumbnail image arrangement unit
9 i: tube current correction unit
10: display unit
11: mechanism control unit
12: x-ray control unit
13: input device
Detailed Description
[ 1] embodiment 1]
Hereinafter, embodiments of the present invention will be described. The present embodiment is applicable to both X-ray CT and fluoroscopy apparatuses.
[1-1. determination of tube Current value i ]
The anode power w (i, v) is defined by the product of the tube current value i and the tube voltage value v, but the tube voltage value v is preferably determined only by the property of the subject that is the object of fluoroscopy of the X-ray, and therefore, in the present embodiment, the tube current value i is used as a parameter for controlling the focal point size.
The focal point size F (w (i, v)) varies depending on the anode power w (i, v), but the variation characteristics differ depending on the type of the X-ray generator. For example, when the maximum value and the minimum value of the focal point size are Fmax and Fmin, and the maximum value and the minimum value of the anode power are Wmax and Wmin, the following description is given, for example
F(w(i、v))＝Fmax w(i、v)＞Wmax
＝f(w(i、v))Wmin＜w(i、v)＜Wmax
Fmin w (i, v) < Wmin,
the anode power w (i, v) is a fixed value when it reaches the minimum maximum value, and the value of f (w (i, v)) is continuously varied from the minimum value to the maximum value in accordance with the anode power w (i, v).
Furthermore, there are also those described as follows, i.e., such as
F(w(i、v))＝F1(w1＜w(i、v)＜w2)
＝F2(w2＜w(i、v)＜w3)
：
：
＝Fn(wn-1＜w(i、v)＜wn)
And the like, in a stepwise manner according to the anode power.
Therefore, a relational expression between the focal spot size F and the anode power w (i, v) is modeled according to the type of the X-ray generator, and F (w (i, v)) … expression (1) is obtained.
Next, a relational expression between the focal length F (w (i, v)) and the 1-pixel size p of the acquired image is obtained. The graph of fig. 9 is obtained when the vertical axis represents the focal size F (w (i, v)) and the horizontal axis represents the 1-pixel size p of the acquired image. For example, if the boundary where the image is blurred is set as
F (p) -2 p … formula (2),
then in the region below f (p) of the graph, the image is not blurred. Further, as the value of the focal size F is larger, the X-ray amount increases and the SN ratio of the image increases, so that it is preferable to adopt a large focal size close to the boundary F (p) of 2 p. The formula (2) indicating the boundary can be determined based on the change characteristic of the formula (1), but may be determined by actual measurement or calculation depending on the structure and function of the target X-ray apparatus because the blur is corrected by image processing or the like and also varies depending on the beam width of the X-ray.
Here, as described above, if the anode power w is controlled only by the tube current value i, the tube current value i (v, p) … (3) is obtained when the tube voltage value v is determined and the 1-pixel size p of the image is obtained from the expressions (1) and (2).
The tube current value i (v, p) determined by using the expression (3) is automatically changed to a value according to the tube voltage value v set by the operator and the 1-pixel size p of the acquired image obtained from the geometric positions of the components of the X-ray imaging apparatus, so that the operator can always take an image that maximizes the performance of the apparatus.
[ calculation of 1-2.1 Pixel size p ]
As a calculation method of the 1-pixel size p, for example, the following formula can be adopted.
The field of view FOV of the photographic image is as follows. (assuming the calculation is done by VC function.)
The 1-pixel size p can be calculated by dividing the FOV by the matrix size of the output image.
In the case of a fluoroscopic image, Y is 0.
(1) Full scan, half scan (half scan) cases
[ number 1]
(FOV)＝Int(2KRfull)
Ldet＝M·Δp
K: correction coefficient (a value of about limitfanangle.0.95 to 1.)
Int (): after the decimal point is cut off
Rfull: radius of the FOV of full scan (mm)
Ldet: horizontal width of detector (mm)
XFCD：FCD(mm)
XFDD：FDD(mm)
Y: amount of movement (mm) from the Y-axis reference position
M: number of detector channels (pix) (main)
Δ p: detector channel spacing (mm) (fpd _ pitch)
(2) Case of offset scan
L shift is 0, and is included in (3) described below.
(3) Offset scan and detector displacement scan conditions
[ number 2]
(FOV)＝Int(2KRoff)
Ldet＝M·Δp
K: correction coefficient (a value of about limitfanangle.0.95 to 1.)
Int (): after the decimal point is cut off
Roff: radius of FOV of offset scan (mm)
Ldet: horizontal width of detector (mm)
Lshift: detector displacement (mm) (det _ shift _ length)
XFCD：FCD(mm)
XFDD：FDD(mm)
Y: amount of movement (mm) from the Y-axis reference position
M: number of detector channels (pix) (main)
Δ p: detector channel spacing (mm) (fpd _ pitch)
[1-3. Structure of embodiment ]
As shown in the block diagram of fig. 1, the X-ray imaging apparatus according to embodiment 1 includes an X-ray tube 1 as an X-ray generator and a detector 3 for receiving an X-ray beam 2 emitted from a focal point F of the X-ray tube 1, which are disposed to face each other with a subject 4 interposed therebetween. The X-ray beam 2 is a pyramid beam centered on the X-ray optical axis L. The detector 3 detects the X-ray beam 2 transmitted through the subject 4 placed in the X-ray beam 2 with two-dimensional spatial resolution, and outputs as a transmission image (transmission data). The X-ray tube 1 and the detector 3 are supported by a displacement mechanism 7 so as to face each other.
The subject 4 is mounted on a rotary table (table)5 via an XY mechanism 8. The rotary table 5 is rotated around a rotary shaft 18 by a rotating/elevating mechanism 6 disposed below the rotary table. The rotation axis 18 is perpendicular to an imaging plane 19 which is a plane including the X-ray optical axis L in the X-ray beam 2. The rotary table 5 is lifted and lowered at right angles to the imaging surface 19 by the rotating/lifting mechanism 6. The subject 4 is moved on the rotation table 5 in both horizontal directions along the imaging surface 19 by the XY mechanism 8, and can be changed in position with respect to the rotation axis 18.
The rotary table 5 is moved along the X-ray optical axis L between the X-ray tube 1 and the detector 3 by the displacement mechanism 7 together with the subject 4 to change the imaging distance (focal point-rotation axis distance) FCD. The detector 3 is moved along the X-ray optical axis L by a displacement mechanism 7 to change a detection distance (focus-detector distance) FDD. This changes the photographing magnification FDD/FCD.
In the present embodiment, the X-ray tube 1 is a micro focus (micro focus) X-ray tube in which the size of the focal point F of the generated X-ray beam 2 is in the order of micrometers (orders), and the Detector 3 is an X-ray I.I (image intensifier tube), a television camera (television camera), or a Flat Panel Detector (FPD), but is not limited thereto.
The transmission image from the detector 3 is sent to the data processing unit 9, and the processing result and the like are displayed on the display unit 10. The CT scan is a scan in which the subject 4 is rotated within the X-ray beam 2, transmission images of the subject 4 in a plurality of directions are obtained by the detector 3, and a plurality of sectional images within a CT scan region (sectional image field of view) are reconstructed from the transmission images obtained by the CT scan by the data processing unit 9. Here, the CT imaging region is a region included in the X-ray beam 2 that constantly measures the subject 4 during one rotation in a normal volume scan.
The data processing Unit 9 and the display Unit 10 are a general computer (computer), and include an input device 13 such as a Central Processing Unit (CPU), a memory (memory), a hard disk (hard disk), a keyboard (keyboard), a mouse (mouse), an interface (interface), and the like, and store software (software) for reconstructing a cross-sectional image from a sequence or data obtained by CT imaging. The operator uses the data processing unit 9 and the display unit 10 to perform menu (menu) selection and condition setting, manual operation of the mechanism unit, display of a moving image of a transmission image, start of CT imaging, reading of a state (status) of the apparatus, display of a sectional image, analysis of a sectional image, display of a projection image, and the like. The display unit 10 also displays data related to the geometric positions of the respective units of the imaging apparatus, such as the FCD value and the FDD value, a thumbnail of a captured image, and a selection screen for various menus and commands.
The data processing unit 9 is connected to a mechanism control unit 11 that controls mechanism units such as the rotation/elevation mechanism 6, the displacement mechanism 7, and the XY mechanism 8. The mechanism control unit 11 controls the movement amounts of the respective units such as the rotation/elevation mechanism 6, the displacement mechanism 7, and the XY mechanism 8 based on a command from the data processing unit 9, and sends a state signal such as an FCD value or an FDD value obtained as a result of the movement to the data processing unit 9.
The data processing unit 9 includes a scan control unit 9a for CT imaging and a reconstruction unit 9b for creating a cross-sectional image, and functions as a CPU. The data processing unit 9 has a position setting unit 9c that sets the geometric positions of the respective units of the imaging apparatus, a position calculating unit 9d that calculates the geometric positions of the X-ray tube 1, the detector 3, and the subject 4 based on the control data of the mechanism control unit 11, a tube current calculating unit 9e, an image processing unit 9f, a thumbnail image generating unit 9g, a thumbnail image arranging unit 9h, and a tube current correcting unit 9i that corrects the tube current value calculated based on an instruction from the operator, and has a configuration unique to the present embodiment.
The position setting unit 9c sets the geometric positions of the respective parts of the imaging apparatus of the X-ray imaging apparatus according to the present embodiment based on the geometric positions given to the respective parts of the imaging apparatus as unique data, the geometric positions of the imaging apparatus given by the operator from the input device 13, and the movement amounts of the X-ray tube 1, the detector 3, and the subject 4 obtained by the position calculating unit 9 d. The position calculator 9d calculates the movement amounts of the X-ray tube 1, the detector 3, and the subject 4 based on control data of the respective mechanism units, such as the rotation/elevation mechanism 6, the displacement mechanism 7, and the XY mechanism 8, controlled by the mechanism controller 11, and outputs the calculated movement amounts to the position setting unit 9 c.
The tube current calculation unit 9e calculates a tube current value i for determining the anode power of the X-ray tube 1 by executing equations (1) to (3) based on a tube voltage value v preset in accordance with the characteristics of the subject 4 or set by an input from an operator and the geometric positions of the respective portions of the imaging apparatus acquired from the position setting unit 9 c. The values specific to the imaging device, i.e., the equations (1) and (2), are preset in the tube current calculation unit 9e by an operator or a device manufacturer.
The image processing unit 9f performs image processing such as resolution (degree of blurring) correction, SN ratio improvement processing, contour enhancement, and noise removal on the captured image created by the reconstruction unit 9b based on an instruction from the operator. The thumbnail generation unit 9g generates thumbnails of the captured image before the image processing created by the reconstruction unit 9b, the resolution correction image, the SN ratio improvement correction image, the contour enhancement image, and the noise removal image performed by the image processing unit 9 f. The thumbnail arranging unit 9h causes the display unit 10 to display the captured images before and after the image processing generated by the thumbnail generating unit 9g in a format designated by the operator.
The tube current correction unit 9i corrects the tube current value i by selecting the thumbnail image displayed on the display unit 10 from the input device 13 by the operator. The correction of the tube current value i is performed by changing the geometric position of each part of the imaging device to change the 1-pixel size p of the acquired image and changing the focal size of the X-ray to indirectly correct the tube current value calculated by the tube current calculation unit 9e in the resolution correction or the SN ratio improvement correction. The tube current correction unit 9i has an output side connected to the mechanism control unit 11, and adjusts the focal size by moving the X-ray tube 1, the detector 3, and the subject 4 according to the correction amount. The input side of the tube current correction unit 9i is connected to a position calculation unit 9d, and the position calculation unit 9d calculates the geometric position of each unit of the imaging apparatus, which changes based on the control data from the mechanism control unit 11.
On the other hand, since the correction by the contour enhancement and the noise removal is the correction by the image processing software, the tube current correction unit 9i directly corrects the tube current value in accordance with the degree of the correction by the contour enhancement and the noise removal input from the input device 13. Therefore, the input side of the tube current correction unit 9i is connected to the input device 13, and receives a selection signal of a predetermined thumbnail arranged in the thumbnail arrangement unit 9h from the input device 13. The output side of the tube current correction unit 9i is connected to an X-ray control unit 12 that calculates the anode power.
The data processing unit 9 is connected to an X-ray control unit 12, and the X-ray control unit 12 controls the anode power of the X-ray tube 1 based on the tube current calculated by the tube current calculating unit 9e, the tube current value i corrected by the tube current correcting unit 9i, and the tube voltage value v set in advance in accordance with the subject 4.
The data processing unit 9 is connected to an input device 13 such as a keyboard, a mouse, and a document reading device, through which an operator inputs various data and commands. The data input from the input device 13 to the data processing unit 9 includes various data input to conventionally known X-ray imaging devices, and specific data of the present embodiment, for example, geometric positions of each part of the imaging device, tube voltage values according to the subject 4, display forms of thumbnails, types of image processing such as contour enhancement and noise removal, and levels (levels) thereof.
[1-4. effects of embodiments ]
(1) Basic operation of CT apparatus
The operation of the present embodiment will be described with reference to fig. 1. First, the operator performs scanning (CT imaging) of the subject 4 as follows. The operator places the subject 4 on the XY mechanism 8, turns on the X-ray, dynamically displays the transmission image of the subject 4 on the display unit 10 in real time (real time), and while observing the image, raises and lowers the subject by the rotation/elevation mechanism 6 to align the subject with the imaging plane 19, and further sets the tube voltage value v, the tube current value i, the integration time, and the view (view) number. Here, the integration time is a time for detecting 1 transmission image, and the number of views is a collection number of transmission images in rotation.
When the operator starts scanning, the rotation table 5 is rotated by the scanning control unit 9a of the data processing unit 9, and a transmission image is collected during one rotation to complete scanning. The CT imaging region included in the X-ray beam 2 is reconstructed and stored by the reconstruction unit 9b from the transmission images corresponding to the number of views obtained in the 360 ° direction by scanning. At this time, the reconstruction unit 9b reconstructs a plurality of sectional images which are orthogonal to the rotation axis 18 and are continuously arranged at equal intervals in the direction of the rotation axis 18, and the plurality of sectional images form three-dimensional data. The three-dimensional data obtained by the scanning may be displayed on the display unit 10 by Multi-planar reconstruction (MPR) display or the like.
(2) Operation of embodiment 1
Fig. 3 is a flowchart for explaining the operation of embodiment 1. In the present embodiment, first, the anode power and the focal size of equation (1) … F (w (i, v)) (S01) are set in the tube current calculation unit 9 e. Next, the position setting unit 9c inputs geometric position data of each unit of the imaging apparatus (S02). Equation (2) … f (p) (f) (p) (S03) for setting the boundary of the image blur in the tube current calculation unit 9 e. The subject 4 is disposed on the XY mechanism 8 on the rotating table 5 (S04). The tube voltage value v corresponding to the subject 4 is set in the tube current calculation unit 9e (S05). The processing of S01 to S05 may be performed in any order.
The tube current calculation unit 9e calculates an optimal tube current value i for obtaining an image with less blur and an improved SN ratio by calculating equation (3) based on the relationship between the 1-pixel size p and the focal size F obtained by the set equations (1) and (2) (S06). The tube current calculation unit 9e calculates a tube current value i based on the obtained anode power w (i, v). The tube current value i obtained by the tube current calculation unit 9e is output to the X-ray control unit 12, and the X-ray control unit 12 calculates anode power w (i, v) from a preset tube voltage value v and the calculated tube current value i (S07), excites the X-ray tube 1 using the obtained anode power w (i, v), and projects a required amount of X-rays to the subject 4. As a result, the captured image with less blur and an improved SN ratio can be displayed on the display unit 10 (S08).
Specifically, when the tube voltage value v is set to 100kV in the subject 4 having the focal length F (w (i, v)), the relational expression between the focal length F (w (i, v)) and the anode power is expressed by expression (1)
F(w(i、v))[um]＝w(i、v)＝i×v[W]…(1)
And, given that the boundary of the image blur is given by equation (2)
F(p)＝2p…(2)
When, according to the formulae (1) and (2), is
F(p)＝2p＝i×v…(3)
The tube current value i obtained by equation (3) was 2 p/v.
For example, according to equation (3), when the X-ray geometry is changed to a 1-pixel size p of 10um, the tube current value i becomes 200uA, while the tube current value i becomes 1000uA when the 1-pixel size p of the acquired image at a certain X-ray geometry position is 50 um. As described above, according to the present embodiment, each time the imaging position is changed and the 1-pixel size p is changed, the tube current value i is automatically changed in accordance with the change.
[1-3. effects of the embodiment ]
The present embodiment has the following effects.
(1) An operator can easily perform an optimum image capturing regardless of the resolution of an acquired image and the SN ratio.
(2) The operator only needs to change the tube voltage value v of the tube voltage value v and the tube current value i, and thus can easily obtain an image with good SN ratio without image blur.
(3) Since the optimum anode power is obtained in accordance with the geometric positions of the respective parts of the imaging apparatus and the tube voltage value v according to the subject 4, an imaged image with less blur, that is, high resolution and an improved SN ratio can be obtained.
[ 2] embodiment 2]
As shown in the flowchart of fig. 4, in embodiment 2, whether or not to perform the resolution or SN ratio correction process on the image captured in embodiment 1 is selected (S51). The selection is performed by an operator outputting a predetermined command from the input device 13 to the mechanism control unit 11. When the correction process is selected (YES in S51), the mechanism controller 11 outputs control data for changing the X-ray tube 1, the detector 3, and the subject 4 by a predetermined movement amount to each mechanism unit such as the rotation/elevation mechanism 6, the displacement mechanism 7, and the XY mechanism 8 (S52). The X-ray tube 1, the detector 3, and the subject 4 move from the imaging position of the layer before correction to the position after correction based on the control data from the mechanism control unit 11. The control data from the mechanism control unit 11 is also sent to the position calculation unit 9d, and the position calculation unit 9d calculates the movement amount of each unit of the imaging apparatus associated with the correction, and sends the calculation result to the position setting unit 9 c.
The position setting unit 9c introduces the corrected geometric position of each portion into equation (1) based on the movement amount of each portion received from the position calculating unit 9d, and the tube current calculating unit 9e calculates the corrected tube current value i by adding equations based on the relationship between the 1-pixel size p and the focal size F obtained from equations (1) and (2) after the correction that are set (S06). That is, by moving each part of the imaging device in a direction of increasing the focal size F, an image with higher resolution and less blur can be obtained, and conversely, by moving each part of the imaging device in a direction of decreasing the focal size F, an image with an improved SN ratio can be obtained.
Subsequently, the thumbnail image generating unit 9g generates thumbnails of the corrected image and the standard image before correction, which are obtained by moving the respective imaging device sections in the direction of increasing the focal size F and in the direction of decreasing the focal size F, and the thumbnail images are displayed on the display unit 10 in a preset format by the thumbnail image arranging unit 9h (S09). Fig. 6 shows an example of a thumbnail display format, in which thumbnails of captured images at respective stages are arranged in a line in the vertical direction with a standard image (an uncorrected image) as the center, while moving in two stages in a direction of increasing the focal size F and in a direction of decreasing the focal size F.
In embodiment 2, a plurality of thumbnails hardware-corrected in resolution and SN ratio can be displayed on the display unit 10 in addition to the standard image. As a result, before the main imaging, a plurality of images having different geometric positions of each part of the imaging apparatus are preliminarily captured, and by displaying the thumbnail images, the operator selects the thumbnail image that is considered to be the best, whereby a captured image having the resolution and the SN ratio required by the operator can be obtained at the time of the main imaging.
[3 ] embodiment 3 ]
Embodiment 3 is an image processing unit 9f that performs software-based image processing for enhancing the outline or removing noise from a captured image, instead of the resolution correction or SN ratio correction processing of embodiment 2, thereby obtaining an image with improved visibility. The other structure of embodiment 3 is the same as embodiment 2. The same components as those in embodiment 2 are denoted by the same reference numerals and their description is omitted.
As shown in the flowchart of fig. 5, in embodiment 3, it is selected whether or not to perform the contour enhancement or noise removal correction process on the image captured in embodiment 1 (S53). The selection is performed by an operator outputting a predetermined command from the input device 13 to the mechanism control unit 11. When the correction process is selected (yes in S53), the mechanism control unit 11 multiplies the tube current value i of the standard image calculated by the tube current calculation unit 9e by a coefficient predetermined in accordance with the correction amount of the contour enhancement or the noise removal to calculate a corrected tube current value i (S54). That is, in the correction processing of line contour emphasis or noise removal, even if the resolution is low due to the large focal size F but the SN ratio is excellent, the image is clear with high resolution, and even if the resolution is high due to the small focal size F but the SN ratio is poor, the SN ratio can be improved. Therefore, by performing contour enhancement or noise removal in accordance with the degree of resolution or SN ratio of the obtained standard image, an image excellent in both resolution and SN ratio can be obtained.
In embodiment 3, thumbnails of the standard image and the image subjected to the correction process of the outline emphasis or the noise removal are generated by the thumbnail generation unit 9g, and are displayed in a preset format on the display unit 10 by the thumbnail arrangement unit 9h (S09). In this case, as in the display example of fig. 6 of embodiment 2, it is possible to perform a multi-stage contour enhancement or noise removal correction process, and to arrange thumbnails of captured images in each stage in 1 line in the vertical direction with a standard image (an uncorrected image) as the center.
In embodiment 2, a plurality of software-corrected thumbnails with outline emphasis or noise removal performed thereon can be displayed on the display unit 10 in addition to the standard images. As a result, a plurality of images having different degrees of outline enhancement and noise removal are preliminarily captured before the main imaging, and thumbnails thereof are displayed, so that the operator selects the best thumbnail, whereby a captured image having the resolution and SN ratio required by the operator can be obtained at the time of the main imaging.
Fig. 7 shows an example of a thumbnail display format in combination of embodiment 2 and embodiment 3. By arranging a plurality of thumbnails obtained by hardware correction for adjusting the resolution and the SN ratio and software correction for contour enhancement or noise removal on a matrix centered on a standard image, it is possible to easily select an optimum imaging condition.
Fig. 8 shows another example of the thumbnail display format when embodiment 2 and embodiment 3 are combined. In fig. 8, thumbnails obtained by the correction processing of outline emphasis or noise removal are displayed in multiple axes with respect to the respective thumbnails shown in fig. 6 obtained by hardware correction for adjusting the resolution to SN ratio. Thereby, more options can be provided to the operator.
The display format is not limited to the thumbnail, and other formats may be used as long as the user interface function is a key (key) capable of inputting a desired numerical value and an arbitrary numerical value range with the acquired optimum image as a reference value and centering on the reference value, and a user interface function capable of changing the focal size in accordance with the numerical value range to obtain an image in which the S/N ratio and resolution (degree of blurring) or contour emphasis and noise removal are finely adjusted.
[4 ] other embodiments ]
The present invention is not limited to the above-described embodiments, and can be embodied by modifying the components in the implementation stage without departing from the gist thereof. Further, various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the above embodiments. For example, some of the components may be deleted from all the components shown in the embodiments. Further, the constituent elements of the different embodiments may be appropriately combined. For example, the present invention is applicable to both X-ray CT and fluoroscopy apparatuses. The method of calculating the 1-pixel size p in the present embodiment is not limited to the above method.
Claims (5)
1. An X-ray imaging apparatus, comprising:
a position setting unit that sets a geometric positional relationship among the X-ray generator, the subject, and the X-ray detector;
a tube current calculation unit that calculates a tube current value i based on the geometric positions of the X-ray generator, the subject, and the X-ray detector acquired from the position setting unit, the calculated change characteristics of the 1-pixel size of the acquired image and the focal size of the anode power for the X-ray generator, and a tube voltage value v according to the subject; and
and an X-ray control unit which obtains anode power of the X-ray generator based on the tube current value i and the tube voltage value v, and controls the output of the X-ray generator based on the anode power.
2. The X-ray imaging apparatus according to claim 1, comprising:
an image processing unit that corrects the resolution or signal-to-noise ratio of the captured image; and
and a tube current correction unit for adjusting the tube current value based on the resolution or signal-to-noise ratio correction value of the image processing unit.
3. The X-ray imaging apparatus according to claim 1 or 2, comprising:
a moving mechanism that moves at least one of the X-ray generator, the subject, and the X-ray detector;
a mechanism control unit that controls the amount of movement of the movement mechanism;
a position setting unit that sets a change in the geometric position of each portion of the imaging apparatus after correction due to movement of at least one of the X-ray generator, the subject, and the X-ray detector; and
the tube current calculation unit calculates the tube current value i based on the geometric positions of the respective portions of the imaging apparatus corrected by the position setting unit.
4. The X-ray imaging apparatus according to claim 1 or 2, comprising:
a thumbnail generation unit that generates thumbnails of the images before and after correction;
a thumbnail arrangement unit that displays the thumbnails in a predetermined format; and
an input device for selecting a predetermined thumbnail from the thumbnails arranged by the thumbnail arranging unit and arranging the thumbnail on the thumbnail arranging unit
Based on the thumbnail selected by the input device, a correction value for obtaining a focal size and/or a tube current value i of a captured image is selected.
5. The X-ray imaging apparatus according to claim 3, comprising:
a thumbnail generation unit that generates thumbnails of the images before and after correction;
a thumbnail arrangement unit that displays the thumbnails in a predetermined format; and
an input device for selecting a predetermined thumbnail from the thumbnails arranged by the thumbnail arranging unit and arranging the thumbnail on the thumbnail arranging unit
Based on the thumbnail selected by the input device, a correction value for obtaining a focal size and/or a tube current value i of a captured image is selected.
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| JP2020027101A (en) | 2020-02-20 |
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