JP2011155997A - Method and apparatus for x-ray imaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for X-ray imaging capable of reducing dosage to a subject. <P>SOLUTION: A method involves: a process for setting the first imaging condition for a fluoroscopic process; a process for setting the second imaging condition for a subtraction imaging process; the fluoroscopic process in which the fluoroscopic imaging is operated based on the imaging condition set in the first imaging condition setting process while the live image is displayed on a display part; a process for determining that a contrast medium reaches near a target site based on the live image displayed on the display part and directing to switch from the fluoroscopic imaging to the subtraction imaging; and the subtraction process for performing the subtraction imaging based on the imaging condition set in the second imaging condition setting process while displaying the subtraction image on the display part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an X-ray imaging method and an X-ray imaging apparatus, and more particularly, to an X-ray imaging method and an X-ray imaging apparatus when performing angiography and the like.

  In general, there are a DA (digital angiography) method and a DSA (digital subtraction angiography) method as an X-ray imaging method when an examination such as angiography is performed on a patient as a subject. The DA method is an X-ray imaging method for obtaining an angiographic image itself. In contrast, the DSA method is an X-ray imaging method in which a digital image is obtained by performing a subtraction process, which is a subtraction process, on a live image after angiography and a mask image before angiography. . When this DSA method is adopted, a clearer blood vessel image can be obtained.

  Patent Document 1 discloses an X-ray diagnostic apparatus that can selectively execute the DA method and the DSA method.

JP 2007-330669 A

  When performing a DSA examination, if the site of interest such as a lesion to be examined is in the deep part of the vascular system, and it takes time for the contrast medium to reach the lesion, DSA imaging is performed. This has to be carried out over a long period of time, causing the problem of increased patient exposure. In particular, in order to obtain a good subtraction image in DSA imaging, it is necessary to obtain an image with a good S / N ratio using a larger dose than in normal X-ray imaging. When it becomes long time, there exists a problem that the exposure amount with respect to a patient becomes very large.

  The present invention has been made to solve the above problems, and provides an X-ray imaging method and an X-ray imaging apparatus capable of reducing the exposure dose to a subject even when imaging is performed by the DSA method. For the purpose.

  The invention according to claim 1 is an X-ray imaging method for imaging an X-ray image by causing an X-ray irradiated from an X-ray tube to pass through a subject and enter an X-ray detection unit. The first imaging condition setting step for setting the imaging conditions of the first imaging method for capturing a live image with the mask image before the contrast agent is injected and the live image after the contrast agent is injected. Based on the second imaging condition setting step for setting the imaging condition of the second imaging method for imaging with a dose and performing subtraction processing, and the imaging condition set in the first imaging condition setting step, the first imaging Based on the first imaging step of displaying the live image on the display unit and the live image displayed on the display unit, it is determined that the contrast medium has reached the region of interest, Whether the shooting method is the first shooting method Based on the switching instruction step for instructing to switch to the second shooting method and the shooting conditions set in the second shooting condition setting step, shooting is performed in the second shooting method, and the subtraction image at that time is displayed. And a second photographing process to be displayed on the screen.

  According to a second aspect of the present invention, there is provided an X-ray imaging apparatus for imaging an X-ray image by causing X-rays irradiated from an X-ray tube to pass through a subject and enter an X-ray detection unit. The first imaging condition storage unit that stores the imaging conditions of the first imaging method for capturing a live image at a high dose with the mask image before the contrast agent is injected and the live image after the contrast agent is injected A second shooting condition storage unit for setting shooting conditions of a second shooting method for shooting and performing subtraction processing, an image memory for storing a fluoroscopic image shot by the first shooting method, and the second shooting method A mask image memory for storing the mask image captured in step 2, a live image memory for storing a live image captured by the second imaging method, a mask image stored in the mask image memory, and a raster image stored in the live image memory. A subtraction unit that performs subtraction processing on the image, a switching unit that transmits a switching signal for switching the shooting method from the first shooting method to the second shooting method, a display unit that displays a shot image, and the first Based on the imaging conditions stored in the imaging condition storage unit, imaging is performed with the first imaging method, the live image is displayed on the display unit, and the contrast agent reaches the vicinity of the target region and is switched by the switching unit. When the switching signal is transmitted, based on the shooting conditions stored in the second shooting condition storage unit, shooting is performed with the second shooting method, and the subtraction image at that time is displayed on the display unit. And a control unit.

  According to the first and second aspects of the present invention, imaging is performed by the first imaging method in which a live image is captured at a low dose until the contrast agent reaches the vicinity of the target region, and the contrast agent is the target region. Since the second imaging method that performs subtraction processing after reaching the vicinity can be used for imaging, the exposure dose to the subject can be reduced even when imaging is performed using the DSA method. .

1 is a schematic diagram of an X-ray imaging apparatus according to the present invention. It is a flowchart which shows the X-ray imaging operation | movement by the X-ray imaging apparatus which concerns on this invention. It is explanatory drawing which shows notionally X-ray imaging operation | movement which concerns on this invention. It is a schematic diagram which shows the display screen at the time of X-ray imaging. It is a schematic diagram which shows the display screen at the time of X-ray imaging.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an X-ray imaging apparatus according to the present invention.

  This X-ray imaging apparatus is for taking a fluoroscopic image by extracting a vascular tissue using the DSA method, and includes a table 2 on which a patient 1 as a subject is placed, an X-ray tube 3, a flat panel detector 4 as an X-ray detection means, a control unit 5, an X-ray tube control unit 6 that controls a tube voltage and a tube current applied to the X-ray tube 3, and an image processing unit 7. Prepare. The control unit 5 is connected to a display unit 8 that displays an X-ray fluoroscopic image and an input device 9 such as a keyboard having a changeover switch 91.

  The control unit 5 includes a fluoroscopic image memory 51 used during fluoroscopic imaging as a first imaging method for capturing a live image at a low dose, a mask image before the contrast agent is injected, and after the contrast agent is injected. A mask image memory 52, a live image memory 53, and a subtraction unit 54 that are used at the time of subtraction imaging as a second imaging method for performing a subtraction process. In addition, the control unit 5 includes a first imaging condition storage unit 56 that stores imaging conditions during fluoroscopic imaging, and a second imaging condition storage unit 57 that sets imaging conditions during subtraction imaging. Further, the control unit 5 includes an arithmetic processing unit 55 that controls the above-described units and executes arithmetic processing.

  Next, an X-ray imaging operation in the case of performing X-ray imaging using the DSA method with this X-ray imaging apparatus will be described. FIG. 2 is a flowchart showing an X-ray imaging operation by the X-ray imaging apparatus according to the present invention. FIG. 3 is an explanatory diagram conceptually showing an X-ray imaging operation according to the present invention, and FIGS. 4 and 5 are schematic diagrams showing a display screen during X-ray imaging.

  In the X-ray imaging apparatus according to the present invention, before the X-ray imaging is started, both the imaging conditions for fluoroscopic imaging and the imaging conditions for subtraction imaging are set in advance. That is, in the conventional X-ray imaging apparatus, it is not assumed that fluoroscopic imaging and subtraction imaging are continuously performed. Therefore, when performing fluoroscopic imaging, imaging conditions such as tube voltage and tube current at the time of fluoroscopic imaging or the number of frames per unit time are set before the start of imaging. Also, when subtraction imaging is performed, imaging conditions such as tube voltage and tube current at the time of fluoroscopic imaging, or the number of frames per unit time are set before the start of imaging. For this reason, it was impossible to perform fluoroscopic imaging and subtraction imaging continuously. In the X-ray imaging apparatus according to the present invention, before starting X-ray imaging, the imaging conditions for fluoroscopic imaging and the imaging conditions for subtraction imaging are set in advance, so that fluoroscopic imaging and subtraction imaging are continuously performed. It is possible to do it.

  That is, when X-ray imaging is started in the X-ray imaging apparatus according to the present invention, first, first imaging conditions for setting imaging conditions for fluoroscopic imaging as a first imaging method for imaging a live image at a low dose. A setting process is executed (step S1). In the first imaging condition setting step, the tube voltage, tube current, X-ray irradiation time, the number of frames per unit time, etc. during fluoroscopic imaging are set. The set shooting conditions are stored in the first shooting condition storage unit 56 shown in FIG. Note that under this radiographic imaging condition, it is only necessary to be able to confirm the progress of the contrast agent. Therefore, a particularly clear image is not required, and a small X-ray dose is sufficient.

  Subsequently, the mask image before the contrast agent is injected and the live image after the contrast agent is injected are captured at a high dose, and the imaging conditions for the subtraction imaging as the second imaging method for performing the subtraction process are set. A second imaging condition setting step is executed (step S2). Also in the second imaging condition setting step, the tube voltage, the tube current, the X-ray irradiation time, the number of frames per unit time, etc. at the time of subtraction imaging are set. The set shooting conditions are stored in the second shooting condition storage unit 57 shown in FIG. Note that, in this imaging condition at the time of subtraction imaging, in order to obtain a good subtraction image, it is necessary to obtain an image with a good S / N ratio using a larger dose than in normal X-ray imaging, so the X-ray dose is It needs to be a large value.

  When the above setting process is completed, shooting is started. At this time, first, the photographing conditions set in the first photographing condition setting step are read (step S3), and fluoroscopic photographing is started after the reading of the photographing conditions is completed (step S4).

  At this time, X-rays irradiated from the X-ray tube 3 and passing through the patient 1 are detected by the flat panel detector 4 as a low-dose live image. The X-ray image detected by the flat panel detector 4 is subjected to image processing in the image processing unit 7 and then temporarily stored in the fluoroscopic image memory 51. The X-ray image is transmitted to the display unit 8 via the control unit 5, and a fluoroscopic image as a live image at the time of fluoroscopy is displayed on the display unit 8.

  Symbols F1, F2, and F3 shown in FIGS. 3 and 4 indicate the fluoroscopic images at this time. These fluoroscopic images F1, F2, and F3 are taken based on a preset number of frames per unit time (FPS / Frame Per Second). As shown in FIG. 4, it can be confirmed that the contrast medium A proceeds in the blood vessel for each of the fluoroscopic images F1, F2, and F3.

  4 (a), (b), and (c), for convenience of explanation, the contrast agent A is progressing for each frame. The imaging intervals of the fluoroscopic images F1, F2, and F3 are, for example, , 30 FPS, and the traveling speed of the contrast medium A between the fluoroscopic images F1, F2, and F3 is actually much higher than the state expressed in FIGS. 4 (a), (b), and (c). Slow.

  In the fluoroscopic imaging state, the fluoroscopic image is always displayed on the display unit 8 as a live video. The operator confirms the progress of the contrast agent based on this fluoroscopic image. If the fluoroscopic imaging is continued in such a state and the contrast medium A advances and reaches near the site of interest such as a lesion to be examined, that is, just before the site of interest, the operator switches the change-over switch in the input device 9. 91 is pressed.

  The changeover switch 91 is for transmitting a switching signal for switching the photographing method from the perspective photographing which is the first photographing method to the subtraction photographing which is the second photographing method. If the changeover switch 91 is pressed by the operator (step S5), the imaging method is switched from low-dose fluoroscopic imaging as the first imaging method to subtraction imaging as the second imaging method. At this time, first, the shooting conditions set in the second shooting condition setting step are read (step S6), and after the reading of the shooting conditions is completed, subtraction shooting is started (step S7). At this time, the mask image before the contrast agent is injected into the blood vessel and the live image after the contrast agent is injected are captured at a high dose, and the subtraction process that is a subtraction process is performed on these images. Subtraction shooting is executed.

  That is, first, X-rays irradiated from the X-ray tube 3 and passing through the patient 1 are detected by the flat panel detector 4 as a high-dose live image. The X-ray image detected by the flat panel detector 4 is subjected to image processing by the image processing unit 7 and then temporarily stored as a mask image M in the mask image memory 52 shown in FIG.

  As the mask image, a one-frame image photographed by the flat panel detector 4 may be used, but as shown in FIG. 3, a mask image M may be created from a plurality of frames of images M1 and M2. . By adopting such a configuration, the mask image M can be made more accurate.

  FIG. 5A shows the mask image M created in this way. This mask image M is a high-precision image with less noise and good S / N ratio because it is photographed at a higher dose than the fluoroscopic image F3 shown in FIG.

  If the mask image M is stored in the mask image memory 52, X-rays irradiated from the X-ray tube 3 and passing through the patient 1 are further detected by the flat panel detector 4 as a high-dose live image. The X-ray image detected by the flat panel detector 4 is subjected to image processing by the image processing unit 7 and then temporarily stored as a live image R in the live image memory 53 shown in FIG.

  When the mask image M is stored in the mask image memory 52 and the live image R is stored in the live image memory 53, the subtraction unit 54 shown in FIG. This subtraction process is a process of subtracting the mask image M from the live image R. As shown in FIG. 3, this subtraction process is performed every time images are taken at regular intervals and live images R 1, R 2, R 3.

  FIGS. 5B and 5C show the subtraction images S1 and S2 created in this way. As shown in these drawings, in the subtraction image S1, the blood vessel image after the contrast agent A is injected is clearly displayed. Further, in the subtraction image S2, the subsequent progress of the contrast agent A is clearly displayed.

  As shown in FIG. 3, the subtraction image S is continuously performed corresponding to the number of frames per unit time (FPS). When the subtraction imaging necessary for diagnosis is completed (step S8), the entire imaging process is completed.

  In the above-described embodiment, as the first imaging method, the fluoroscopic imaging that does not store the captured video is adopted, but the captured video may be stored.

DESCRIPTION OF SYMBOLS 1 Patient 2 Table 3 X-ray tube 4 Flat panel detector 5 Control part 6 X-ray tube control part 7 Image processing part 8 Display part 9 Input device 51 Perspective image memory 52 Mask image memory 53 Live image memory 54 Subtraction part 55 Operation processing part 56 first imaging condition storage unit 57 second imaging condition storage unit 91 changeover switch A contrast agent F fluoroscopic image M mask image R live image S subtraction image

Claims (2)

In an X-ray imaging method for imaging an X-ray image by causing X-rays irradiated from an X-ray tube to pass through a subject and enter an X-ray detection unit,
A first shooting condition setting step for setting shooting conditions of a first shooting method for shooting a live image at a low dose;
Second imaging conditions for setting the imaging conditions of the second imaging method in which the mask image before the contrast agent is injected and the live image after the contrast agent is injected are captured at a high dose and the subtraction processing is performed. A setting process;
Based on the shooting conditions set in the first shooting condition setting step, the first shooting step of performing shooting with the first shooting method and displaying the live image on a display unit;
Based on the live image displayed on the display unit, a switching instruction step for determining that the contrast agent has reached the vicinity of the target region and instructing to switch the imaging method from the first imaging method to the second imaging method;
Based on the shooting conditions set in the second shooting condition setting step, the second shooting step of performing shooting in the second shooting method and displaying the subtraction image at that time on the display unit;
An X-ray imaging method comprising: In an X-ray imaging apparatus that captures an X-ray image by allowing X-rays emitted from an X-ray tube to pass through a subject and enter an X-ray detection unit,
A first imaging condition storage unit that stores imaging conditions of a first imaging method for capturing a live image at a low dose;
Second imaging conditions for setting the imaging conditions of the second imaging method in which the mask image before the contrast agent is injected and the live image after the contrast agent is injected are captured at a high dose and the subtraction processing is performed. A storage unit;
An image memory for storing a fluoroscopic image photographed by the first photographing method;
A mask image memory for storing a mask image photographed by the second photographing method;
A live image memory for storing a live image shot by the second shooting method;
A subtraction unit that performs subtraction processing on the mask image stored in the mask image memory and the live image stored in the live image memory;
Switching means for transmitting a switching signal for switching the photographing method from the first photographing method to the second photographing method;
A display unit for displaying captured images;
Based on the imaging conditions stored in the first imaging condition storage unit, imaging is performed with the first imaging method, the live image is displayed on the display unit, and the contrast agent reaches the vicinity of the target region and When a switching signal is transmitted by the switching means, based on the shooting conditions stored in the second shooting condition storage unit, shooting is performed with the second shooting method, and the subtraction image at that time is displayed on the display unit. A shooting control unit to be displayed;
An X-ray imaging apparatus comprising:

Images