JPH08117218A - Inter-image computing method and ct device - Google Patents

Abstract

PURPOSE: To provide a computed image with high accuracy even if operation is performed between an image in the course of input operation and an image in the course of out operation. CONSTITUTION: Images I1-In to be operated are fetched from a storage device (step S1). The respective images I1-In are aligned in such a manner that the image positions of cradles in the images I1-In agree with each other (step S2). Operation such as subtraction, addition, reformation, and 3D is conducted for the aligned images I1-In (step S3). A computed image as arithmetic result is output (step S4). Accordingly, inter-image operation is conducted after shifting between images is detected according to the image positions of cradles and corrected, so that even if inter-image operation is conducted between an image in the course of in operation and an image in the course of out operation, a computed image with high accuracy can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-image operation method and a CT (Computed Tomography) apparatus, and more specifically, an inter-image operation method for performing an operation between two or more images after aligning each image. And a CT device.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of an example of a conventional X-ray CT apparatus. The X-ray CT apparatus 500 includes an operation console 1, a table device 18, and a scanning gantry 9. The operation console 1 includes an input device 2 that receives an operator's instruction and information, a central processing unit 53 that executes a scan process, an image reconstruction process, an inter-image calculation process, and a table device 18 that sends control signals and the like. Interface 4 for outputting to scanning gantry 9 and data collection buffer 5 for collecting data acquired by scanning gantry 9
A CRT 6 for displaying a scout image, a cross-sectional image, a calculation image generated by calculation between images, and a storage device 7 for storing various programs and data. The table device 18 mounts an object on a cradle 18c and moves in the ± Z-axis directions. Although not shown, the scanning gantry 9 includes an X-ray controller, an X-ray tube,
It is provided with a collimator, a detector, a data acquisition unit, a rotation controller for rotating an X-ray tube and the like around the body axis of the subject. As shown in FIG. 8, the cradle 18c of the table device 18 is supported by a guide roller 8r so that the subject K can be placed thereon and moved.

FIG. 9 is a flow chart of inter-image calculation processing executed by the central processing unit 53 of the X-ray CT apparatus 500. At step C1, the images I1 to In (n
≧ 2) is taken out from the storage device 7. In step C2,
The calculation is performed on the taken out images I1 to In. As this calculation, subtraction
There are additions, additions, reformations, and 3D (three-dimensional). In step C3, the calculation image of the calculation result is output. That is, it is displayed on the CRT 6 or stored in the storage device 7.

FIG. 10 is an explanatory diagram of a subtraction image. FIG. 10A shows the cradle 18c.
While moving in the -Z direction (while performing the IN operation),
A cross-sectional image I1 at one position reconstructed based on scan data obtained by performing a helical scan. In FIG. 10B, after injecting the contrast agent into the subject K, a helical scan is performed while moving the cradle 18c in the + Z direction (while performing the out operation), and based on the obtained scan data, the scan is performed again. Section image I2 at one configured position (same position as the section image I1)
Is. FIG. 10C is a subtraction image U obtained by subtracting the sectional image I1 from the sectional image I2. Only the blood vessels can be observed by the subtraction image U.

[0005]

The subtraction image U in FIG. 10C is an ideal case, and in reality,
As shown in FIG. 11, a subtraction image U ′ is obtained in which the images of tissues other than blood vessels and the cradle 18c are not completely erased. That is, in the above-described conventional CT apparatus 500, if the inter-image calculation is performed between the image during the in-motion and the image during the out-motion, the accuracy of the calculated image obtained becomes low. Therefore, an object of the present invention is to provide an inter-image calculation method and a CT apparatus that can obtain a highly accurate calculation image even if an inter-image calculation is performed between an image in in-motion and an image in out-motion. Especially.

[0006]

According to a first aspect of the present invention, in the inter-image calculation method for performing calculation between two or more images of a subject on a cradle, the position of the cradle in each image is calculated. Align each image to match,
There is provided an inter-image operation method characterized by performing an operation between two or more aligned images.

In a second aspect, the present invention is a CT apparatus including a cradle on which a subject is placed and an inter-image operation means for performing an operation between two or more images, and the positions of the cradle in each image are matched. The CT is characterized by comprising position correction means for aligning the respective images so that the images are aligned with each other, and inter-image computation means for computing between the two or more aligned images.
Provide equipment.

According to a third aspect of the present invention, in the CT apparatus having the above-mentioned structure, the cradle has a CT value different from that of the cradle and is provided with a marker member long in the moving direction of the cradle, and the position correction is performed. The means provides a CT device characterized by aligning each image so that the marker members in each image are aligned.

[0009]

The function of the inventor of the present invention is
It has been found that the reason why the accuracy of the calculation image obtained from the image during the in operation and the image during the out operation is low is that the position of the cradle of the table device is slightly different between the in operation and the out operation. . That is, there is a limit to the accuracy of the cradle shape (particularly the side surface that contacts the guide roller) and the support structure (particularly the cantilever structure for protruding the cradle), so the position of the cradle may differ between in-operation and out-operation. Will be a little different. For this reason, the image positions of the subject and the cradle in the image during the in operation are slightly deviated from the image positions of the subject and the cradle in the image during the out operation. However, conventional CT
In the apparatus, since the calculation is performed without considering the displacement of the position, the accuracy of the calculation image obtained from the image during the in-operation and the image during the out-operation is low.

Therefore, in the inter-image calculation method according to the first aspect and the CT apparatus according to the second aspect, the images are aligned so that the image positions of the cradle in the two or more images are aligned with each other, and the positions are aligned. The calculation is performed between two or more combined images. As a result, the deviation between the image positions of the subject and the cradle in the image during the in-motion and the image positions of the subject and the cradle in the image during the out-motion is corrected, so that a highly accurate calculation image can be obtained. It should be noted that the present invention is not limited to the calculation between the images of the IN motion and the OUT motion, but can be applied to the calculation between the plurality of images in either the IN motion or the OUT motion.

In the CT apparatus according to the third aspect, a marker member having a CT value different from that of the cradle and long in the moving direction of the cradle is attached to the cradle, and each image is made to match the marker member in each image. I tried to align them. Since the marker member can accurately detect the positional deviation between the images, the positional deviation can be accurately corrected.

[0012]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. The present invention is not limited to this. First Embodiment FIG. 1 is a block diagram of an X-ray CT apparatus according to the first embodiment of the present invention. The X-ray CT apparatus 100 includes an operation console 1, a table device 8 and a scanning gantry 9. The operation console 1 includes an input device 2 that receives an operator's instruction and information, a central processing unit 3 that executes a scan process, an image reconstruction process, an inter-image calculation process, and a table device 8 that sends control signals and the like. Scanning gantry 9
Interface 4 for outputting to, a data collection buffer 5 for collecting data acquired by the scanning gantry 9, a CRT 6 for displaying a scout image, a cross-sectional image, a calculation image generated by calculation between images, and a program and data are stored. And a storage device 7. The table device 8
Moves an object on the cradle 8c in the ± Z axis directions. The cradle 8c is made of a material having a CT value different from that of the cradle 8c (for example, an acrylic resin when the cradle 8c is a carbon plastic) and has a long marker 8m in the Z direction which is the moving direction of the cradle 8c.
Is buried. The cross-sectional shape of the marker 8m is such that tangential artifacts generated by the marker 8m do not overlap the image of the subject (here, an inverted triangle). Although not shown, the scanning gantry 9 has X
It is equipped with a ray controller, an X-ray tube, a collimator, a detector, a data collecting unit, a rotation controller for rotating the X-ray tube and the like around the body axis of the subject. As shown in FIG. 2, the cradle 8c of the table device 8 is supported by a guide roller 8r so that the subject K can be placed thereon and moved.

FIG. 3 is a flow chart of inter-image calculation processing executed by the central processing unit 3 of the X-ray CT apparatus 100.
In step S1, the images I1 to In (n ≧) to be calculated.
2) is taken out from the storage device 7. In step S2, the images I1 to In are aligned so that the image positions of the cradle 8c in the taken out images I1 to In are aligned.
In step S3, calculation is performed on the aligned images I1 'to In'. This calculation includes subtraction, addition, reformation, 3D, and the like. In step S4, a calculation image of the calculation result is output. That is, it is displayed on the CRT 6 or the storage device 7
To be stored.

FIG. 4 is an explanatory diagram of image alignment in step S2. First, as shown in FIG. 4A, the reference position Ps (Vs, H
s) is set in advance. Next, as shown in FIG. 4B, the position A (Vai, Hai) of the left end point and the position B (Vbi, Hbi) of the left end point of the image of the marker 8m in the certain image Ii.
To detect. Next, as shown in FIG. 4C, the left end point A ′ of the image of the marker 8m in the position-corrected image Ii ′.
Moves parallel to the position (Vs, Hs), and then rotates about the left end point A'so that the right end point B'is horizontal with the left end point A '.

According to the above X-ray CT apparatus 100, the positional deviation between the images I1 to In is accurately detected from the image position of the marker 8m, and the positional deviation is corrected, and then the inter-image calculation is performed. Even if the inter-image calculation is performed between the image in operation and the image in out operation, a highly accurate operation image can be obtained.

-Second Embodiment- FIG. 5 is a block diagram of an X-ray CT apparatus according to the second embodiment of the present invention. The X-ray CT apparatus 200 has the same configuration as the conventional X-ray CT apparatus 500 described in FIG. 7, except that the central processing unit 13 of the operation console 1 is different. The central processing unit 13 is the same as the central processing unit 3 of the first embodiment described with reference to FIG. 1, but the processing contents of the image alignment in step S2 are slightly different. That is, first, as shown in FIG. 6A, the reference position Ps (Vs, Hs) is set in advance on the reference image Is. Next, as shown in FIG. 6B, the position A (Vai, Ha) of the left end point of the image of the cradle 8c in the certain image Ii.
i) and the position B (Vbi, Hbi) of the left end point are detected.
Next, as shown in FIG. 6C, the position-corrected image I
The left end point A'of the image of the cradle 8c in i'is located at the position (V
s, Hs), and then rotates about the left end point A'so that the right end point B'is horizontal with the left end point A '.

According to the X-ray CT apparatus 200 described above, since the positional deviation between the images I1 to In is accurately detected from the image position of the cradle 8c, and the positional deviation is corrected, the inter-image calculation is performed. Even if the inter-image calculation is performed between the image in operation and the image in out operation, a highly accurate operation image can be obtained.

The cradle 8c may be provided with a position detecting hole equivalent to the marker 8m instead of the marker 8m.

[0019]

According to the inter-image calculation method and the CT apparatus of the present invention, the inter-image calculation is performed after detecting and correcting the positional deviation between the images based on the image position of the cradle.
Even if the inter-image calculation is performed between the image in the in operation and the image in the out operation, a highly accurate operation image can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an X-ray CT apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a cradle in the X-ray CT apparatus in FIG.

FIG. 3 is a flowchart of inter-image calculation processing in the X-ray CT apparatus in FIG.

FIG. 4 is an explanatory diagram of inter-image position correction in the X-ray CT apparatus in FIG.

FIG. 5 is a block diagram of an X-ray CT apparatus according to a second embodiment of the present invention.

6 is an explanatory diagram of inter-image position correction in the X-ray CT apparatus in FIG.

FIG. 7 is a block diagram of an example of a conventional X-ray CT apparatus.

8 is a cross-sectional view of a cradle in the X-ray CT apparatus in FIG.

9 is a flowchart of inter-image calculation processing in the X-ray CT apparatus in FIG.

FIG. 10 is an explanatory diagram of creating a subtraction image.

FIG. 11 is a view showing an example of a conventional actual subtraction image.

[Explanation of symbols]

 100,200 X-ray CT apparatus 1 Operation console 3,13 Central processing unit 8 Table device 8c Cradle 8m Marker 9 Scanning gantry Is Reference image Ii image Ii 'Position corrected image

Claims (3)

[Claims] 1. In an inter-image calculation method for performing a calculation between two or more images of a subject on a cradle, the images are aligned so that the positions of the cradle in each image are aligned, and the alignment is performed. An inter-image calculation method, characterized in that calculation is performed between two or more images described above. 2. A CT apparatus comprising a cradle on which a subject is placed and an inter-image calculation means for performing calculation between two or more images, and aligning the images so that the positions of the cradle in the images are matched. A CT apparatus, comprising: a position correction means for performing an operation and an inter-image operation means for performing an operation between two or more aligned images. 3. The CT apparatus according to claim 2, wherein the cradle includes a marker member having a CT value different from that of the cradle and long in a moving direction of the cradle, and the position correcting means includes each image. A CT device characterized in that each image is aligned so that the marker members therein are aligned.