JP2000175903A - Radio-ct instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously obtain plural sheets of different image reconstitution condition such as a wide visual field image and a narrow visual field image. SOLUTION: After preparing difference raw date from raw data read from a raw data memory, an image reconstituting part takes the convolution of difference raw data weighted by a cos term and two kinds of reconstitution function by a convolution processing part 213 and applies back projection processing to obtained two kinds of convolution data by a back projection processing part 214 to prepare the wide visual field image 1 and the narrow visual field image 2, etc., to store this in an image memory. After then, the image reconstituting part sends the images 1 and 2 to a display part 22 to simultaneously display on a screen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray image processing apparatus that processes projection data collected by scanning an object to reconstruct an image.
The present invention relates to a line CT apparatus (CT scanner).

[0002]

2. Description of the Related Art At present, an X-ray CT apparatus (hereinafter, referred to as CT) has an X-ray focal point 1 for generating a fan-shaped X-ray beam (fan beam) as shown in FIG. The single slice CT having the detector 2 in which a plurality of detection elements 8 are arranged in one line is mainly used. Such CT
Then, while rotating the X-ray focal point 1 and the detector 2 around the subject, data of the X-ray intensity (referred to as projection data) passing through the subject is collected a plurality of times, for example, 1000 times in one rotation, and is obtained. The data is processed to reconstruct the image.

[0003] The collected data (called raw data)
The image reconstructing unit performs weighting processing with a cos term, performs convolution processing with a reconstruction function, performs back projection processing on an image data memory, reconstructs an image, and stores the image in the image memory.

At this time, the reconstruction function determines the resolution and noise of the image. When the reconstruction function is a high-frequency suppression type function, a smooth image with small noise is obtained instead of a low resolution, and a high-frequency emphasis type function produces a large image instead of a sharp image with a high resolution. The data pitch set in the image data memory determines the magnification of the image, and the position determines the position of the image. The matrix size of the image data memory controls the amount of back-projection calculation together with the image resolution and noise. 51
The 2 × 512 matrix size has better resolution, noise, computational complexity,
Everything is big. The number of projections in the back projection determines the resolution of the image and the amount of calculation of the back projection. Reducing the number of projections results in lower resolution but less computation.

For example, for differential diagnosis by pathological examination,
As shown in FIG. 7, there is known a needle biopsy in which a needle 4 is pierced into a target 3 such as a tumor to collect cells. At this time, if a needle biopsy is performed while looking at the tomographic image, the needle 4 can be reliably applied to the target 3. Therefore, a needle biopsy is often performed while reconstructing and observing a slice including the target 3 by CT. Will be

Also, a technique called difference reconstruction is known, which is obtained by back-projecting a difference between raw data collected in phase to conventional image data or back-projecting raw data collected in phase. There is known a technique of adding a difference between partial images to a conventional image and updating the image with a small amount of calculation.

[0007]

As described above, there is a demand for obtaining an appropriate fluoroscopic image without moving a patient for safety in CT fluoroscopy when performing a needle biopsy or the like. When piercing the needle, a fluoroscopic image with a wide visual field is required because a wide field of view from the punctured site to a target such as a tumor is desired. Then, when moving the needle towards the target,
We want to observe the narrow field of view near the target in detail to confirm that the target tissue has been reliably collected.
Although the field of view is narrow, a fluoroscopic image that allows the details of the region of interest to be understood is required. Thus, when performing a needle biopsy or the like, there is a demand that is inconsistent with the required image, but there has been a problem that the above-mentioned request cannot be answered because conventionally only one fluoroscopic image was obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to form a plurality of images having different image reconstruction conditions, for example, an image having a wide field of view and an image having a narrow field of view. An object of the present invention is to provide an X-ray CT apparatus which can be obtained at the same time.

[0009]

To achieve the above object, a first aspect of the present invention is an X-ray beam source for exposing an object to an X-ray beam, and an X-ray beam source. X having a detector array for detecting an X-ray beam emitted from
X-ray CT apparatus for reconstructing an image from data collected by scanning the subject by exposing the subject to X-rays while rotating the X-ray beam source around the subject An image reconstruction means for reconstructing a plurality of images having different image reconstruction conditions from data collected by the scan, and a display for displaying a plurality of images reconstructed by the image reconstruction means on a screen Means.

According to the first aspect, for example, if an image having a wide field of view and an image having a narrow field of view having different image reconstruction conditions are reconstructed and displayed simultaneously, a needle is inserted when performing a biopsy. Sometimes, the surgeon looks at the image in a wide field of view, performs the procedure while recognizing a wide range from the site where the needle is stabbed to the target such as a tumor, and when the needle is advanced toward the target, it looks at the image with a narrow field of view By observing the narrow visual field near the target in detail, it is possible to confirm whether the target tissue has been reliably collected.

The image reconstructing means of the second invention reconstructs a plurality of images having different image reconstructing conditions by using difference data between data collected in a current rotation and data collected in a previous rotation. Constitute.

[0012] The image reconstruction means of the third invention is means for creating difference data by taking the difference between the data collected in the current rotation and the data collected in the previous rotation, and weighting the difference data. Then, means for obtaining a plurality of pieces of convolution data by performing convolution with a plurality of reconstruction functions, and performing back projection processing on each of the plurality of pieces of convolution data to reconstruct a plurality of pieces of image data Means.

The image reconstructing means according to a fourth aspect of the present invention includes: means for calculating difference between data collected in a current rotation and data collected in a previous rotation to generate difference data; and weighting the difference data. Then, a convolution with one type of reconstruction function is performed to obtain one type of convolution data, and a back projection process is performed on the one type of convolution data to regenerate a plurality of pieces of image data. Configuring means.

A fifth aspect of the present invention is characterized in that an X-ray beam source for projecting an X-ray beam toward a subject and a detector array for detecting the X-ray beam emitted from the X-ray beam source X-ray detection means having an X-ray beam, and an X-ray beam is emitted while rotating the X-ray beam source around the object to scan the object to reconstruct an image from data acquired by scanning the object. In a line CT apparatus, image reconstruction means for reconstructing an image so as to satisfy an image reconstruction condition using difference data between data collected in a current rotation and data collected in a previous rotation by the scan, A display unit for displaying an image reconstructed by the image reconstructing unit on a screen, and an image in which a magnification of a part or all of one piece of image data reconstructed by the image reconstructing unit is changed. Expansion Comprising a changing unit, wherein the display unit is to display the magnification ratio change image created in the above.

A sixth aspect of the present invention is characterized in that a matrix size of the one image data is reduced on an image memory storing the one image data and a part of the one image data is reduced. Alternatively, the object is to create image data in which the entire enlargement is changed with the reduced matrix size.

According to a seventh aspect of the present invention, the image reconstructing means calculates difference between data collected in a current rotation and data collected in a previous rotation to generate difference data, and weights the difference data. Then, a convolution with one kind of reconstruction function is performed to obtain one kind of convolution data, and a back projection process is performed on the one kind of convolution data to obtain one piece.
Means for reconstructing a piece of image data, and means for creating image data obtained by enlarging a part of the reconstructed image data, and displaying the enlarged image data on the display means.

An eighth feature of the present invention is that while the image reconstructed by the image reconstructing means is displayed on the display means,
When a request to change the enlargement ratio of the image occurs, a unit is provided for changing the enlargement ratio of a part or all of the displayed image to create an image, and the display unit includes the created enlargement ratio change image. Is displayed first, and the image reconstruction unit changes the image reconstruction condition to reconstruct the requested enlargement ratio change image, and the display unit displays the reconstructed enlargement ratio change image. In other words, the image is displayed instead of the first displayed image.

A ninth feature of the present invention is that while the image reconstructed by the image reconstructing means is displayed on the display means,
When a request to change the enlargement ratio of the image is issued, the image reconstructing means changes the image reconstruction condition and reconstructs a plurality of images including the requested enlarged ratio change image.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the X-ray CT apparatus of the present invention. The CT apparatus includes a system control unit 10, a bed 11, a gantry / bed control unit 12, a bed moving unit 13, an X-ray control unit 14,
High voltage generator 15, X-ray beam source 16, detector 17, rotating frame 18, data acquisition unit 19, acquired data storage device 20, image reconstruction unit 21, display unit 2
And 2.

The image reconstruction unit 21 includes a raw data memory 211, an image memory 212, and a convolution processing unit 2 for performing a convolution between the raw data and the reconstruction function.
13. It has a back-projection processing unit 214 that performs back-projection on the convolution data to obtain image data.

Next, the operation of this embodiment will be described. The system control unit 10 controls the gantry / couch as a gantry / couch control signal using the rotation speed, the slice thickness, the fan angle, and the like among the helical scan conditions such as the slice thickness and the rotation speed input using an input device (not shown). Output to the unit 12. Further, the system control unit 10 transmits an X-ray beam generation control signal for controlling X-ray beam generation to the X-ray control device 1.
4 is output. Further, the system control unit 10
A detection control signal indicating the detection timing of the line beam is output to the data collection unit 19. Further, the system control unit 10 outputs a data collection control signal for data collection to the data collection unit 19. Further, the system control unit 10 sends a control signal for image reconstruction to the image reconstruction unit 2.
Output for 1

The gantry / bed control unit 12 rotates the rotary gantry 18 based on the gantry / bed control signal output from the system control unit 10 and also transmits the bed moving signal to the bed moving unit 1.
3 is output. The couch moving unit 13 obtains a moving amount of the couch 11 per one rotation of the rotating gantry 18 based on the couch moving signal output by the crib / couch controlling unit 12, and moves the couch 11 by this moving amount.

The X-ray controller 14 is provided with the system controller 10
The timing of the high voltage generation by the high voltage generator 15 is controlled on the basis of the X-ray beam generation control signal output by (1). The high voltage generator 15 supplies a high voltage for irradiating the X-ray beam to the X-ray beam source 16 in accordance with a control signal from the X-ray controller 14. X-ray beam source 1
Numeral 6 irradiates an X-ray beam with the high voltage supplied from the high voltage generator 15. The detector 17 detects an X-ray beam emitted from the X-ray beam source 16 and transmitted through the subject 100.

The rotating gantry 18 holds the X-ray beam source 16 and the detector 17. In addition, the rotating base 18 is
The X-ray beam source 16 is rotated by a gantry rotating mechanism (not shown).
Is rotated about a rotation axis passing through an intermediate point between the detector and the detector 17.

The data collection unit 19 collects the X-ray beam (actually, a detection signal) detected by the detector 17 in accordance with the data collection control signal output by the system control unit 10. The acquired data storage device 20 stores the X-ray beam detection signals acquired by the data acquisition unit 19, supplies the X-ray beam detection signals to the image reconstruction unit 21 as necessary, and stores them in the raw data memory 211.

The image reconstruction unit 21 includes a raw data memory 21
Convolution processing on the raw data stored in 1.
A perspective image or the like is reconstructed by performing a back projection process or the like. The display unit 22 displays the image reconstructed by the image reconstructing unit 21 on a monitor (not shown).

Reconstructing an image while continuously rotating the X-ray beam generator 16 and the detector 17 and irradiating X-rays to collect data is hereinafter referred to as CT fluoroscopy. However, this also includes a case where the bed 11 or the gantry is moved.

The subject 100 is sleeping on the bed 11. The operator stands beside the bed 11 and sets the position of the bed 11 so that the target such as a tumor is reconstructed by the image reconstruction unit 21. The operator performs a test scan once, and specifies the position and range (size, enlargement ratio) for reconstructing the two types of images from the reconstructed images displayed on the display unit 22 from an operation unit (not shown). For example, this time, as shown in Fig. 2, different image reconstruction conditions are specified so that the vicinity of the tumor is specified and one image can be obtained with a wide field of view and the other image can be obtained with a narrow field of view. Suppose you did.

Here, the image 1 has a pixel size of 0.6 mm,
Image matrix 51 at reconstruction center (0 mm, 0 mm)
2. The projection number is 500/1 rotation, the image 2 has a pixel size of 0.1 mm, the image matrix size is 256 at the reconstruction center (90 mm, 50 mm), and the projection number is 1000/1 rotation.

Thereafter, the surgeon instructs CT fluoroscopy, and in response to this, the system control unit 10 rotates the X-ray beam source 16 and the detector 17, and outputs X-rays from the X-ray beam source 16 to the subject. Exposure to 100. The data collection unit 19 collects 1000 data per rotation, and after the collected data is stored in the collected data storage device 20, the data is sent to the image reconstruction unit 21.

The image reconstruction unit 21 reconstructs, for example, two images 1 and 2 having different image reconstruction conditions.
The operation of the image reconstruction unit 21 will be described. Here, the image reconstruction conditions include an image enlargement ratio, a reconstruction function, a reconstructed image matrix, the number of projections, and the like. First, the raw data collected this time is read from the collected data storage device 20 and stored in the raw data memory 211. Next, data of one phase before rotation is read from the raw data memory 211, and a difference from the data collected this time is obtained (hereinafter, referred to as difference raw data).

The convolution processing unit 213 weights the raw difference data with the cos term, and convolves with the two types of functions to generate two types of convolution data and sends them to the back projection processing unit 214. For example, convolution is performed with a high-frequency suppression type reconstruction function, and the convolution data 1 is used for the back projection processing of the image 1, and the high frequency enhancement type reconstruction function and the convolved data 2 are used for the back projection processing of the image 2. To do.

Thus, the image 1 is an image having a wide field of view,
Because it is convolved with the high-frequency suppression type reconstruction function, a smooth image with little noise is obtained. Image 2 is an image with a narrow field of view. Is obtained. The image reconstruction unit 21 sends these two pieces of image data to the display unit 22 at regular intervals.

The display section 22 displays two images 1 and 2 as shown in FIG. The surgeon makes the needle 4 reach the target 3 while observing the entire area from the portion where the needle 4 is stuck to the target 3 in the image 1 having a wide visual field to the vicinity of the target 3 in an image 2 having a narrow visual field.

According to the present embodiment, the image reconstruction unit 21
Thus, it is possible to reconstruct the smooth image data having a wide field of view including the target 3 with little noise and the image data having the wide field of view including the target 3 with high resolution, and simultaneously display them on the screen of the display unit 22. Thus, the surgeon can simultaneously view the image 1 having a wide visual field and the image 2 having a narrow visual field.

Thus, when the surgeon pierces the needle 4, the operator views the wide field from the piercing site to the target 3 such as a tumor in the image 1.
When the needle 4 is pierced and then advanced toward the target 3, it is easy to see whether the tissue of the target 3 has been reliably collected by observing the narrow visual field near the target 3 with the image 2 in detail. Can be confirmed. The display unit 22 may display the images 1 and 2 alternately on the screen.

Next, a second embodiment of the X-ray CT apparatus according to the present invention will be described. Also in this example, the image reconstructing unit 21 reconstructs the image 1 having a wide visual field and the image 2 having a narrow visual field. At this time, until the convolution processing, the image 1,
2 are the same as those in the first embodiment shown in FIG. 1 except that they have the same processing. However, since the configuration of the apparatus is the same, the configuration shown in FIG. 1 will be described below.

Next, the operation of this embodiment will be described. The image reconstructing unit 21 calculates a difference between the data collected in the current rotation and the data of the same phase one rotation before (raw difference data).
Take.

The convolution processing section 213 weights the difference raw data with the cos term, convolves with the reconstruction function to generate one type of convolution data, and sends it to the back projection processing section 214. The reconstruction function uses, for example, a function of an intermediate type between a high-frequency suppression type and a high-frequency emphasis type.

The back projection processing unit 214
Using two memory areas of the image memory 212, two types of images are respectively reconstructed from the one type of data described above.

The back projection processing unit 214
The two data of the convolution data 1 are added and back-projected to the memory area of the image 1, and the back-projection is performed without adding the convolution data 2 to the memory area of the image 2 to obtain two types of image data. The image reconstruction unit 21 sends these two pieces of image data to the display unit 22 at regular intervals. The image display unit 22
Two images 1 and 2 are displayed.

Also in this embodiment, the image 1 having a wide field of view and
An image 2 with a narrow visual field can be obtained at the same time, and the same effect as that of the first embodiment shown in FIG. 1 can be obtained.
Moreover, since the convolution processing unit 213 only needs to generate one type of convolution data, the image processing time of the image reconstructing unit 21 can be shortened accordingly.

Next, a third embodiment of the X-ray CT apparatus according to the present invention will be described. In this example, the image reconstruction unit 21 initially reconstructs and displays, for example, the image 1 having a wide visual field, and reconstructs, for example, the narrow visual field image 2 according to an instruction of the operator. Since the configuration of the apparatus is the same except for the embodiment, the configuration shown in FIG. 1 will be described below.

Next, the operation of this embodiment will be described. The subject 100 is sleeping on the bed 11. The operator is a bed 1
1 stands next to the target such as a tumor,
The position of the bed 11 is set so as to be reconfigured in Step 1. The operator instructs CT fluoroscopy, and the system control unit 10 rotates the X-ray beam source 16 and the detector 17 to irradiate the subject 100 with X-rays from the X-ray beam source 16.

As a result, the data collected by the data collecting unit 19 is sent to the image reconstructing unit 21 to be reconstructed, and one image is successively updated and displayed on the display unit 22 as in the conventional case. The image reconstruction condition of this image is, for example, the same condition as the image 1 having a wide field of view described in the first embodiment.

The operator performs CT fluoroscopy using the above-mentioned image, and under image reconstruction conditions different from those of the first image, for example, under the same conditions as image 2 having a narrow field of view described in the first embodiment.
Reconstruction of the second image is instructed from an operation unit (not shown). This instruction is transmitted to the image reconstruction unit 21 via the system control unit 10.

In response to this, the image reconstructing section 21 reads from the raw data memory 211 a portion of the already created image 1 that overlaps with the image 2, and stores it in a predetermined pixel size.
An image 2 as shown in FIG. 4 is created by enlarging the image so as to form a 6 matrix, and this is stored in the image memory 212 as a provisional image 2. The image 2 stored in the image memory 212 is sent to the display unit 22 and displayed.

Thereafter, the image reconstructing unit 21 creates difference raw data from the current and previous raw data in the raw data memory 211 in accordance with the conditions of the image 1 and the image 2 as in the first embodiment. I do. Convolution processing unit 213
Is convolved with the difference raw data weighted by the cos term and the two types of reconstruction functions to generate two types of convolution data, and back-projects each convolution data by the back-projection processing unit 214, By creating the image 1 and the image 2 in the respective memory areas of the image memory 212, the images 1 and 2 are updated, and a moving image is displayed on the display unit 22 like a cine display.

According to the present embodiment, for example, when a needle biopsy is performed while viewing an image 1 having a wide field of view, an image 2 having a narrow field of view is obtained.
When it is desired to see the vicinity of the target 3 in more detail, in this example, a predetermined portion of the already created image 1 can be enlarged to create a temporary image 2 with a wide field of view in a short time. It can be displayed immediately and provided to the surgeon. The desired image 2 before a predetermined time elapses, such as one rotation
Is displayed, which is preferable for the surgeon.

After that, the images 1 and 2 are created and switched by the same processing as in the first embodiment.
The image 2 with higher image quality can be displayed in place of the provisional image 2, and the same effect as in the first embodiment can be obtained.

Although the image 2 cannot be seen immediately, if the above-mentioned instruction to reconstruct the second image is given, the provisional image 2 is not created, and the image reconstruction , The image 1 and the image 2 are reconstructed, and the image 1 and the image 2 are displayed.

Next, a fourth embodiment of the X-ray CT apparatus according to the present invention will be described. The configuration and operation of this example are the same as those of the third embodiment, but it is assumed that the image memory capacity and the calculation capacity of the image memory 212 of the image reconstruction unit 21 are limited. For example, the image memory 212 has 512 × 5
It is assumed that there is only an image memory capacity for one 12-matrix image and a calculation ability for back-projecting data of 1,000 views per rotation to an image of 512 × 512 matrix.

Next, the operation of this embodiment will be described. Conventionally, one CT scan is performed. The image reconstruction conditions of the image 1 are as follows: image size 0.6 mm, reconstruction center (0 m
m, 0 mm). The system control unit 10 sends an image matrix 512 × 512 and a projection number 10 to the image reconstructing unit 21.
Reconfiguration by 00/1 rotation is instructed, and the reconfiguration is performed under the conditions.

At this time, the surgeon instructs the second CT fluoroscopy from an operation unit (not shown). The image reconstruction conditions of the image 2 are as follows: the pixel size is 0.1 mm;
mm).

The system control unit 10 includes a reconstruction processing unit 21
, An image matrix 256 × 256, and reconstruction by projection 1000/1 rotation are instructed, and the reconstruction processing unit 21 instructs the back projection processing unit 214. The back projection processing unit 214 reads the data of the image 1 from the image memory 212, and
The data of image 1 is 256 ×
The image data is converted into a 256 matrix and stored in an area of a 256 × 256 matrix size of the image memory 212 as shown in FIG.

In the same manner as described in the third embodiment, the image 1 of the 512 × 512 matrix is enlarged (interpolated).
Then, image data of a 256 × 256 matrix is generated, and as shown in FIG.
It is stored in an area of 6 matrix size.

Thereafter, the back projection processing section 21
Reference numeral 4 denotes a memory area of the image memory 212 having a size of 512 × 512 matrix as shown in FIG.
By dividing and using at least two memory areas of a matrix size, two images 1 and 2 are reconstructed from one image data.

According to the present embodiment, the image reconstruction unit 21
Even when the capacity and calculation capacity of the image memory 212 are limited, a plurality of images can be reconstructed like the images 1 and 2. In this case, since the images 1 and 2 as described above can be reconstructed simultaneously while the capacity and the calculation capacity of the image memory 212 remain unchanged, the first embodiment can be performed without increasing the cost of the apparatus as compared with the prior art. The same effect as described above can be obtained.

In each of the embodiments described above, a configuration in which two images 1 and 2 are simultaneously or sequentially created has been described. However, three or more images can be easily formed in the same configuration. Can be created. In particular, when the number of images is large, the screen of the display unit 22 is divided into, for example, a multi-screen and each image is displayed.

[0060]

As described in detail above, according to the first to ninth aspects of the present invention, a plurality of images having different image reconstruction conditions, for example, an image having a wide visual field and an image having a narrow visual field can be simultaneously formed. Obtainable.

According to the fifth to eighth aspects of the present invention, an image obtained by changing the enlargement ratio of an already reconstructed image can be displayed in a short time.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an example of an image designated to be displayed by an operator.

FIG. 3 is a diagram showing an example of two images having different image reconstruction conditions displayed on a display unit shown in FIG. 1;

FIG. 4 is a diagram showing an example of an image 2 created by enlarging a predetermined portion of the image 1;

FIG. 5 is a block diagram showing an example of memory area division use of an image memory.

FIG. 6 is a diagram showing an arrangement example of an X-ray focal point and a detector.

FIG. 7 is a diagram showing an example of a fluoroscopic image used for a needle biopsy.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 System control part 11 Couch 12 Cradle / bed control part 13 Couch moving part 14 X-ray control device 15 High voltage generator 16 X-ray beam generation source 17 Detector 18 Rotation gantry 19 Data collection part 20 Collection data storage device 21 Image replay Configuration unit 22 Display unit 211 Raw data memory 212 Image memory 213 Convolution processing unit 214 Back projection processing unit

Continued on the front page F term (reference) 4C093 AA22 BA10 CA28 FD12 FD13 FE08 FE22 FF13 FG08 5B057 AA09 BA03 CA08 CA12 CA16 CB08 CB12 CB16 CC01 CD05 CE02 CE03 CE05 DA04 DB02 DB09 DC32

Claims (9)

[Claims] An X-ray for irradiating an X-ray beam toward a subject
A X-ray beam source, X-ray detection means having a detector array for detecting an X-ray beam emitted from the X-ray beam source, and rotating the X-ray beam source around the subject. X-ray CT for reconstructing an image from data collected by scanning the subject by irradiating an X-ray beam
In the apparatus, an image reconstructing means for reconstructing a plurality of images having different image reconstruction conditions from data collected by the scan, and displaying the plurality of images reconstructed by the image reconstructing means on a screen An X-ray CT apparatus comprising: a display unit. 2. The image reconstructing means reconstructs a plurality of images having different image reconstruction conditions by using difference data between data collected in a current rotation and data collected in a previous rotation. 2. The X-ray CT according to claim 1, wherein
apparatus. 3. The image reconstructing unit calculates difference between data collected in a current rotation and data collected in a previous rotation to generate difference data, and after performing a weighting process on the difference data. A means for obtaining a plurality of convolution data by taking a convolution with a plurality of reconstruction functions, and a means for performing back projection processing on each of the plurality of convolution data to reconstruct a plurality of image data, The X-ray CT apparatus according to claim 1, further comprising: 4. The image reconstructing unit calculates difference between data collected in a current rotation and data collected in a previous rotation to generate difference data, and after performing weighting processing on the difference data. Means for obtaining convolution data with one kind of reconstruction function to obtain one kind of convolution data; means for performing back projection processing on the one kind of convolution data to reconstruct a plurality of pieces of image data The X-ray CT apparatus according to claim 1, comprising: 5. An X-ray for irradiating an X-ray beam toward a subject
A X-ray beam source, X-ray detection means having a detector array for detecting an X-ray beam emitted from the X-ray beam source, and rotating the X-ray beam source around the subject. X-ray CT for reconstructing an image from data collected by scanning the subject by irradiating an X-ray beam
In the apparatus, image reconstruction means for reconstructing an image so as to satisfy an image reconstruction condition by using difference data between data collected in a current rotation by the scan and data collected in a previous rotation; Display means for displaying an image reconstructed by the reconstructing means on a screen; enlargement factor for creating an image obtained by changing an enlargement factor for a part or all of one piece of image data reconstructed by the image reconstructing means An X-ray CT apparatus, comprising: a change unit; and the display unit displays the created magnification change image. 6. The image memory storing the one image data, reducing the matrix size of the one image data and changing the enlargement of a part or all of the one image data. The X-ray CT apparatus according to claim 5, wherein the reduced image data is created with the reduced matrix size. 7. An image reconstructing unit, which obtains a difference between data collected in a current rotation and data collected in a previous rotation to generate difference data, and after performing a weighting process on the difference data, Means for obtaining convolution data with one kind of reconstruction function to obtain one kind of convolution data; means for performing back projection processing on the one kind of convolution data to reconstruct one piece of image data; 6. An X-ray CT apparatus according to claim 5, further comprising: means for creating image data obtained by enlarging a part of the reconstructed image data, wherein the enlarged image data is displayed on the display means. apparatus. 8. When a request for changing an enlargement ratio of the image occurs while an image reconstructed by the image reconstruction unit is being displayed on the display unit, the display unit performs the display by the enlargement ratio change unit. First, a magnification ratio changed image created by changing a magnification ratio of part or all of the image in the image is displayed, and the image reconstructing means changes the image reconstruction condition to change the requested magnification ratio. 6. The X-ray CT apparatus according to claim 5, wherein an image is reconstructed, and the display unit displays the reconstructed magnification-changed image in place of the first displayed image. 9. When an image magnification change request is issued while an image reconstructed by the image reconstructing means is being displayed on the display means, the image reconstructing means sets an image reconstruction condition. 6. The X-ray CT apparatus according to claim 5, wherein a plurality of images including the requested magnification change image are changed and reconstructed.