WO2019044983A1

WO2019044983A1 - X-ray ct device and image generating method

Info

Publication number: WO2019044983A1
Application number: PCT/JP2018/032143
Authority: WO
Inventors: 俊裕利府
Original assignee: 株式会社根本杏林堂; 株式会社コノシュア
Priority date: 2017-08-30
Filing date: 2018-08-30
Publication date: 2019-03-07
Also published as: JPWO2019044983A1

Abstract

An image data processing unit (160) of this CT device is characterized by performing: a process of acquiring movement information data on the basis of a first image and a second image; a process of performing at least one of a process of generating a first estimated image Im(A)' at a time t(B) by using the movement information data to deform the first image, and a process of generating a second estimated image Im(C)' at the time t(B) by using the movement information data to deform the second image; and a6: a process of combining a third image (Im(B)) and either the first estimated image (Im(A)') or the second estimated image (Im(C)') to generate an estimated tomographic image of a location of interest at the time t(B).

Description

X-ray CT apparatus and image generation method

The present invention relates to an X-ray CT apparatus and an image generation method, and more particularly to provide an X-ray CT apparatus and an image generation method and the like which are excellent in time resolution and can reduce artifacts due to movement of an object. .

Conventionally, X-ray computed tomography (CT) devices, Magnetic Resonance Imaging (MRI) devices, Positron Emission Tomography (PET) devices, ultrasound diagnostic devices, angiography imaging devices, etc. are known as medical image diagnostic devices. is there.

In an X-ray CT apparatus, a subject is irradiated with X-rays, and an X-ray that has passed through the body of the subject is detected by a detector to acquire raw data, which is subjected to predetermined preprocessing to be projected data Generate Then, the projection data is used to reconstruct an image, and a tomographic image of the region of interest of the subject is generated. As image reconstruction, a method of reconstructing an image from scan data in the range of 360 ° and a method of reconstructing an image from scan data in the range of 180 ° + fan beam angle (α) are known. ing. In the case of a fan beam, data of 180 ° + α is used as described above, but in the case of a parallel beam, data of 180 ° may be used, and conversion between fan beam data and parallel beam (fan -Also known as para-transformation etc. per se.

Patent Document 1 relates to a technique for imaging a moving object (for example, the heart in one example), and for example, as shown in FIG. 16, it is disclosed to obtain data on the amount of movement of the object by comparing two images. It is done. Specifically, using the comparison image 1330 of the

objects

1311 and 1312 of the first image 1310 and the

objects

1321 and 1322 of the second image 1320, the movement amount of the object can be known. According to claim 1 of the same document, an intermediate time between a first time corresponding to a first image and a second time corresponding to a second image based on data of the amount of movement of the object. It is described that the image is obtained by reconstruction.

International Publication WO2015 / 126205

In the method of Patent Document 1, although the image is generated based on the data of the motion amount, the image is generated only by performing reconstruction. The document does not disclose or suggest the generation of a final image regardless of reconstruction.

Therefore, an object of the present invention is to provide an X-ray CT apparatus, an image generation method, and the like which are excellent in time resolution and can reduce an artifact due to the movement of an object by a method different from that of Patent Document 1.

An X-ray CT apparatus according to an aspect of the present invention is as follows:
A gantry having an emitter for emitting X-rays and a detector for detecting the X-rays;
An image data processing unit that performs an operation based on detection data from the detector;
An X-ray CT apparatus comprising
The image data processing unit
Generating an image using data including the first projection data, the second projection data, and the third projection data;
a1: processing of performing partial reconstruction using the first projection data to generate a first image of an object at time t (A);
a2: Partial reconstruction is performed using second projection data which is opposite data of the first projection data, and the second object of the object at time t (C) after time t (A) Processing to generate an image,
a3: Partial reconstruction is performed using the third projection data between the first projection data and the second projection data, and time t (A) between time t (A) and time t (C) A process of generating a third image in B);
a4: processing of acquiring data of motion information based on the first image and the second image;
a5: processing of generating the first estimated image at time t (B) by deforming the first image using the data of the motion information, and using the data of the motion information, the second A process of performing at least one of a process of deforming the image and generating a second estimated image at time t (B);
a6: processing of combining the third image with the first estimated image or the second estimated image to generate an estimated tomographic image of a region of interest at time t (B);
An X-ray CT apparatus characterized in that

As described above, the first projection data and the second projection data are "opposite data", which means that they are 180 ° opposite data. The invention is applicable to both parallel beam and fan beam CT devices.

(Explanation of terms)
-"Image data processing unit" has, for example, a CPU (one or more processors) that performs arithmetic processing, a memory, an interface, etc., and executes various functions by executing a computer program stored in the memory. It may be a computer that realizes
-"Subject" basically refers to a human, but may be for imaging an animal.
“Operator” includes a doctor, a medical worker (eg, radiologist, nurse), and the like.
In the present specification, “a drug solution injector” basically refers to a drug solution injector for injecting a drug solution such as a contrast agent (for example, an iodine-based agent). The drug solution injector may be used by being disposed in the vicinity of the X-ray CT apparatus. The drug solution injector in one form comprises the following components:
-One or more piston drive mechanisms,
-1 or more control units (control units), and
-One or display etc.

One embodiment of the liquid injector may include an injection head and a console connected thereto. In this case, (i) the injection head may be provided with a piston drive mechanism, and the console may be provided with a control unit and a display, or (ii) both the injection head and the console may be provided with a control unit And (iii) displays may be provided on both the infusion head and the console.

According to the present invention, it is possible to provide an X-ray CT apparatus, an image generation method, and the like which are excellent in time resolution and capable of reducing an artifact due to the movement of an object.

It is a figure which shows typically the structure of the X-ray CT apparatus which concerns on one form of this invention. It is a flowchart which shows the procedure of the image generation method which concerns on one form of this invention. It is a flowchart which shows the more specific procedure of the image generation method which concerns on one form of this invention. It is a figure for demonstrating the scan range and data which were scanned by CT apparatus. It is sinogram data which shows a horizontal direction as a channel number of a detector, and a vertical direction as a scan angle. It is a figure which shows the deformation | transformation movement of the image in time t (A), and the image in time t (C). It is a figure which shows carrying out deformation | transformation movement of the image of time t (A) to the image in time t (B). It is a figure for demonstrating the image generation of another aspect. It is a schematic diagram which shows the data which shifted and produced | generated by angle (beta). It is a figure for demonstrating preparation of the presumed image using a pair of data set. FIG. 6 is a diagram showing an image generated from each data set. It is a figure for demonstrating making an intermediate | middle estimated image from the image part with a motion. It is a figure which shows the intermediate | middle estimation image between edges. It is a figure which shows the other example of a data set. It is a figure for demonstrating the image generation at the time of utilizing a double-tube system. It is a figure for demonstrating the movement amount regarding the movement of a target object (prior art).

Embodiments of the present invention will be described below with reference to the drawings.

1. First Embodiment [Configuration]
An X-ray CT apparatus 1 (also referred to simply as “CT apparatus 1”) shown in FIG. 1 includes a gantry 100 and a control unit 150 connected thereto. Although not shown in FIG. 1, the CT apparatus 1 also includes a bed on which the subject is placed and moved. In the present embodiment, the gantry 100 itself may use a conventionally known one. The basic functions (control of operation of gantry, reconstruction of tomographic image layer, etc.) of the control unit 150 can also be implemented with a conventionally known configuration.

Gantry
The gantry 100 is provided with an X-ray irradiator 101 that emits X-rays toward the subject S, and an X-ray detector 111 disposed opposite to the X-ray irradiator. These are held by the rotation mechanism 105, and configured to integrally rotate at the time of imaging (at the time of scanning).

The X-ray irradiator 101 has an X-ray tube (not shown), and generates a X-ray upon receiving a high voltage pulse generated from a high voltage generator (not shown). The irradiated X-rays may have, for example, a conical or pyramidal beam shape. Although not depicted in FIG. 1, the X-ray irradiation unit 101 is provided with a collimator having a slit of a predetermined width, whereby a fan angle of X-ray (a spread angle in the channel direction (details below)) Is to be prescribed.

The rotation mechanism 105 has a rotation frame 102 which is formed to a size surrounding the subject S and rotates around the subject S at the time of scanning. The rotation mechanism 105 may be provided with a plurality of pairs of the X-ray irradiator 101 and the detector 111. However, in the present embodiment, only one pair is provided as an example.

The X-ray detector 111 is one in which a plurality of X-ray detection elements (not shown) are arranged along the channel direction (details described below). The X-ray detection element outputs intensity data of X-rays transmitted through the subject S as an electric signal (raw data).

The X-ray detector 111 may have, for example, multiple rows of surface detectors arranged respectively in the slice direction and the channel direction. The “slice direction” corresponds to the body axis direction of the subject S, and the “channel direction” corresponds to the rotation direction of the X-ray irradiator 101. By using such a multi-row X-ray detector, imaging of a three-dimensional imaging region having a width in the slice direction becomes possible by scanning of one rotation (approximately half rotation in the case of half scanning).

The X-ray detector 111 is connected to a data acquisition unit 106 including a data acquisition circuit 104 called a DAS (data acquisition system). In one example, the data acquisition circuit 104 periodically integrates an IV converter that converts the current signal of each channel of the X-ray detector 111 into a voltage, and this voltage signal in synchronization with the X-ray irradiation cycle. And an integrator. Further, an amplifier for amplifying the output signal of the integrator, and an analog-digital converter for converting the output signal of the amplifier into a digital signal are provided. The data acquisition unit 106 performs predetermined pre-processing on the signal from the detector and outputs it as “projection data”.

The preprocessing is not particularly limited, but may be, for example, logarithmic conversion processing, offset processing, sensitivity correction processing, beam hardening processing, or the like.

[control unit]
The control unit 150 includes, for example, a scanner controller 151, an input device 153, a display device 155, a storage device 157, an image data processing unit 160, and the like.

The control unit 150 is an example, and is configured by one computer, and specifically, a processing device such as a central processing unit (CPU) or a graphic processing unit (GPU), and a read only memory (ROM) And a storage device (not shown) such as a RAM (Random Access Memory) or an HDD (Hard Disc Drive). The storage device stores a control program for executing the function of each unit. A processing device such as a CPU executes each program stored in the storage device to execute each function. It is also possible to configure the control unit 150 with a plurality of computers. For example, the computer including the scanner controller 151 and the computer including the image data processing unit 160 may be configured separately.

As the input device 153, for example, a device such as a keyboard or a mouse used for input from the operator is provided. Besides, in addition or as an alternative, a voice input device, a non-contact motion detection device or the like may be used. It is also possible to use a touch pad or a touch pen.

The display device 155 may be provided with one or more displays. The storage device 157 may also be anything as long as it can store predetermined data (projection data, generated image data, etc.), and uses a hard disk drive (HDD) or a solid state drive (SSD) can do.

The scanner controller 151 is a control unit for controlling the operation and the like of each part of the gantry 100 of the CT apparatus 1, and may be a conventionally known one. Although not limited, the scanner controller 151 may control operations of the X-ray irradiation unit 101, the detector 111, the rotation mechanism 105, a high voltage generation unit (not shown), and the like.

[Image data processing unit]
The image data processing unit 160 (i) generates a tomographic image based on the data output from the data acquisition unit 106 (function) and (ii) generates an estimated tomographic image according to the present embodiment. It has a part (function) that executes a function (details below). In addition to that, it also has a function of rendering the generated tomographic image, etc. However, since a conventionally known method can be used for this, detailed description will be omitted.

For example, the above (i) may be performed by the reconstruction processing unit, and as a specific example, reconstruction is performed based on the projection data output from the data acquisition unit 106, Tomographic image data (two-dimensional data or three-dimensional volume data) is generated. For the reconstruction, for example, any method such as Fourier transform method, convolution back projection method, successive approximation method, integral integration method, filter back projection method, etc. can be adopted. The volume data may be generated by performing interpolation processing using a plurality of reconstructed tomographic image data.

More specifically, for reconstruction, conventionally known techniques such as Feldkamp method or cone beam reconstruction method can be used. The Feldkamp method is a reconstruction method in the case where projection rays intersect the reconstruction surface like a cone beam. The cone beam reconstruction method is a reconstruction method which corrects projection data according to the angle of the ray with respect to the reconstruction surface as a method in which the error of the cone angle is suppressed more than the Feldkamp method.

The above (ii) will be described in more detail in the description of the operation to be described later, but by reading all or part of scan data of 180 ° + additional angle β (see FIG. 4) and performing partial reconstruction. It may be imaging.

The image data processing unit 160 also has the function of comparing two images to obtain data of motion information. For acquisition of data of motion information, for example, edge detection of an image may be performed to acquire information such as a movement amount and / or a deformation amount of a predetermined point, and a direction. Various other methods can be adopted as a technique for acquiring motion vector information.

The image data processing unit 160 also has a function to deform and move the first image and / or the second image based on the data of the motion information acquired as described above. Specifically, the first image and / or the second image is generated so as to generate an intermediate image between the first image (time t (A)) and the second image (time t (C)) Has a function to move the Note that “deformed movement” means either performing deformation only, performing movement only, or performing both of them, and is necessarily limited to always performing both deformation and movement. It is not a thing.

The image data processing unit 160 also partially reconstructs the first image and / or the second image generated by the deformation movement and a part of the scan data in order to generate a final estimated tomographic image. It also has a function of superimposing an image obtained in detail (described in detail later) into one image.

[Operation]
Hereinafter, the operation of the CT apparatus 1 of the present embodiment configured as described above will be described. Although the CT apparatus 1 of this embodiment also has a function of general tomographic image generation known in the prior art, the description thereof is omitted, and the procedure of generating an estimated tomographic image which is the main feature of the present application. The explanation will be focused on Although flowcharts are shown in FIG. 2 and FIG. 3, the method of the present invention is not necessarily limited to that order, and the order of one or more steps is changed without departing from the scope of the present invention. Or you may make it implement simultaneously.

(Overall schematic flow)
An outline of a flow from imaging by the CT apparatus 1 to tomographic image generation is as shown in FIG. That is, first, in this example, the contrast agent is injected into the subject in step S1. Then, in step S2 at which a predetermined time has elapsed from the start of contrast agent injection, the CT apparatus 1 performs a scan. In step S3, predetermined preprocessing and the like are performed on the data obtained thereby to generate projection data, and then in step S4, a predetermined image generation process is performed based on the projection data.

(Generation of estimated image by motion collection)
First, as a premise of generation of an estimated image according to an embodiment of the present invention, as shown in FIG. 4, it is assumed that there is data obtained by scanning an object. This is data in the range of 180 ° + additional angle β. Generating an image based on such data reduces the time required for scanning (scan time) as compared to the case of so-called full reconstruction. Therefore, it is preferable at the point which can improve time resolution. The angle β is preferably in a range of, for example, 10 ° to 120 ° in one embodiment. In one embodiment, it is preferable that the rotational speed of the emitting unit is in the range of 0.2 sec / rotation to 60 sec / rotation.

The data used in the present embodiment can be easily understood as data of 180 ° + data of additional angle β as shown in FIG. Specifically, data 120 in FIG. 5 (which may be regarded as sinogram data) is data including projection data A, projection data B, and projection data C in order from the rotation angle 0 degree side (upper end side in the figure). is there.

(Step S11)
Using the data 120, in step S11, partial reconstruction is first performed using the first projection data A to generate a first image Im (A) corresponding to this range.

FIG. 6 is a diagram for explaining the positional relationship and the like of the scan time and the image corresponding thereto. The horizontal axis indicates time, and the vertical axis indicates the image position of the object. Here, it is assumed that the first projection data A is captured at time t (A), and the image Im (A) is displayed at the time t (A).

(Step S12)
Next, in step S12, partial reconstruction is performed using the second projection data C, and a second image Im (C) corresponding to this range is generated. The second projection data C is data corresponding to the opposite beam whose angle is shifted by 180 ° with respect to the first projection data A. In FIG. 6, the image Im (C) is displayed at the time t (C).

In the case of reconstructing and imaging each of such opposing data, if the object does not move between time t (A) and t (C), the image Im (A) and the image Im ( C) will be substantially identical. However, in the present embodiment, it is assumed that the object at a specific position in the image moves from the time t (A) to t (C) by a predetermined distance d1 (see FIG. 6).

(Step S13)
Referring back to the flowchart of FIG. 3 again, in step S13, the third projection data B is used to generate an image Im (B) corresponding to this portion.

(Step S14)
Now, as described above, the position and shape of the object at time t (A) and the position of the object at time t (C) by reconstruction and imaging for each of the projection data A and C. You will know the shape. Therefore, based on these two images Im (A) and Im (C), it is possible to obtain data of motion information of the object.

As motion information, in this embodiment, it is assumed that the image Im (A) of the object at time t (A) moves linearly or substantially linearly until time t (C) (FIG. 6). See also dashed line L ₁ ).

(Step S15)
Thus, if data of motion information is obtained, for example, the image Im (A) at time t (A) is deformed and moved to an image at time t (B), as shown in FIG. The estimated image Im (A) 'in (B) can be generated. The estimated image Im (A) ′ can be realized, for example, by image processing in which the position is linearly moved, or the size and shape are linearly deformed, using data of motion information. The data processing may be nonlinear data processing that is not necessarily linear in a strict sense, but linear.

By superimposing the estimated image Im (A) ′ thus obtained and the image Im (B) corresponding to the scan range B, an estimated tomographic image at time t (B) is generated. Note that the estimated image Im (C) ′ at time t (B) may be generated based on the image Im (B) at time t (C), and may be superimposed on the image Im (B).

Furthermore, as another method, for example, Im (A) ′ modified from the image Im (A) and Im (C) ′ modified from the image Im (C) are prepared, and the following equation You may choose to do the superposition with:
[(Im (A) ′ + Im (C) ′) / 2] + Im (B)
According to such a method, even when the contrast agent concentration largely changes during scanning, the change can be reduced, which is preferable.

According to the above series of steps, it is possible to generate an estimated tomographic image of the object based on the data of 180 ° + additional angle β (see FIG. 5). In particular, the estimated tomographic image finally obtained by the method of the present embodiment is generated by virtually preparing images of the same time (here, time t (B)) and superimposing them. Therefore, it is possible to obtain a good image with excellent temporal resolution and reduced motion artifacts with relatively simple data processing without requiring reconstruction processing. Moreover, it is preferable also in the point which can reduce the exposure dose of a test object compared with the case of a full scan.

As mentioned above, although this invention was demonstrated along a specific example, this invention is not limited to said content, It can change suitably in the range which does not deviate from the meaning. Further, the present invention can be variously modified without departing from the scope of the present invention, and is not limited to the above example. The technical matters disclosed as certain embodiments of the present specification can be combined with other embodiments without departing from the spirit of the present invention.

(Other aspects)
With respect to "time t (B)" (see FIG. 6), this time does not necessarily have to be exactly halfway between the first time t (A) and the second time t (C). It may be any time between the two times t (A) and t (C).

The estimated tomographic image generated in step S15 (see FIG. 3) may be displayed on one or more display devices 155 of the CT apparatus 1, but is not necessarily limited thereto. The data may be stored in the storage device 157 or a predetermined external storage means, and may be displayed on another device.

In the above-described embodiment, it has been described that the computer that constitutes a part of the CT apparatus performs the image generation process according to an aspect of the present invention, but another computer may perform the image generation process. In this case, as an example, the image generation processing program according to an aspect of the present invention may be installed on a predetermined computer so that the image generation processing can be performed.

In the above example, the images Im (A) and Im (B) are generated using the data of the opposite beam. The images Im (A) and Im (B) are two images that are essentially the same if there is no movement of the subject. As described above, movement and / or deformation occur between the image Im (A) and the image Im (B) when the subject moves. Information on movement and deformation can be obtained by comparing the two images. In the above embodiment, information on the movement and deformation is used, but if it is the images Im (A) and Im (B) from which such information can be obtained, the data is not necessarily limited to the opposite data, You may use the data of For example, assume a scan in which the tube is rotated several times. In this case, for example, projection data A during one rotation (see FIG. 5) and projection data A 'during the next rotation (data delayed by 360 ° with respect to the previous projection data A) And may be used. The two images created from these data will also move and / or deform if there is movement of the subject. Then, information on movement and deformation can be obtained similarly to the above by comparing the two images.

Referring to FIGS. 4 and 5, it has been described that the angle β is in the range of 10 ° to 120 ° as an example. Assuming that the angle β is 10 °, projection data B (see FIG. 5) is data of an angle (that is, 170 °) from 10 ° to 180 °. In the present invention, it is also possible to use projection data B in such a range.

Basically, projection data may be obtained from an imaging device, but the present invention is not necessarily limited to this. For example, the configuration may be such that projection data stored in a data storage device other than the imaging device is used. In addition, as an example, at least two component images (for example, a component image captured in a first time phase and a component image captured in a second time phase) are used, from which information on movement and deformation is obtained. , And may generate an estimated image using the motion / deformation information. Although it is not limited, the first time phase is (a + b) and the second time phase is (b + c), and the first time phase image and the second time phase image The movement / deformation information may be obtained by comparison or subtraction processing.

As for the imaging apparatus, other modality (MRI: Magnetic resonance imaging, angiography apparatus, PET: positron emission tomography, and SPECT: Single Photon Emission Computed Tomography) other than the X-ray CT apparatus can be used.

Although various forms applicable to the present invention have been described above, these matters do not apply only to the first embodiment, and can be applied to other embodiments and modifications of the present application. It should be noted that.

2. Second Embodiment In the present invention, an image may be generated by the following method. That is, in this example, first, as shown in FIG. 8, it is assumed that there is scan data (including data A to C, A and C are opposite data) for 180 ° + β, and this is used . First, with respect to the region I (180 ° range), reconstruction is performed based on the data of A + B to generate a corresponding first image (see also Im (A + B) in FIG. 9).

Next, with respect to the region II (180 ° range shifted from the region I by β), reconstruction is performed based on the data of B + C to generate a corresponding second image (Im (B + C in FIG. 8). See also)).

As described above, when two images are obtained, motion information can be obtained based on them as in the above-described embodiment, and the intermediate time (time t (B And the above-described embodiment) can be generated.

Such a method, that is, a method using data A and C shifted by an angle β can be implemented by a general CT apparatus, for example, by a conventionally known half reconstruction method, and is useful.

[Generation of estimated image using a pair of data sets]
It is also possible to generate an estimated tomographic image by using a pair of data sets as shown in FIG. The details will be described below. The following procedure includes, by way of example, the following steps:
-Prepare a pair of data sets,
-Image generation based on datasets,
-Difference operation between generated images,
-Detection of image parts that did not move,
-Detection of moving image parts,
-Generation process of an estimated intermediate image estimated from a moving image part.

(Preparation of data set)
The data 220 of FIG. 10 is data including two scan data for 180 °, and includes a first data set 221 and a second data set 222. The first data set 221 includes data of the area a and data of the area b, and each data is, for example, data for an angle of 90 °. The second data set 222 is shifted by 90 ° with respect to the first data set 211, and is composed of the data of the area b and the data of the area c. These data are also data for an angle of 90 ° as an example. Here, the data in the area b is duplicate data in the first and

second data sets

221 and 222.

Let t (A), t (B) and t (C) be the central times collected for the regions a, b and c. Data is collected in the order of the area a to the area c.

The pair of

data sets

221 and 222 may be, for example, ones respectively generated by reconstruction processing on the CT apparatus side. In the following description, although an example of generating an “image” using projection data collected by a CT apparatus will be described, naturally, the present invention relates to an image data set having a plurality of data in the body axis direction. It can also be implemented and may be premised on the use of volume data.

The image processing apparatus (not shown) includes a CPU (one or more processors) for performing arithmetic processing and an image processing unit having a memory, an interface, etc., and a computer program stored in the memory. Implement various functions by executing. The image processing apparatus may be provided as a stand-alone device or may be provided as part of another apparatus.

(Generation of image based on data set)
Next, the image processing apparatus (not shown) performs half reconstruction processing based on the first data set 221, and generates a corresponding first image Img1 (see FIG. 11). In addition, half reconstruction processing is performed based on the second data set 222 to generate a second image Img2.

(Difference operation between generated images, etc.)
Next, the image processing apparatus (not shown) performs a difference operation between the first image Img1 and the second image Img2. Specifically, as an example, an absolute value of (first image-second image) may be taken, and this value may be determined whether it is zero or not. A difference of zero means that the image portion has not moved. On the other hand, the part where the difference is not zero means the part of the image that has moved.

To explain with reference to the example of FIG. 11, in this example, the first image Img1 is divided into an image portion Img (f) having no motion and an image portion Img1 (m) having motion. Understandable. Similarly, the second image Img2 is divided into an image portion Img (f) having no motion and an image portion Img2 (m) having motion.

As understood from FIG. 11, the first image Img1 and the second image Img2 have relative motions and partially differ in the position of the object on the image. In this example, the image portions Img (f) are common. The remaining image portion Img1 (m) changes so as to move to the image portion Img2 (m) from time t (A) to t (C).

(Process of generating estimated image estimated from moving image part)
However, since it is unclear where the object was at time t (B) as it is, generation of an estimated image is performed by the following steps:

Specifically, in one example, edge extraction processing is performed on the image site Img1 and the image site Img2, and in order to determine how each of the image site Img1 and the image site Img2 corresponds, Perform registration process. As a result, estimated intermediate images Img 'can be drawn at those intermediate positions (see also FIGS. 12 and 13). The "intermediate position" may not necessarily be exactly halfway between the image sites Img1 and Img2. As edge extraction, various methods and algorithms known in the prior art can be used, and they are not limited to specific ones.

Then, one final estimated tomographic image can be generated by combining the image portion Img (f) that has not moved and the estimated intermediate image Img ′ generated above.

The invention described above can be expressed as follows:
(P1) An image processing apparatus for generating a tomographic image using projection data obtained by imaging an object by an imaging apparatus, the image processing apparatus including an image processing unit,
The image processing unit
Projection data of a first data set (221) obtained by the imaging device and projection of a second data set (222) whose angle is deviated by 90 ° (or a predetermined angle) with respect to the first data set The process of identifying data and
Generating a first image from projection data of the first data set;
Generating a second image from projection data of the second data set;
A process of obtaining a difference between the first image and the second image, and identifying a portion without movement (Img (f)) and a portion with movement in the first and second images;
A process of generating an intermediate estimated image (Img ′) using data (Img1 (m)) of the first image part having movement and data Img2 (m) of the second image part having movement ,
A process of combining the portion without movement (Img (f)) and the intermediate estimated image (Img ′) to generate an overall estimated image;
An image processing device that is configured to

(P2) In the image processing apparatus,
The first data set includes data of time (t (A)) and time (t (B)),
The second data set includes data of time (t (B)) and time (t (C)).

(P3) In the image processing apparatus,
The entire estimated image is an estimated image at time t (B).

Note that the invention of the image processing apparatus described above can be expressed as an invention of an image generation method and an image generation program using the image processing apparatus:
(P4) a first image and a second created based on the projection data of the first data set and the projection data of the second data set that is offset by a predetermined angle with respect to the first data set An image generating method for generating an estimated image using an image, comprising:
Calculating a difference between the first image and the second image to identify a non-moving part and a moving part in the first and second images;
Generating an intermediate estimated image using the data of the first image portion in motion and the data of the second image portion in motion;
Combining the non-moving portion and the intermediate estimated image to generate an overall estimated image. And a computer program for causing a computer or a specific data processing unit to perform the method.

In the above description, the first data set 221 includes two areas a and b, and the second data set 222 also includes two areas b and c. However, the present invention may use a data set including three or more multiple regions.

For example, assume a data set as shown in FIG. The first data set A220 includes areas a, b, c, d, and the second data set A 221 includes areas c, d, e, f. That is, the second data set A 221 is data delayed from the first data set by a and b.

In such data sets A220 and A221, the regions c and d are common parts (corresponding to the region b in FIG. 10). On the other hand, the areas a and e are opposite data, and the areas b and f are opposite data. Even in such a case, using the intermediate estimated image generated based on the opposed data of the regions a and e and another intermediate estimated image generated based on the opposed data of the regions b and f Then, estimated image generation similar to that of the above embodiment can be implemented. Specifically, those intermediate estimated images may be combined into a partially reconstructed image based on the common part (regions c, d).

[Use of double tube system]
As described above, the CT apparatus 1 (see FIG. 1) may have a plurality of tubes, but based on the projection data collected by the CT apparatus of such a plurality of tubes, the following It is also possible to perform such an estimated image generation.

As a premise, as shown in FIG. 15A, it is assumed that a first emitting unit 101a and a second emitting unit 101b are provided with an angle of 90 °. In order to perform image reconstruction by half reconstruction, it is sufficient if there is data for 180 ° as a whole (parallel beam equivalent. In the case of fan beam, 180 ° + fan angle, but in the following “180 ° Data, etc.)). Then, in such a configuration, projection data for each 90 ° may be collected by each of the

emission units

101a and 101b. In addition, although the data of “90 °” are described here, the present invention is not necessarily limited to this.

Specifically, as shown in FIG. 15B, the first emission part 101a is rotated from the position of angle 0 ° to the position of angle (90 ° + β), and the second emission part 101b is angle 90 °. Rotate from the position of to the position of angle (180 ° + β).

Then, the data of 180 ° as a whole obtained as a result is divided into a plurality of regions a, b, c (c1, c2), d, e as shown in FIG. 15 (b). The time of data collection is the center time of each area. That is, for the regions a, b, c (c1) scanned by the first emission unit 101a, data are collected at times t (A), t (B), t (C), respectively, and the second emission Data will be collected at time t (A), t (B) and t (C) for the regions c (c2), d and e scanned by the unit 101b, respectively.

Here, attention is paid to the area c. The area c1 is the data scanned by the first emission unit 101a, and the area c2 is the data scanned by the second emission unit 101b, which differ from the same direction for the same object Data collected at time (C) and t (A) respectively:
c1 ... collected at time t (C) c2 ... collected at time t (A)

Also, regarding the areas a and e that are opposite data,
a ... collection at time t (A) e ... collection at time t (C).

The data in the regions a and e are collected at different times in this way, but since they are opposite data, if there is movement between time t (A) and t (C), the generated image Will be different.

As subsequent processing, an image a '(not shown) corresponding to time t (B) is created from the data of the regions a and e. Then, from c1 and c2, an image c '(not shown) corresponding to time t (B) is created. As these processes, the same idea as in the first embodiment can be used. Using the data prepared in this way, an estimated image at time t (B) can be generated at (a ′ + b + c ′ + d).

According to the above-described method, since it is possible to perform image generation using data collected by rotating a two-tube system by approximately 90 °, there is an advantage that time resolution can be improved.

(Supplementary note)
This specification further discloses the following invention (note that the reference numerals in parentheses do not limit the present invention at all):
1. A gantry (100) having an emitting unit (101) for emitting an X-ray and a detector (111) for detecting the X-ray;
An image data processing unit (160) for performing an operation based on detection data from the detector;
An X-ray CT apparatus (1) comprising
The image data processing unit (160)
An image is generated using data (120) including the first projection data (A), the second projection data (C) and the third projection data (B),
a1: processing of performing partial reconstruction using the first projection data (A) to generate a first image (Im (A)) of the object at time t (A);
a2: Partial reconstruction is performed using the second projection data (C) which is the opposite data of the first projection data (C), and the above at time t (C) after time t (A) A process of generating a second image (Im (C)) of the object;
a3: Partial reconstruction is performed using the third projection data (B) between the first projection data and the second projection data, and the time between time t (A) and time t (C) A process of generating a third image (Im (B)) at time t (B);
a4: processing of acquiring data of motion information based on the first image and the second image;
a5: A process of generating the first estimated image (Im (A) ′) at time t (B) by transforming the first image using the data of the motion information, and the data of the motion information A process of using at least one of the process of transforming the second image and generating the second estimated image (Im (C) ′) at time t (B);
a6: A combination of the third image (Im (B)) and the first estimated image (Im (A) ') or the second estimated image (Im (C)') at time t (B) Generating an estimated tomographic image of the region of interest in
An X-ray CT apparatus characterized in that

In the above, both of a5 and a6 can be implemented, but only one of the processes of a5 and a6 may be performed. The present invention also discloses a computer device (for example, a work station or the like) having a function corresponding to the image data processing unit (160). That is, the present invention may be expressed as an invention of a computer apparatus such as a workstation, not an invention of an X-ray CT apparatus, and the image processing as described above is executed by the computer apparatus Good.

2. An X-ray CT apparatus, wherein a scan angle for generating the first to third projection data is 180 ° + additional angle (β).

3. An X-ray CT apparatus, wherein the first projection data (A) and the second projection data (C) are data corresponding to scan data for the additional angle (β).

4. The X-ray CT apparatus, wherein the additional angle (β) is in the range of 10 ° to 120 °.

5. The X-ray CT apparatus, wherein the rotation speed of the light emitting unit is in the range of 0.1 sec / rotation to 60 sec / rotation.

6. The X-ray CT apparatus, wherein the data of the image is a single slice image or a multi-slice volume image.

7. A method of generating a medical image using data including first projection data, second projection data and third projection data obtained by scanning and imaging a subject with an X-ray CT apparatus (or simply, A method of generating a medical image using data including the first projection data, the second projection data, and the third projection data),
b1: performing partial reconstruction using the first projection data to generate a first image of the object at time t (A);
b2: Partial reconstruction is performed using second projection data which is opposite data of the first projection data, and the second object of the object at time t (C) after time t (A) Generating an image;
b3: Partial reconstruction is performed using the third projection data between the first projection data and the second projection data, and time t (A) between time t (A) and time t (C) Generating a third image in B);
b4: acquiring motion information data based on the first image and the second image;
b5: transforming the first image using the data of the motion information to generate a first estimated image at time t (B), and using the data of the motion information to generate the second image A process of performing at least one of the steps of deforming and generating a second estimated image at time t (B);
b6: combining the third image and the first estimated image or the second estimated image to generate an estimated tomographic image of a region of interest at time t (B);
Image generation methods, including:

The present invention can also be expressed as an invention of a computer program as follows. That is, the image generation program is an image generation program for executing a method of generating a medical image using data including the first projection data, the second projection data, and the third projection data. , Have one or more computers (processors) perform the following steps:
c1: performing partial reconstruction using the first projection data to generate a first image of the object at time t (A);
c2: Partial reconstruction is performed using second projection data which is opposite data of the first projection data, and the second object of the object at time t (C) after time t (A) Generating an image;
c3: Partial reconstruction is performed using the third projection data between the first projection data and the second projection data, and time t (A) between time t (A) and time t (C) Generating a third image in B);
c4: acquiring motion information data based on the first image and the second image;
c5: using the data of the motion information, deforming the first image, and generating a first estimated image at time t (B); and using the data of the motion information, the second Performing at least one of the steps of transforming the image and generating a second estimated image at time t (B);
c6: combining the third image and the first estimated image or the second estimated image to generate an estimated tomographic image of a region of interest at time t (B).

Note that the invention described above regarding the X-ray CT apparatus 2. To 5. The technical features of can of course also be expressed as a method invention and a computer program invention. In addition, an implementation subject of each step of the method and each step executed by the computer program is not necessarily limited to a single computer (processor).

8. A gantry (100) having an emitting unit (101) for emitting an X-ray and a detector (111) for detecting the X-ray;
An image data processing unit (160) for performing an operation based on detection data from the detector;
An X-ray CT apparatus (1) comprising
The image data processing unit (160)
An image is generated using data (120) including the first projection data (A), the second projection data (C) and the third projection data (B),
d1: a process of performing partial reconstruction using the first projection data (A) to generate a first image (Im (A)) of the object at time t (A);
d2: Partial reconstruction is performed using the second projection data (C) which is opposite data of the first projection data, and the target object at time t (C) after time t (A) A process of generating a second image (Im (C));
d3: Partial reconstruction is performed using the third projection data (B), which is between the first projection data and the second projection data, and between the time t (A) and the time t (C) A process of generating a third image (Im (B)) at time t (B);
d4: a process of acquiring motion information data based on the first image and the second image;
d5: processing of generating the first estimated image (Im (A) ′) at time t (XB) by using the data of the motion information to deform the first image, and the data of the motion information A process of using at least one of the process of transforming the second image and generating the second estimated image (Im (C) ′) at time t (B);
d6: The average of the first estimated image (Im (A) ') and the second estimated image (Im (C)') is calculated, and that image and the third image (Im (B)) Processing for generating an estimated tomographic image of the site of interest at time t (B) by combining
An X-ray CT apparatus characterized in that

The expression “the average of the first estimated image (Im (A) ′) and the second estimated image (Im (C) ′) is expressed as“ [Im (A) ′ + Im ( C) ') / 2].

The present application also discloses the invention of goods expressed as the invention of method and the invention of computer program. Although the aspect such as half reconstruction has been described above as an example, the present invention is not limited thereto, and may be applied to the case of utilizing full reconstruction (360 ° reconstruction) without departing from the spirit of the present invention. It is.

1 X-ray CT device (imaging device)
100

gantry

101, 101a, 101b X-ray irradiation unit 102 rotation frame 104 data acquisition circuit (DAS)
105 rotation mechanism 106 data acquisition unit 120 data 150 control unit 151 scanner controller 153 input device 155 display device 157 storage device 160 image data processing unit (data processing unit)

Claims

A gantry having an emitter for emitting X-rays and a detector for detecting the X-rays;
An image data processing unit that performs an operation based on detection data from the detector;
An X-ray CT apparatus comprising
The image data processing unit
Generating an image using data including the first projection data, the second projection data, and the third projection data;
a1: processing of performing partial reconstruction using the first projection data to generate a first image of an object at time t (A);
a2: Partial reconstruction is performed using second projection data which is opposite data of the first projection data, and the second object of the object at time t (C) after time t (A) Processing to generate an image,
a3: Partial reconstruction is performed using third projection data between the first projection data and the second projection data, and time t (A) between time t (A) and time t (C) A process of generating a third image in B);
a4: processing of acquiring data of motion information based on the first image and the second image;
a5: using the data of the motion information, deforming the first image, and generating a first estimated image at time t (B); and using the data of the motion information, the second A process of performing at least one of a process of deforming the image and generating a second estimated image at time t (B);
a6: processing of combining the third image and the first estimated image or the second estimated image to generate an estimated tomographic image of a region of interest at time t (B);
An X-ray CT apparatus characterized in that
The X-ray CT apparatus according to claim 1, wherein a scan angle for generating the first to third projection data is 180 ° + additional angle.
The X-ray CT apparatus according to claim 1, wherein the first projection data and the second projection data are data corresponding to the additional angle.
The X-ray CT apparatus according to claim 2 or 3, wherein the additional angle is in a range of 10 属 to 120 属.
The X-ray CT apparatus according to any one of claims 1 to 4, wherein a rotation speed of the emission unit is in a range of 0.1 sec / rotation to 60 sec / rotation.
The X-ray CT apparatus according to any one of claims 1 to 5, wherein the data of the image is a single slice image or a multi-slice volume image.
A method of generating a medical image using data comprising first projection data, second projection data and third projection data, comprising:
b1: performing partial reconstruction using the first projection data to generate a first image of the object at time t (A);
b2: Partial reconstruction is performed using second projection data which is opposite data of the first projection data, and the second of the object at time t (C) after time t (A) Generating an image;
b3: Partial reconstruction is performed using third projection data between the first projection data and the second projection data, and time t (A) between time t (A) and time t (C) Generating a third image in B);
b4: acquiring motion information data based on the first image and the second image;
b5: using the data of the motion information to deform the first image to generate a first estimated image at time t (B); and using the data of the motion information, the second Performing at least one of the steps of transforming the image and generating a second estimated image at time t (B);
b6: combining the third image and the first estimated image or the second estimated image to generate an estimated tomographic image of a region of interest at time t (B);
Image generation methods, including:
A gantry having an emitter for emitting X-rays and a detector for detecting the X-rays;
An image data processing unit that performs an operation based on detection data from the detector;
An X-ray CT apparatus comprising
The image data processing unit
Generating an image using data including the first projection data, the second projection data, and the third projection data;
d1: processing for performing partial reconstruction using the first projection data to generate a first image of the object at time t (A);
d2: Partial reconstruction is performed using second projection data which is opposite data of the first projection data, and a second one of the objects at time t (C) after time t (A) Processing to generate an image,
d3: Partial reconstruction is performed using third projection data between the first projection data and the second projection data, and time t (A) between time t (A) and time t (C) A process of generating a third image in B);
d4: a process of acquiring motion information data based on the first image and the second image;
d5: using the data of the motion information to deform the first image to generate a first estimated image at time t (B), and using the data of the motion information, the second A process of performing at least one of a process of deforming the image and generating a second estimated image at time t (B);
d6: The average of the first estimated image and the second estimated image is taken, and the image and the third image are combined to generate an estimated tomographic image of the region of interest at time t (B) Processing and
An X-ray CT apparatus characterized in that
An X-ray CT apparatus comprising: a gantry having an emission unit for emitting an X-ray and a detector for detecting the X-ray; and an image data processing unit for performing an operation based on detection data from the detector,
The image data processing unit
e1: processing of generating two images by reconstructing by shifting time by a predetermined angle using continuous scan data;
e2: generating an image at an intermediate time between the two images;
An X-ray CT apparatus that is configured to perform.