JPH1119078A - X-ray ct device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the dosage of a patient or an operator without inviting the image quality deterioration of a tomographic image by a method wherein a channel collimator which suppresses the radiation of an X-ray to the outside of a region being set when a projection data is measured by rotating an X-ray source, is arranged. SOLUTION: A channel collimator 210 is provided to a body B to be inspected in a manner to be close to an X-ray tube 200 which generates an X-ray by a high voltage being fed from a high voltage generating device 104. Then, the channel collimator 210 is controlled by a controller 211, and an X-ray radiation range in the channel direction is limited to an interested region A which can be set in advance. When the interested region A is set, as a first step, various kinds of tables are stored in a system controller. Then, a motor is rotatedriven, and a curtain-form lead-shielding plate of the chanenl collimator 210 is stretched or shrunk by a timing belt, and a scanning of the interested region during a scanning is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus for obtaining a tomographic image of the inside of a body such as a patient using X-rays.
When continuously measuring substantially the same cross-section, X-ray irradiation that can minimize the amount of X-ray irradiation outside the set (interest) region and reduce the amount of exposure to a patient, an operator, or a specific tissue is possible.
The present invention relates to a line CT apparatus.

[0002]

2. Description of the Related Art X-ray CT apparatuses have already been widely used in medical treatment and the like, and various usages have been made by users. For example, recently, when performing histological examination or treatment of a lesion percutaneously, an X-ray CT
It has been practiced to use the device as a puncture guide.
As described above, by performing the tissue examination and treatment of the lesion under the guide of the X-ray CT apparatus, the operation time is reduced, and the accuracy is considered to be improved.

[0003] By the way, as a method of guiding with such an X-ray CT apparatus, puncturing and CT imaging are alternately and intermittently repeated so as to confirm the position of the tip of a puncture needle, or CT imaging. Is performed continuously, and images are sequentially displayed so that the position of the puncture needle can be immediately confirmed. Among them, especially in the latter method,
Since a tomographic image can be obtained in real time, there is an advantage that the operation time is further reduced.

[0004]

However, in the above-described method in which CT imaging is performed intermittently or continuously, the X-ray exposure due to the intermittent or continuous CT imaging is required for a patient or an operator. Is a problem. On the other hand, in order to reduce the dose, the X-ray tube current may be lowered to lower the irradiation dose. However, the decrease in the irradiation dose (mAs = mA × sec) is caused by the X-ray fluctuation noise. This means that the image quality of the tomographic image is significantly deteriorated.

[0005] In view of the above-mentioned problems in the prior art, the present invention is advantageous even when the X-ray imaging is performed continuously or intermittently at the time of puncturing with the guide of the X-ray CT apparatus. It is an object of the present invention to provide an X-ray CT apparatus capable of reducing the exposure of a patient or an operator without lowering the image quality of a tomographic image to be obtained.

[0006]

According to the present invention, in order to achieve the above object, the X-ray source is continuously rotated to measure the projection data of the subject continuously plural times, In an X-ray CT apparatus that reconstructs a tomographic image of a subject based on data and sequentially displays the tomographic images on a display device, a region of interest for setting an irradiation range of the X-ray from the X-ray source within the subject An X-ray CT apparatus comprising: a setting unit; and a channel collimator that suppresses irradiation of X-rays outside the region set by the region of interest setting unit when the projection data is measured by rotating the X-ray source. To provide.

In the present invention, the X-ray C
In the T apparatus, further, a tomographic image in a region in which X-ray irradiation is suppressed by the channel collimator outside the region of interest set by the region of interest setting means,
An image processing device that can be reconstructed using previous data is provided and displayed by the image processing device.

Further, according to the present invention, in the X-ray CT apparatus described above, the channel collimator is suppressed by the X-ray irradiation area set by the region-of-interest setting means in the plurality of continuous measurements. Control was performed to obtain projection data suppressed by the channel collimator so as to obtain normal projection data that is not performed or a larger area than the region of interest.

Further, according to the present invention, in the X-ray CT apparatus described above, furthermore, the measurement is gradually performed between the region of interest set by the region of interest setting means and the normal scan range by the X-ray CT apparatus. Means for measuring projection data while irradiating the subject with X-rays while reducing or enlarging the area is provided. Furthermore, in the present invention, ordinary projection data which is not suppressed by the X-ray irradiation region set by the region of interest setting means or projection data which is suppressed by the channel collimator so as to obtain a region larger than the region of interest is obtained. If not, an image processing apparatus capable of reconstructing the projection data outside the region of interest from the scan data of the region of interest by externally performing interpolation is provided.

According to the present invention, in the X-ray CT apparatus described above, the region-of-interest setting means displays an inner / outer boundary of the set region of interest on the display device.

That is, according to the present invention, the region of interest setting means and the channel collimator make it possible to take an image without irradiating X-rays as much as possible except for the region of interest set. The image was made possible by reconstructing by applying previously measured data and the like.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. First, FIG. 2 shows an overall configuration of an X-ray CT apparatus according to an embodiment of the present invention. As is clear from the figure, this X-ray C
The T device is equipped with a display device 100, a host computer 101 controlling the whole device, an X-ray generation system, an X-ray detection system, etc., a scanner system 102 capable of continuous scanning by a slip ring, and a pre-processing of images. Processing apparatus 103 including a preamplifier (indicated by reference numeral 106 in FIG. 3) which is responsible for image reconstruction processing or various analysis processing
And a high voltage generator 104 for supplying a high voltage to the X-ray generation system, and a patient table 105 on which a subject is placed
Etc. Although not shown, the host computer 101 has a keyboard, a mouse, a tracking ball, and the like as its input devices.

FIG. 3 is a detailed explanatory view of the scanner system 102. According to the X-ray CT apparatus of the present invention, an X-ray tube for generating X-rays by a high voltage supplied from a high voltage generator 104 A channel collimator 210 is provided close to the sample 200 and between the sample B and the subject. The movement of the channel collimator 210 in the X-axis direction in the figure is controlled by the controller 211. That is, the channel collimator 210 can limit the X-ray irradiation range in the channel direction to the region of interest A that can be set in advance. Reference numeral 250 in the drawing indicates a detector of the scanner system 102.

Next, the structure of the channel collimator 210 which characterizes the present invention is schematically shown in FIGS. As shown in FIG. 4A, the channel collimator 210 has a trapezoidal outer collimator case 212.
A compensating filter 213 is provided, and a lead shielding plate 214 is provided at a bottom portion thereof. FIG. 4B shows the structure of the lower surface of the channel collimator 210. A pair of guides 2 are provided on both sides of the lead shielding plate 214.
15 and 215 are provided, and the expansion and contraction of the lead shielding plate 214 is controlled by the operation of a motor 216 having an encoder and the like and a timing belt 217.
5A and 5B show a contracted state and an expanded state of the lead shielding plate 214, respectively.

As shown in the above-mentioned figure, a collimator case 212 further includes a system controller 2 for performing overall control of the entire channel collimator 210.
11 and a motor driver 2 for driving the motor 216
18 are provided. Note that the system controller 211 and the motor driver 218 may be attached to other than the collimator case 212.

The system controller 211
Performs overall control of the entire channel collimator 210 as described above. For example, when setting the region of interest A of the present invention, several types of tables are stored in the controller as the first stage. Further, the motor driver 218 drives the motor 216 to rotate, and the rotation of the motor is transmitted to the timing belt 217, whereby the timing belt 217 is connected to the curtain-shaped lead shielding plate 2.
14 is expanded or contracted, thereby enabling a region of interest scan during scanning. FIGS. 4 and 5 are examples, and there may be other channel collimator structures and control mechanisms (means).

Next, the flow of imaging in the X-ray CT apparatus described above will be described. According to the X-ray CT apparatus of the present invention, when a site to be imaged is known in advance, it can be used for a biopsy of a tumor by, for example, post-operative reexamination or CT fluoroscopy. The photographing procedure will be described with reference to FIG. That is, by irradiating the X-ray only to the region of interest, which is the part to be imaged, low exposure in the X-ray CT apparatus is realized.

As for the flow of shooting, when shooting is started,
First, a scanogram is displayed (step S11), and then a precise shooting range is determined (step S12). In this precise imaging range determination, after the patient has been set on the table 105, the above scanogram is first obtained to determine the imaging position of the tomographic image. The setting of the number of shots is performed on the displayed scanogram. The shooting range includes items related to the start of shooting, the shooting interval, the number of shots, and the like. For example, in the case of a spiral scan, the shooting start position, the table moving speed, the number of scans, and the like are also set.

After that, precision imaging is performed (step S13). In this precision imaging, the host computer sets, for example, a tube voltage or a tube current in the high voltage generator 104 according to the conditions set above. Further, in the patient table 105, the moving speed and the like in the spiral scan are set. At the time of this precise imaging, the channel collimator 210 is at a normal position, and X-rays are incident on all channels. Therefore, in the subsequent reconstruction of the precise image (step S14), a sufficiently diagnosable image is obtained.

Subsequently, a photographing slice (step S15)
Is determined (step S16). That is, when the above-described precision imaging is completed, in the imaging slice,
The surgeon observes the photographed image and, for example, in the case of a reexamination, selects a slice suitable for the part to be observed most. In addition, in the case of CT fluoroscopy, information on the periphery of the target such as the position of the target tissue (tumor) and whether there is an important tissue on the puncture route to the target is obtained, and a puncture slice for CT fluoroscopy is determined. . Further, in the region of interest determination, a region to be irradiated with X-rays on the slice determined above, that is, a region of interest A is set. The setting of the region of interest is performed, for example, by drawing a circular region or an elliptical region on the display screen of the display device 100 using a pointing device such as a mouse or a trackball as an input device as shown in FIG. By doing so, X-rays are prevented from being irradiated to the outside of the set region of interest as much as possible.
Further, the table moving slice direction is set (step S17).

Next, a reference scan (Step S)
18) In response to an instruction from the host computer 101,
The patient table 105 moves the tabletop to the selected slice position. Here, imaging (reference scan) is performed at a normal position of the channel collimator 210 with an X-ray dose suitable for the purpose of CT fluoroscopy, such as for reexamination or puncturing, and further, slice position And setting of the region of interest is confirmed (step S19).

Subsequently, a normal scan interval is set (step S20). In the setting of the normal scan interval, the number of times the channel collimator 210 performs shooting at a normal position during continuous shooting is set before shifting to continuous shooting or the like described below. It should be noted that the finer the setting, the less the time lag of the image outside the region of interest, and the more precise the image can be obtained, but the dose does not decrease much. The photographing interval can also be set automatically as a set. In that case,
Settings stored in the host computer 101 in advance,
For example, "perform normal scan once every 10 slices"
Etc. may be used as they are, or instead of such automatic setting, for example, “3
A setting such as "Once every 0 slices" is also possible. Also,
The setting may be such that “normal scan is not performed during continuous speed scan”. In this case, data outside the region of interest is executed in step S18 or data of the reference scan is embedded and image reconstruction processing is performed. Will be done.

Finally, if a desired image is obtained by the above-described reference scan (step S18), the flow shifts to continuous shooting (step S21) and image reconstruction (step S22). In the continuous imaging, the continuous-speed imaging or the puncture imaging set as described above is performed, and the imaging data thus captured is sequentially reconstructed, thereby forming a temporally continuous tomographic image.

Here, the control of the channel collimator 210 whose detailed configuration has been described with reference to FIG. 4 will be described below with reference to FIG. First, as shown in FIG. 8A, the focal position (Xs, Y
A line connecting s) to the rotation center is defined as a y-axis, and a line perpendicular to the y-axis and the rotation center is defined as an x-axis.

Here, the collimators 401 and 402 (corresponding to the lead shielding plate 214 of the channel collimator 210) can be moved in the x direction as described above, and as a result, also shown in FIG. In this way, the mechanism can arbitrarily limit the X-ray irradiation range for each of a plurality of X-ray sources.

Now, assuming that the region of interest is defined by a circle having a radius r centered on the center coordinates (Xc, Yc) in FIG. 8A, the set X-ray irradiation range looks into the focal point. The angle is from θL to θR. Therefore, the amount of movement of the collimators 401 and 402 on the x-axis from the normal positions is △ XL and △ XR in the figure. Here, the normal positions of the collimators 401 and 402 are defined as XL0 and XR0, while the focus of the X-ray is calculated.
Considering the point focus as described above, the coordinates are (Xs, Y
When defined as s), the position coordinates (XL0− △ XL, XR0− △ XR) of the collimators 401 and 402 change at each projection angle.

Since the means for obtaining the movement amounts ΔXL, ΔXR of the collimators 401 and 402 from the normal positions can be obtained by the following formula, they are obtained in advance. Further, it is also possible to approximate with a periodic function such as a trigonometric function without using the following calculation formula.

That is, the above-mentioned ΔXL and ΔXR are obtained as follows.

(Equation 1) Here, d is a distance between two points of the focal point and the center coordinate of the region of interest. And, if θL and θR are expressed using this d,
It looks like this:

(Equation 2)

(Equation 3) Here, d ₀ is the distance from the X-ray focal point to the rotation center of the scanner. Then, using these θL and θR,
Expressing ΔXL and ΔXR is as follows.

(Equation 4)

(Equation 5)

That is, by controlling the positions of the channel collimators and the collimators 401 and 402 at each projection angle in accordance with ΔXL and ΔXR obtained as described above, FIG.
As shown in (1), only the region of interest of the subject is irradiated with X-rays. In the above example, the region of interest has been described as a circle. However, the shape of the region of interest is not limited to a circle, and may be set to, for example, an ellipse. In that case, the following △ XL, △ XR
Will be added to the procedure for determining

Next, image reconstruction using projection data obtained by irradiating only a region of interest with X-rays limited to the region will be described. As described above, the projection data obtained by irradiating only the region of interest with the X-rays limited is, as shown by the thick solid line in FIG. 9, the data in the region shielded by the above collimator, after offset correction. Becomes almost zero. Therefore, in the channels ia and ib in FIG.
An extremely high frequency component is generated. Therefore, if the obtained projection data is used as it is in an image reconstruction process, an artifact will be generated on the image.
In order to solve this, as already proposed by the present applicant (Japanese Patent Application No. Hei 9-112302), a process of embedding the pre-measured projection data into the data of the area shielded by the collimator is performed. .

This is realized, for example, by the image processing apparatus 103 shown in FIG. That is, in the figure, the image processing device 103 includes a reconstruction arithmetic unit 11 and a weighted image adder 12, and outputs the result to the display device 100.
Then, the reconstruction calculator 11 includes a projection data memory 20,
It comprises a pre-processing calculator 21, a fan beam-parallel beam converter 22, a filter correction calculator 23, and a back projection calculator 24. On the other hand, the weighted image adder 12 includes seven image memories 10 (# 1 to # 7) and seven weight coefficient multipliers 13
(W1 to W7 are weighting coefficients) and an adder 25.

In this example, the image processing device 103
For example, reconstruction can be performed in less than one second per image. This means that divided reconstructed images are successively obtained at 30 ° width one after another. Further, one reconstructed screen adds the latest newly obtained 30 ° width reconstructed divided image to the previous one. It is because of what can be achieved. For example, when the angle is updated at a width of 30 °, a reconstructed image of 12 sheets / second can be obtained.

The reconstruction calculator 11 includes a preprocessor by the calculator 21, a parallel beam by the fan beam-parallel beam converter 22, a filter correction by the calculator 23, and a back projection calculator 24. To obtain a reconstructed image. This reconstruction operation is 3
This is not a collective reconstruction for 60 °, but an addition operation for the divided reconstructed images obtained from the parallel beam data with a partial angular width (for example, 30 ° width).

The weighted image adder 12 sequentially assigns the divided reconstructed images obtained by the reconstruction operation unit 11 to the memories # 1 to # 7 of the image memory 10 sequentially. For example, the divided reconstructed image g1 is assigned to # 1, the divided reconstructed image g2 is assigned to # 2,..., And the divided reconstructed image g7 is assigned to # 7 and stored. .., Etc. The subsequent divided and reconstructed images g8, g9,... Are allocated and stored in such a way that g8 replaces g1 with # 1, g2 replaces g2 with # 2, and so on.

The multiplier 13 weights each of the divided images by multiplying the images of the memories # 1 to # 7 in association with the weighting factors W1 to W7. The adder 25 performs total addition to obtain one reconstructed image.

FIG. 11 shows the concept of the reconstructed image processing by the image processing apparatus 103 described above. That is, the effective data range obtained by the pre-scan or the normal scan is as shown by PSC in FIG. 11A, whereas the X-ray is limited to the region of interest of the present invention and irradiated. The obtained projection data is a continuous scan, or, if the scan is repeated continuously, such as fluoroscopy,
As shown by CSC in FIG. 11B, the image data outside the region of interest A is temporally discontinuous, and high image quality cannot be obtained.

Therefore, as shown in FIG. 11C, during the above-described continuous scan or continuous scan such as fluoroscopic imaging, the channel collimator 210 performs the scan (pre-scan or normal scan) PSC at a normal position. Do
At the time of continuous scan CSC before and after this scan, by embedding projection data closest in time, low-exposure can be achieved, and reconstructed image processing capable of improving image quality even in the region outside the region of interest A is realized. it can. That is,
This makes it possible to obtain an image with a small temporal difference with low exposure in the area inside and outside the area of interest A, and obtain an image that is easier to see. In the above description,
This is an explanation of the case where PSC data may exist.
If there is no data, it can be dealt with by performing a foreign search interpolation outside the region of interest from the region of interest data. FIG. 17 illustrates this. A simple least squares method or a higher-order interpolation such as Newton's interpolation may be used for the outer interpolation. When using extrapolation, P
Although the image quality is obviously deteriorated as compared with the case where SC data is used, discontinuous data can be avoided.

As described above, the image outside the region of interest A is a high-quality image in which temporal differences are eliminated as much as possible (projection data of prescan or normal scan which is closest in time). However, there is a considerable time difference from the image in the region of interest A. Therefore, when the present invention is used for continuous scanning or fluoroscopy, an image outside the region of interest A is mistaken for an image in the region of interest A,
This could lead to misdiagnosis of the surgeon.

Therefore, in the present invention, as a means for clearly indicating the boundary between the inside and outside of the region of interest A, as shown in FIG. This is prevented by specifying it. As a means for clearly indicating the boundary line BL, a boundary line surrounding the region of interest A may be drawn (a circle in FIG. 12) by a line of a conspicuous color such as red with a meaning of a warning, or In a black and white monitor, a black or white line may be used, or the line may be blinked to make it easy for a viewer to recognize.

Next, another embodiment according to the present invention will be described. The configuration is described in FIGS.
The description is omitted here.

In another embodiment, the region-of-interest scan according to the present invention is performed particularly when the region to be imaged is known in advance, such as a post-operative reexamination or CT biopsy. The photographing flow will be described with reference to FIG. As is clear from this figure, in the other embodiment, the flow of the photographing is almost the same as that shown in FIG. 6, and the steps denoted by the same reference numerals are the same as those described above. Are omitted, and step S20 ', which is a feature of the method, will be described.

That is, the above-described reference scan (step S18) and region of interest confirmation (step S1)
After step 9), in step S20 ′, it is possible to set the interval of the normal scan and further set the enlarged imaging of the region of interest. That is, if the reduction / enlargement setting is selected here, the region of interest A
And the area of the normal scan gradually approach, in other words,
From the normal scan range or the set range to the region of interest A, a scan in which the measurement range is gradually reduced can be performed.

That is, in the case of the above enlargement, the measurement range gradually increases from the region of interest A to the normal scan region. In the reduction, if the region of interest A is circular, the circle of the normal scan range or the set range gradually decreases, and finally the measurement range reaches the region of interest A (in the case of enlargement, the reverse is true). Measurement). And this reduction (or expansion)
While the data captured outside the region of interest A is used for the correction of the image reconstruction described above, the image quality of the range image outside the region of interest A can be improved.

In this embodiment, when the reduction / enlargement photographing is selected, the radius or the center coordinates of the circle of the region of interest A may change during scanning in some cases.
However, as shown in FIG. 8, it is apparent that the control of the channel collimator 210 according to the above-described embodiment operates even when the coordinates of the center of the region of interest A and the coordinates of the rotation center are shifted. .

However, the operation when the reduction / enlargement photographing is selected will be described below for the sake of simplicity assuming that the center coordinates and the rotation center of the region of interest A are the same. still,
With such an assumption, the only parameter that changes is the value of the radius r of the region of interest A. FIG. 14 shows a photographing situation when the photographing range of the region of interest A is gradually reduced (or enlarged). .

As shown in FIG. 14, the channel collimator 210 gradually reduces or enlarges the image from the normal scan area to the area of interest A during a scan such as a continuous scan or a fluoroscopy. By embedding only a plurality of or a single piece of projection data in a region which cannot be obtained by its own scan, with normal scan and time, high image quality can be obtained.

For the sake of simplicity, this process will be described using projection data when the scanner 102 has made one rotation and the X-ray source 200 is directly above as shown in FIG. That is, it is assumed that the X-ray irradiation range is gradually reduced from the normal scan region to the region of interest A for each rotation. According to this, the projection data obtained in each scan (first to fourth scans) is as shown in FIG.

That is, what is shown by the solid bold line in FIG. 15 is the effective data range. Specifically, first,
In the scan, the effective range is the widest, and conversely, the data range of the fourth scan (scan of the region of interest A) is the narrowest. Therefore, of the data obtained by the second scan,
The projection data in the range shielded by the collimator is supplemented by the projection data from the first scan. Further, the data of the second scan is embedded in the projection data shielded by the collimator of the third scan data, including the data of the second scan, including the data embedded from the first scan. Furthermore, for the data of the fourth scan,
It is embedded in the third data.

As described above, according to the processing of the present embodiment, since the third data includes the data of the first and second scans, the third data is shielded by the collimator of the fourth scan. The range of data is supplemented by the first to third data. As a result, data is sequentially embedded using data that is closer in time, so that an image outside the region of interest A is reconstructed as a high-quality image.

In the above description with reference to FIG. 15, only the case where the measurement area is reduced is described. However, the present invention is not limited to this case. A method of reconstructing an image from both reduced and enlarged photographing is also possible.

That is, in FIG. 16, the projection data obtained by the measurement is indicated by a straight line for explanation. That is, the solid line portion in the figure is effective data actually obtained (not shielded by the channel collimator), and the broken line is data in a range where measurement is not performed. In the description of FIG. 16, there is a first scan to a seventh scan, each of which shows data obtained at the l-th projection angle of one scan,
It is assumed that the measurement range changes for each scan.
Also, as is clear from the figure, the first and seventh scans are normal scans, and the fourth scan is a scan of only the region of interest A.

In these projection data, a method for reconstructing an image from the first to fourth projection data is as follows.
Since it is similar to the above, the description is omitted here. Then, the reconstruction processing from the fifth scan that has performed the enlarged scan supplements the data in the area that is not measured by being blocked by the channel collimator with the second and first scan data,
In the sixth scan, the data is supplemented with the data of the first scan. Although not shown, after the seventh scan, reconstruction processing is performed using the data units of the above-described combinations. In this way, since the data is sequentially embedded using data that is closer in time, the region of interest A
It becomes possible to reconstruct images other than the above as high-quality images.

[0053]

As is apparent from the above detailed description,
ADVANTAGE OF THE INVENTION According to the X-ray CT apparatus which becomes this invention, in a reexamination, CT fluoroscopy, etc., it becomes invalid by using the region-of-interest scan which irradiates an X-ray only to the area | region (region of interest) to which the part to image beforehand was limited. Exposure can be reduced. In addition, by embedding temporal data in advance for data other than the region of interest, an image with less artifacts can be reconstructed. That is, with these, it is possible to obtain an accurate high-quality image with a relatively small difference in time even for an image in a region outside the region of interest with low exposure.

According to the present invention, since the exposure of the subject or the operator can be reduced without lowering the tube current, a highly accurate diagnosis or operation can be performed without deteriorating the image quality. In addition, measures for preventing misdiagnosis are taken by clearly displaying boundaries on the inside and outside of the region of interest on the image.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a region of interest scan that is a feature of an X-ray CT apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram showing an entire configuration including a circuit configuration of the X-ray CT apparatus of the present invention.

FIG. 3 is a detailed explanatory view of a scanner system of the X-ray CT apparatus of the present invention.

FIG. 4 is a detailed explanatory view of a channel collimator of the X-ray CT apparatus of the present invention.

FIG. 5 is an explanatory diagram illustrating an operation of a lead shielding plate of the channel collimator.

FIG. 6 is a flowchart illustrating a flow of imaging in the X-ray CT apparatus of the present invention.

FIG. 7 is a diagram illustrating an example of a method of setting a region of interest in the flow of the above-described imaging.

FIG. 8 is a geometric explanatory view of the operation of the channel collimator in the X-ray CT apparatus of the present invention.

FIG. 9 is a graph showing projection data in a region of interest scan obtained by the channel collimator.

FIG. 10 is a circuit block diagram illustrating an example of an image processing apparatus in the X-ray CT apparatus according to the present invention.

FIG. 11 is a view for explaining a method of scanning a region of interest and correcting data outside the region of interest in the X-ray CT apparatus of the present invention.

FIG. 12 is a diagram for explaining an example of clearly indicating boundaries inside and outside a region of interest in the X-ray CT apparatus of the present invention.

FIG. 13 is an X-ray CT according to another embodiment of the present invention.
6 is a flowchart illustrating a flow of photographing in the device.

FIG. 14 is an explanatory diagram of enlargement (reduction) imaging of a region of interest in the X-ray CT apparatus according to another embodiment.

FIG. 15 is an explanatory diagram of a refining method from reduced imaging in the X-ray CT apparatus according to the other embodiment.

FIG. 16 is an explanatory diagram of a reconstruction method from reduced-magnification imaging in the X-ray CT apparatus according to the other embodiment.

FIG. 17 is a diagram illustrating a modification (foreign interpolation) of FIG. 11;

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Display device 101 Host computer 102 Scanner 103 Image processing device 104 High voltage generator 105 Patient table 200 X-ray source 210 (401, 402) Channel collimator 211 Controller 214 Lead shielding plate 250 Detector A Region of interest B Subject

Claims (6)

[Claims] An X-ray source is continuously rotated to continuously measure projection data of a subject a plurality of times, and a tomographic image of the subject is reconstructed on the basis of the projection data and displayed on a display device. In an X-ray CT apparatus for sequentially displaying, when a region of interest setting means for setting an irradiation range of the X-ray from the X-ray source in the subject, and measuring the projection data by rotating the X-ray source, An X-ray CT apparatus, further comprising: a channel collimator for suppressing X-ray irradiation outside the region set by the region of interest setting means. 2. The X-ray CT apparatus according to claim 1, further comprising: a tomographic image in a region outside the region of interest set by said region of interest setting means, where irradiation of X-rays is suppressed by said channel collimator. An X-ray CT apparatus comprising an image processing apparatus capable of reconstructing with previous data, and embedding and displaying the image by the image processing apparatus. 3. The X-ray CT apparatus according to claim 2, wherein the channel collimator is not suppressed by the X-ray irradiation region set by the region of interest setting unit in the plurality of continuous measurements. An X-ray CT apparatus controlled so as to obtain projection data. 4. The X-ray CT apparatus according to claim 2, further comprising: a region of interest set by said region-of-interest setting means;
Alternatively, the projection data is measured while irradiating the subject with X-rays while gradually reducing or enlarging the measurement region between the scan range suppressed by the channel collimator so as to obtain a region larger than the region of interest. An X-ray CT apparatus characterized by comprising means. 5. The X-ray CT apparatus according to claim 2, wherein normal projection data which is not suppressed by the X-ray irradiation region set by said region-of-interest setting means, or a region which is sufficiently larger than said region of interest. In order to obtain, when the projection data suppressed by the channel collimator cannot be obtained, an image processing apparatus capable of reconstructing the projection data of the region of interest from the region-of-interest scan data by performing extrapolation interpolation. X-ray C characterized by comprising
T device. 6. The X-ray CT apparatus according to claim 1, wherein said region-of-interest setting means displays inside and outside boundaries of said set region of interest on said display device. .