JP4374089B2 - X-ray CT system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray CT apparatus that can be used for puncture under a CT guide.
[0002]
[Prior art]
There is an example in which a CT image is used as a puncture guide when performing a tissue examination or treatment of a lesion percutaneously. Helps improve the accuracy of examinations and treatments.
In the CT guide method, puncture and CT imaging are alternately repeated to confirm the position of the tip of the puncture needle and the like from the CT image, and CT imaging and puncture are both performed continuously, and CT obtained continuously There is a method of performing puncture while viewing an image.
[0003]
The CT apparatus applied to the CT guide method is a single slice CT apparatus that images a single tomographic plane. Although the tomographic plane to be observed may move due to the progress of the puncture needle, the position control of the subject bed and the scanner (including the tilt angle) is performed so that the tomographic plane to be moved is selected in the single slice CT apparatus. Do.
[0004]
On the other hand, there are multi-slice CT apparatuses capable of imaging a plurality of slice positions with respect to the single-slice CT apparatus. The multi-slice CT apparatus is an apparatus that enables imaging of a plurality of slice planes with one rotation.
[0005]
[Problems to be solved by the invention]
If a CT apparatus capable of multi-slice can be used as a CT apparatus for a CT guide instead of a single slice CT apparatus, it is expected that a change in tomographic plane can be easily handled.
[0006]
An object of the present invention is to provide an X-ray CT apparatus that makes it possible to use a multi-slice for a CT guide.
[0007]
[Means for Solving the Problems]
In the present invention, an X-ray source that emits X-rays having a two-dimensional extent and a slice direction perpendicular thereto, an X-ray having the extent, can be detected, and are divided into multiple slices in the slice direction. A collimator provided between the X-ray detector group and the X-ray source and the subject and capable of controlling the diaphragm so that X-rays can be irradiated to any one or a plurality of slice sections in the slice direction. Setting means for setting one or more slice sections of the collimator, means for controlling the collimator according to the setting, and X-rays radiated to the subject through the controlled collimator and obtained from the corresponding X-ray detector An X-ray CT apparatus comprising: processing means for reconstructing and displaying an image based on a detection signal.
[0008]
Furthermore, the present invention provides an X-ray apparatus that sequentially captures and displays a tomographic surface of a site including a puncture needle or a portion near the puncture needle when the puncture needle enters the subject.
An X-ray source that emits X-rays having a two-dimensional extension and a slice extension perpendicular thereto, and an X-ray that can detect the X-rays having the extension and are divided into multiple slices in the slice direction A collimator which is provided between the X-ray detector group, the X-ray source and the subject, and which can be controlled so that X-rays can be irradiated to any one or a plurality of slice sections in the slice direction; A setting means for setting one or a plurality of slice sections of the collimator selected so as to photograph a part including or near the part including the first part, a means for controlling the collimator according to the setting, and a target through the controlled collimator. Disclosed is an X-ray CT apparatus comprising processing means for reconstructing and displaying an image based on an X-ray detector signal emitted to a specimen and obtained from a corresponding X-ray detector.
[0009]
Furthermore, the present invention provides the processing means described above.
When one collimator section is selected and set by the setting means, the image reconstruction in that section is performed by the sequential reconstruction method, and a plurality of collimator sections are selected and set by the setting means. In addition, the image reconstruction in the main section selected from the sections is performed by the sequential reconstruction method, and the image reconstruction in the sub-section other than the main section is performed by the batch reconstruction method or the sequential reconstruction method. The X-ray CT apparatus according to claim 2, wherein the reconstructed image thus obtained is displayed on the display surface according to the number of sections.
[0010]
Furthermore, the present invention includes automatic selection means for automatically selecting one or a plurality of slice sections based on the displayed CT image or reconstruction data, and outputs the output of the selection means to the setting means. An intended X-ray CT apparatus is disclosed.
[0011]
Furthermore, the present invention discloses a multi-slice X-ray CT apparatus in which the batch reconstruction method at the sub-position is performed at a frame rate smaller than the frame rate at the main position.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing an outline of an X-ray CT apparatus suitable for multi-slice according to the present invention. Opposite to the X-ray source 1, a multi-slice X-ray detector (X-ray detection group) 2 is provided. The X-ray detector 2 has five multi-slice detection section planes (P₀~ P_Four) And each detection section plane (P₀~ P_Four) Has a large number of fan beam detection elements in a direction perpendicular to the paper surface. Here, the fan beam refers to an X-ray irradiated to the selected slice section when one section of the slice plane is selected, and a plurality of continuous slice planes (for example, P₁And P₂) Is selected, P₁And P₂Refers to X-rays irradiated respectively.
[0013]
The collimators 3 and 4 are X-ray shielding means for determining a slice surface to be selected and its X-ray irradiation width. The collimators 3 and 4 are position-controlled independently of each other. Of course, simplified means that are not independently controlled are possible. A general multi-slice CT apparatus also has collimators 3 and 4, and these collimators 3 and 4 are linked to each other, and position control is performed so that X-rays can be irradiated (apertured) to selected measurement slice sections.
The independent position control of the collimators 3 and 4 means that the selection of multi-slice sections is one selection, two selections, three selections, etc. However, it is because it chose arbitrarily. This selection is to deal with changes in the tomographic plane as the puncture needle moves, and to monitor one or more of the tomographic plane including the tip of the needle and / or its vicinity in order to monitor the movement status Because the fault plane is displayed together. And the position and number of tomographic planes to be displayed are variously changed.
For example, by controlling the position of the collimators 3 and 4 with the progress of the puncture needle (for example, the progress of the tip), (P₀) → (P₁) → (P₁, P₂) → (P₂, P_Three) → (P₂, P_Three, P_Four) → (P_Three)
As described above, the slice section and number are arbitrarily selected.
A mechanism for driving the collimators 3 and 4 is the drive unit 5, and a means for controlling the drive unit 5 according to an instruction from the host computer 10 is the control unit 6. In FIG. 1, all slice sections P₀~ P_FourAn example is shown in which the positions of the collimators 3 and 4 are controlled so as to emit X-rays.
[0014]
The measurement circuit 100 captures the detection signal of the X-ray detector 2. Although the measurement circuit 100 has various configurations, the switch matrix circuit 101 is used in the present embodiment. This is a switch circuit capable of selecting a detection signal corresponding to a multi-slice section.₁Only or P₁And P₂Various slice division selections can be performed. Such selection may be performed by the switch matrix circuit 101 provided as hardware, but may be performed by software.
[0015]
FIG. 2 shows the entire system of the CT apparatus shown in FIG. This system includes a host computer 10, a patient table 11, a scanner 12, an image processing device 13, a display device 14, and a high voltage generator 15. The scanner 12 has the X-ray source 1 shown in FIG. 1 and the multi-slice X-ray detector 2 arranged at a position opposite to the X-ray source 1, and the patient table 11 enters and exits the opening to perform CT imaging. The host computer 10 controls the movement of the table 11 and the CT imaging, the position control of the collimators 3 and 4, the control of taking in the measurement data, and the like. The function of the control part 6 of FIG. 1 is included. The high voltage generator 15 works for generating X-rays. The image processing device 13 converts the detection signal from the multi-slice X-ray detector 2 into data, and performs image reconstruction and other various image processing. The display device 14 displays various images such as CT images. One or more images are to be displayed. For example, P₁, P₂If the slice position is selected, P₁, P₂Two images G obtained from₂, G_ThreeAnd P₂, P_Three, P_FourIf the slice position is selected, P₂, P_Three, P_FourImage G obtained from_Three, G_Four, G_FiveIt is.
[0016]
FIG. 3 shows an example in which the puncture needle is advanced into the liver under CT guide, and FIG.₂FIG. 3B shows a slice plane P when the needle is further advanced._ThreeAn example of selection is shown below. Thus, depending on the position of the needle, the slice plane including the tip of the needle is P₂→ P_ThreeThe collimators 3 and 4 are moved to P in FIG.₂Selected, P in FIG._ThreeThe position is controlled so that is selected. Thus, the slice plane P in FIG.₂CT image is obtained and displayed. When the needle advances further, slice plane P_ThreeCT image is obtained and displayed. As described above, the slice division may be set by the host computer 10 using the switch matrix 101 provided in the measurement circuit 100 of FIG. 1 or by software.
[0017]
FIG. 4 shows an example in which the slice planes before and after the slice plane at the tip of the needle are selected simultaneously. At the position of the needle in FIG.₂Corresponds to slice plane P₁And P_ThreeIs the tomographic plane located before and after. On the other hand, when the needle further enters, as shown in FIG. 4B, the slice surface where the needle exists is P._ThreeThe front and back slice planes are P₂, P_FourIt becomes. In FIG. 4 (a), P₁, P₂, P_ThreeIs also selected and P in FIG.₂, P_Three, P_FourIn addition, it is possible to simultaneously observe images of tomographic planes before and after the site where the needle is located. Therefore, in the example as shown in FIG.₁, P₂, P_ThreeThe positions of the collimators 3 and 4 are controlled so as to select P, and in the example as shown in FIG.₂, P_Three, P_FourThe position of the collimators 3 and 4 is controlled so as to select.
[0018]
When performing a CT guide, it is necessary to quickly obtain a CT image while taking an image as the puncture needle enters. For this purpose, it is necessary to increase the processing speed of image reconstruction, and there are various known examples and prior applications (Japanese Patent Publication No. 1-23136, Japanese Patent Application Laid-Open No. 8-24252, Japanese Patent Application No. 10-120511). Therefore, if they are employed, CT images can be obtained quickly. These reconstruction methods are defined as sequential reconstruction methods.
[0019]
For example, a method of improving the reconstruction processing speed by sequentially updating the projection data by a part (60 ° unit) of the projection data for one rotation is adopted. For example, in an example in which one CT image is obtained with 360 ° projection data, most of the reconstruction data for the previous rotation (data obtained with a view of 0 ° to 360 °) (60 ° to 360 °). 360 °) reconstruction data is added (synthesized) with the view data of 0 ° -60 ° of the next rotation.
That is, the data obtained up to the previous time
View data from 0 ° to 360 ° …… (1)
The reconstructed data of the 60 ° view from 0 ° to 60 ° of the current data is the reconstructed data of the 60 ° view from 0 ° to 60 ° obtained up to the previous time (the previous meaning from this time). Use it instead to get a single CT image.
(Reconstruction data of 60 ° to 360 ° view obtained until the previous time) + (Reconstruction data of 0 ° to 60 ° view this time) …… (2)
Similarly, the reconstruction data for the current 60 ° -120 ° view is used in place of the 60 ° -120 ° view reconstruction data obtained up to the previous time (meaning the previous time from this time). Thus, one more CT image is obtained.
(Reconstruction data of the 120 ° to 360 ° view obtained until the previous time), (Reconstruction data of the previous 0 ° to 60 ° view), (Reconstruction data of the current 60 ° to 120 ° view) ...... (3)
In this way, instead of performing batch reconstruction after obtaining the data for one rotation obtained in the latest rotation, reconstruction is performed sequentially when data for 60 ° at the latest rotation is obtained. By using this, the reconstruction processing speed is substantially improved.
[0020]
In (2) and (3), if the latest 60 ° data is obtained and reconstruction is performed using all 360 ° data at once, the processing speed will be reduced to use all the data. To do. Therefore, for example, the result of reconstruction in (2) (previous 60 ° to 360 ° view data) can be used as it is, and in the reconstruction of (2), reconstruction is performed for data of 0 ° to 60 minutes. A back projection method is employed in which a single reconstructed image is obtained by a kind of addition of both reconstructed data. According to this back projection method, one reconstructed image in (2) can be obtained by only two processes: a reconstruction process for 0 ° to 60 ° and a kind of addition process. Further rapid processing can be realized. The contents of a kind of addition processing are described in the various known examples and prior applications. The above is an example of (2), but the same applies to (3).
[0021]
Rather than the example of obtaining one image from one slice plane shown in FIG. 3, it is necessary to devise to obtain a corresponding number of images from a plurality of slice planes shown in FIG. In general, reconstruction is realized by one reconstruction means, and three reconstruction processes are performed by one reconstruction means in order to obtain three CT images from three slice planes as shown in FIG. Is required. If the reconstruction process is performed three times, a processing time for three times is required, and a rapid CT image may not be obtained.
Therefore, we propose an effective method. Of the slice planes in FIG. 3, the slice plane that is truly desired is P in FIG.₂In FIG. 3 (b), P_ThreeThis image requires real-time characteristics, and P in FIG.₁, P_Three, P in FIG.₂, P_FourIn many cases, real-time performance is not necessary. Therefore, P in FIG.₂, P in FIG._ThreeFor the central slice plane as described above, reconstruction is performed sequentially by the processes as described in (2) and (3) above. On the other hand, P in FIG.₁, P_ThreeFIG. 3 (b) P₂, P_ThreeFor such secondary slice planes, such a method was not taken, and the problem was dealt with by reducing the number of processing points.
This will be specifically described.
[0022]
FIG. 5 shows three reconstruction modes. FIG. 5 (a) shows one slice plane P as shown in FIGS. 3 (a) and 3 (b).₂Or P_ThreeThis is an example of reconfiguring only the normal mode. In the normal mode, in the case of 360 ° rotation per second (one rotation), six measurements 1 to 6 are performed in 60 ° view units, and reconfiguration is performed while updating 60 ° sequentially. Do. That is, by performing 1/6 divided view reconstruction, the reconstructed image is updated every 1/6 second. This follows the method shown in the above-mentioned (2) and (3).
On the other hand, when the image of the slice plane to be observed is the main image, examples of reconstructing one or two adjacent slice plane images (referred to as sub-images) are shown in FIGS. . FIG. 5B shows an example in which a reconstructed image of one adjacent image is obtained as a sub-image (P in FIG.₂Against P₁To P_Three5 (b) shows an example in which FIG. 5 (b) obtains two adjacent reconstructed images as sub-images (P in FIG. 4 (a)).₁And P_Three, P in FIG. 4 (b)₂And P_Four).
[0023]
The reconstructed image as one adjacent sub-image in FIG. 5B is obtained by reconstructing one sheet at a time for each rotation. Of course, this may be handled as a sequential reconstruction by reducing the frame rate. Here, since one sheet is obtained for each rotation, sequential reconstruction at 60 ° is not performed. Furthermore, since one sheet is reconstructed for each rotation, reconstruction is performed with a small amount of data and a small matrix size (lowering the frame rate) that can shorten the time required for the reconstruction. However, the measurement data for the sub-image is obtained by one rotation of 0 ° to 360 °, and the number of the measurement data (projection data) is not different from the case of the main image. This is because the data is reconstructed all at once and the amount of data and the matrix size are reduced to shorten the processing time. For example, the sub-image matrix size is set to 128 × 128 with respect to the main image matrix size of 512 × 512, and is further reconfigured to 1 frame / second. Since the reconstruction time is proportional to the matrix size, one sub-tomographic image is reconstructed in approximately 6/16 seconds (180 ° reconstruction-so-called half scan-3/16 seconds). it can. If there is one example of reconstruction means, the reconstruction time (τ₁However, the update of the reconstruction of the main image is delayed, but there is no significant influence because of the minute time width. Further, it is better if the reconstruction means is realized by a high-speed computing unit. Also, the matrix size of the main image is set to the time τ₁It can also be solved by temporarily reducing only the 60 ° division unit that overlaps with. In this case, it is preferable to take a method of enlarging at the time of display. Also, time τ₁In addition to the 60 ° division unit at the time of overlapping with each other, only when the mode is set to the proximity one-sheet interrupt mode as shown in FIG. 5B, the size is smaller than the 512 × 512 matrix size for all division units and is enlarged at the time of display. You may take a way. Naturally, reconstruction can be performed with data of about 180 degrees, and reconstruction can be performed by thinning out the number of projection data, but there are many problems in image quality.
[0024]
FIG. 5C is an example of the proximity two-sheet interrupt mode, and shows an example in which the first sub-image and the second sub-image are reconstructed in units of 180 °, for example.
Although the sub-image is reconstructed in 360 ° units in FIG. 5 (b), there is a method in which the interval is further widened and reconstructed in intervals of 720 ° units or 540 ° units. In FIG. 5C, the first and second sub-images are each set at 180 ° unit intervals, but this is not limited to this interval. For example, there may be examples such as 360 ° intervals and 540 ° intervals. The interval may be determined depending on how important the main image is as an image.
In another example, reconstruction processing of two adjacent sub-tomographic images can be interrupted and processed. FIG. 5C shows a case in which the first and second sub-tomographic images are reconstructed at 1 frame / second, respectively. The delay is further increased compared to interruption of one sub-tomographic image, but reconstruction is performed. If the matrix size is further reduced and the FOV (Field of View: effective field of view) is reduced (to prevent the resolution from being lowered when the matrix is reduced), the delay is sufficiently reduced.
As a system, it is preferable to have a switching means capable of switching modes as shown in FIGS. 5 (a), 5 (b), and 5 (c). This switching may be performed manually (keyboard or mouse) or automatically.
[0025]
FIG. 6 is a display example of the main image in FIG. 5A, and FIG. 7 is a display example of one main image and two sub images in FIG. 5C. The display size of the sub image is small.
[0026]
FIG. 8 shows an implementation example with one reconfiguration means. The projection data memories 20 to 24 store the slice plane P.₀~ P_FourAnd projection data obtained for each slice plane is stored correspondingly. The projection memory processing device 25 selects one memory for reconstruction from the memories 20 to 24, and performs various preprocessing and interpolation processing for compensating for data shortage for the projection data fetched from the memory. The image reconstruction device 26 reconstructs projection data obtained by preprocessing, interpolation processing, or the like by backprojection or the like. The image memory processing device 28 adds the reconstruction result, enlargement / reduction, interpolation for increasing the shortage of the reconstructed image (increasing the number of images), etc., and the reconstructed image obtained thereby for each slice plane. The divided image memories 29, 30, and 31 are sorted and stored (for example, P₁And P₂And P_Three29 is P₁, 30 is P₂, 31 is P_ThreeBecome).
The main / sub image processing device 32 designates the main image and the sub image from the image memories 29, 30, and 31 and displays them as the main image 33 and the sub images 34 and 35 on the display screen.
The instruction code generator 27 generates various instruction codes for the devices 25, 28, and 32 to realize the necessary control as described above.
The reconstruction device 26 performs sequential reconstruction by dividing by 60 ° for the main image, and reconstructs the sub-image according to the determined matrix size at the timing as shown in FIG. 5C.
[0027]
FIG. 9 shows an implementation example with two reconstruction means. This shows a configuration example diagram for completely eliminating the delay of the reconstruction processing time required for the sub-image. One feature is that a reconstruction device 41 for main images and a reconstruction device 42 for sub-images are provided as reconstruction means. Reference numerals 42 and 43 are processing devices corresponding to the processing devices 25 and 28 in FIG. 8, and are used for the same processing and switching selection. Other symbols are the same as in FIG. The main tomographic image reconstruction device 41 reconstructs the main tomographic image under conditions sufficient for both the matrix size and the frame rate (in the example, 512 pixels, 6 frames / second). The sub-tomographic image reconstruction device 42 differs depending on the sub-tomographic image reconstruction conditions. For example, by reducing the frame rate to half (3 frames / second), two sub-tomographic images are reconstructed with sufficient resolution. it can. Further, by reducing the number of pixels to 256 × 256, almost four sub-tomographic images can be reconstructed. If there are reconstruction means for the total number of main tomograms and sub tomograms, all images can be reconstructed under the best conditions, or more may be provided, but it is necessary to consider the increase in price Needless to say.
[0028]
Of the reconstructed images, the image stored in the main tomographic image memory 29 is displayed in the main tomographic image display area of the display device shown in FIG. The stored image of the adjacent cross section is displayed. As new images are reconstructed, they are updated sequentially.
The CT value of the designated ROI in the secondary tomographic image is monitored, and when the change in CT value becomes large, the secondary tomographic image can be automatically switched to the main tomographic image, or switching can be urged.
[0029]
An embodiment in which the slice plane where the tip of the needle exists can be automatically selected as the main image according to the entry position of the puncture needle under the CT guide will be described.
As shown in FIG. 3A to FIG.₂→ P_ThreeThe main image is changed to P as shown in FIG. 4 (a) to FIG. 4 (b).₂→ P_ThreeMove to. This movement of the main image can be detected by the observer observing the CT display image, and as a result, the slice plane is the main image and which is the sub-image by the observer's keyboard or cursor instruction. Enter and switch screens. It would be convenient if it would be possible to automatically determine the slice plane that will be the main image and the slice plane that will be the sub-image in the computer instead of switching according to such an instruction from the observer. An implementation example for this will be described below.
[0030]
(1) First example.
If the slice plane where the tip position of the puncture needle exists can be automatically recognized, the slice plane becomes the slice plane for the main image. The image for the puncture needle can be adopted as an example in which the CT value takes a value different from that of other image portions. For example, the CT threshold value of the puncture needle is determined, a linear image that is within this range and is a straight line is used as the puncture needle, its tip is found, and the slice surface on which this tip is located is the slice surface existing at that time This existence slice plane is selected as a main image and displayed. Further, since the CT value changes suddenly at the approach position of the tip, it can be automatically recognized by automatically monitoring the CT value that has changed suddenly.
(2) Second example.
This is the method shown in FIG. The slice surface can be almost understood by the inclination θ of the puncture needle. For example, in FIG. 10, when the horizontal component axis of the puncture start position is the Z axis, the puncture start position is Z = 0, and the slice plane P₂The boundary width on the Z axis₁Ask for. Then, the Z-axis components ΔZ and Z of the needle tip at the angle θ₁And Z₁If ≧ ΔZ, the tip of the needle is slice plane P₂And Z₁If ΔZ, the needle tip is slice plane P₂It belongs to.
However, it is a rough method to obtain the needle tip position ΔZ only by the inclination θ, and it is preferable to consider the length of the needle more accurately. In addition, although two axes of Y and Z are used, it is actually preferable to consider the X axis perpendicular to the YZ axis.
(3) A third example.
In the case of FIG. 10, the tip of the needle tip is P₂And P_ThreeIt is in a state that straddles. In such a case, P₂And P_ThreeAnd the tip of the needle tip Z₁The surrounding slice state including To that end, for example, P_ThreeZ is the center of the measurement area₂P₂, P_ThreeA method of interpolating the two using ΔZ is employed. Specifically, if the interpolated projection data is P, weighting is performed as shown in the following equation.
P = (1-W) · P₂+ W ・ P_Three
W = ΔZ / Z₂
Then, this data is reconstructed to obtain a CT image. In such a method, the needle tip is Z as shown in FIG.₁P when it is in the vicinity₂, P_ThreeThe average image (composite image) can be confirmed, and information before and after the needle tip can always be provided to the operator, so that the accuracy and safety of the procedure are improved. In addition, if it is determined automatically, the possibility that the desired image may not be obtained due to the measurement error of the puncture needle inclination and insertion depth is considered, so it is more secure if the operator changes the interpolation weight. Will increase. Note that the composition can be performed on the reconstructed data.
(4) Data that should be subject to automatic recognition.
Including what has been described in (3) above, either projection data or reconstruction data is possible.
(5) About automatic switching hardware.
Finally, an automatic switching instruction can be given to the instruction code generator 27 from the upper level. Here, upper means is a means for recognizing the tip of the needle, and this means may be provided in 25, 28, 40, 43 in FIGS. 8 and 9, or as a separate means. It may be allowed.
[0031]
The present invention is not stipulated by the type of detector (fourth generation type, etc.), the number of columns, the reconstruction method, and the like.
[0032]
【The invention's effect】
According to the present invention, when performing a procedure under a CT guide, the X-ray irradiation range can be changed according to the cross-sectional position of the needle tip, so that necessary information can be provided with a minimum exposure.
[Brief description of the drawings]
FIG. 1 is a diagram showing a basic concept of the present invention.
FIG. 2 is a system configuration example diagram of the present invention.
FIG. 3 is a diagram illustrating an example of selection of one slice position.
FIG. 4 is a diagram illustrating an example of selecting multiple slice positions.
FIG. 5 is a diagram illustrating various selection modes and reconstruction.
FIG. 6 is an example of a CT image for CT guide.
FIG. 7 is a diagram showing an example of main and sub CT images for CT guide.
FIG. 8 is a block diagram for main and sub CT image selection.
FIG. 9 is a block diagram for main and sub CT image selection.
FIG. 10 is an explanatory diagram of automatic selection of main and sub CT images.
[Explanation of symbols]
1 X-ray source
2 X-ray detector for multi-slice
3, 4 Collimator
5 Drive unit
6 Control unit
P₁~ P_Four  Multi slice plane
10 Host computer
11 Patient table
12 Scanner
13 Image processing device
14 Display device
15 High voltage generator

Claims (3)

An X-ray source that irradiates a subject with X-rays extending in a two-dimensional direction;
One row of detectors arranged opposite to the X-ray source and having a plurality of channels of detection elements arranged in a direction orthogonal to the body axis of the subject are further arranged in a plurality of rows in the body axis direction of the subject, A multi-slice X-ray detector that detects transmitted X-rays of the subject as projection data,
A scanner unit for rotating the X-ray source and the multi-slice X-ray detector around the subject;
Reconstructing means for reconstructing a tomographic image of the subject using projection data from a plurality of angular directions detected by the multi-slice X-ray detector rotated by the scanner unit;
Display means for displaying a tomographic image of the subject reconstructed by the reconstruction means;
Of the X-rays arranged between the X-ray source and the subject and irradiated by the X-ray source, the transmitted X-rays of the subject can irradiate a desired row of the multi-slice X-ray detector. And a collimator movable to shield X-rays other than the X-rays applied to the desired row;
Setting means for setting a row to be shielded by a collimator among the rows of the multi-slice X-ray detector, a plurality of rows to be left unshielded ;
Using the projection data of the subject corresponding to a plurality of columns of the multi-slice X-ray detector left unshielded while shielding the columns to be shielded, Control means for reconstructing a tomographic image and controlling the collimator, the scanner unit, the reconstruction means and the display means so that the reconstructed tomographic images of the subject are displayed in separate display areas. When,
With
In the reconstruction, one of the plurality of columns is a main tomographic image, and the remaining column is a sub-tomographic image, and the main tomographic image has a predetermined matrix size. The partial tomographic image is obtained by a sequential reconstruction method obtained by combining the projection data for the partial view angle with the reconstruction data obtained by the previous rotation, and the sub tomographic image has a matrix size smaller than the matrix size of the main tomographic image An X-ray CT apparatus characterized in that it is obtained by reconstruction from the projection data of that column obtained at each rotation .   The X-ray according to claim 1, wherein the control unit controls the collimator, the scanner unit, and the reconstruction unit based on an update of a tomographic image of the subject displayed on the display unit. CT device.   The control means switches tomographic images in different columns obtained by the reconstruction means so that a puncture needle to be punctured into the subject is always included in a tomographic image of the subject displayed on the display means. The X-ray CT apparatus according to claim 1, wherein the X-ray CT apparatus is controlled.

Images