JPH1021372A - X-ray ct device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT device in which picture data with high image- quality can be provided in the proper number. SOLUTION: This device is provided with an X-ray beam generating source 11 which irradiates a tester with an X-ray beam, detector 13 which detects the X-ray beam irradiated from the X-ray beam generating source 11 as a detection signal, slicing direction re-constituting filter function storage means which stores plural filter functions for making the resolution of the slicing direction variable as slicing direction re-constituting filter functions, and re- constitution processing part 19 which obtains data on an objective slice based on the detection signal detected by the detector 13 which detects the X-ray beam irradiated from the X-ray beam generating source 11 by using the slicing direction re-constituting filter function stored in the slicing direction re-constituting filter function storage means.

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, and more particularly to an X-ray CT apparatus capable of changing the resolution of image data in a slice direction.

[0002]

2. Description of the Related Art In recent years, a tomographic image of a subject is obtained by moving a couch in the body axis direction of the subject while rotating an X-ray beam source for emitting X-rays and a detector for detecting X-rays. Various X-ray CT apparatuses using helical scan have been proposed. FIG. 35 shows an X-ray CT apparatus that performs such a helical scan. As shown in FIG. 35, the X-ray CT apparatus 110 that performs helical scan is
And a gantry that rotates the rotary gantry 125 based on the gantry control signal output from the gantry control signal, and outputs a gantry movement signal to the gantry movement unit 115. Bed control unit 11
3 and a bed moving unit 11 for moving the bed 115a based on the bed moving signal output by the gantry / bed control unit 113.
5, an X-ray controller 117 for controlling the timing of high voltage generation based on the X-ray beam generation control signal output by the system control unit 111, and X-ray control of the high voltage for exposing the X-ray beam A high voltage generator 119 generated according to a control signal from the unit 117;
X-rays are exposed by the high voltage supplied from the
X-ray beam source 121, detector 123 for detecting X-ray beam, rotating base 125 for rotating X-ray beam source 121 and detector 123, X-ray beam detected by detector 123 (actually, Is a detection signal) in correspondence with a data collection control signal output by the system control unit 11 to obtain projection data,
An interpolation processing unit 129 for interpolating projection data at a target slice position based on the projection data collected by the data collection unit 127, and reconstructing image data based on the projection data interpolated by the interpolation processing unit 129. Image reconstruction unit 1
31 and a display unit 133 for displaying image data reconstructed by the image reconstruction unit 131 on a monitor.

In an X-ray CT apparatus using a helical scan, a single slice (fan beam) CT, a double slice CT, a multi slice (cone beam) CT
Is being developed. The single slice CT is shown in FIG.
As shown in (a), an X-ray beam source for irradiating a fan-shaped X-ray beam, a plurality of channels,
000 channels arranged in a line. In the single slice CT, the X-ray beam source and the detector are rotated around the subject, and for one rotation, for example, 1000 times.
Data is collected (one data collection is referred to as one view), and image data is reconstructed based on the data.

[0004] Double slice CT is used in FIG.
As shown in (b), an X-ray beam source for irradiating a fan-shaped X-ray beam and two detector rows in which N channels are arranged in an arc shape are arranged in the Z-axis direction (N channels × 2).
Column) two-dimensional detector. In the double slice CT, the X-ray beam source and the detector are rotated around the subject, and N × 2 × 1000 data is collected in one rotation.
Image data is reconstructed based on the data.

[0005] Further, the multi-slice CT is shown in FIG.
(C) As shown in FIG.
A line beam source and detector rows in which N channels are arranged in an arc are arranged in M rows in the Z-axis direction (N channels × N rows).
A two-dimensional detector. In the multi-slice CT, the X-ray beam source and the detector are rotated around the subject, N × M × 100 data are collected in one rotation, and image data is reconstructed based on the data.

[0006] Single slice CT, double slice C
T, in multi-slice CT, when the number of channels of the detector 123 is N, as shown in FIG.
The angle connecting both ends in the channel direction is defined as the fan angle. In double slice CT and multi slice CT, when the number of segments of the detector 123 is M as shown in FIG.
The angle connecting the one focus F to both ends of the detector 123 in the column direction is defined as a cone angle. Further, as shown in FIG. 37A, the distance from the focal point F of the X-ray beam source 121 to the center of rotation is FCD (Focus-Center-Distance), the effective visual field diameter is FOV (Field of View), and the X-ray Beam source 1
The distance from the focal point F to the detector 123 is denoted by FDD (Fo).
cus-Detector-Distance).

The scan time required to collect data for creating one image is called an effective scan time. Correction of an artefact caused by movement of the intestinal tract at the time of photographing the abdomen or body movement of the patient is called PMC. In order to suppress artifacts, it is also effective to relatively suppress the influence of body motion by shortening the effective scan time.

Further, as shown in FIGS. 38 (a) and 38 (b), the bed is moved in the body axis direction of the subject while rotating the X-ray beam source 121 and the detector 123 about the center of rotation. Various X-ray CT apparatuses using helical scan for obtaining a tomographic image of a subject by using the method have been proposed.

FIG. 39 shows a helical scan by indicating the rotational phase on the vertical axis and the direction of the Z axis (body axis) on the horizontal axis (hereinafter referred to as a scan diagram).

For image reconstruction, 360 ° projection data at a slice position is necessary. As is apparent from FIG. 39, in a helical scan with a single slice CT, one data at a slice position is provided. There is only. Therefore, data is interpolated in the slice direction to be data at a target slice position. This interpolation method includes a 360 ° interpolation method and a counter beam interpolation method.

FIG. 40A shows a set of X-ray beams used in the 360 ° interpolation method on a scan diagram. As shown in FIG. 40A, in the 360 ° interpolation method,
This is a method of linearly interpolating two in-phase X-ray beams (the original beam 1 and the original beam 2) close to the target slice position by the inverse ratio of the distance. In the 360 ° interpolation method, as shown in FIG. 40A, the distance between the slice position of the original beam 1 and the original beam 2 (the X-ray beam center at the center of rotation) is equal to the slice thickness t.
Is equal to

FIG. 40 (b) shows the original beam and the opposite beam used in the opposite beam interpolation method on a scan diagram. As shown in FIG. 40 (b), in the facing beam interpolation method, interpolation between the original beam and the facing beam is performed.
In the counter beam interpolation method, as shown in FIG. 40B, the distance between the slice position of the original beam and the slice position of the counter beam is の of the slice thickness t. The beam distance is short.

The response (slice profile) of the system in the slice direction is not exactly rectangular but slightly collapsed (trapezoidal or unimodal).
FIG. 41 shows an example of a single-peak slice profile. As shown in FIG. 41, the half width in the slice profile is called an effective slice thickness. Effective slice thickness, S / N
The ratio and the like are one of the important factors that affect the image quality.

The effective slice thickness in the helical scan interpolation becomes smaller as the distance between the two X-ray beams to be interpolated becomes shorter. The distance between two X-ray beams is one rotation (360
In the 360 ° interpolation method, which is a slice thickness t corresponding to (°) minutes, the slice thickness is increased by 40% (1.4 t), and the distance between the two X-ray beams is the slice thickness t / 2 corresponding to about a half rotation. In the beam interpolation method, the slice thickness is increased by 10% (1.1
t). Therefore, the effective slice thickness in single slice CT is determined by a combination of the beam thickness t at the time of scanning and the two types of interpolation methods, and can be said to be almost fixed.

Further, for example, image data is stacked to form voxel data, and some threshold processing is performed to display the data as three-dimensional image data. In the three-dimensional processing, since the threshold processing is performed, the image quality may be lower than the image data used for image interpretation, but there is a demand that the resolution in the body axis direction be increased. However, the resolution in the body axis direction is limited to 1.4t or 1.1t as described above.

In the abdominal examination, a wide area such as 150 (mm) is photographed.
When collecting with a thick X-ray beam, a partial effect occurs. The partial effect is an apparent CT value that is generated when a part of an X-ray beam passes through an object or the like, and the shadow becomes lighter, or an artifact due to a non-linear effect.

Therefore, the partial effect can be suppressed by collecting with a thin X-ray beam. However, when collecting a wide area by single slice CT, it is impossible to collect a thin X-ray beam in a short time, so that a thick X-ray beam is collected. Multi-slice CT can solve the above problem because a plurality of thin X-ray beams can be collected at the same time. However, when image data of 2 (mm) thickness is successively displayed to a radiologist, 150 (m)
In the entire range of m), 75 images need to be read, and the burden on the doctor is too large to be practical. Further, in the case of thin image data, the low-contrast rendering ability and the S / N ratio are reduced. Therefore, it may be desired to read image data of a slightly thick image data of about 5 (mm) in the abdomen where low contrast is important.

In the X-ray CT apparatus, the projection data (raw data) is subjected to a convolution process with a so-called reconstruction function or reconstruction filter as shown in FIG. Reconstruct the data. At this time, the spatial frequency and the S / N ratio, which are main factors of the image quality of the reconstructed image data, depend on the shape of the reconstruction function. The better the S / N ratio, the higher the low-contrast rendering ability, but the better the spatial frequency characteristic, the higher the high-contrast rendering ability. For example, the reconstruction function F shown in FIG.
Comparing C1 and FC5, the reconstruction function FC1 which has a good S / N ratio and emphasizes the low frequency region has a higher low contrast rendering ability, but has a better spatial frequency characteristic and the reconstruction function FC5 which emphasizes the high frequency region. However, high contrast rendering ability is high.

In the clinic, this reconstruction function is selected according to the imaging site such as the head, abdomen, and lung field, and the spatial frequency and the S / N ratio are selected for each site. In other words, the scan time is short and the imaging range is wide due to body motion, so the X-ray exposure is small, the X-ray absorption by the subject is large, and the abdomen and the like that tend to generate noisy image data have low contrast. An emphasis on the reconstruction function (in the example shown in FIG. 42, the reconstruction function FC1
, Etc.). For a stationary object such as a head or an ear, the scan time can be lengthened and the amount of X-ray exposure can be increased, so that the S / N ratio is good. Therefore, a reconstruction function emphasizing spatial frequency characteristics (reconstruction function in the example shown in FIG. The configuration function FC4) is used.

[0020]

However, the effective slice thickness in the conventional single-slice CT is determined by a combination of the beam thickness t at the time of scanning and two types of interpolation methods, 360 ° interpolation method and counter beam interpolation method. Therefore, there is a problem that it becomes almost fixed.

In the conventional multi-slice CT, the above problem can be solved because a plurality of thin X-ray beams can be collected at the same time. However, when image data of 2 (mm) thickness is displayed to the radiologist one after another, 150 (mm) is obtained. In the range, 75 images need to be read, and the burden on the doctor is too large to be practical. Further, in the case of thin image data, the low-contrast rendering ability and the S / N ratio are reduced. Therefore, it may be desired to read image data of a slightly thick image data of about 5 (mm) in the abdomen where low contrast is important. Further, when a contrast agent is injected into the subject, it is desired to observe the change in the manner of staining in the early stage of the contrast, and to observe the image data emphasizing the time resolution and to observe the stained state in the middle and late stages of the contrast. There is also a demand for reading image data with good image data.

The present invention has been made in view of the above problems, and has as its object to provide an X-ray CT apparatus capable of providing high-quality image data in an appropriate number.

[0023]

According to a first aspect of the present invention, there is provided an X-ray beam source for projecting an X-ray beam toward a subject, and an X-ray beam source for projecting an X-ray beam from the subject. Detecting means for detecting the emitted X-ray beam as a detection signal; slice direction reconstruction filter function storage means for storing a plurality of filter functions for varying the resolution in the slice direction as slice direction reconstruction filter functions; An X-ray beam is emitted from an X-ray beam source, and data on a target slice is stored in the slice direction reconstruction filter function storage means based on a detection signal detected by the detection means. And a processing unit that obtains using a slice direction reconstruction filter function.

In the X-ray CT apparatus according to the first aspect,
An X-ray beam is emitted from an X-ray beam source, and data on a target slice is sliced in a slice direction stored in a slice direction reconstruction filter function storage unit based on a detection signal detected by the detection unit. It is obtained using a reconstruction filter function. This makes it possible to provide high-quality image data in an appropriate number.

According to a second aspect of the present invention, there is provided an X-ray beam source for irradiating an X-ray beam toward a subject, and the X-ray beam source.
Detecting means for detecting an X-ray beam emitted from a line beam source as a detection signal, and a slice direction for storing a plurality of filter functions having different shapes as slice direction reconstruction filter functions in order to make the resolution in the slice direction variable. Reconstruction filter function storage means, couch moving means for moving the couch on which the subject is placed in the body axis direction of the subject, and generating an X-ray beam while rotating the X-ray beam source Moving the couch by the couch moving means, and reconstructing the data on the target slice based on the detection signal detected by the detecting means in the slice direction reconstructing filter function storing means stored in the slice direction reconstructing filter function storing means. And a processing unit for performing interpolation using a constituent filter function.

In the X-ray CT apparatus according to the second aspect,
An X-ray beam is generated while rotating the X-ray beam source, and the couch is moved by the couch moving means, and data on the target slice is re-sliced in the slice direction based on the detection signal detected by the detection means. The interpolation is performed using the slice direction reconstruction filter function stored in the configuration filter function storage means. This makes it possible to provide high-quality image data in an appropriate number.

According to a third aspect of the present invention, there is provided an X-ray beam source for projecting an X-ray beam toward a subject, and an X-ray beam source.
Detecting means for detecting an X-ray beam emitted from a line beam source as a detection signal, and a slice direction for storing a plurality of filter functions having different shapes as slice direction reconstruction filter functions in order to make the resolution in the slice direction variable. Reconstruction filter function storage means, couch moving means for moving the couch on which the subject is placed in the body axis direction of the subject, and intermittently moving the couch by the couch moving means in the opposite axial direction of the subject. Moving, generating an X-ray beam while rotating the X-ray beam generation source, causing the detection means to detect a detection signal at a predetermined slice position, and detecting data on a target slice by the detection means. Based on the detected signal, using a slice direction reconstruction filter function stored in the slice direction reconstruction filter function storage means. And summarized in that a means.

In the X-ray CT apparatus according to the third aspect,
The bed moving means intermittently moves the bed in the opposite axis direction of the subject, generates the X-ray beam while rotating the X-ray beam source, and detects the detection signal of the predetermined slice position by the detecting means. And the data on the slice
The slice direction reconstruction filter function stored in the slice direction reconstruction filter function storage unit is obtained based on the detection signal detected by the detection unit. This makes it possible to provide high-quality image data in an appropriate number.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an X-ray CT according to the present invention.
It is a block diagram showing a 1st embodiment of a device.

As shown in FIG. 1, the X-ray CT apparatus 1 includes a system control unit 3, a gantry / bed control unit 5, an X-ray controller 7, a high-voltage generator 9, and an X-ray beam source. 11, a detector 13 as a detecting unit, a switching unit 15, a data collecting unit 17, a reconstruction processing unit 19 as a processing unit,
And a display device 21.

The system control unit 3 outputs the slice thickness, the rotation speed, and the like input using an input device (not shown) to the gantry and the bed control unit 5 as a gantry and bed control signal. In addition, the system control unit 3 controls the rotation of the rotating base 5a,
A gantry for adjusting the collimator 5b, controlling the feed rate of the bed 5c, and outputting a bed control signal to the gantry and the bed control section 5 and an X for controlling X-ray beam generation.
A line beam generation control signal is output to the X-ray controller 7. Further, the system control unit 3 outputs a detector row switching signal for switching a detector row for collecting projection data to the switching unit 15 and outputs a data collection control signal indicating a data collection timing to the data collection unit. 17 is output.

The gantry / bed control unit 5 includes a system control unit 3
Based on the gantry and bed control signals output by the above, the rotating gantry 5a is rotated, the collimator 5b is adjusted, and the feed speed of the bed 5c is adjusted.

The X-ray controller 7 controls the timing of high voltage generation based on the X-ray beam generation control signal output from the system control unit 3.

The high voltage generator 9 generates a high voltage for irradiating the X-ray beam according to a control signal from the X-ray controller 7.

The X-ray beam source 11 includes a high-voltage generator 9
The X-ray beam is emitted by the high voltage supplied from.
Here, the third segment to the tenth segment of the detector 13 are used.
The X-ray beam is exposed to eight rows up to the segment.

The detector 13 detects the X-ray beam emitted from the X-ray beam source 11 and transmitted through the subject. As shown in FIG. 2, the detector 13 has twelve detector rows from a first segment to a twelfth segment. First
The height (thickness) in the Z-axis direction at the rotation center of the segment and the twelfth segment is 8 (mm), the height in the Z-axis direction at the rotation center of the second segment and the eleventh segment is 4 (mm), The height of the third segment and the tenth segment in the Z-axis direction at the rotation center is 2 (mm), the height of the fourth segment and the ninth segment in the Z-axis direction at the rotation center is 1 (mm), The height of the segment, the sixth segment, the seventh segment, and the eighth segment in the Z-axis direction at the center of rotation is 0.5 (mm).

The switching unit 15 switches the detector rows of the detectors 13 that collect data at the same time. Here, the third segment of the detector is the first data, the fourth to sixth segments are the second data, the seventh to ninth segments are the third data, and the first segment is the first data.
Switching is performed so that the 0 segment is simultaneously acquired as the fourth data.

The data collection section 17 converts the detection signal detected by the detector 13 into a digital signal to generate projection data, and collects the projection data in accordance with the data collection control signal output from the system control section 11. The data collection unit 17 performs various corrections such as X-ray intensity correction and detector sensitivity correction on the collected projection data.

The reconstruction processing unit 19, as shown in FIG.
A slice direction reconstruction filter function processing unit 23, a slice direction reconstruction filter function storage unit 25 as a slice direction reconstruction filter function storage unit, a reconstruction function processing unit 27, a reconstruction function storage unit 29, an image reconstruction Component 31
And a control unit 33. Based on the projection data output from the data collection unit 17, the projection data at the target slice position is interpolated by filter interpolation using a counter beam, and the interpolated projection data is used as a basis. Next, the image data is reconstructed.

Slice direction reconstruction filter function processing unit 2
Reference numeral 3 denotes filter processing in the slice direction using the set slice direction reconstruction filter function based on the projection data of the helical scan of four rows and multiple rotations output from the data acquisition unit 17 to perform one-rotation for one row. Is interpolated.

Slice direction reconstruction filter function storage unit 2
Reference numeral 5 stores a slice direction reconstruction filter function having characteristics as shown in FIG. For example, as shown in FIG. 5, the filter function FLT00 in the slice direction is the same as that without the filter and has the smallest effective slice thickness. As shown in FIG. 6, the filter width is small, the weight is uniform, the effective slice thickness is small, and the contrast is high. A slice direction reconstruction filter function FLT01 having a high resolution but a slightly poor S / N ratio, as shown in FIG. 7, has a small filter width and a large weight at the center and has an effective slice thickness of the slice direction reconstruction filter function FLT.
01 slice direction reconstruction filter function FLT0
2. A slice direction reconstruction filter function FLT03 having a small filter width as shown in FIG. 8 and a large weight near the end and having an effective slice thickness greater than the slice direction reconstruction filter function FLT01, and a filter width as shown in FIG. In the slice direction reconstruction filter function FLT11, which has a uniform effective weight and a standard effective slice thickness and image quality, the filter width is medium and the effective slice thickness is large as shown in FIG. Slice direction reconstruction filter function FL
Slice direction reconstruction filter function FLT thinner than T11
12, the slice width reconstruction filter function FLT13 whose filter width has a large weight near the end and has an effective slice thickness larger than the slice direction reconstruction filter function FLT11 as shown in FIG. 11, and the filter width as shown in FIG. Has a large and equal weight, and the effective slice thickness is slightly thicker, S /
A slice direction reconstruction filter function FLT21 having a high N ratio and a high low contrast resolution, as shown in FIG. 13, a slice having a large filter width, a large weight at the center, and a thinner effective slice thickness than the slice direction reconstruction filter function FLT21. Direction reconstruction filter function FLT22, FIG.
As shown in the figure, the slice direction reconstruction filter function F having a large filter width and a large weight near the end and having a larger effective slice thickness than the slice direction reconstruction filter function FLT21.
LT23, as shown in FIG. 15, the filter width is maximum, the weight is equal, the effective slice thickness is quite large, the S / N ratio is quite good, the low contrast resolution is high, and the slice direction reconstruction filter function FLT31, as shown in FIG. FIG. 17 shows a slice direction reconstruction filter function FLT32 having a maximum filter width and a large weight at the center and having an effective slice thickness smaller than the slice direction reconstruction filter function FLT31.
As shown in (1), a slice direction reconstruction filter function FLT33 having a maximum filter width and a large weight near the end and having an effective slice thickness larger than the slice direction reconstruction filter function FLT31 is stored.

The slice direction reconstruction filter function is not limited to the slice direction reconstruction filter function described above, but may be of any shape. For example, as shown in FIG. 18, a slice direction reconstruction filter function FLT41 having a characteristic as a high-pass filter having a negative weight near the end may be used.

The reconstruction function processing unit 27 is set by the input device out of the projection data interpolated by the slice direction reconstruction filter function processing unit 23 and the reconstruction function stored in the reconstruction function storage unit 29. Convolution processing of the reconstructed function.

The reconstruction function storage unit 29 stores a reconstruction function as shown in FIG. 42, similarly to the aforementioned conventional X-ray CT apparatus. For example, as shown in FIG. 42, a reconstruction function FC that emphasizes a low-frequency region and is excellent in low-contrast rendering ability.
1. Reconstruction function FC2, which suppresses the low-frequency region below reconstruction function FC1, Reconstruction function FC3, which further suppresses the low-frequency region below reconstruction function FC1, low-frequency region and high-frequency region, A reconstruction function FC4 excellent in margin and low-contrast rendering ability; a reconstruction function FC5 slightly lowering a low-frequency region than the reconstruction function FC4; a reconstruction function FC6 emphasizing a higher-frequency region than the reconstruction function FC4; Reconstruction function FC7, reconstruction function F that emphasizes high frequency regions, has high spatial resolution, and makes the edges of blood vessels clear
Reconstruction function FC slightly lowers the high frequency range than C7
8 is stored.

The image reconstructing section 31 has a centering processing section 31a and a back projection section 31b. The centering processing section 31a once performs back projection on a predetermined centering axis. , Back-projecting each pixel constituting the image data to reconstruct the image data.

The control unit 33 controls the operation timing of the filter processing by the slice direction reconstruction filter function processing unit 23 and controls the operation timing of the convolution processing by the reconstruction function processing unit 27. further,
The control unit 33 controls the operation timing of the back projection process performed by the image reconstruction unit 31.

The display device 21 displays the image data reconstructed by the image reconstruction unit 31 of the reconstruction processing unit 19 on a monitor. Further, the display device 21 includes an image memory (not shown), and records the reconstructed image data.

Next, the operation of the X-ray CT apparatus 1 according to the first embodiment will be described with reference to FIG. In the X-ray CT apparatus 1 according to the first embodiment, helical scan is performed under the following conditions.

[0049]

[Table 1] Number of detectors for simultaneous data collection Nseg = 4 Number of detector channels Nch = 1000 Height (thickness) of each column in the Z-axis direction Dseg = 8, 4, 2, 1, 0.5, 0.5, 0.5, 0.5 , 1,2,4,8 (mm) Total thickness of detector 32 (mm) Distance between focus and rotation center FCD = 600 (mm) (Focus-Center-Distance) Distance between focus and detector FDD = 1200 ( mm) (Focus-Detector-Distance) Effective field diameter FOV = 500 (mm) (Field of View) Effective field angle (fan angle) φ = 50 ° Total number of detector rows Nseg = 12 First, abdomen as the first examination The case of shooting will be described. The target image data has high image quality equivalent to image data having an effective slice thickness of 5 (mm) without a partial effect.

First, the operator places the subject on the bed 5c, inputs patient information such as patient ID and name using an input device (not shown), and prepares for examination by taking a scanogram (step). S1). An imaging range (150 (mm)) in the body axis direction is determined based on the scano image, and the FOV size is set to the L size (as shown as FOV in FIG. 37A), the X-ray beam is applied from the focal point F to the entire detector. The maximum FOV size at the time of exposure is LL, and the size becomes smaller in the order of L, M, S, SS below), tube current 200 (mA), tube voltage 1
20 (kV), input the reconstruction function as FC3 for abdomen.
The operation up to this point is the same as the operation of the conventional X-ray CT apparatus.

Further, the operator uses the input device (not shown) to instruct the system control unit 3 to collect four rows of projection data with the number of detector rows being the collection mode and to set the beam thickness to 2 (m).
m), using the bed feed speed as the shooting mode, 4 rows / rotation =
8 mm / rev (high image quality mode), and a slice direction reconstruction filter function as FLT 21 to make the final effective slice thickness 5 (mm) (Step S)
3).

In this state, when an operator inputs a shooting start command from an input device (not shown), the system control unit 3
Is a gantry for controlling the rotation of the rotary gantry 5a, the adjustment of the collimator 5b, and the feed speed of the couch 5c, and outputs a couch control signal to the gantry and the couch control unit 5 and controls the generation of X-ray beams. Is output to the X-ray controller 7. When the gantry / bed control signal is output, the gantry / bed control unit 5 rotates the rotating gantry 5a, adjusts the collimator 5b based on the gantry / bed control signal, and further feeds the bed 5c. To adjust. When the X-ray beam generation control signal is output, the X-ray controller 7 causes the high voltage generator 9 to generate a high voltage. In addition, the system control unit 3 outputs a detector row switching signal for switching a detector row for collecting projection data to the switching unit 15 and outputs a data collection control signal indicating data collection timing to the data collection unit. 17 is output. When this detector row switching signal is output,
The switching unit 15 switches so that the detection signals can be collected from eight columns of the third to tenth columns.

As a result, the X-ray beam is emitted from the X-ray beam source 11, the bed 5c is moved, and the helical scan is started. When the data collection control signal is output, the data collection unit 17
The detection signal detected by the detector 13 is converted into a digital signal and collected as projection data at a predetermined timing.

At this time, the X-ray beams are supplied to the X-ray beam source 11 in eight columns from the third column to the tenth column under designated conditions.
And data is collected by the data collection unit 17. That is, data is collected only in the columns indicated by oblique lines in FIG. 20 (a) shows a detector array of the detector 13, FIG. 20 (b) shows a case where data is collected from all the detector arrays, and FIG. 20 (c) shows the second to eleventh columns. FIG. 20D shows a case where data is collected from 10 columns.
FIG. 20 shows a case where data is collected from eight columns in the tenth column.
FIG. 20E shows a case where data is collected from four columns from the fourth to ninth columns, and FIG. 20F shows a case where data is collected from four columns from the fifth to eighth columns. ) Shows a case where data is collected from two columns of the sixth and seventh columns.

In this case, since the data of the unequal eight columns is collected, the data collection unit 17 performs data processing (addition or averaging, etc.) on the detection signals of the fourth, fifth, and sixth columns to obtain the second data. Then, the detection signals in the seventh, eighth, and ninth columns are subjected to data processing (addition or averaging, etc.) to obtain third data. That is, the third column is the first data, the fourth, fifth, and sixth columns are the second data, the seventh, eighth, and ninth columns are the third data, the tenth column is the fourth data, and the first, second, third, and fourth data are Collect four rows simultaneously.
In addition, the data collection unit 17 adds
Various corrections such as X-ray intensity correction and detector sensitivity correction are performed (step S5).

After the projection data is collected by the data collection unit 17 and various corrections are made, the control unit 33 of the reconstruction processing unit 19 temporarily stores the projection data. Further, the slice direction reconstruction processing unit 23 performs a filtering process in the slice direction using the set slice direction reconstruction filter function FLT21 based on the projection data of the helical scan of the four rows and a plurality of rotations, and performs the filtering in the slice direction. The rotation projection data is interpolated (step S7). In the slice direction reconstruction filter function FLT21, interpolation is performed using projection data relatively far from the target slice position.
The interpolated projection data is relatively thick.

When the projection data is interpolated by the slice direction reconstruction processor 23, the reconstruction function processor 27 performs a convolution process on the interpolated projection data and the reconstruction function FC3. Then, the centering processing unit 31a
, The image is once back-projected onto a predetermined centering axis, and then back-projected onto each pixel constituting the image data by the back-projection unit 31b to reconstruct the image data (step S9).

At this time, since the projection data is reconstructed from the projection data having the thickness, the image data having the thickness is reconstructed.
Image data of the desired effective slice thickness of 5 (mm) is obtained. However, originally, interpolation data was created by processing projection data collected with a beam thickness of 2 (mm). Therefore, the partial effect of this image data is equivalent to image data of an effective slice thickness of 2 (mm). Quite good.
Also, since the image data is composed of the number of photons collected in a wide range, the S / N ratio is equivalent to image data of an effective slice thickness of 5 (mm). That is, the reconstructed projection data has a partial suppression effect equivalent to image data having an effective slice thickness of 2 (mm), a high S / N ratio equivalent to image data having an effective slice thickness of 5 (mm), and low contrast rendering capability. have.

The image data reconstructed by the reconstruction processing section 19 is sequentially supplied to the display device 21 and
(Step S11).

The doctor performs image interpretation on the monitor of the display device 21. Alternatively, whether the image is recorded on the display device 21 and the image is read later, or the image is read by the image reading workstation after the data is transferred to the image reading workstation,
Once the image data is dropped on the film, the image may be read on the film. Among these, when reading images on a monitor, the number of images to be read becomes 30 in the range of 150 (mm), and the reading time can be reduced. In addition, when the image is read on a film, it can be accommodated by two films, and the reading time can be similarly reduced.

Next, when the doctor interprets the image on the display device or on the workstation for image interpretation and finds that the artifact due to the movement of the intestinal tract is strong in certain image data, prepares to perform the image interpretation on the PMC image. . That is, the target image data is displayed, and the PMC is instructed. Here, the PMC image is an image in which artifacts are suppressed by reducing the execution scan time.

When giving the PMC instruction, the operator changes the set slice direction reconstruction filter function FLT21 to the slice direction reconstruction filter function FLT01 using an input device (not shown), and instructs a reconstruction retry.

When the slice direction reconstruction filter function is changed and a reconstruction retry is instructed, the system control unit 3 changes the slice direction reconstruction filter function to FLT01 to the reconstruction processing unit 19 and reconfigures it. It instructs to perform the configuration again (step S13YES). Accordingly, the reconstruction processing unit 19 sets the slice direction reconstruction filter function to F
It is changed to LT01 (step S15), the projection data stored in the control unit 33 is read out, and the projection data is interpolated using the changed slice direction reconstruction filter function FLT01 to reconstruct the image data again (step S15).
7, S9). Then, this reconstructed image data is
The images are sequentially displayed on the monitor of the display device 21 or transferred and displayed on the monitor of the workstation for image reading (step S11). In this way, abdominal imaging and its interpretation are performed by helical scanning.

Next, the case where the head is photographed as the second inspection will be described with reference to FIG. Here, the target image data is equivalent to image data having an effective slice thickness of 10 (mm) at the top of the head because the structure such as bones is simple, and the other skull base is equivalent to image data having an effective slice thickness of 5 (mm). .

First, the operator places the subject on the bed 5c, inputs patient information such as a patient ID and a name using an input device (not shown), and prepares for examination by taking a scanogram (step). S21). The imaging range in the body axis direction is determined based on this scano image, the FOV size is S size, the tube current is 300 (mA), the tube voltage is 120 (kV), and the reconstruction function is F.
Enter C4. The operation up to this point is the same as the conventional X-ray C
The operation is the same as that of the T device.

Further, the operator uses the input device (not shown) to instruct the system control unit 3 to set the collection mode to four columns.
Beam thickness 2 (mm), shooting mode 4.5 rows / rotation = 9
mm / rev (High quality mode 2). In addition, the final image quality and the effective slice thickness
The slice direction reconstruction filter function is input as FLT31 at the top of the head and FLT21 at the skull base in order to set the S / N ratio and the reduction of the number to 10 (mm), and to set the effective slice thickness to 5 (mm) at the skull base. (Step S23).

In this state, when the operator inputs a shooting start command from an input device (not shown), the system control unit 3
Is a gantry for controlling the rotation of the rotary gantry 5a, the adjustment of the collimator 5b, and the feed speed of the couch 5c, and outputs a couch control signal to the gantry and the couch control unit 5 and controls the generation of X-ray beams. Is output to the X-ray controller 7. When the gantry / bed control signal is output, the gantry / bed control unit 5 rotates the rotating gantry 5a, adjusts the collimator 5b based on the gantry / bed control signal, and further feeds the bed 5c. To adjust. When the X-ray beam generation control signal is output, the X-ray controller 7 causes the high voltage generator 9 to generate a high voltage. In addition, the system control unit 3 outputs a detector row switching signal for switching a detector row for collecting projection data to the switching unit 15 and outputs a data collection control signal indicating data collection timing to the data collection unit. 17 is output. When this detector row switching signal is output,
The switching unit 15 switches so that the detection signals can be collected from eight columns of the third to tenth columns.

As a result, the X-ray beam is emitted from the X-ray beam source 11, the bed 5c is moved, and imaging by helical scan is started. This allows
The X-ray beam is emitted from the X-ray beam source 11, and the bed 5c is moved to start imaging by helical scan. When the data collection control signal is output, the data collection unit 17 converts the detection signal detected by the detector 13 into a digital signal and collects it as projection data at a predetermined timing.

At this time, the X-ray beam is supplied to the X-ray beam source 11 in eight columns from the third column to the tenth column under designated conditions.
And data is collected by the data collection unit 17.

In this case, since the data of the unequal eight columns is collected, the data collection unit 17 processes the detection signal of the third column by the first data and the detection signals of the fourth, fifth, and sixth columns by data processing. (Addition or average, etc.) to obtain the second data.
Data processing (addition or averaging, etc.) is performed on the detection signals in the 8th and 9th columns, and the 3rd data and the detection signals in the 10th column are simultaneously collected as the 4th data in the 4th column. The data collection unit 17 performs various corrections such as X-ray intensity correction and detector sensitivity correction on the collected projection data (step S25).

After the projection data is collected by the data collection unit 17 and various corrections are made, the control unit 33 of the reconstruction processing unit 19 temporarily stores the projection data. Further, the slice direction reconstruction processing unit 23 performs a filtering process in the slice direction using a set slice direction reconstruction filter function based on the projection data of the helical scan of a plurality of rotations of four columns, and performs one rotation per column. Interpolate the projection data for minutes.

At this time, since the FLT 21 is specified as the slice direction reconstruction filter function in the skull base region in the first half of the examination, the projection data is interpolated using the FLT 21. Interpolation using the slice direction reconstruction filter function FLT21 results in projection data having a relatively large thickness.

Since FLT31 is specified as the slice direction reconstruction filter function in the parietal region in the latter half of the examination, the projection data is interpolated using FLT31 (steps S27NO and S31). The interpolation using the slice direction reconstruction filter function FLT31 results in projection data having a thickness greater than the interpolation using the slice direction reconstruction filter function FLT21.

When the projection data is interpolated by the slice direction reconstruction processing unit 23, the reconstruction function processing unit 27 performs a convolution process on the interpolated projection data and the reconstruction function FC4. Then, the centering processing unit 31a
, The image is once back-projected to a predetermined centering axis, and then back-projected to each pixel constituting the image data by the back-projection unit 31b to reconstruct the image data (step S33).

Of the reconstructed image data, the image data of the skull base region is reconstructed from the projection data interpolated using the slice direction reconstruction filter function FLT21, so that the effective slice thickness is 5 (mm). , The S / N ratio is good, and the image quality is high with the partial effect suppressed. Further, among the reconstructed image data, the image data of the parietal region is reconstructed from the projection data interpolated using the slice direction reconstruction filter function FLT31, so that the effective slice thickness is 10 (mm).
, The S / N ratio is further improved, and the image quality is excellent in the low-contrast rendering ability.

The image data reconstructed by the reconstruction processing unit 19 is sequentially supplied to the display device 21 and
(Step S35).

When the doctor interprets the displayed image data on the monitor and finds an abnormal shadow near the top of the head, the doctor re-examines the thinned image data only in the top area again. Prepare for interpretation. That is, an area is set by displaying a scano image (steps S37 YES, S3).
9), the slice direction reconstruction filter function is changed from FLT31 to FLT21, and a reconstruction retry is instructed (steps S27YES and S29).

When the slice direction reconstruction filter function is changed and a reconstruction retry is instructed, the reconstruction processing unit 1
9 is a modified slice direction reconstruction filter function FLT
01, the projection data is interpolated to reconstruct the image data again (steps S31, S33). Then, the reconstructed image data is sequentially displayed on the monitor of the display device 21 (step S35). The image data displayed on the monitor is image data thinned to an image data of an effective slice thickness of 5 (mm). This allows the doctor to perform detailed interpretation. In this way, head imaging and image interpretation are performed by helical scanning.

Next, the case where lung field imaging is performed as a third inspection will be described with reference to FIG. When taking an image of the lung field, for example, the subject may be a subject who has difficulty breathing, and it is desired to minimize the breath holding time. That is, shooting is performed in the high-speed mode in which the shooting time is the shortest as the shooting mode. At this time, the target image data has an effective slice thickness of 5 (m
The image quality is equivalent to the image data of m) and excellent in high contrast rendering ability.

First, the operator places the subject on the bed 5c, inputs patient information such as a patient ID and a name using an input device (not shown), and prepares for examination by photographing a scanogram (step). S1). The imaging range in the body axis direction is determined based on this scano image, the FOV size is M size, the tube current is 200 (mA), the tube voltage is 120 (kV), and the reconstruction function is FC.
Enter 7. The operation so far is the same as the conventional X-ray CT.
The operation is the same as that of the device.

Further, the operator uses the input device (not shown) to instruct the system control unit 3 to collect four collection modes,
Beam thickness 2 (mm), shooting mode 3.5 rows / rotation = 1
Input 4mm / rev (High-speed mode 1). The slice direction reconstruction filter function is input as FLT11 in order to set the final effective slice thickness to 5 (mm) (step S3).

In this state, when a photographing start command is input from an input device (not shown) by the operator, the system control unit 3
Is a gantry for controlling the rotation of the rotary gantry 5a, the adjustment of the collimator 5b, and the feed speed of the couch 5c, and outputs a couch control signal to the gantry and the couch control unit 5 and controls the generation of X-ray beams. Is output to the X-ray controller 7. When the gantry / bed control signal is output, the gantry / bed control unit 5 rotates the rotating gantry 5a, adjusts the collimator 5b based on the gantry / bed control signal, and further feeds the bed 5c. To adjust. When the X-ray beam generation control signal is output, the X-ray controller 7 causes the high voltage generator 9 to generate a high voltage. In addition, the system control unit 3 outputs a detector row switching signal for switching a detector row for collecting projection data to the switching unit 15 and outputs a data collection control signal indicating data collection timing to the data collection unit. 17 is output. When this detector row switching signal is output,
The switching unit 15 switches so that the detection signals can be collected from eight columns of the third to tenth columns.

As a result, the X-ray beam is emitted from the X-ray beam source 11, the bed 5c is moved, and the helical scan is started. This allows
The X-ray beam is emitted from the X-ray beam source 11, and the bed 5c is moved to start imaging by helical scan. When the data collection control signal is output, the data collection unit 17 converts the detection signal detected by the detector 13 into a digital signal and collects it as projection data at a predetermined timing.

At this time, the X-ray beam is supplied to the X-ray beam source 11 in eight columns from the third column to the tenth column under designated conditions.
And data is collected by the data collection unit 17.

In this case, since the data of the unequal eight columns is collected, the data collection unit 17 processes the detection signals of the third column by the first data and the detection signals of the fourth, fifth, and sixth columns by data processing. (Addition or average, etc.) to obtain the second data.
Data processing (addition or averaging, etc.) is performed on the detection signals in the 8th and 9th columns, and the 3rd data and the detection signals in the 10th column are simultaneously collected as the 4th data in the 4th column. Further, the data collection unit 17 performs various corrections such as X-ray intensity correction and detector sensitivity correction on the collected projection data (step S5).

After the projection data is collected by the data collection unit 17 and various corrections are made, the control unit 33 of the reconstruction processing unit 19 temporarily stores the projection data. Further, the slice direction reconstruction processing unit 23 performs a filtering process in the slice direction using the set slice direction reconstruction filter function FLT11 based on the projection data of the helical scan having a plurality of rotations of four columns, and performs the filtering in the slice direction. The rotation projection data is interpolated (step S7). Here, the projection data interpolated using the slice direction reconstruction filter function FLT11 becomes projection data having a thickness of 5 (mm) which does not change much from the thickness of 4 (mm) originally possessed by the X-ray beam.

When the projection data is interpolated by the slice direction reconstruction processing unit 23, the reconstruction function processing unit 27 performs a convolution process on the interpolated projection data and the reconstruction function FC7. Then, the centering processing unit 31a
, The image is once back-projected onto a predetermined centering axis, and then back-projected onto each pixel constituting the image data by the back-projection unit 31b to reconstruct the image data (step S9).

At this time, the image data reconstructed from the projection data interpolated by the slice direction reconstruction filter function FLT11 is equivalent to image data having an effective slice thickness of 5 (mm). Despite shooting at a high speed (14 mm / rev), image data equivalent to image data of an effective slice thickness of 5 (mm) with good image quality is obtained by the effect of the slice direction reconstruction filter function FLT11.

The image data reconstructed by the reconstruction processing section 19 is sequentially supplied to the display device 21 and
(Step S11). The doctor
Image interpretation is performed on the monitor of the display device 21. In this way, the lung field imaging and its interpretation are performed by the helical scan.

As described above, in the first embodiment, the slice direction reconstruction filter functions having different shapes are stored in the plural slice direction reconstruction filter function storage unit 25, and the slice signals are stored on the basis of the detection signal detected by the detector 13. In addition, projection data interpolation for a target slice position is performed by using a slice direction reconstruction filter function stored in the slice direction reconstruction filter function storage unit 25 that corresponds to a predetermined condition. In addition, it is possible to obtain high-quality image data in an appropriate number.

Next, a second embodiment of the X-ray CT apparatus according to the present invention will be described. Note that X in the first embodiment shown in FIG.
Since only the line CT apparatus and the reconstruction processing unit 19 are changed, only the changed reconstruction processing unit 19 is shown in FIG.

In the X-ray CT apparatus according to the second embodiment, the S / N ratio of the image data is determined based on the beam thickness, FOV size, imaging region, etc.
The ratio and the presence or absence of the partial effect are predicted, and the thickness of the X-ray beam to be collected and the slice direction reconstruction filter function are automatically set from the target image conditions such as the effective slice thickness and the image quality. is there.

As shown in FIG. 22, the reconstruction processing section 19 of the second embodiment includes a slice direction reconstruction filter function selection section 35 in addition to the reconstruction processing section 19 of the first embodiment shown in FIG. It is provided.

Slice direction reconstruction filter function selector 3
Stores, in advance, a plurality of tables showing slice direction reconstruction filter functions corresponding to a plurality of image conditions and a plurality of tables showing slice direction reconstruction filter functions corresponding to a plurality of inspection conditions. Priority table indicating the priority of the table in advance corresponding to various processes, three-dimensional processing, etc., and stores image conditions, inspection conditions, the tables (1) to (8), and the priority table. The slice direction reconstruction filter function and the beam thickness are selected correspondingly.

As a table showing the slice direction reconstruction filter function corresponding to the image condition, for example, as shown in FIG. 23, the slice direction reconstruction filter function corresponding to the effective slice thickness / beam thickness of the target image is shown. Table (1), image quality priority items (high contrast resolution,
Table (2) showing the slice direction reconstruction filter function corresponding to the time resolution, low contrast resolution, and standard image quality, and the slice direction reconstruction filter function corresponding to the image purpose (interpretation, three-dimensional processing, PMC). Table (3), and a table (4) indicating the slice direction reconstruction filter function corresponding to the FOV size (LL, L, M, S, SS).

FIG. 2 is a table showing slice direction reconstruction filter functions corresponding to inspection conditions.
As shown in FIG. 4, a table (5) showing the slice direction reconstruction filter functions corresponding to the imaging and observation sites (head, chest, abdomen, lumbar spine, bones, etc.), and the imaging elapsed time (immediately, middle, late) Table (6) showing a slice direction reconstruction filter function corresponding to, and a slice direction reconstruction filter corresponding to SN (SN (mA.kV, FOV, beam thickness)) calculated from X-ray conditions (tube current) Table (7) showing the function,
A table (8) indicating a slice direction reconstruction filter function corresponding to the scan mode (bed moving speed / effective slice thickness of the target image) is stored.

In the standard processing, for example, as shown in FIG. 25, priority 1 is table (1), table (8), table (3), table (7), table (7)
(2), table (5), table (4), table (6), 3
At the time of dimension processing, a priority order table in which priority order 1 is set as table (3) is stored. These tables (1) to (8)
The operator can change the priority order table using an input device (not shown).

Next, as an operation example of the second embodiment, a case of performing abdominal imaging will be described with reference to FIG. First, the operator places the subject on the bed 5c and inputs patient information such as a patient ID and a name using an input device (not shown), and then prepares for an examination by photographing a scano image (step S41).
The imaging range in the body axis direction is determined based on this scano image, and F
OV size is L size, tube current 200 (mA), tube voltage 1
20 (kV), input the reconstruction function as FC3. The operation up to this point is the same as the operation of the conventional X-ray CT apparatus.

Further, the operator inputs an object to be photographed to the abdomen to the system controller 3 using an input device (not shown), sets the effective slice thickness of the target image to 5 (mm), and sets the photographing mode to the high image quality mode. (4 rows / rotation = 8 (mm) / rev)
Is input (step S43). The data input by these operators is transmitted from the system control unit 3 to the reconstruction processing unit 19.

When the data is transmitted, the reconstruction processing unit 1
The slice direction reconstruction filter function selection unit 35 selects a slice direction reconstruction filter function and a beam thickness based on the tables (1) to (8) and the priority order table (step S45). Here, the slice direction reconstruction filter function FLT21 is selected, and the beam thickness 2 (mm) is selected. In addition, the system control unit 3 sets the collection mode to four-column collection because the shooting mode is the high-quality mode (four columns / rotation). The reconstruction processing unit 19 displays these on the monitor of the display device 21. The operator confirms this and presses the execution key or the "OK" key.

In this state, when a photographing start command is input from an input device (not shown) by the operator, the system control unit 3
Is a gantry for controlling the rotation of the rotary gantry 5a, the adjustment of the collimator 5b, and the feed speed of the couch 5c, and outputs a couch control signal to the gantry and the couch control unit 5 and controls the generation of X-ray beams. Is output to the X-ray controller 7. When the gantry / bed control signal is output, the gantry / bed control unit 5 rotates the rotating gantry 5a, adjusts the collimator 5b based on the gantry / bed control signal, and further feeds the bed 5c. To adjust. When the X-ray beam generation control signal is output, the X-ray controller 7 causes the high voltage generator 9 to generate a high voltage. In addition, the system control unit 3 outputs a detector row switching signal for switching a detector row for collecting projection data to the switching unit 15 and outputs a data collection control signal indicating data collection timing to the data collection unit. 17 is output. When this detector row switching signal is output,
The switching unit 15 switches so that the detection signals can be collected from eight columns of the third to tenth columns.

Thus, the X-ray beam is emitted from the X-ray beam source 11, the bed 5c is moved, and the helical scan is started. This allows
The X-ray beam is emitted from the X-ray beam source 11, and the bed 5c is moved to start imaging by helical scan. When the data collection control signal is output, the data collection unit 17 converts the detection signal detected by the detector 13 into a digital signal and collects it as projection data at a predetermined timing.

At this time, the X-ray beams are supplied to the X-ray beam source 11 in eight columns from the third column to the tenth column under designated conditions.
And data is collected by the data collection unit 17.

In this case, since data of unequal eight columns is collected, the data collection unit 17 processes the detection signal of the third column with the first data and the detection signals of the fourth, fifth, and sixth columns with data processing. (Addition or average, etc.) to obtain the second data.
Data processing (addition or averaging, etc.) is performed on the detection signals in the 8th and 9th columns, and the 3rd data and the detection signals in the 10th column are simultaneously collected as 4th data in the 4th column. The data collection unit 17 performs various corrections such as X-ray intensity correction and detector sensitivity correction on the collected projection data (step S47).

When the projection data is collected by the data collection unit 17 and various corrections are made, the control unit 33 of the reconstruction processing unit 19 temporarily stores the projection data. Further, the slice direction reconstruction processing unit 23 performs a filtering process in the slice direction using the set slice direction reconstruction filter function FLT21 based on the projection data of the helical scan of the four rows and a plurality of rotations, and performs the filtering in the slice direction. The projection data for the rotation is interpolated (step S49).

When the projection data is interpolated by the slice direction reconstruction processor 23, the reconstruction function processor 27 performs a convolution process on the interpolated projection data and the reconstruction function FC3. Then, the centering processing unit 31a
, The image is once back-projected onto a predetermined centering axis, and then back-projected onto each pixel constituting the image data by the back-projection unit 31b to reconstruct the image data (step S51).

At this time, since the projection data having the thickness is reconstructed, the image data having the thickness is reconstructed.
Image data of the desired effective slice thickness of 5 (mm) is obtained. However, originally, interpolation data was created by processing projection data collected with a beam thickness of 2 (mm). Therefore, the partial effect of this image data is equivalent to image data of an effective slice thickness of 2 (mm). Quite good.
Also, since the image data is composed of the number of photons collected in a wide range, the S / N ratio is equivalent to image data of an effective slice thickness of 5 (mm). That is, the reconstructed projection data has a partial suppression effect equivalent to image data having an effective slice thickness of 2 (mm), a high S / N ratio equivalent to image data having an effective slice thickness of 5 (mm), and low contrast rendering capability. have.

The image data reconstructed by the reconstruction processing section 19 is sequentially supplied to the display device 21 and
(Step S53).

When a doctor interprets the displayed image data on the monitor, and wants to recognize shadows and perform detailed interpretation with thinner image data, the doctor needs to read the effective slice thickness of the target image data. Is set to 3 (mm), and reconfiguration retry is instructed.

When a reconfiguration instruction is issued, the changed data is sent from the system control unit 3 to the reconfiguration processing unit 1.
9 is transmitted.

When the data is transmitted, the reconstruction processing unit 1
The slice direction reconstruction filter function selector 35 changes the slice direction reconstruction filter function based on the tables (1) to (8) and the priority order table (step S).
55 YES, S57). Here, the slice direction reconstruction filter function selection unit 35 changes the slice direction reconstruction filter function from FLT21 to FLT11. And
The reconstruction processing unit 19 reads the projection data stored in the control unit 33, interpolates the projection data using the changed slice direction reconstruction filter function FLT01, and reconstructs image data again (Step S49, S51).
Then, the reconstructed image data is sequentially displayed on the monitor of the display device 21 or transferred and displayed on the monitor of the workstation for image interpretation (step S53).
The image data displayed on the monitor is reconstructed from the projection data interpolated by using the relatively narrow slice direction reconstruction filter function FLT11, so that the image data has an effective slice thickness of 3 (mm). It is thinner. This allows the doctor to perform detailed interpretation.

Next, as an operation example of the second embodiment, an example in which three-dimensional image processing means is provided will be described with reference to FIG. First, the operator places the subject on the bed 5c and inputs patient information such as a patient ID and a name using an input device (not shown), and then prepares for an examination by photographing a scano image (step S41). The imaging range in the body axis direction is determined based on the scano image, the FOV size is set to the S size, and the tube current 3 is set.
00 (mA), tube voltage 120 (kV), reconstruction function FC5
Enter The operation up to this point is the same as the operation of the conventional X-ray CT apparatus.

Further, the operator uses the input device (not shown) to input a subject to be photographed to the abdomen to the system control unit 3 and input an effective slice thickness of a target image of 5 (mm) and three-dimensional processing. (Step S43). The data input by these operators is transmitted from the system control unit 3 to the reconstruction processing unit 19.

When the data is transmitted, the reconstruction processing unit 1
The slice direction reconstruction filter function selection unit 35 selects a slice direction reconstruction filter function and a beam thickness based on the tables (1) to (8) and the priority order table (step S45). Here, the slice direction reconstruction filter function FLT21 is selected, and the beam thickness 2 (mm) is selected. In addition, the system control unit 3 sets the collection mode to four-column collection because the shooting mode is the high-quality mode (four columns / rotation).

In this state, when a photographing start command is inputted from an input device (not shown) by the operator, the system control unit 3
Is a gantry for controlling the rotation of the rotary gantry 5a, the adjustment of the collimator 5b, and the feed speed of the couch 5c, and outputs a couch control signal to the gantry and the couch control unit 5 and controls the generation of X-ray beams. Is output to the X-ray controller 7. When the gantry / bed control signal is output, the gantry / bed control unit 5 rotates the rotating gantry 5a, adjusts the collimator 5b based on the gantry / bed control signal, and further feeds the bed 5c. To adjust. When the X-ray beam generation control signal is output, the X-ray controller 7 causes the high voltage generator 9 to generate a high voltage. In addition, the system control unit 3 outputs a detector row switching signal for switching a detector row for collecting projection data to the switching unit 15 and outputs a data collection control signal indicating data collection timing to the data collection unit. 17 is output. When this detector row switching signal is output,
The switching unit 15 switches so that the detection signals can be collected from eight columns of the third to tenth columns.

Thus, the X-ray beam is emitted from the X-ray beam source 11, the bed 5c is moved, and the helical scan is started. This allows
The X-ray beam is emitted from the X-ray beam source 11, and the bed 5c is moved to start imaging by helical scan. When the data collection control signal is output, the data collection unit 17 converts the detection signal detected by the detector 13 into a digital signal and collects it as projection data at a predetermined timing.

At this time, the X-ray beam is supplied to the X-ray beam source 11 in eight columns from the third column to the tenth column under designated conditions.
And data is collected by the data collection unit 17.

In this case, since data of eight non-uniform columns is collected, the data collecting unit 17 processes the detection signals of the third column with the first data and the detection signals of the fourth, fifth, and sixth columns with data processing. (Addition or average, etc.) to obtain the second data.
Data processing (addition or averaging, etc.) is performed on the detection signals in the 8th and 9th columns, and the 3rd data and the detection signals in the 10th column are simultaneously collected as 4th data in the 4th column. The data collection unit 17 performs various corrections such as X-ray intensity correction and detector sensitivity correction on the collected projection data (step S47).

When projection data is collected by the data collection unit 17 and various corrections are made, the control unit 33 of the reconstruction processing unit 19 temporarily stores the projection data. Further, the slice direction reconstruction processing unit 23 performs a filtering process in the slice direction using the set slice direction reconstruction filter function FLT21 based on the projection data of the helical scan of the four rows and a plurality of rotations, and performs the filtering in the slice direction. The projection data for the rotation is interpolated (step S49).

When the projection data is interpolated by the slice direction reconstruction processor 23, the reconstruction function processor 27 performs a convolution process on the interpolated projection data and the reconstruction function FC5. Then, the centering processing unit 31a
, The image is once back-projected onto a predetermined centering axis, and then back-projected onto each pixel constituting the image data by the back-projection unit 31b to reconstruct the image data (step S51).

At this time, since the projection data is reconstructed from the projection data having the thickness, the image data having the thickness is reconstructed.
Image data of the desired effective slice thickness of 5 (mm) is obtained. However, originally, interpolation data was created by processing projection data collected with a beam thickness of 2 (mm). Therefore, the partial effect of this image data is equivalent to image data of an effective slice thickness of 2 (mm). Quite good.
Also, since the image data is composed of the number of photons collected in a wide range, the S / N ratio is equivalent to image data of an effective slice thickness of 5 (mm). That is, the reconstructed projection data has a partial suppression effect equivalent to image data having an effective slice thickness of 2 (mm), a high S / N ratio equivalent to image data having an effective slice thickness of 5 (mm), and low contrast rendering capability. have.

The image data reconstructed by the reconstruction processing section 19 is sequentially supplied to the display device 21 and
(Step S53).

The doctor checks the image data on the monitor of the display device 21 and stores the image data in a film or a hard disk device, a magneto-optical disk device (not shown), or the like. After confirming the position, an instruction for three-dimensional processing is given using an input device (not shown).

When an instruction for three-dimensional processing is issued, the system control unit 3 instructs the reconstruction processing unit 19 to change the slice direction reconstruction filter function to one for three-dimensional processing.

When an instruction to change the slice direction reconstruction filter function for the three-dimensional processing is given, the slice direction reconstruction filter function selection unit 35 of the reconstruction processing unit changes the slice direction reconstruction filter function to FLT00. (Steps S55 YES and S57). Then, the reconstruction processing unit 19 reads the projection data temporarily stored in the control unit 33, interpolates the projection data using the changed slice direction reconstruction filter function FLT00, and reconstructs image data again ( Steps S49 and S51).

This slice direction reconstruction filter function FL
T00 is extremely thin as shown in FIG. 5, and the interpolated projection data has the smallest thickness. Therefore, the reconstructed image data also has the smallest effective slice thickness (2 (mm)). Since this image data has some artifacts, it is not suitable for Tsugami's interpretation unless some processing is performed for a purpose other than special interpretation. The special interpretation purpose is, for example, to widen a window for observing a bone so that an allowable range of an artifact is wide, and it is desired to give priority to a thinner effective slice thickness.

In the case of three-dimensional processing, threshold value processing is performed to create a three-dimensional image, so that some artifacts are not affected. If the effective slice thickness is large, the resolution of the final three-dimensional image is degraded.

Next, a three-dimensional image processing means (not shown) creates voxel data based on the image data having an effective slice thickness of 2 (mm). The doctor performs threshold processing on the voxel data and colors the voxel data to create a three-dimensional image expressing bones, tumors, blood vessels, and the like. Since this three-dimensional image is created based on thin image data having an effective slice thickness of 2 (mm), it is smooth and has high resolution in the slice direction.

Next, an example in which a contrast agent is used as an operation example of the second embodiment will be described with reference to FIG. First, the operator places the subject on the bed 5c and inputs patient information such as a patient ID and a name using an input device (not shown).
A scano image is taken to prepare for inspection (step S6)
1). Based on this scano image, the imaging range in the body axis direction (15
0 (mm)), the FOV size is M size, the tube current is 200 (mA), the tube voltage is 120 (kV), and the reconstruction function is FC.
Enter 2. The operation so far is the same as the conventional X-ray CT.
The operation is the same as that of the device.

Further, the operator uses the input device (not shown) to input the abdominal contrast to the imaging target and input the effective slice thickness of the target image to 5 (mm) to the system control unit 3 (step S63). ). The data input by these operators is transmitted from the system control unit 3 to the reconstruction processing unit 19.
Sent to.

When the data is transmitted, the reconstruction processing unit 1
The slice direction reconstruction filter function selector 35 selects a slice direction reconstruction filter function and a beam thickness based on the tables (1) to (8) and the priority order table (step S65). Here, the slice direction reconstruction filter functions FLT01 and FLT21 are selected, and the beam thickness 2 (mm) is selected. Also, the system control unit 3
, The shooting mode is 4 rows / rotation = 8 (mm) / rev, and the collecting mode is 4 rows. The reconstruction processing unit 19 displays these on the monitor of the display device 21. The operator confirms this and presses the execution key or the "OK" key.

In this state, when the operator inputs a shooting start command from an input device (not shown), the system control unit 3
Is a gantry for controlling the rotation of the rotary gantry 5a, the adjustment of the collimator 5b, and the feed speed of the couch 5c, and outputs a couch control signal to the gantry and the couch control unit 5 and controls the generation of X-ray beams. Is output to the X-ray controller 7. When the gantry / bed control signal is output, the gantry / bed control unit 5 rotates the rotating gantry 5a, adjusts the collimator 5b based on the gantry / bed control signal, and further feeds the bed 5c. To adjust. When the X-ray beam generation control signal is output, the X-ray controller 7 causes the high voltage generator 9 to generate a high voltage. In addition, the system control unit 3 outputs a detector row switching signal for switching a detector row for collecting projection data to the switching unit 15 and outputs a data collection control signal indicating data collection timing to the data collection unit. 17 is output. When this detector row switching signal is output,
The switching unit 15 switches so that the detection signals can be collected from eight columns of the third to tenth columns.

As a result, the X-ray beam is emitted from the X-ray beam source 11, the bed 5c is moved, and photographing by helical scan is started. This allows
The X-ray beam is emitted from the X-ray beam source 11, and the bed 5c is moved to start imaging by helical scan. When the data collection control signal is output, the data collection unit 17 converts the detection signal detected by the detector 13 into a digital signal and collects it as projection data at a predetermined timing.

At this time, the X-ray beams are applied to the X-ray beam source 11 in eight columns from the third column to the tenth column under designated conditions.
And data is collected by the data collection unit 17.

In this case, since the data of the unequal eight columns is collected, the data collection unit 17 processes the detection signals of the third column by the first data and the detection signals of the fourth, fifth, and sixth columns by data processing. (Addition or average, etc.) to obtain the second data.
Data processing (addition or averaging, etc.) is performed on the detection signals in the 8th and 9th columns, and the 3rd data and the detection signals in the 10th column are simultaneously collected as the 4th data in the 4th column. The data collection unit 17 performs various corrections such as X-ray intensity correction and detector sensitivity correction on the collected projection data. Here, a helical scan is repeatedly performed in a specified range at predetermined intervals. In this example, a slice direction reconstruction filter function is selected corresponding to the elapsed imaging time.

For example, since the movement of the contrast agent corresponds to the body movement in the early stage of the contrast, an artefact occurs, and in addition to the importance of the change in the way the contrast agent is stained, the slice direction reconstruction processing unit 23 , Using the narrow slice direction reconstruction filter function FLT01 with priority on the time resolution,
Further, only the projection data of 180 degrees + fan angle is interpolated (steps S69 and S71).

When the projection data is interpolated by the slice direction reconstruction processor 23, the reconstruction function processor 27 performs a convolution process on the interpolated projection data and the reconstruction function FC2. Then, the centering processing unit 31a
, The image is once back-projected to a predetermined centering axis, and then back-projected to each pixel constituting the image data by the back-projection unit 31b to reconstruct the image data (step S73).

Here, in the early stage of the imaging, reconstruction is performed based on the projection data of 180 ° + fan angle, so that the effective scan time is about half of one rotation, and good image data with high time resolution can be obtained. Then, the image data reconstructed by the reconstruction processing unit 19 is sequentially supplied to the display device 21 and displayed on the monitor of the display device 21 (Step S).
75).

In the middle and late stages of the contrast, the contrast medium is distributed almost stably, and it is desired to examine in detail how to stain with image data having a good S / N ratio. Direction reconstruction filter function F
The projection data is interpolated using the LT 21 (step S6).
9, S71).

When the projection data is interpolated by the slice direction reconstruction processing section 23, the reconstruction function processing section 27 performs a convolution process on the interpolated projection data and the reconstruction function FC2. Then, the centering processing unit 31a
, The image is once back-projected to a predetermined centering axis, and then back-projected to each pixel constituting the image data by the back-projection unit 31b to reconstruct the image data (step S73).

Since normal reconstruction is performed in the middle and late stages of the contrast, image data having a high S / N ratio and a low-contrast rendering ability can be obtained. Then, the reconstruction processing unit 1
The image data reconstructed by step 9 is sequentially supplied to the display device 21 and displayed on the monitor of the display device 21 (step S75). The doctor performs image interpretation on the monitor of the display device 21.

As described above, in the X-ray CT apparatus according to the second embodiment, the thickness of the beam to be collected and the slice direction reconstruction filter function are automatically set according to the image conditions such as the effective slice thickness and the image quality. Thus, in addition to the effects of the first embodiment, the burden on the operator can be reduced.

In the first and second embodiments, the detector 13 having a plurality of detector rows having different heights in the Z-axis direction is used, but the present invention is not limited to this. 36 (C), a plurality of detector rows having the same height in the Z-axis direction (for example, when the height in the Z-axis direction is 1).
The detector 13 having (20 (mm) detector rows) may be used.

In this case, as shown in, for example, FIGS. 28A to 28D, image conditions such as an effective slice thickness and image quality of target image data are selected from among slice direction reconstruction filter functions having different filter widths. , The slice direction reconstruction filter function is selected. At this time, as shown in FIG. 28A, the effective slice thickness of the target image data is 2 (m) as a slice direction reconstruction filter function in the slice direction reconstruction filter function storage unit 25 in advance.
m), for the target image data having an effective slice thickness of 3 (mm) as shown in FIG. 28 (b), and for the target image data as shown in FIG. 28 (c). An effective slice thickness of 5 (mm) and an effective slice thickness of target image data of 10 (m) as shown in FIG.
m) are stored, and the one corresponding to the image condition is selected from these. Further, as in the case of the above-described second embodiment, the slice direction reconstruction filter function may be automatically selected in accordance with the image condition.

Although the first and second embodiments use the slice direction reconstruction filter function as shown in FIGS. 5 to 18, the present invention is not limited to this. A directional filter function may be used.

For example, FLT0, FLT1, FLT2, FLT3 are stored in the slice direction reconstruction filter function storage unit 25.
Those having the four filter strengths are stored in advance.
These slice direction reconstruction filter functions FLT0, FLT
The resolution in the slice direction of FLT1, FLT2, and FLT3 deteriorates as the number increases from FLT0. For example, for the slice direction reconstruction filter function FLT3, image data for 5 images (5 images) is added, for FLT2, image data for 3 images is added, and for FLT1, image data for 1 image is added. Also, FLT0 is equivalent to a so-called deconvolution process in which high-pass filter processing is performed in the slice direction on the same pixel.

Here, for example, with a four-row detector, 2 (mm) × 4
It is assumed that scanning is performed at a bed feed speed of 8 (mm / rev) with a row of 8 (mm) beams. In this case, in the reconstruction process 19, the image data is reconstructed at intervals of 1 (mm). At this time, when the image pitch is specified by the operator as 2 (mm), the reconstruction processing unit 19 uses FLT2 as the slice direction reconstruction filter function, and calculates the slice position of each slice position by the following equation (1). Create image data.

[0148]

(Equation 1) The image data reconstructed by the reconstruction processing unit 19 is sequentially supplied to the display device 21 and displayed on the monitor of the display device 21 for interpretation by a doctor.

Basically, the smoothing process (bundling process) in the slice direction is performed by image addition, and the sharpening process in the slice direction is performed by a high-pass filter / deconvolution process in the slice direction of the same pixel. It is. Therefore, the present invention can be applied to a single slice CT. When adjacent image data is created, image data may be created by the difference addition method of the following equation (2).

[0150]

(Equation 2) Incidentally, the preceding numeral is not limited to this.

Next, a third embodiment of the X-ray CT apparatus according to the present invention will be described. The configuration of the X-ray CT apparatus according to the third embodiment is the same as that of the X-ray CT apparatus according to the second embodiment.
Illustration and detailed description are omitted.

In the X-ray CT apparatus according to the third embodiment, as shown in FIG.
The present invention is also applicable to a case where a static scan for obtaining projection data by rotating by 0 degrees is performed. Therefore, the slice direction reconstruction filter function storage unit 25 stores
In addition to the slice direction reconstruction filter functions in the second embodiment, the slice direction reconstruction filter functions FLT-A, FLT-B, FLT-C, FLT- as shown in FIG.
D and FLT-E are stored in advance.

The slice direction reconstruction filter function FLT−
A is a normally used one (normal mode), and FIG.
0, as shown in FIG. 31, the first data is data 1, the second data is
The data is data 2, the third data is data 3, and the fourth data is data 4. Slice direction reconstruction filter function F
LT-B is a bundle mode, and as shown in FIGS. 30 and 32, data 1 is obtained by adding the first data and the second data, and data 2 is obtained by adding the third data and the fourth data. . The slice direction reconstruction filter function FLT-C is:
In the bundle mode, as shown in FIG. 30, the first data, the second data, the third data, and the fourth data are added to obtain data 1. Slice direction reconstruction filter function FLT-
In D, as shown in FIG. 30, the first data is data 1, the second data and the third data are added to make data 2 and the fourth data are data 3. As shown in FIG. 30, the slice direction reconstruction filter function FLT-E performs addition processing on the second data and the third data to obtain data 1 (the first data and the second data are not used).

Next, the operation of the third embodiment will be described with reference to FIG. First, the operator places the subject on the bed 5c and inputs patient information such as a patient ID and a name using an input device (not shown), and then prepares for an examination by photographing a scanogram (step S81). The imaging range (150 (mm)) in the body axis direction is determined based on the scano image, the FOV size is set to the S size, the tube current is 300 (mA), and the tube voltage is 120 (k).
V), input the reconstruction function as FC4 for the head. The operation up to this point is the same as the operation of the conventional X-ray CT apparatus.

Further, the operator uses the input device (not shown) to input a subject to be photographed as a head image to the system control unit 3, set the effective slice thickness of the target image to 4 (mm), and set the photographing mode to the skull. Static high quality mode in the bottom area,
At the top of the head, a static high-speed mode is input (step S83). The data entered by these operators
It is transmitted from the system control unit 3 to the reconstruction processing unit 19.

When the data is transmitted, the reconstruction processing unit 1
In step 9, the collection mode and the like are set for each area. That is, in the skull base region, the beam thickness is 2 (mm), the acquisition mode is 4 rows acquisition, the bed feed is 8 (mm / step), and the slice direction reconstruction filter function is FLT-B in the bundle mode. In the crown area, the beam thickness is 4 (mm), the acquisition mode is 4 rows, the couch feed is 16 (mm / step), and the slice direction reconstruction filter function is FLT-A in the normal mode (step S85). . The reconstruction processing unit 19 displays these on the monitor of the display device 21. The operator confirms this and presses the execution key or the "OK" key.

In this state, when a photographing start command is input from an input device (not shown) by the operator, the system control unit 3
Is a gantry for controlling the rotation of the rotary gantry 5a, the adjustment of the collimator 5b, and the feed speed of the couch 5c, and outputs a couch control signal to the gantry and the couch control unit 5 and controls the generation of X-ray beams. Is output to the X-ray controller 7. When the gantry / bed control signal is output, the gantry / bed control unit 5 rotates the rotary gantry 5a, adjusts the collimator 5b based on the gantry / bed control signal, and further moves the step of the bed 5c. To adjust the distance and timing. When the X-ray beam generation control signal is output, the X-ray controller 7 causes the high voltage generator 9 to generate a high voltage. Thus, shooting by static scan is started.

Here, the system control unit 3 moves the couch 5c by 8 (mm) for each scan in the skull base region and by 16 (mm) for each scan in the crown region. Further, the collimator 5b is controlled in accordance with the required irradiation width to control the opening width to reduce unnecessary exposure, and the switching unit 15 is switched so that the data collection unit 17 collects necessary data.
In addition, the data collection unit 17 adds
Various corrections such as X-ray intensity correction and detector sensitivity correction are performed (step S87).

After the projection data is collected by the data collection unit 17 and various corrections are made, the slice direction reconstruction processing unit 23 of the reconstruction processing unit 19 adjusts the slice direction reconstruction filter function according to the set slice direction reconstruction filter function. Obtain projection data.

Here, in the skull base region, as shown in FIG. 31, the first data and the second data are added using the slice direction reconstruction filter function FLT-B, and the data 1, the third data and the fourth data are processed. Data 2 is obtained by adding data.

In the parietal region, as shown in FIG. 32, the first data is data 1, the second data is data 2, and the third data is data 3 using the slice direction reconstruction filter function FLT-A.
The data is data 3 and the fourth data is data 4 (step S89).

When the projection data is interpolated by the slice direction reconstruction processor 23, the reconstruction function processor 27 performs a convolution process on the interpolated projection data and the reconstruction function FC4. Then, the centering processing unit 31a
, The image is back-projected once to a predetermined centering axis, and then back-projected to each pixel constituting the image data by the back-projection unit 31b to reconstruct the image data (step S91).

At this time, in the skull base region, 4 (mm) thick image data is obtained by the partial effect corresponding to the 2 (mm) thick image data. In addition, in the parietal region, since four slices can be obtained at one time, the scan time can be reduced.

The image data reconstructed by the reconstruction processing unit 19 is sequentially supplied to the display device 21 and
(Step S93). The slice position of the image data near the skull base is between the slice positions of the first data and the second data as indicated by arrows at the center and right side of FIG. The image reconstruction pitch at this time is 4 (m
m). Then, the doctor performs image interpretation on the monitor of the display device 21.

Here, the doctor wants to reconstruct the current image pitch finely in order to find an abnormal shadow when reading the image data of the skull base and to compare and read the image data obtained by the previous examination. In this case, the doctor sets the image reconstruction pitch to 2 (mm) and instructs reconstruction retry (step S).
95YES).

As a result, the reconstruction processing unit 19 performs filter processing in the slice direction using the slice direction reconstruction filter function obtained by changing the combination of projection data addition processing as shown on the right side of FIG. Image data having a thickness of 4 (mm) at the slice position indicated by the arrow on the right side is obtained (steps S89 and S91).

Then, the image data reconstructed this time and the image data reconstructed last time are combined, and the reconstructed pitch 2
(Mm) and are sequentially displayed on the monitor of the display device 21 (step S93).

As described above, in the X-ray CT apparatus according to the third embodiment, the slice direction reconstruction filter function storage 25
The slice direction reconstruction filter function for static scan is stored in the memory, and the slice direction reconstruction filter is selected in accordance with the imaging target, the beam thickness, and the characteristics of the target image. Can be obtained in an appropriate number.

In each of the first, second, and third embodiments, the reconstruction function and the slice direction reconstruction filter function are not limited to the above examples. For example, the slice direction reconstruction filter The shape of the function (width and weight)
Any shape may be used.

Further, in both the first embodiment and the second embodiment,
The present invention can also be applied to a single slice CT using filter interpolation. Further, in both the first embodiment and the second embodiment, the slice thickness is not limited to the above example. For example, when the slice thickness is 4 (mm), ten slices from the second row to the eleventh row are used. Is exposed to an X-ray beam to collect data. That is, data is collected only in the hatched columns in FIG. In this case, since data of ten unequal columns is collected, the four data in the third, fourth, fifth, and sixth columns are processed (addition or averaging, etc.) to obtain second data.
Similarly, the data in the seventh, eighth, ninth, and tenth columns are processed and the third
Data. That is, the second column is the first data, the third, fourth, fifth and sixth columns are the second data, the seventh, eighth, ninth and tenth columns are the third data, the eleventh column is the fourth data, and the first, second, and third data , 4 data are collected simultaneously. Further, in the first and second embodiments, the filter interpolation method using the opposite beam has been described as an example of the interpolation method.
The present invention is not limited to this, and for example, a combination of the adjacent interpolation method and the filter interpolation method may be used.

Furthermore, the shape (width and weight) of the slice direction reconstruction filter function is not limited, and may be any shape (width and weight).

Further, in the first and second embodiments, the case where the unequal 12-row detector 13 is used has been described as an example. However, the present invention is not limited to this. Four-row sampling may be used.
Collection by other shapes such as a zero-row detector may be used. Further, a linear multi-slice detector or a plane detector may be used.

Furthermore, in the first and second embodiments, the slice direction reconstruction filter function has been described using the function forms shown in FIGS. 5 to 18. However, the present invention is not limited to this. Expression method may be used. For example, it is assumed that the interpolation data of the target slice position (Z0) is obtained as shown in the following expression (3), and the interpolation data of a plurality of slice positions (Z = Z0 + Δk) before and after the target slice position is considered. Considering weighted addition, a slice direction reconstruction filter function may be used with the widths (Δ and k) of the plurality of slice positions (Z = Z0 + Δ k) and the weight W (k).

[0174]

(Equation 3)

[0175]

As described above, according to the first aspect of the present invention, an X-ray beam is emitted from an X-ray beam source, and data on a target slice is detected by a detecting means. Since the acquisition is performed using the slice direction reconstruction filter function that makes the resolution in the slice direction variable based on the signal, it is possible to provide high-quality image data in an appropriate number.

According to the second aspect of the present invention, the X-ray beam is generated while rotating the X-ray beam generation source, and the couch is moved by the couch moving means. Since interpolation is performed using a slice direction reconstruction filter function that varies the resolution in the slice direction based on the detection signal detected by the detection unit, it is necessary to provide high-quality image data in an appropriate number. Becomes possible.

Further, according to the third aspect of the present invention, the couch is moved intermittently in the opposite axial direction of the subject by the couch moving means, and the X-ray beam is generated while rotating the X-ray beam source. A slice direction reconstruction filter function for causing a detection signal at a predetermined slice position to be detected by a detection unit, and for changing data on a target slice based on the detection signal detected by the detection unit, and changing a resolution in a slice direction. Therefore, it is possible to provide high-quality image data in an appropriate number.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of a detector.

FIG. 3 is a block diagram illustrating an internal configuration of a reconstruction processing unit.

FIG. 4 is a diagram showing characteristics and characteristics of a slice direction reconstruction filter function.

FIG. 5 shows a slice direction reconstruction filter function (FLT0)
FIG.

FIG. 6 shows a slice direction reconstruction filter function (FLT0)
It is a figure which shows 1).

FIG. 7 shows a slice direction reconstruction filter function (FLT0).
FIG.

FIG. 8 shows a slice direction reconstruction filter function (FLT0
It is a figure which shows 3).

FIG. 9 shows a slice direction reconstruction filter function (FLT1).
It is a figure which shows 1).

FIG. 10 shows a slice direction reconstruction filter function (FLT1).
FIG.

FIG. 11 shows a slice direction reconstruction filter function (FLT1).
It is a figure which shows 3).

FIG. 12 shows a slice direction reconstruction filter function (FLT2
It is a figure which shows 1).

FIG. 13 shows a slice direction reconstruction filter function (FLT2
FIG.

FIG. 14 shows a slice direction reconstruction filter function (FLT2
It is a figure which shows 3).

FIG. 15 shows a slice direction reconstruction filter function (FLT3
It is a figure which shows 1).

FIG. 16 shows a slice direction reconstruction filter function (FLT3
FIG.

FIG. 17 shows a slice direction reconstruction filter function (FLT3
It is a figure which shows 3).

FIG. 18 shows a slice direction reconstruction filter function (FLT4
It is a figure which shows 1).

FIG. 19 is a flowchart showing a flow of an operation (first inspection and third inspection) of the first embodiment.

FIG. 20 is a diagram showing a detector array for collecting data.

FIG. 21 is a flowchart showing a flow of an operation (second inspection) of the first embodiment.

FIG. 22 is a block diagram illustrating a configuration of a reconstruction processing unit of an X-ray CT apparatus according to a second embodiment of the present invention.

FIG. 23 is a table showing slice direction reconstruction filter functions corresponding to a plurality of image conditions.

FIG. 24 is a table showing slice direction reconstruction filter functions corresponding to a plurality of inspection conditions.

FIG. 25 is a table showing the priority order of image conditions and inspection conditions.

FIG. 26 is a flowchart showing the flow of the operation of the second embodiment.

FIG. 27 is a flowchart showing the flow of the operation of the second embodiment.

FIG. 28 is a diagram showing another slice direction reconstruction filter function.

FIG. 29 is a diagram illustrating a static scan.

FIG. 30 is a diagram showing a slice direction reconstruction filter function for static scan.

FIG. 31 is a flowchart showing the flow of the operation of the third embodiment.

FIG. 32 shows a slice direction reconstruction filter function FLT-B.
FIG.

FIG. 33 shows a slice direction reconstruction filter function FLT-A.
FIG.

FIG. 34 shows a slice direction reconstruction filter function FLT-B.
FIG. 6 is a diagram showing a process performed by the STA and a slice position.

FIG. 35 is a block diagram showing a schematic configuration of a conventional example.

FIG. 36 shows a single slice CT and a double slice CT
FIG. 4 is a schematic diagram showing a multi-slice CT.

FIG. 37 is a circuit diagram showing an internal configuration of (1) shown in FIG. 1;

FIG. 38 is a diagram for explaining FCD, FOV, and FDD.

FIG. 39 is a diagram (scan diagram) showing a helical scan by writing the rotational phase on the vertical axis and the direction of the Z axis (body axis) on the horizontal axis.

FIG. 40 is a diagram for explaining a 360-degree interpolation method and a counter beam interpolation method.

FIG. 41 is a diagram showing a slice profile.

FIG. 42 is a diagram showing a reconstruction function.

FIG. 43 is a diagram showing characteristics of the reconstruction functions (FC1, FC5).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray CT apparatus 3 System control part 5 Stand, bed control part 5a Rotating stand 5b Collimator 5c Bed 7 X-ray controller 9 High voltage generator 11 X-ray beam source 13 Detector 15 Switching part 17 Data collecting part 19 Re Configuration processing unit 21 Display device 23 Slice direction reconstruction filter function processing unit 25 Slice direction reconstruction filter function storage unit 27 Reconstruction function processing unit 29 Reconstruction function storage unit 31 Image reconstruction unit 33 Control unit 35 Slice direction reconstruction filter Function selector

Claims (6)

[Claims] An X-ray for irradiating an X-ray beam toward a subject
X-ray beam source, detection means for detecting an X-ray beam emitted from the X-ray beam source as a detection signal, and a filter function for changing the resolution in the slice direction as a slice direction reconstruction filter function Slice direction reconstruction filter function storage means for storing a plurality of, X-ray beam is emitted from the X-ray beam source, data on the target slice, based on the detection signal detected by the detection means, An X-ray CT apparatus, comprising: processing means for acquiring using a slice direction reconstruction filter function stored in the slice direction reconstruction filter function storage means. 2. An X-ray for irradiating an X-ray beam toward a subject
X-ray beam source, detection means for detecting the X-ray beam emitted from the X-ray beam source as a detection signal, and filter functions having different shapes in the slice direction to make the resolution in the slice direction variable. A slice direction reconstruction filter function storage means for storing a plurality of filter functions as a filter function; a bed moving means for moving a bed on which the subject is placed in the body axis direction of the subject; and rotating the X-ray beam source. While generating an X-ray beam, moving the couch by the couch moving means, and extracting data on a target slice based on the detection signal detected by the detection means. Processing means for performing interpolation using a slice direction reconstruction filter function stored in the X-ray CT apparatus. 3. An X-ray for irradiating an X-ray beam toward a subject
X-ray beam source, detection means for detecting the X-ray beam emitted from the X-ray beam source as a detection signal, and filter functions having different shapes in the slice direction to make the resolution in the slice direction variable. A slice direction reconstruction filter function storage means for storing a plurality of filter functions as filter functions; a bed moving means for moving a bed on which the subject is placed in a body axis direction of the subject; and a bed moved by the bed moving means. Moving the X-ray beam generating source intermittently, generating an X-ray beam while rotating the X-ray beam generating source, and detecting a detection signal at a predetermined slice position by the detecting means, thereby obtaining data on a target slice. The slice direction reconstruction filter stored in the slice direction reconstruction filter function storage means based on the detection signal detected by the detection means. An X-ray CT apparatus, comprising: processing means for acquiring using a Luther function. 4. A selection for selecting a slice direction reconstruction filter function corresponding to a target image condition and an inspection condition from among slice direction reconstruction filter functions stored in the slice direction reconstruction filter function storage means. The X-ray CT apparatus according to any one of claims 1 to 3, further comprising means. 5. The slice direction reconstruction filter function storage means stored in the slice direction reconstruction filter function storage means based on a detection signal detected by the detection means, the processing means comprising: A predetermined slice direction reconstruction filter function is obtained from among the filter functions, and then the data on the target slice is re-used using the slice direction reconstruction filter function corresponding to the target image condition and the inspection condition. The X-ray CT apparatus according to any one of claims 1 to 3, wherein the X-ray CT apparatus is acquired. 6. The slice direction reconstruction filter function storage means stored in the slice direction reconstruction filter function storage means on the basis of a detection signal detected by the detection means. The X-ray according to claim 2, wherein the X-ray is acquired from a filter function using a slice direction reconstruction filter function corresponding to a slice thickness of target image data and a detection signal detected by the detection unit. CT device.