JP2000070258A - X-ray ct device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT device capable of obtaining the tomographic image of an appropriate space resolution by setting the parameter and data of a filter processing corresponding to an arbitrarily set display visual field. SOLUTION: This X-ray CT device is provided with a scanner 5 provided with an X-ray source 1 and an X-ray detector 2 arranged oppositely to the X-ray source 1 for scanning the periphery of an examinee body 3 and obtaining projection data, a console 9 for setting the size of the display visual field (FOV) of the tomographic image for obtaining and displaying the tomographic image of the examinee body 3, an image computation part 7 for reconstituting and computing the tomographic image resulting from making the projection data obtd. by the scanner 5 correspond to the size of the FOV set by the console 9, and image display part 8 for displaying the tomographic image computed by the image computation part 7 on a screen, and a general control part 10 for performing read control from a parameter memory for a filter so as to change a variable used for an image reconstitution filter processing used in the image display part 8 based on the size of the FOV set by the console 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus for performing a filtering process used in a reconstruction operation for obtaining a tomographic image from projection data of a subject, and particularly to a display field of view (FOV: FOV) of the tomographic image. F ield O f V iew) of the filtering process in accordance with the size is improved, as is done properly X
The present invention relates to a line CT apparatus.

[0002]

2. Description of the Related Art A conventional X-ray CT apparatus includes an X-ray source for irradiating an X-ray to an object placed on a bed, and an X-ray detector arranged opposite to the X-ray source to detect X-rays transmitted through the object. And a scanner equipped with a scanner. The scanner scans around the subject to collect a plurality of projection data, and a tomographic image of the subject is image-reconstructed from the projection data.

In such an X-ray CT apparatus, when an operator sets a part of a subject such as a head and an abdomen on a console, parameters of a filter process at the time of image reconstruction are also set at the same time. For example, in the filter processing of the tomographic image for the head, since a fine spatial resolution of the brain or the like is required, it has been set to use a parameter having a higher spatial resolution than the filter for the abdomen.

[0004]

However, in the conventional X-ray CT apparatus, the FOV can be arbitrarily set by the operator. When a large FOV tomographic image is reconstructed using the parameters of the filter processing described above, there is a problem that granular noise is conspicuous, and a small change in density may be mixed with the granular noise.

[0005] Further, when a tomographic image of a small FOV is reconstructed by using abdominal filter processing parameters, there is a problem that a tomographic image having a small change in CT value may not be displayed properly.

The present invention has been made to solve the above problems, and has as its object to arbitrarily set a display field of view (FOV).
An object of the present invention is to provide an X-ray CT apparatus capable of obtaining a tomographic image having an appropriate spatial resolution by setting parameters and data of a filtering process corresponding to the above.

[0007]

An object of the present invention is to provide a scanner which has an X-ray source and an X-ray detector arranged opposite to the X-ray source and scans around a subject to obtain projection data; Display field size setting means for setting the size of the display field for obtaining and displaying a tomographic image of the sample, and the size of the display field set by the display field size setting means for projecting data obtained by the scanner. Means for reconstructing the tomographic image associated with the display means, display means for displaying on the screen the tomographic image computed by the reconstruction computing means,
Means for changing a variable used for image reconstruction filter processing used in the reconstruction calculating means based on the size of the display field of view set by the display field size setting means. Achieved by the device.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the X-ray CT apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram of the X-ray CT apparatus according to the embodiment of the present invention.

As shown in FIG. 1, an X-ray CT apparatus according to the present invention comprises an X-ray source 1, an X-ray detector 2 disposed opposite a subject 3 placed on a bed 4, and an X-ray detector 2. A scanner 5 having a brush and a slip ring constituting a power supply unit of the source 1 and a signal extraction unit of the X-ray detector 2 is electrically connected to the X-ray source 1 via the power supply unit of the scanner 5. A high-voltage power supply 6 and an image calculation unit 7 electrically connected to the X-ray detector 2 via the signal extraction unit of the scanner unit 5
And an image display unit 8 electrically connected to the image calculation unit 7
And a general control unit 10 electrically connected to each of the bed 4, the scanner unit 5, the high voltage power supply 6, the image display unit 8 and the console 9.

An X-ray source 1 irradiates a subject 3 with X-rays. X
The X-ray detector 2 detects X-rays transmitted through the subject 3. The bed 4 places the subject 3 thereon. The scanner 5 rotates the X-ray source 1 and the X-ray detector 2 around the subject 3. The high-voltage power supply 6 supplies the X-ray source 1 with different conditions of tube voltage, tube current, and application time to the X-ray source 1 adapted to imaging. The image calculation unit 7 places the subject 3 on the bed 4 and emits X-rays from the X-ray source 1 to the subject 3 while rotating the X-ray source 1 and the X-ray detector 2 around the subject 3. A tomographic image at a desired tomographic plane position is reconstructed from a plurality of projection data collected in this way. The image display unit 8 displays the tomographic image reconstructed by the image calculation unit 7.
The operator inputs various display conditions, such as the FOV of the tomographic image, to the image display unit 8 of the console 9. The overall control unit 10 controls the rotation of the scanner 5, the setting of the voltage and current of the high-voltage power supply 6, the setting of the application time, and the image reconstruction of the image calculation unit 7, and based on the display conditions input to the console 9. Then, the image display unit 8 is controlled.

Next, the configuration of the image calculation unit 7 in FIG. 1 will be described with reference to FIG. FIG. 2 shows the image calculation unit 7 of FIG.
3 is a functional block diagram of FIG.

As shown in FIG. 2, the image calculation unit 7 includes a filter parameter memory 7a electrically connected to the overall control unit 10, and a measurement data memory 7b electrically connected to the X-ray detector 2. And the filter parameter memory 7
a, an image reconstruction calculation unit 7c electrically connected to the measurement data memory 7b and the image display unit 8.

The filter parameter memory 7a stores filter parameters corresponding to the part of the subject in advance, indicates the address of the parameter corresponding to the FOV by the general control unit 10, and stores the parameter from the indexed address. It is read out and output to the image reconstruction calculation unit 7c. The reading at this time includes reading the parameters as interpolation data, such as appropriately changing the update value of the address value.

Further, the updated value of the read address of the parameter may be multiplied and read. The measurement data memory 7b stores the projection data from the X-ray detector 2, and outputs the stored projection data to the image reconstruction calculation unit 7c.
The image reconstruction calculation unit 7c performs a calculation for reconstructing a tomographic image from the projection data of the subject, and outputs the tomographic image to the image display unit 8. The operation for reconstructing this tomographic image includes a filtering process.

Next, the operation of the X-ray CT apparatus according to this embodiment will be described. The general control unit 10 puts the subject 3 on the bed 4 and emits X-rays from the X-ray source 1 to the subject 3 while rotating the X-ray source 1 and the X-ray detector 2 around the subject 3. To control the scanner 5 to collect a plurality of projection data,
The image calculation unit 7 is controlled so that the projection data is stored in the measurement data memory 7a. The operator goes to the console 9
The OV is set, and the FOV data is output to the filter parameter memory 7a via the overall control unit 10. The image reconstruction calculation unit 7c performs image reconstruction calculation including filter processing from the projection data stored in the measurement data memory 7b and the filter parameters corresponding to the FOV data stored in the filter parameter memory 7a, and performs a tomographic image. And outputs the tomographic image to the image display unit 8. The overall control unit 10 controls the image display unit 8 to display the tomographic image output from the image reconstruction calculation unit 7c on the image display unit 8.

Further, it was confirmed by the following experiment that an appropriate spatial resolution was obtained by the filter processing of the present embodiment. (1) When the pitch per pixel of the tomographic image to be reconstructed is smaller than the channel pitch of the detector, interpolation of the filter processing parameters is not performed. (2) When the pitch per pixel of the tomographic image to be reconstructed is larger than the channel pitch of the detector, interpolation of filter processing parameters is performed.

Thus, when the FOV is small, a clear image can be obtained without losing the spatial resolution.
Is large, it is possible to obtain a tomographic image capable of suitably observing a minute change in the CT value.

[0018]

The present invention has the effect of providing an X-ray CT apparatus capable of obtaining a tomographic image having an appropriate spatial resolution by setting parameters and data for filter processing corresponding to an arbitrarily set FOV. Play.

[Brief description of the drawings]

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

FIG. 2 is a functional block diagram of an image calculation unit in FIG. 1;

[Explanation of symbols]

 7 Image calculation unit 7a Parameter memory for filter 10 General control unit

Claims (1)

[Claims] 1. An X-ray source and an X-ray arranged opposite to the X-ray source
A scanner having a line detector and scanning around the subject to obtain projection data, a display field size setting means for setting a display field size for obtaining and displaying a tomographic image of the subject, and Means for reconstructing a tomographic image corresponding to the size of the display field of view set by the display field size setting means on the projection data obtained by the scanner; Display means for displaying on a screen, and means for changing a variable used for image reconstruction filter processing used in the reconstruction calculation means based on the size of the display field of view set by the display field size setting means. X characterized by the following:
Line CT device.