JPS6024822A - Dynamic ct apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This α-mei belongs to the technical field of X-ray diagnostic equipment, and more specifically, it produces tomographic images by performing a CT scan while giving a contrast agent to a subject. The present invention relates to a dynamic CT device.

[Technical background of the invention and its problems]

In recent years, with the increase in the speed of X-ray CT scanners, 614 dynamic scans have been developed to track changes in contrast agent concentration over time in the trough region of the subject by scanning the subject over time while applying a contrast agent to the subject. has begun to be practiced.

In conventional dynamic scanning, as shown in Fig. 1, a relative -1 quadrature data base (tk) ( However, ■(−
1, 2, ......, n), the detection data output from the X-ray detection system is A/D converted and the data obtained by log shaking is 1t (tk) (ri Dashi, k=0
．． 1. Image reconstruction processing is performed on the projection data obtained by subtracting the calibration data C (usually water data) from the absolute image P(tk) (however, k=0.1.2,...
. . . , n) is obtained. Note that here, P (t o
) is the data of the tomographic image of the subject when the contrast medium has not yet reached the predetermined site within the subject, and P (t t
), P (t 2 ) ...... is lj inside the subject, the contrast agent reaches a fixed site, and the contrast agent concentration changes over time. Next, the contrast image data P(t,), 1(t2)
・---P (tn) to -no [layered data P (t
o ), a series of relative image data P
'(tk).

However, as mentioned above, conventional dynamic scanning requires two subtraction processes for each data in addition to the reconstruction process, which not only prolongs the calculation time but also requires limited projection processing. Data (180°+
Segment images that are reconstructed by creating all projection data (660°) through projection interpolation (fan angle) have a problem in that artifacts that depend on the angular component of the data are likely to occur due to the interpolation process.

[Purpose of the invention]

This invention was made in view of the circumstances of the AiJ article, and it is possible to directly obtain relative image data, which is the final data necessary for dynamic studies, in 1' and 6 speeds.
It is an object of the present invention to provide a dynamic CT apparatus irt that can also remove artifacts from segment images.

[Summary of the invention]

1) The steps of this invention to achieve the purpose of IJ are:
In a dynamic CT system, a contrast medium is administered to the subject to contrast a specific site within the subject, while projection data is obtained by an X-ray CT scan, and the image is reconstructed based on the projection data to obtain a subtraction system. A first memory that stores projection data of The apparatus is characterized by comprising a subtraction means for using the subtraction data obtained in image reconstruction for image reconstruction.

[Embodiments of the invention]

FIG. 2 is a schematic block diagram showing one embodiment of the present invention.

In Fig. 2, 1 is the first switch,
X-ray data output from the X-ray detection system is input, and the input X-ray data is stored in the first memory 2 and the second memory 6 according to the type 1 by the open side 1 of the controller (not shown).
and output to the sixth memory 4.

The first memory 2 records the contrast r+! from the X-ray data after the contrast medium reaches the I-tsu-1 foot region within the subject. IrIL
When the degree changes over time, the data that gives J-i the 6'L image\\%%χ\R(it),..., 1 is also ([
. ) is a frame memory with case Ivj. The second memory 6 stores a cross section R of the X-ray data before the contrast agent reaches a predetermined position 1-1 within the subject. This is a frame memory that stores calibration data.

Reference numeral 5 designates a second switch which, under the control of a controller (not shown), selects either data 11 (tQ) or calibration data stored in the second memory 4 and the sixth memory 4, respectively. is output to the subtractor B (11η configuration, and the calibration data is transferred during the normal scan, and the data R(to) is transferred during the dynamic scan. Data i(,(
1), 几(t2)...R(t n, ) has a configuration in which data 几(10) transferred via the second switch 5 is subtracted. 7 is an image reconstruction device,
We will introduce a configuration in which the subtraction image is reconstructed using the data output from the subtraction device 6. 8 indicates the fourth
data P'(t l), P'(
t2), . . . p'(t,) is stored therein.

With the above configuration, the X output from the X-ray detection system
Of the ray data, the X-ray data that gives a contrast image is stored in the first memory 2, and the data that gives a tomographic image before reaching the contrast M'l is stored in the second memory. 6, the data R(tl) stored in the first memory 2,
The take R(to) transferred via the second switch 5 is subtracted from R(t 2 )−=−R(t o), and the image 1 is
The image reconstruction device 7 reconstructs the subtraction image using the data obtained by subtraction, and sequentially adds a contrast agent (li'aPL).
Data P that gives a subtraction image when changes.
'(t 1 ), P'(t 2 )...P'(
tn) in the fourth memory 8 in preparation for a subsequent dynamic study.

As described in 11J, according to the above embodiment, by using only one subtractor 6, it is possible to convert the raw data level to subtraction 1.
Data processing can be performed at high speed because the data can be assembled into multiple images. Further, the data R(t, )) stored in the second memory 6 and the calibration data stored in the sixth memory 4 are subtracted by the subtracter 6, and the image reconstruction device 6 calculates the absolute value by -1. If you reconstruct the image and store the data P(to) that gives an absolute image in the memory of Era 5 (not shown), the data P(to) that gives an absolute -1 image.
Data P giving a subtraction image which is a relative image to
'(t 1), P'(tz),...P'(t n
), data P(t+), P(t2), which easily provides an absolute image in which the contrast agent is imprinted.
...P (t n ) can be obtained.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and can be implemented with appropriate modifications within the scope of the gist of the invention. Needless to say.

In the embodiment described above, what is stored in the first memory 2 and the second memory B is the outer circumference of the subject centered on the body axis of the subject x ff? J? This is projection data obtained when the object rotates once or once, but it may also be projection data that provides segment images.

In other words, the X s that occurs in the segment image
Most of the artifacts that depend on the tube rotation angle arise from areas that are not changed by the contrast agent. The first memory 2 stores data in which the X-ray tube is rotated by a predetermined angle, for example, 210°, around the outer circumference of the subject when the contrast agent concentration changes over time after the contrast agent reaches a predetermined site within the corkscrew. The projection take Rkl (where 1 (corresponds to time +li+, l corresponds to the rotation angle of the X-ray tube) obtained by If the outer circumference of the subject is traced at a predetermined angle before the agent reaches the object, the projection data l(,
From the memory 2 and the second memory ro, the projection take RkA and ■ of the same angle also tiie Ol,
It is also possible to perform legal boundary processing for Rk1-ROe and correct the projection take. In this way, a subtraction image without artifacts can be re-created using segment images at the stage of segment image data. /Yo, subtraction [Elephant 1] (Prior to IL7 formation, it is necessary to interpolate the segment image data and place the data for 60u and the ZERO interpolation processing device in front of the drawing ladle configuration device 7. ,
Needless to say.

〔Effect of the invention〕

According to this invention, high-speed data processing in dynamic scanning can be achieved with a simple configuration without significantly changing the conventional scanner system.
For data based on segment images, it is possible to provide a dynamic CT apparatus that can prevent the occurrence of angle-dependent artifacts. In addition, the relative I [! In 11 cases, artifacts such as shading due to beam hardening around substances with high X-ray absorption coefficients such as bones hardly occur, so it is highly effective in diagnosing YiJ, 9 catties, cerebellum, and bone marrow. A dynamic CT system can be provided. Furthermore, if the base image before contrast is filed separately for 44 images, an absolute image can be obtained by simply adding both base songs to one contrast image, which is a relative image.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional method for obtaining one subtraction image, and FIG. 2 is a block diagram showing an embodiment of this process. 2...First memory, 6...Second memory, 6.
・Subtractor.

Claims (1)

[Claims] X Tsutomu! In a dynamic CT device that obtains projection data through CT scanning, reconstructs an image based on the projection data, and obtains a subtraction image, a first memory stores projection data after contrast imaging and a first memory stores projection data before contrast imaging. and subtraction means for subtracting the projection data read from the second memory from the projection data read from the first (1) memory, and using the obtained subtraction data for image reconstruction. A dynamic CT device characterized by: