JPS6274338A - Automatic zooming ct scanner - 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] The present invention relates to a CT scanner having an auto-zooming means.

(Technical background of the invention) For example, in second-generation CT scanners, area enlarging techniques have been used in the past, but such area enlarging techniques enlarge the data collected by the data collecting unit as shown in FIG. After performing image reconstruction processing at a magnification of 1x to create a cross-sectional image of the entire area of the subject, this cross-sectional image is projected on a CRT display, and the enlarged area is determined visually from the cross-sectional image on the CRT, and the center of enlargement and magnification ratio are determined. By determining this, the user specifies it using a trackball or stick, reconstructs an enlarged image from the raw data, and performs zooming and enlargement display.

[Problems with background technology]

However, in the area enlarging technique described above, the area of interest is enlarged by displaying it on a CRT after performing reconstruction processing using the collected data, so there is a problem in that it takes a long time to enlarge the area of interest. Furthermore, when enlarging a subject that is very small compared to the entire reconstruction area and effectively displaying it on the entire CRT screen, very complicated operations are required, which is not practical.

[Purpose of the invention]

The present invention was made with attention to the above points, and
Since the enlargement i1m is automatically determined from projection data in a predetermined direction, the enlargement center position and enlargement ratio are determined, and an enlarged image is created by reconstruction, the time required for area enlargement processing can be significantly shortened, and artificial An object of the present invention is to provide an auto-zooming CT scanner capable of easily enlarging an area without undergoing extensive operations.

(Summary of the Invention) The present invention extracts projection data in a predetermined direction from a sinogram of collected data collected by a scanning operation and converts it into 2 fli using a threshold setting means.
Expanded VAIIi from this binarized data! This is an auto-zooming CT scanner that determines an enlargement center position and an enlargement ratio by calculation, and performs image reconstruction processing using these enlargement center position data and enlargement ratio data.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 8. FIG. 1 is an overall configuration diagram of a general second generation CT scanner to which the device of the present invention is applied, FIG. 2 is a diagram schematically representing the configuration of the device of the present invention, and FIG. 3 is a diagram showing the operation of the device. A schematic flowchart, FIG. 4 is an explanatory diagram for determining the enlargement center position and enlargement ratio, FIGS. 5 to 7 are diagrams showing projection data at a predetermined angle, and FIG. 8 is a reconstruction means. It is an explanatory diagram.

In FIG. 1, reference numeral 10 denotes a scanner body, in which an annular translation frame 14 is slidably mounted on a guide rail 11.11, on which a radiation generator 12 and a radiation detector 13 are fixedly mounted so as to face each other. , transmits the rotation of the translation drive unit 15 to the translation frame 14 to
3 is configured to translate. Further, the scanner main body 10 is configured such that a rotary table 16 is installed approximately at the center of the translation frame 14, and this rotary table 16 is rotated by a predetermined angle in steps by a rotation drive unit 17. 18 is a radiation beam, 19 is a subject, and 20 is a data acquisition unit.

On the other hand, the control system of the scanner body 10 controls the entire scanner ff1.
A control console 21 performs preprocessing by importing collected data from the data collection unit 20 based on commands from the control console 21, and also performs normal reconstruction processing in cooperation with the image reconstruction processing unit 22. an image processing control means 23 for reconstructing an enlarged area image by determining the enlargement center position and enlargement ratio, and the system console 21;
A mechanism control section 24, a radiation control section 25, etc., which drive the drive sections 15, 17 and the radiation generator 12 using control signals sent from the control section 12 are provided. Although not shown, the image processing control means 23 takes in data from the f-event collecting section 20 using the angle rotation pulses taken out from the drive section 15 and 17 as timing.

26 is a CRT display that displays normal reconstructed images and area enlarged images.

Thus, the image processing control means 23 and the image reconstruction processing section 22 can be represented, for example, in a schematic configuration as shown in FIG. In the figure, 31 is a central processing unit (hereinafter referred to as CPU), from which a bus 32 is derived, and a threshold value setter 34 is connected to this bus 32 via an I10 interface 33. Also, a memory 35 for the purpose of temporarily holding program data, constants for calculations, and processing data, and a data collection unit 2
a pre-processing means 36 for correcting the collected data collected by the pre-processing means 36; an enlargement center and an enlargement ratio for extracting projection data in a predetermined direction from the sinogram corrected by the pre-processing means 36 and calculating an enlargement center position and an enlargement ratio by 1EIii calculation; Further, a calculation means 37, a convolver processing means 38 for performing composition processing, a pack block processing means 39 for performing back projection processing, and the like are provided.

Note that the threshold value setter 34 sets a threshold value δ when binarizing in order to extract and enlarge the material of interest of the subject 19.
This is the part that determines the For example, when iron is embedded in rubber such as a tire, the iron has a high X-ray absorption rate. In this case, it is possible to set a large threshold value and select and enlarge only the portions with high absorption rates. Therefore, threshold 1
The straight line δ is obtained empirically or by calculation from the type and diameter of the material, which is usually ignored, and is stored in the memory 35 from the threshold setting device 34 via the I10 interface 33.

Next, an example in which area enlargement is performed using a CT scanner having the above configuration will be described. First, C of the present invention
The T-scanner performs traverse scanning of both units 12 and 13 via the translation frame 14 by the translation drive unit 15 based on the second generation scanning method as in the past, and rotates by the rotation drive unit 17 after one traverse is completed. The table 1G is rotated in steps of a predetermined angle, and data is collected while repeating these movements.

Then, as shown in step S1 in FIG. 3, the data collected by the data collection unit 20 is preprocessed by the preprocessing means 36 including the CPU 31 to obtain raw data called a sinogram, which is stored in the memory 35. Ru.

After that, as in step S2, projection data in four directions at 45-degree intervals or two directions at 90-degree intervals are extracted from the raw data, an enlarged area is determined from the projection data, and the enlarged center positions RXo and 'SIO are obtained. , find the magnification factor ω.

In other words, the center and radius of the smallest circle that does not allow the subject 19 to protrude is determined. Next, in step S3, the enlargement center position X obtained in step S2 from the raw data
A cross-sectional image having o, yO and magnification factor ω is reconstructed, and this image data is stored in the memory 35 and displayed on the CRT display 26 (step 84).

Next, see FIGS. 4 to 7 for an example in which the expansion center position IFXo, 'I10 and the expansion rate ω are calculated by the expansion center and expansion rate calculation means 37 using projection data in two directions at 90 degree intervals, for example. and explain. First, from the sinogram stored in the memory 35, for example, 0 degree and 90 degree projection data are selected from among the four directions shown in FIG. 5 (step 511), and 0 degree projection data (see FIG. 6). is binarized using the threshold value δ set by the threshold value setter 34, and both ends of the "1" portion at the back of this 211i data are set as Xl and X2 (step 51
2). However, an appropriate value for the threshold value δ at this time is 5 to 10 times the rms noise of the air portion.

Then, as shown in step 813 and FIG.
To enlarge the area ftXt,X2, double it by a factor. The multiplied att at this time is Xl.

Assuming X2, X2 = ((X2-Xt) y'2't+k (
(X2-Xt ＞/2)...(1))l
= ((X2-Xt)/2)-k ((X2-X2
), ·'2)...It can be determined by (2).

Next, for the 90 degree projection data (see Figure 7), rAIayl and y2 are similarly calculated using the following equations (
Step 514). In the case of two directions, k is 1.3
~1.4 is a suitable value.

V2 = ((Y2-Yt)/2) →-k ((Y2-Yl),'21...(3)
yl −((Y2 −Yl )/2) −k ((Y2 −Yt )/2) ・・・
(4) Further, once each X, y region has been determined, the enlargement center position @X, y is determined using the following arithmetic expression, as shown in step 815.

XQ = (Xt +X2)/2...
...(5) yo −(y+ +y2 )/2
......(6) Similarly, regarding the magnification rate ω, the above w
4 area XL.

Calculate using X2, 'lx, y2 (
step 816).

ω-Ro / fl/2 (X2-x1 unit + 0'2 ”
h)" 1... (7) However, RO in the above equation is the radius of the reconstruction area when the magnification rate is 1.

After determining the enlargement center position and enlargement ratio as described above, the enlargement interval is reconstructed based on step S3 in FIG. This reconstruction processing is performed using three back projection processing means shown in FIG. 2, and the method of the processing can be explained with reference to FIG. Now, the reconstruction center (X
o , yo ) and magnification rate ω (=rO/RO), the equation of back projection to the point (x, y) shown in Fig. 8 is F (x, y) - Σfθ (X, 1 θ - ΣP(θ, x',y
' is the relationship between x and y. Therefore, from equations (9) and (10), the pack projection equation for the enlarged image is F'(x'
,y') - ΣP(θ, ((X'/ω)+Xg)cosθθ-((y'/'ω)+yO)sjnθ)...
(10) It is shown as follows. In this equation, if we take θ as a side entry for each x', y', then the enlarged image F'(x',y')
is obtained. This enlarged image is displayed on the CRT display 26 based on step S4 shown in FIG.

Therefore, according to the configuration of the embodiment described above, when creating a cross-sectional image of an object smaller than the reconstruction area, that is, the data collection area, the threshold value can be arbitrarily set according to the material of the object, etc. If you do this, you can magnify and display the material made of the material, and also automatically select the magnification rate according to the size of the object and use the screen effectively for display, so you do not have to artificially specify the area to be enlarged. It is possible to display the area of interest without having to do so.

Further, since it is not necessary to create a reconstructed image for the entire area as in the conventional method, an enlarged image can be created in a single time, and the inspection efficiency and accuracy of the object can be improved.

Note that, although the above embodiment has been described with respect to a second generation CT scanner, it can be similarly applied to other generations of CT scanners. Further, in the above embodiment, the enlargement center tiL position and the enlargement ratio are determined from projection data obtained from two directions at 90 degrees or from four directions at 45 degrees. The position and magnification may also be determined. Further, although the threshold value is stored in the memory 35 in advance, it may be arbitrarily set at any time depending on the subject 19 and the material of the subject. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

〔Effect of the invention〕

As described in detail above, according to the present invention, an area of interest is automatically determined from projection data in a predetermined direction, an enlargement center position and an enlargement ratio are obtained, and an enlarged image is constructed. Therefore, it is possible to provide an auto-zooming 0-image scanner that can greatly shorten the time for area enlargement processing and can easily enlarge the fA area without any manual operation.

[Brief explanation of drawings]

Figure 1 shows a general second generation C made by applying the device of the present invention.
The overall configuration of the T-scanner is shown in Fig. 2. Fig. 2 is a diagram schematically showing the structure of the device of the present invention. Fig. 3 is a flowchart schematically showing the operation of the device. Fig. 4 shows the magnification center position and magnification rate. Explanatory diagram for finding. 5 to 7 are diagrams showing projection data at a predetermined angle,
FIG. 8 is an explanatory diagram showing water content enlarged by reconstruction means;
FIG. 9 is an operation flowchart illustrating a conventional area enlarging technique. 10... Scanner body, 12... Radiation generator, 1
3... Radiation detector, 20... Data collection unit, 22
. . . image edge configuration processing unit, 23 . . . image processing control means, 26 . . . CRT display, 31 .
3.4... Shigii geomeimeter, 35... Memory, 37
. . . Enlargement center and enlargement ratio calculation means, 38 . . . Convolver processing means, 39 . . . Pack explosion processing means. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 $2 Figure 3 Figure 4 Figure 5 Figure 6 ■ Figure 7

Claims (2)

[Claims] (1) Threshold setting means for extracting projection data in a predetermined direction from a sinogram of collected data collected by a scanning operation and binarizing it with a predetermined threshold; The image forming apparatus is provided with an enlargement center position and an enlargement ratio calculating means for determining an enlargement area from data binarized using a threshold value and calculating the enlargement center position, and using data of the enlargement center position and enlargement ratio for image reconstruction. An auto-zooming CT scanner characterized by: (2) The auto-zooming CT scanner according to claim 1, wherein the predetermined directions for obtaining projection data are four directions at 45-degree intervals or two directions at 90-degree intervals.