JPS63135137A - Radiation ct - 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 (Industrial Application Field) The present invention is characterized in that a radiation source such as The present invention relates to radiation CT in which the group is rotated synchronously and radiographic data is collected in each direction.

(Prior Art) FIG. 6 shows the spatial arrangement of skin tone data using an offset detection method in a typical third generation CT (explained in the case of X-rays). In the figure, 1 is X! which moves along an arc Lxh and irradiates the subject. ! The Q source 2 houses a subject therein, and P is the center of the image reconstruction area for reconstructing its tomographic image.

A detector 3 is composed of a large number of detector cells and detects the X-rays irradiated onto the reconstruction region 2. Let C be the center point of the detector cell at the center of the detector group. Each detector cell is arranged at equal intervals on an arc, and is at equal angular intervals (sample angle) of Δγ when viewed from the X-ray source 1. while rotating on the circumference LX,
Collect scan data in each direction. By the way, a straight line connecting a point X (hereinafter referred to as "-") on the circumference of the X-ray source 1, Lx, and a center position C of the detector 3, and a straight line connecting X and the center P of the reconstruction area 2 (hereinafter simply referred to as "center P") An angular offset of Δγ/4 is provided between the direct aXP connecting the detector 3
is arranged with respect to X, with its center C being offset from the center P by an angle Δγ/4. In this way, the sixth
As shown in the figure, each X 1 of view data 1800 points apart from each other
By arranging the m M path to interpolate with each other at the center of the reconstruction region 2, it is possible to improve the spatial resolution in the radial direction and improve the resolving power.

(Problems to be Solved by the Invention) In order to employ the above method, view data in each direction of 360' is required, and a scan time corresponding to 36° is required, so the exposure dose also corresponds to 360'. It will be the same.

The present invention has been made in view of the above-mentioned points, and its purpose is to enable a narrow rotation angle of 180 degrees, thereby shortening the scanning time and enabling high-speed scanning.
111ta11 is also aimed at realizing radiation CT with less radiation.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, arranges a radiation source such as an In radiation-a CT, in which a single source and a group of detectors are rotated synchronously and radiographic data is collected in each direction, the position of the detector group can be controlled spatially and temporally to obtain data on the offset angle of the detector. The method is characterized in that it is changed in accordance with the direction of acquisition, and scanned so that each radiation transmission path between adjacent or nearby view data interpolates with each other at least in the center of the reconstruction region.

(For f\) Radiation [1] It is decided to control the spatial position of the generation and irradiate the radiation.Pyu data at an arbitrary position and nearby data are None of the transmission paths overlap and reinforce each other,
Each data is collected as different data.

(Example) First, the present invention will be explained in detail. FIG. 1 is a diagram showing the geometrical arrangement of a scanning system for explaining the present invention in detail. In the figure, the same parts as in FIG. 6 are labeled with the same arrows. In the figure, the detector 3 has a large number of detector cells [)i
(i-...C-1,C.

C+1...), and each detector cell Qi is
They are arranged at equal angular intervals Δγ (at the same time at equal intervals) in a circular arc -E with X as the center and line segment XC as the radius.

The straight line XC has an angle δ with the straight line XP, and the detector 3 is arranged offset. XP intersects the positive direction of the x-axis at the center P without making an angle θ. This geometry is the same as typical for third-generation X-ray CT; in the θ direction, the detector 3 directs the fan beam X-rays (pulses) under a geometry with an offset of δ. Collect the corresponding pyu data.

The X-ray source 1 rotates on the circumference LX and collects view data in each direction.

Scanning in this method is to change the offset amount δ of the detector in accordance with the position of the X-ray source 1 by the slight displacement of the detector group.

(1) Scanning is performed sequentially in each of the following directions. (Take GW Su4yan as an example.) View number Angle Offset horn 1M
Mouth θ0 δ2nd θ
. −Δθ −δI 3rd θo2Δ
θ δ 4th θ. −3Δθ
-δ': : 2N-1st θo-(2N2)Δ0 δ 2N-th θo-(2N 1)Δθ -δ'Here, Δθ is the angle between views and is determined in advance from the requirements of image quality etc. during scanning. put. Further, the CCW direction is defined as a positive direction, and the CW force direction is defined as a negative direction. δ is written as Δγ/4 as before. The set value of δ' will be explained with reference to FIG. Figure 2 is intentionally enlarged for clarity. In the figure, X is the position of the X-ray source 1 in the 11th view, X'
is the position of the X-ray source 1 in the second view. It is assumed that the straight line IXP connecting X and the center P is orthogonal to the X axis. X
The angle formed by the X-ray path when the irradiated X-ray from ' is irradiated between adjacent detector cells is Δγ, XP, ．． Let the offset angle from X' be 1 δ', and let B be the perpendicular line drawn from A1X' to the X axis at the point where a straight line making an angle of δ' to X'P intersects with the x axis. Also, the offset angle δ of X is Δγ/4, and the length on the X axis with respect to the offset angle δ is a/4 (a is the length on the X axis with respect to Δγ), so You can choose the length to be a/4. In the figure, calculate the angle δ' for AP=a/4.

If we set zx'AB-α, then α=δ in △X' PA
'-1-2×'p8-δ'+(π/2-Δθ)=π/2
−(80−δ′) ...(1) Also, Δγ−
a/12...(2)△X'
At Pa, lPX'B-zXPX' -Δθ PA-PB-AD = a /4 to a74 = 1stnΔθ-/CO8Δθ-cotα...
・(3) From equations (1), (2), and (3), A? Meeting Δ γ /4== Il sin Δ
θ − / CO8Δ θ・cot (π/2−(80−δ′))Δγ/4=sir1 Δθ−Cog
Δθ・tan (Δθ−δl) tan (Δθ−δ′)−(sin Δθ−Δγ/4
)/COS Δθ , °, δ′ −80−jan′ ((sinΔθ−
Δγ/4)/COS Δθ) However, it is assumed that all angles in the above equation are expressed in radians. Moreover, when Δθ is small, δ' → Δγ/4.

Data in the reconstruction area 2 from each view offset by angles δ and -δ' as described above is collected from a position as shown in FIG. In the figure, the same parts as in FIG. 2 are marked with the same symbols.

However, FIG. 3 is enlarged for explanation purposes.

K is the point where the radiation transmission path due to X intersects with the X axis.

The point where the radiation transmission path by [, X' intersects the X axis is G,
If H is G, the intervals between H and L are approximately a/2, and it can be seen that interpolation is performed near the center of the reconstruction area 2 even if there is no opposing view.

(2) Perform image reconstruction corresponding to the scan data.

The geometrical relationship between the (2i-1)th and 21st views of the scan data (1) is as shown in FIG. In the figure, the same parts as in Figure 1 are labeled with the same numbers. D, D
' is the position X of X-ray source 1.

This is the position of the detector 3 corresponding to X'. In the figure, it is clear that the transmitted X-ray paths are interpolated with each other in a considerable area of the reconstruction area, and the effective sample data is increased.

An embodiment of X[ICT using such a principle is shown in FIG. 5. In the figure, the same parts as in FIG. 1 are given the same reference numerals. In the figure, reference numeral 9 indicates a gantry 1 on which a subject 10 is placed.
This is a table for moving and accommodating the subject 10 in the horizontal direction with respect to the hole in the center of the subject 1. The gantry 11 is formed so that its cross section is indicated by 11'. That is, Xl
The ll11 is rotating with the gantry 11 and the detector 3 around the center P around the subject 1o, and the rotation is controlled by the table gantry control t by the gantry rotation scanning mechanism 12.
This is done under the control of 111iiiIZ13. The table gantry control unit 13 also controls the table 9 so that the subject 10 is appropriately placed within the reconstruction area 2, and also controls the rotation of the detector displacement scanning mechanism 14. . The structure of the detector displacement scanner MI114 will be described later. Reference numeral 15 denotes a high-voltage Xf11 tube control unit that supplies high voltage to the X-ray 1 [Gil, and is controlled by the X-ray generation control device 16. 17 is the table gantry control device 13 and X-ray generation control! This is an operation photographing control device that controls the operation timing and the shadow imaging timing of the device 16.

18 is a data acquisition device that collects transmitted X-ray intensity signals detected by the detector 3; this data is processed by a data processing device 19;
sent to. 20 is a large-capacity storage device for storing the data from the data processing device 19; 21 is an image display device for displaying the image reconstructed by the data processing device 19; and 22 is a photographing device for displaying the image. be.

Next, the operation of the apparatus of the embodiment configured as described above will be explained. Operation/I! Based on the control signal of the shadow sub-control device 17, the table gantry control device 13 accommodates the table 9 on which the subject 10 is mounted in the gantry 11, rotates the gantry 11, and simultaneously controls the XaR raw control device 116. The X-ray generation control device 16 controls the X-ray source 1 as described in the above-mentioned principle explanatory diagram.
High pressure is applied to the Xm source 1 while controlling the irradiation timing by a signal given to the high voltage XSS control section 5. The detector 3 detects the X-rays that have passed through the reconstruction region 2, and the data is collected by the data acquisition device 18.

The obtained data is subjected to appropriate processing in the data processing device 19, such as logarithmic conversion and X-ray intensity correction, and is stored in the mass storage device 2o.

In this way, when the data of the 2N view is complete, normal image reconstruction processing is performed in the data processing device 19, and the obtained image is displayed on the image display device 21, and if necessary, it can be displayed on the photography control device 22. Photographed.

FIG. 7 is a diagram showing the structure of the detector displacement scanning mechanism. In the figure, the same parts as in FIG. 1 are given the same reference numerals. In the figure, 14 is fixed to a gantry rotating frame (not shown), and a detector 3 is connected to one end of the frame via an arm 32.
It is a detector displacement scanning mechanism to which a detector 3 is attached and which moves the detector 3 in a tangential direction, and is composed of a base 30 and an arm attachment part 31 eccentrically attached to the base 30.

32 is an arm that connects the arm attachment part and the detector 3; 33 is an anti-photography support that supports the detector 33; and 34 is an arm that supports the detector 3 so as to be rotatable only in the tangential direction. It is a support body. Every time the xta source 1 moves from the first pico to the second view and from the second view to the 3i-th view under the control of the table gantry control W device 13, the detector displacement scanning mechanism 14 is also rotated. . For each view of the X-ray source 1, the base 30 rotates half a rotation, the eccentrically mounted arm mounting part 31 moves to the far point and the return point, and the detection 33 is moved to the left of the figure through the arm 32 at an angle δ (displacement length). Lδ, where L...Y), and move it to the right by an angle δ' (displacement length δ'). This causes the detector 3 to have an off-set angle of δ and -δ' for each view with respect to the center P.

As explained below, it is sufficient that the data collection range by scanning is about 1806+α (α is the fan angle of the X-ray beam including the reconstruction area 2).

However, it goes without saying that there may be more than that.

Therefore, (1) The scan time can be much shorter than in the case of 360°.

(2) Therefore, high-speed scanning is possible.

(3) High-quality imaging with high resolution is possible with a small rotation angle. (Same resolution as before with less rotation angle 1)
Image quality is obtained. ) (4) High-speed scanning can reduce the effects of body movements and organ movements.

(5) At the same time, it only takes a short time to stop breathing, so the burden on thinking can be reduced.

(6) By interpolating the transmitted radiation paths of one or more adjacent views (or nearby views), high-speed scanning is possible, and imaging with higher resolution and higher image quality can be achieved with fl'1
I can do it. If the aperture width of the detector is small enough,
A sufficient improvement in resolution can be expected with a projection system having the same geometric arrangement.

(7) The effect of (6) above can be achieved with a very small radiation exposure m and a small number of detectors.

Note that the present invention is not limited to the above embodiments. For example, the following f transformation can be considered.

(1) As a scanning method (a) Δθ may be different for each view.

([]) The way in which δ is given may also be δ≠Δγ/4. This cutoff δ' may be expressed as in the following equation.

δ′−Δθ−jan−′ ((sinΔθ−Δγ/2
+δ), 'cosΔθ) (c) If 80 changes, δ' also changes, so the value of δ may also be changed for each view.

(d) Also, δ−−Δγ/4 δme=Δθ−jan−1((SinΔθ+Δγ/4)/
cos Δθ).

(e) Of course, the scanning direction may be CCW.

(2) Each tJ! between three or more adjacent or nearby views! It is also possible to scan spheres with l-ray transmission paths that interpolate with each other at least in the center of the reconstruction area.

(3) Various reconstruction algorithms can be employed.

(4) Various modifications of the configuration of the X-ray CT apparatus are possible.

(Effects of the Invention) As described in detail below, according to the present invention, 180°
+α Only a narrow rotation angle of the culm is required, therefore, the skill time is short and high-speed scanning is possible, making it possible to realize a CT device with high resolution and high image quality while having a low asthma line. pain to.

The practical effects are extremely large, such as being able to reduce the burden and also reduce the effects of body movements.

[Brief explanation of the drawing]

Fig. 1 is a detailed explanatory diagram of the present invention, Fig. 2 is an enlarged explanatory diagram for the total n of offset distances δ', Fig. 3 is an enlarged explanatory diagram of the interpolation situation, and Fig. 4 is an enlarged explanatory diagram of the adjacent view data path. Spatial layout diagram, Figure 5 is a lower diagram of one embodiment of the present invention, Figure 6 is a spatial layout diagram of scan data of the conventional third generation CT offset detection method, and Figure 7 is a diagram of detector displacement. FIG. 3 is a diagram showing the structure of a scanning mechanism. 1...XWA source 2...Reconstruction area 3...
- Detector 9... Table 10... Subject 11.11'... Gantry 12... Gantry rotation scanning mechanism 13... Table gantry control a device 14... Detector displacement scanning mechanism 15. ...High-pressure X-ray tube control unit 16...X-ray generation control device 17...Operation imaging control device 18...Data collection device 19...Data processing device 20...Human composition record 1 device 21 ... Image display device 22 ... Photographic projection device 30
...Base 31...Arm mounting part 32...
・Arm 33...Vibration isolation support 34...1 degree of freedom support Patent applicant: Yokogawa Medical Systems Co., Ltd. Kakuyumi 2
Figure 3; Cocoon 4 Figure 3;

Claims (1)

[Claims] A radiation source such as X-rays and a group of detectors are arranged facing each other across the reconstruction area that accommodates the subject, and the radiation source and the group of detectors are rotated synchronously to collect radiographic data in each direction. In radiation CT, by spatially and temporally controlling the position of the detector group, the amount of offset of the detector is changed corresponding to the direction of data acquisition, and each radiation transmission path between adjacent or nearby view data is at least Radiation CT characterized by scanning in a manner that interpolates with each other in the center of a reconstruction region.