JPH08299319A - Scanning method, multiplex detector and x-ray ct device - Google Patents

Abstract

PURPOSE: To restrain the occurrence of an area having a drop in sensitivity distribution by setting the prescribed intervals in a data acquisition direction at the time of acquiring data from a plurality of positions in parallel via the use of a multiplex detector, and keeping a detector angle identical for maintaining the prescribed pitch for a scanning position. CONSTITUTION: In the case of helical scanning, an X-ray tube 11, a collimator 12 and a dual detector 13 are rotated for a specimen H and relatively moved along the specimen H. Data acquisition is thereby repeated at different scanning positions. In this case, a scanning position L2 has the same angle of the dual detector 13 relative to a scanning position L1 and the specimen H, and a pitch P is set at the position expressed by the equation II. Similar processes are repeated thereafter. Also, an interval I is set between data acquisition areas A and B as shown in the equation I, provided that N stands for a data acquisition position number, M for recurrent numbers of 1, 2 and so forth, (f) for the breadth of the flat section of sensitivity distribution, (t) for the breadth of a gradient at both sides of the flat section, and (r) for a value expressed as 0<=r<=2.t.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning method, a multiple detector and an X-ray CT (Computed Tomography) apparatus. More specifically, the present invention relates to a scanning method, a multiple detector, and an X-ray CT apparatus capable of suppressing the generation of a lowered portion of the sensitivity distribution.

[0002]

2. Description of the Related Art FIG. 11 is a schematic perspective view of a dual detector which is an example of a multiple detector. This dual detector 13 'is a two-stage detector array (Array) 13
This is a structure in which a and 13b are arranged in parallel. The detector array 1
3a has a structure in which a large number of detectors Ci are arranged in a line in an arc shape. The number of detectors Ci is 800, for example. The detector array 13b has the same structure.

FIG. 12 is an explanatory view of a situation in which an object is scanned by an X-ray CT apparatus equipped with the above dual detector 13 '. At the scanning position L1, the X-ray emitted from the X-ray tube 11 is emitted from the slit 1 of the collimator 12 '.
After passing through 2 m, the beam is focused into an X-ray beam (Beam) Xm, passes through the subject H, and enters the dual detector 13 ′. Therefore, the detector arrays 13a and 13b can simultaneously acquire data at the two data acquisition portions A and B. The sensitivity distributions Sd and Sd of the respective data acquisition portions A and B along the direction in which the detector arrays 13a and 13b are arranged in parallel are X
It is determined by the sensitivity distribution on the radiation source side and the sensitivity distribution of the detector Ci, and has a substantially trapezoidal shape with a flat center and both sides inclined. The width of the flat portion is f, and the width of the inclined portions on both sides is t. When performing a helical scan, the X-ray tube 11, the collimator 12 ', and the dual detector 13' are rotated with respect to the subject H, and the subject H is relatively moved along the subject H, which is different. Data acquisition is repeated at the scanning position.

FIG. 13 shows a situation in which the subject is scanned at the scanning position L2. The scanning position L2 is a scanning position in the vicinity of the scanning position L1 (FIG. 12) where the angle of the dual detector 13 ′ with respect to the subject H is the same. In other words, the scanning position is one rotation cycle after the scanning position L1. Scanning position L
The distance between 1 and the scanning position L2 is the pitch P.

FIG. 14 shows rotation cycles T1, T2, T3, T.
4 shows the relationship between the scanning positions L1, L2, L3, L4 at No. 4 and the positions of the data acquisition portions A, B at those scanning positions L1, L2, L3, L4. FIG. 15 shows the relationship between the data acquisition portions A and B and the sensitivity distribution. Assuming that the distance between the shoulders (the joint between the flat portion and the inclined portion) of the sensitivity distribution of the data acquisition portion at the two nearest scanning positions is the shoulder distance r, the pitch P is P = 2 · f + 2 · t + r ( It is represented by 1). Therefore, as shown in FIG. 16, the pitch P =
If 2 · f + 2 · t, the shoulder distance r = 0, the flat portion of the sensitivity distribution of the data acquisition portion at the two nearest scanning positions is continued, and the uniformity of the sensitivity distribution can be improved. .

[0006]

In the above-mentioned conventional scanning method, the sensitivity distribution uniformity is improved by overlapping some of the sensitivity distributions of the data acquisition portions at the two nearest scanning positions. ing. However, as shown in FIG. 17, the sensitivity distribution of the data acquisition portion A of the detector array 13a and the sensitivity distribution of the data acquisition portion B of the detector array 13b at one scanning position do not overlap, so here the sensitivity distribution There is a problem that the lowering part s of s is generated. Therefore, an object of the present invention is to provide a scanning method, a multiple detector, and an X-ray CT apparatus that can suppress the occurrence of a portion where the sensitivity distribution deteriorates.

[0007]

According to a first aspect of the present invention, the present invention provides a multiple detector in which N (≧ 2) stages of detector arrays in which two or more detectors are arranged in a row are arranged in parallel or one detector array. Using multiple detectors in which N (≧ 2) detectors are arranged side by side in parallel to acquire data at N data acquisition portions, the multiple detectors are arranged in parallel in the parallel direction with respect to the subject. In a scanning method in which the scanning is repeated at different scanning positions while relatively moving, the width of the flat portion of the sensitivity distribution along the juxtaposed direction of each data acquisition portion is f, and the widths of the inclined portions on both sides of the flat portion are t.
When the shoulder distance is r (0 ≦ r <2 · t) and the number of regressions is M (= 1, 2, ...), I = N · M (f + r) between each data acquisition part The interval I of + r−2 · t (2) is provided, and the pitch P of the scanning positions in the nearest vicinity where the angle of the multiple detector with respect to the subject is the same is P = N (f + r) (3) A scanning method characterized by the above. In the above configuration, the regression number M is one parameter for changing the interval I. That is, even if the number N of multiple steps, the width f of the flat portion, the width t of the inclined portion, and the distance r between shoulders are the same, the interval I can be changed by changing the regression number M. If the regression number M = 1, the interval I can be minimized.

In a second aspect, the present invention provides a multiple detector in which N (≧ 2) stages of detector arrays in which two or more detectors are arranged in a row are arranged in parallel or one detector in N (. ≧ 2) In multiple detectors arranged in parallel, the width of the flat part of the sensitivity distribution along the parallel direction of each detector is f, and the widths of the inclined parts on both sides of the flat part are t, respectively, and the number of regressions To M (= 1, 2,
...), N = 2 and M = 1 and f between each stage.
When t = t, an interval I of N · M · f−2t <I ≦ N · M (f + t) −t (4) is provided, and when N = 2 and M = 1 and f = t is not satisfied, There is provided a multiple detector characterized in that an interval I of N · M · f−2t ≦ I ≦ N · M (f + t) −t (5) is provided.

According to a third aspect, the present invention provides an X-ray tube,
A collimator, a multiple X-ray detector in which N (≧ 2) stages of detector arrays in which a large number of detectors are arranged in a line in an arc shape are arranged side by side, the X-ray tube, the collimator, and the multiple X-ray detector. And a rotation control means for rotating the X-ray tube around the subject, and a movement control means for relatively moving the X-ray tube, the collimator, and the multiple X-ray detector in the juxtaposed direction with respect to the subject. In the X-ray CT apparatus, the X-ray tube, the collimator, and the multiple X-ray detector are used to acquire data in parallel at N data acquisition portions, and in that case, the parallel direction of the data acquisition portions is set. The width of the flat portion of the sensitivity distribution along is defined as f, and the widths of the inclined portions on both sides of the flat portion are defined as t,
Let the distance between shoulders be r (0 ≦ r <2 · t), and let the number of regressions be M (=
1, 2, ...), an interval I of I = N · M (f + r) + r−2 · t (6) is provided between each data acquisition portion, and the rotation control means and the movement control are performed. Means is used to rotate the X-ray tube, the collimator, and the multiple detector with respect to the subject, and the data acquisition is repeated at different scanning positions while relatively moving in the juxtaposed direction. There is provided an X-ray CT apparatus characterized in that the angle P of the multiple detectors with respect to the sample is the same and the pitch P of the scanning positions in the nearest neighborhood is P = N (f + r) (7).

[0010]

In the scanning method according to the first aspect, when data is acquired in parallel at the data acquisition parts at N locations by using the multiple detector, I = N.M ( An interval I of f + r) + r−2 · t (2) is provided. Further, when the above-mentioned data acquisition is repeated at different scanning positions while moving the multiple detector relative to the object, the pitch P of the scanning positions is P = N (f + r) (3). As a result, as will be described later with reference to FIG.
Not only can some of the sensitivity distributions of the data acquisition parts at the two nearest scanning positions overlap each other,
It becomes possible to overlap some of the sensitivity distributions of the N data acquisition portions at one scanning position with each other. Therefore, it is possible to suppress the occurrence of the lowered portion of the sensitivity distribution and improve the uniformity of the sensitivity distribution as compared with the conventional case. If the interval I> 0, cross talk can be reduced. Also, one moving speed is sufficient.

In the multiplex detector according to the second aspect, when N = 2 and M = 1 and f = t between each stage, N.multidot.f-2t <I.ltoreq.N.multidot.M ( f + t) -t (4) at intervals I and N = 2 and M = 1 and f = t are not satisfied, then N · M · f−2t ≦ I ≦ N · M (f + t) −t (5) ), The space I is provided. As a result, the scanning method according to the first aspect can be suitably implemented, the occurrence of a portion where the sensitivity distribution deteriorates can be suppressed, and the uniformity of the sensitivity distribution can be improved as compared with the conventional case.
Further, since the interval I> 0, crosstalk can be reduced. Also, one moving speed is sufficient.

In the X-ray CT apparatus according to the third aspect,
When data is acquired in parallel at N data acquisition parts using an X-ray tube, a collimator, and a multiple X-ray detector, I = N · M (f + r) + r− between each data acquisition part. An interval I of 2 · t (6) is provided. Further, when the X-ray tube, the collimator, and the multiple detector are rotated and relatively moved with respect to the subject by using the rotation control unit and the movement control unit and the data acquisition is repeated at different scanning positions, the scanning position of the scanning position is changed. The pitch P is P = N (f + r) (7). As a result, the scanning method according to the first aspect can be suitably implemented, the occurrence of a portion where the sensitivity distribution deteriorates can be suppressed, and the uniformity of the sensitivity distribution can be improved as compared with the conventional case. If the interval I> 0, crosstalk can be reduced. Also,
Only one movement speed is required.

[0013]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. The present invention is not limited to this.

FIG. 1 is a block diagram of an X-ray CT apparatus according to an embodiment of the present invention. This X-ray CT apparatus 100 includes an operation console 1, an imaging table 8 and a scanning gantry 9.
Is provided.

The operation console 1 outputs an input device 2 for receiving an operator's instructions and information, a central processing unit 3 for performing overall control and data processing, and a control signal etc. to a photographing table 8 and a scanning gantry 9. Control interface 4, a data collection buffer 5 for collecting data acquired by the scanning gantry 9, and a CRT 6 for displaying an image and the like. The imaging table 8 includes a movement controller and puts a subject on it and moves it in the body axis direction. The scanning gantry 9 rotates the X-ray controller 10, the X-ray tube 11, the collimator 12, the dual detector 13, the data acquisition unit 14, and the X-ray tube 11 around the body axis of the subject. The rotation controller 15 is provided.

FIG. 2 is an explanatory view of a situation of scanning by the X-ray CT apparatus 100. X at scanning position L1
The X-ray radiated from the X-ray tube 11 passes through the two slits 12 a and 12 b of the collimator 12 and the X-ray beams Xa and X
It is focused on b, passes through the subject H, and enters the dual detector 13. Therefore, the detector arrays 13a and 13b can simultaneously acquire data at the two data acquisition portions A and B.

The collimator 12 has shields 12 at both ends.
1, 123, and the central shielding part 122. The central shielding part 122 prevents unnecessary exposure of the subject H.

Detector array 1 of the dual detector 13
3a and 13b are arranged in parallel with an interval I. The sensitivity distributions Sd and Sd of the data acquisition portions A and B along the parallel arrangement direction of the detector arrays 13a and 13b are determined by the sensitivity distribution on the X-ray source side and the sensitivity distribution of the detector, and the center is flat. It has a trapezoidal shape with both sides inclined. The width of the flat part is f,
The width of the inclined portions on both sides is t.

When performing a helical scan, the X-ray tube 11, the collimator 12, and the dual detector 13 are rotated with respect to the subject H, and they are relatively moved along the subject H at different scanning positions. Repeat data acquisition.

FIG. 3 shows a situation in which the subject is scanned at the scanning position L2. This scanning position L2 is the scanning position in the vicinity of the scanning position L1 (FIG. 2) and the subject H with the same angle of the dual detector 13. In other words, the scanning position L
The scanning position is one rotation cycle after one. The pitch P is the distance between the scanning position L1 and the scanning position L2. The scanning position L0 is a scanning position one rotation cycle before the scanning position L1. The scanning position L3 is the scanning position one rotation cycle after the scanning position L2.

FIG. 4 shows the rotation cycles T1, T2, T3, T4.
4 shows the relationship between the scanning positions L1, L2, L3, L4 at and the positions of the data acquisition portions A, B at these scanning positions L1, L2, L3, L4. FIG. 5 shows the relationship between the data acquisition portions A and B and the sensitivity distribution. Nearest 2
When the distance between the shoulders (the joint between the flat portion and the sloped portion) of the sensitivity distribution of the data acquisition portion at one scanning position is the shoulder distance r,
The interval I is I = 2 · f + 3 · r−2 · t (8). The pitch P is P = 2 · f + 2 · r (9) Therefore, as shown in FIG.
= T, if the interval I = 0 and the pitch P = 2 · f, the shoulder distance r = 0, and the flat portion of the sensitivity distribution of the data acquisition portion at all scanning positions continues and the sensitivity distribution The uniformity of can be improved. In addition, as shown in FIG.
When f> t, the interval I = 2 · f−2 · t, pitch P
= 2 · f, the shoulder distance r = 0, the flat portion of the sensitivity distribution of the data acquisition portion continues at all scanning positions, and the uniformity of the sensitivity distribution can be improved. Also, the interval I> 0
Therefore, crosstalk can be reduced.

Generally, if the distance I and the pitch P are changed and the shoulder distance r is selected from "0" to "2.multidot.t" while satisfying the above equations (8) and (9), the object H to the subject H is determined. Not only can the sensitivity distributions of the data acquisition portions at the two nearest scanning positions where the angles of the dual detector 13 are the same be overlapped with each other, but also the data acquisition can be performed at two positions at one scanning position. Part of the sensitivity distributions of the parts can be made to overlap each other, the occurrence of the part where the sensitivity distribution is lowered can be suppressed, and the uniformity of the sensitivity distribution can be improved. Also, the interval I
If> 0, crosstalk can be reduced. Also, one moving speed is sufficient.

FIG. 7 shows another relationship between the data acquisition portions A and B and the sensitivity distribution. The interval I is set to I = 4 · f + 5 · r−2 · t (10), and the pitch P is set to P = 2 · f + 2 · r (11). While satisfying these equations (10) and (11), the interval I and the pitch P are changed to change the shoulder distance r from "0" to "2".
If the angle between the dual detectors 13 with respect to the object H is the same, and part of the sensitivity distributions of the data acquisition portions at the two nearest scanning positions can be made to overlap each other by selecting between t ″ and t ″. Without, the sensitivity distributions of the two data acquisition parts at one scanning position can be partially overlapped with each other, the occurrence of the sensitivity distribution deterioration part can be suppressed, and the sensitivity distribution uniformity can be improved. Yes, the interval I> 0
Therefore, crosstalk can be reduced. Also, one moving speed is sufficient.

FIG. 8 shows the relationship between the data acquisition portions A, B and C and the sensitivity distribution when a triple detector (a multiple detector having three detector arrays arranged in parallel) is used instead of the dual detector 13. Is shown. The interval I between the stages is I = 3 · f + 4 · r−2 · t (12), and the pitch P of the nearest scanning positions where the triple detector angle with respect to the subject is the same, P = 3・ F + 3 ・ r (13) While maintaining these equations (12) and (13), the interval I and the pitch P are changed to change the shoulder distance r from "0" to "2".
-If selected between t ", not only can the sensitivity distributions of the data acquisition portions at the two nearest scanning positions with the same angle of the triple detector with respect to the subject be overlapped with each other, Part of the sensitivity distributions of the three data acquisition parts at one scanning position can be made to overlap each other, the occurrence of the part where the sensitivity distribution is lowered can be suppressed, and the uniformity of the sensitivity distribution can be improved. Also, the interval I> 0,
Crosstalk can be reduced. Moreover, one moving speed is sufficient.

FIG. 9 shows another relationship between the data acquisition portions A, B and C and the sensitivity distribution when the triple detector is used. The interval I between the stages is I = 6 · f + 7 · r−2 · t (14), and the pitch P of the nearest scanning positions where the angle of the triple detector with respect to the subject is the same, P = 3・ F + 3 ・ r (15) While maintaining these equations (14) and (15), the interval I and the pitch P are changed to change the shoulder distance r from "0" to "2".
-If selected between t ", not only can the sensitivity distributions of the data acquisition portions at the two nearest scanning positions with the same angle of the triple detector with respect to the subject be overlapped with each other, Part of the sensitivity distributions of the three data acquisition parts at one scanning position can be made to overlap each other, the occurrence of the part where the sensitivity distribution is lowered can be suppressed, and the uniformity of the sensitivity distribution can be improved. Also, the interval I> 0,
Crosstalk can be reduced. Moreover, one moving speed is sufficient.

Here, as can be seen from the relationship between FIG. 6 and FIG. 7 or the relationship between FIG. 8 and FIG. 9, even if N, f, and r are the same, it is possible to suppress the occurrence of the lowered portion of the sensitivity distribution at a plurality of different intervals I. . Therefore, the numbers 1, 2, ... Are assigned to such a plurality of intervals I in ascending order of distance. When this number is defined as the regression number M, the above description can be generalized as follows. That is, the width of the flat portion of the sensitivity distribution along the juxtaposed direction of each data acquisition portion is f, the width of the inclined portions on both sides of the flat portion is t, and the shoulder distance is r (0 ≦ r
<2 · t) and the number of regressions is M (= 1, 2, ...), I = N · M (f + r) + r−2 · t (2) I is set, the pitch P of the scanning positions in the vicinity where the angle of the multiple detectors with respect to the subject is the same and is P = N (f + r) (3), and the regression number M and the shoulder distance r are appropriately set. If selected (for example, M = 1, r = 0), the sensitivity distributions of the data acquisition portions at the two nearest scanning positions where the angles of the multiple detectors with respect to the subject are the same are made to overlap each other. Not only is it possible to partially overlap the sensitivity distributions of the N data acquisition portions at one scanning position with each other, but it is possible to suppress the occurrence of the sensitivity distribution deterioration portion, Uniformity can be improved. If the interval I> 0, crosstalk can be reduced. Also, one moving speed is sufficient.

As shown in FIG. 10, even if the conventional dual detector 13 'is used, the interval I between the data acquisition portions A and B at two locations is obtained by using the collimator 12 according to the present invention.
The present invention can be implemented by determining the above-mentioned equation (2) and the pitch P by the above-mentioned equation (3). Also,
The present invention can be applied to the case where the helical scan is not performed or the case where a multiple detector in which detectors are arranged in multiple stages is used instead of the detector array.

[0028]

According to the scanning method, the multi-detector and the X-ray CT apparatus of the present invention, it is possible to suppress the occurrence of the lowered portion of the sensitivity distribution and improve the uniformity of the sensitivity distribution. It also becomes possible to reduce crosstalk. Also, one moving speed is sufficient.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a situation of scanning by the X-ray CT apparatus in FIG.

FIG. 3 is another explanatory diagram of a situation of scanning by the X-ray CT apparatus in FIG.

FIG. 4 is an explanatory diagram of a positional relationship between a rotation cycle, a scanning position, and a data acquisition portion.

FIG. 5 is an explanatory diagram showing overlapping of sensitivity distributions of data acquisition portions.

FIG. 6 is an explanatory diagram showing an overlap of sensitivity distributions of a data acquisition portion when r = 0.

FIG. 7 is a general explanatory diagram showing an overlap of sensitivity distributions of data acquisition portions.

FIG. 8 is a general explanatory diagram showing an overlap of sensitivity distributions in a data acquisition portion when a triple detector is used.

FIG. 9 is another general explanatory diagram showing the overlap of sensitivity distributions in the data acquisition part when a triple detector is used.

FIG. 10 is an explanatory diagram for carrying out the present invention using a conventional dual detector.

FIG. 11 is a schematic view of a conventional dual detector.

12 is an explanatory diagram of a situation of scanning by the X-ray CT apparatus in FIG. 11.

FIG. 13 is another explanatory diagram of a situation of scanning by the X-ray CT apparatus in FIG.

FIG. 14 is an explanatory diagram of a positional relationship between a rotation cycle, a scanning position, and a data acquisition portion.

FIG. 15 is an explanatory diagram showing overlapping of sensitivity distributions of data acquisition portions.

FIG. 16 is an explanatory diagram showing an overlap of sensitivity distributions of a data acquisition portion when r = 0.

FIG. 17 is an explanatory diagram of a conventional problem.

[Explanation of symbols]

 100 X-ray CT apparatus 1 Operation console 8 Imaging table 9 Scanning gantry 11 X-ray tube 12, 12 'Collimator 13, 13' Dual detector 13a, 13b Detector array A, B Data acquisition part L0-L4 Scanning position

Claims (3)

[Claims] 1. A multiple detector in which N (≧ 2) stages of detector arrays in which two or more detectors are arranged in a row are arranged in parallel, or a multiple detector in which one detector is arranged in N (≧ 2) stages. N using the detector
In a scanning method in which data acquisition is performed in parallel at the data acquisition portions of the locations is repeated at different scanning positions while the multiple detector is relatively moved in the juxtaposed direction with respect to the subject, The width of the flat portion of the sensitivity distribution along the installation direction is f, the width of the inclined portions on both sides of the flat portion is t, the shoulder distance is r (0 ≦ r <2 · t), and the regression number is M. When (= 1, 2, ...), an interval I of I = N · M (f + r) + r−2 · t is provided between each data acquisition portion, and the angle of the multiple detector with respect to the subject is the same. In the scanning method, the pitch P of the scanning positions closest to is P = N (f + r). 2. A multiple detector in which N (≧ 2) stages of detector arrays in which two or more detectors are arranged in a row are arranged in parallel or a multiple detector in which one detector is arranged in N (≧ 2) stages. In the detector, the width of the flat portion of the sensitivity distribution along each of the detectors in the parallel direction is f, the width of the inclined portions on both sides of the flat portion is t, and the regression number is M (= 1, 2, ...) between each stage, when N = 2 and M = 1 and f = t, an interval I of N · M · f−2t <I ≦ N · M (f + t) −t is set. Empty, when N = 2 and M = 1 and f = t are not satisfied, a multiple detector characterized in that an interval I of N · M · f−2t ≦ I ≦ N · M (f + t) −t is opened. 3. An X-ray tube, a collimator, a multiple X-ray detector in which N (≧ 2) stages of detector arrays in which a plurality of detectors are arranged in a line in an arc shape are arranged in parallel, and the X-ray tube. Rotation control means for rotating the collimator and the multiple X-ray detector around the subject, the X-ray tube, the collimator and the multiple X-ray detector in the juxtaposed direction with respect to the subject. In an X-ray CT apparatus having a movement control means that moves relative to each other, data is acquired in parallel at N data acquisition parts by using the X-ray tube, the collimator, and the multiple X-ray detector. , F is the width of the flat portion of the sensitivity distribution along each of the data acquisition portions in the juxtaposed direction, and t is the width of the inclined portions on both sides of the flat portion, and the shoulder distance is r (0 ≦ r <2 ·
t) and the number of regressions is M (= 1, 2, ...), an interval I of I = N · M (f + r) + r−2 · t is provided between each data acquisition portion, and the rotation is performed. Using the control means and the movement control means, the X-ray tube, the collimator, and the multiple detector are rotated with respect to the subject and the data are acquired at different scanning positions while relatively moving in the juxtaposed direction. Repeatedly, at that time, the angle P of the multiple detectors with respect to the subject is the same, and the pitch P of the scanning positions in the nearest neighborhood is P = N (f + r).