JP3612553B2 - X-ray irradiation method for moving body measurement by high-speed X-ray CT - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray irradiation method suitable for measuring a moving body (moving body, deformed body) by high-speed X-ray CT. More specifically, in addition to industrial nondestructive inspection, multiphase flow measurement, opaqueness For moving object measurement by high-speed X-ray CT, which can be used effectively for visualizing and measuring moving objects that move or deform at relatively high speeds, such as flow distribution and powder cross-section distribution measurements such as powder transport It relates to an X-ray irradiation method.
[0002]
[Prior art]
Usually, X-ray CT is used to measure the density distribution in the cross section of a stationary object such as a human organ or structure. If it is a stationary object, there is no problem in irradiating X-rays from various directions over time.
However, when the subject moves or deforms during imaging, the signal information at the time of image reconstruction becomes inconsistent, and the motion of the subject appears as an error (artifact) on the image. In particular, when an object with a small dimension passes through the measurement cross section at high speed, the distance that the object moves within the time from the first X-ray irradiation to the last X-ray irradiation cannot be ignored, so that a large error occurs in the reconstructed image. Occurs. This becomes more conspicuous as the size of the object is smaller and the speed is larger. In order to reduce this error, there are methods of limiting the speed of the object and shortening the irradiation time, but the former reduces the experimental range and the latter significantly reduces the signal level.
[0003]
More specifically, in the high-speed X-ray CT having a plurality of X-ray sources fixedly arranged, conventionally, the X-ray source surrounding the measurement object has been irradiated in order from the end. The object moves in the axial direction within the time until the irradiation and the final irradiation are completed. During this time, the first several irradiations only illuminate one side of the object, the last several irradiations illuminate the other side of the moving object, and these data are used as image reconstruction data. Stored. However, a large error occurs on the reconstructed image because the object is moving and only one surface is intensively irradiated at a certain time.
[0004]
Conventionally, as for high-speed X-ray CT, there are Japanese Patent Publication No. 5-60381 (ultra-high-speed X-ray CT scanner) and JP-A-10-295682 (high spatial resolution high-speed X-ray CT scanner). Nothing has been found to improve the measurement accuracy to the extent that it can be applied even when a small object passes through a measurement section at high speed.
[0005]
[Problems to be solved by the invention]
The present invention has been made to solve such problems, and its technical problem is basically to provide an X-ray irradiation method for greatly increasing the measurement accuracy of high-speed X-ray CT. More specifically, in measurement of moving objects and deformed objects by high-speed X-ray CT, it is possible to accurately measure even small-sized measuring objects that move at high speed by greatly reducing errors in image reconstruction. The object is to provide an X-ray irradiation method which is made possible.
[0006]
[Means for Solving the Problems]
The X-ray irradiation method for moving body measurement by high-speed X-ray CT of the present invention for solving the above-mentioned problem is that a plurality of X-ray sources are arranged at equal intervals only in a specific range over a half circumference around the measurement object. When X-ray irradiation is performed to obtain a reconstructed image of a measurement object by high-speed X-ray CT, any two X-ray sources in which the irradiation order is continuous are in relation to the center of the arc connecting the X-ray source positions. The X-ray source is sequentially selected so that the positions are separated by 60 ° or more, and pulsed X-rays are irradiated, so that X-rays from at least three directions of X-ray source are emitted around the measurement object. It is characterized by irradiating.
[0008]
In the X-ray irradiation method in the high-speed X-ray CT having the above-described configuration, the order of X-ray irradiation from a large number of X-ray sources around the measurement object is appropriately set. Even in the case where the measurement object that has been changed to move, X-rays can be evenly irradiated around the measurement object within a short time when the movement distance is small. In particular, the order of X-ray irradiation, irradiation with X-rays seeking a combination of X-ray source area of the triangle formed by the position of the three X-ray source is maximized. Further, among the three sides of the triangle X-ray irradiation in order from the long side corresponds to irradiating the periphery of the measurement object uniformly in a short time. As a result, the contradiction in the image reconstruction principle can be reduced, so that false images on the reconstructed image of the moving / deformed body can be greatly reduced.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a view for explaining an embodiment of an X-ray irradiation method for moving object measurement by high-speed X-ray CT according to the present invention.
As shown in the figure, in the high-speed X-ray CT, a large number of fixed X-ray sources A1 to A18 are fixedly arranged around the measurement object B. These X-ray sources sequentially irradiate the measurement object B with pulsed X-rays, but even if the measurement object B moves or deforms during the irradiation, the movement distance and deformation amount are not changed. In order to irradiate X-rays from as uniform a direction as possible within a negligible time, the order of irradiation of each X-ray source is set as described below.
[0010]
That is, after irradiation from one of the X-ray sources first, X-rays are irradiated from an X-ray source located in the opposite direction as much as possible, and X-ray sources having different angles as much as possible are further irradiated. By repeating the above, it becomes possible to evenly irradiate X-rays to the moving or deforming object.
More specifically, the order of irradiation of pulsed X-rays from a large number of X-ray sources arranged around the measurement object B is at a position shifted by at least 60 ° or more around the measurement object. It is assumed that irradiation is sequentially performed from the radiation source, whereby X-rays can be irradiated evenly around the measurement object B in a short time, and further on both sides of the central axis C passing through the center of the measurement object B. The X-ray source is selected based on the index of maximizing the area of the triangle composed of the three points of the X-ray source by alternately selecting the X-ray sources positioned and irradiating the X-ray. It is appropriate to perform X-ray irradiation in order from the long side of the three sides of the triangle.
[0011]
The case where the X-ray source is selected on the basis of the index of maximizing the area of the triangle will be described in detail with reference to the drawings. The order of X-ray irradiation is first set to X-ray sources A1, A2, A3. In order. This is a method of selecting an X-ray source that maximizes the area of a triangle formed by connecting three X-ray sources, and is a reference for uniformity when irradiating from three directions. At this time, the triangles of the X-ray sources A4, A3, and A2 have the same area, but may be started from either one. If irradiation is started in the order of the X-ray sources A1, A2, and A3, the combination having the largest triangular area from three of the remaining X-ray sources is the X-ray sources A4, A5, and A6. The next combination is the X-ray sources A7, A8, A9 as the combination having the largest triangular area among the remaining X-ray sources. In the same manner, this is performed in numerical order until the last combination is completed.
[0012]
Such criteria for selection and irradiation order follow the following rules.
(1) A combination of three points that maximizes the area of a triangle formed by three X-ray sources is selected.
(2) Select the left and right of the central axis C alternately.
(3) The order turns from the longest side.
When there are 18 radiation sources as in the example shown in FIG. 1, the order of irradiation based on this method is the order of A1, A2,...
[0013]
In the X-ray irradiation method in high-speed X-ray CT having the above-described configuration, the order of X-ray irradiation from a large number of X-ray sources around the measurement object B is evenly irradiated around the measurement object in a short time. Therefore, even when the measurement object moves, the contradiction in the image reconstruction principle can be reduced, and the false image on the reconstructed image of the moving / deformed object can be greatly reduced. In particular, the order of X-ray irradiation, irradiation with X-rays seeking a combination of X-ray source area of the triangle formed by the position of the three X-ray source is maximized, further, among the three sides of the triangle X-ray irradiation in order from the long side corresponds to irradiating the periphery of the measurement object uniformly in a short time.
[0014]
Therefore, in the measurement of moving objects and deformed objects by high-speed X-ray CT, the error in image reconstruction is greatly reduced, and the noise level is greatly reduced even with a minute measurement object moving at high speed with high accuracy. An X-ray irradiation method that enables measurement can be provided.
[0015]
【The invention's effect】
According to the X-ray irradiation method in the high-speed X-ray CT of the present invention described in detail above, as compared with the conventional case, X-ray irradiation is performed sequentially from the end of the arranged X-ray sources. Since the above-mentioned false image is reduced and the asymmetry of the measurement object is relaxed, the measurement accuracy is remarkably improved, and the measurement accuracy of the measurement object having a small size and moving at high speed is improved. The scope of application can be greatly expanded.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment of an X-ray irradiation method for moving object measurement by high-speed X-ray CT according to the present invention.
[Explanation of symbols]
A1 to A18 X-ray source B Measurement object C Center axis

Claims (2)

In the X-ray irradiation for obtaining a reconstructed image of the measurement object by high-speed X-ray CT, arranging a plurality of X-ray sources at equal intervals only in a specific range over a half circumference around the measurement object,
The X-ray source is sequentially selected so that any two X-ray sources in which the irradiation sequence continues are located at a position 60 ° or more away from the center of the arc connecting the X-ray source positions. X-rays of
An X-ray irradiation method for moving object measurement by high-speed X-ray CT, wherein X-rays are emitted from an X-ray source in at least three directions around a measurement object . 2. The X-ray irradiation is performed by alternately selecting X-ray sources positioned on both sides of a central axis passing through the center of the arc connecting the X-ray source positions perpendicularly to the arc plane. The X-ray irradiation method for moving body measurement by the described high-speed X-ray CT.

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