JPH0471540A - X-ray ct device - Google Patents

Abstract

PURPOSE:To simply obtain a fluoroscopic image from an optional direction by generating a scannogram based on the data obtained by fan beams with the same rotary phase or parallel beams in the same direction within the data obtained by a helical scan. CONSTITUTION:The X-ray data of a person under test P detected by a helical scan are sent to a data collecting circuit 7 as electrical signals, the data are sent to a pre-processing circuit 8 after signal processing, the data processed with logarithmic conversion are sent to a magnetic disk 9, and all data are stored. The projection data obtained by the pre-processing circuit 8 are also sent to a data re-arranging circuit 13, and a scannogram is generated based on the data obtained by fan beams 20a-20d... with the same rotary phase within the obtained data for generating a fluoroscopic image by fan beams and based on the data obtained by parallel beams 26a, 26b...-29a, 29b... in the same direction within the obtained data for generating a fluoroscopic image by parallel beams. The fluoroscopic image from an optional direction can be simply obtained without photographing separately.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Field of Application) The present invention relates to
The present invention relates to an X-ray CT apparatus that reconstructs a tomographic image of a subject based on data regarding linear absorption coefficients, and particularly relates to an XIICT apparatus that performs so-called helical scanning in which the subject is moved in the body axis direction during scanning.

(Prior Art) Recently, as shown in FIG. 11, for example, as shown in FIG. tube 101
and a direction perpendicular to the circle drawn by the detector 102) that performs a so-called helical scan. In this case, as shown in FIG.
The locus 103 relative to the subject P of 01 draws a spiral shape, and when reconstructing an image, for example, the locus 103
Using the data corresponding to the part from point a to point 3, the image is reconstructed by regarding this as data for one rotation connected to point a, and the tomographic image of subject P is obtained. get. In such helical scanning, the subject P can be scanned in a short time.
It has the advantage of being able to obtain three-dimensional information.

Further, by moving only the subject P in the axial direction without rotating the X-ray tube 101 and the detector 102 and performing imaging, a fluoroscopic image (scanogram) of the subject P can be obtained.

(Problem to be Solved by the Invention) However, in the case of the above-mentioned conventional technology, in order to create a scanogram, it is necessary to perform imaging to obtain the scanogram separately from the helical scan, so it is time-consuming. there were. Another drawback is that a transparent image can only be obtained from one direction.

The present invention has been made to solve the problems of the prior art described above, and its purpose is to provide an X-ray CT apparatus that can easily obtain fluoroscopic images from any direction using helical scanning. Our goal is to provide the following.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention includes an X-ray tube that irradiates a subject with X-rays, and an X-ray tube that detects the X-rays that have passed through the subject. In an X-ray CT apparatus that performs a helical scan in which a relative trajectory of a detector with respect to a subject draws a spiral shape, and reconstructs an image based on data obtained by the helical scan, the helical scan The present invention is characterized in that it is provided with scanogram creation means for creating a scanogram based on data obtained from fan beams having the same rotational phase or mutually parallel beams in the same direction.

(Function) In the X-ray CT apparatus of the present invention having the above configuration, a scanogram is created by the scanogram creation means using the data obtained by helical scanning, so there is no need to separately perform imaging to obtain the scanogram. It doesn't take much time. Further, by appropriately selecting the rotational phase of the fan beam or the direction of the parallel beam that provides data used when creating a scanogram by the scanogram creation means, a perspective image of the subject from any direction can be obtained.

(Example) Below, an example of the present invention will be described based on the drawings. 1st
The figure is a block diagram showing the configuration of an X-ray CT apparatus according to an embodiment of the present invention.

In this X-ray CT apparatus, during imaging, an X-ray tube 2 and a detector 3 installed in a gantry 1 rotate around the subject P, and a bed top 4 on which the subject P is placed drives the bed. The circuit 5 drives the subject P in the body axis direction (direction perpendicular to the circle drawn by the X-ray tube 2 and detector 3). That is, a helical scan is performed in which the relative trajectories of the X-ray tube 2 and detector 3 with respect to the subject P draw a spiral shape.

At this time, the X-ray tube 2 is supplied with power by the high voltage generating circuit 6 and irradiates the subject P with X-rays, and the detector 3 detects the X-rays that have passed through the subject P.

Data regarding the X-ray absorption coefficient of the subject P detected by the detector 3 is sent as an electrical signal to the data acquisition circuit 7, where the signal is processed and then sent to the preprocessing circuit 8. The preprocessing circuit 8 performs processing such as logarithmic conversion on this signal and sends the obtained projection data to the magnetic disk 9, where all the data obtained by the helical scan is stored. The image reconstruction unit 10 reads projection data from the magnetic disk 9, performs arithmetic processing on these data, and reconstructs an image. This reconstructed image is stored in the image memory circuit 11
The tomographic image of the subject P is stored on the magnetic disk 9 via the display monitor 12 and displayed as a tomographic image of the subject P.

The projection data obtained by the preprocessing circuit 8 is also sent to a data sorting circuit 13 as a scanogram creating means, and this data sorting circuit 13 can create a scanogram that is a perspective image of the subject P. can. This scanogram creation operation will be described later. The created scanogram is stored on the magnetic disk 9 via the image memory circuit 11, while being displayed on the screen of the display monitor 12. Note that 14 in the figure indicates a CPU that controls each part of the apparatus (system control).

Next, the scanogram creation operation in the data rearrangement circuit 13 will be explained in detail.

■When creating a perspective image using a fan beam First, among the data obtained by helical scanning, fan beams 20a, 2 with the same rotational phase as shown in Fig. 2 are used.
Only the data obtained from 0 b , 20 c , 20 d . . . are taken out and arranged in the order of their position relative to the subject P. Figure 3 shows, for example, a fan beam 20
Fig. 3a is a view of Fig. 2a seen from above in Fig. 2; Also, the second
Reference numeral 21 in the figures and FIG. 3 indicates the X-ray focal position. By arranging the data as described above, a scanogram 22, which is a perspective image of the subject P, as shown in FIG. 4 is created.

The solid line portion in FIG. 4 indicates the arranged data portion.

By the way, as shown in FIG. 5, when the X-ray tube 2 is at position A and position B, there is a channel for observing the same X-ray path indicated by the dotted line in the same figure, and in this way, the same channel is observed. The opposing X-ray beams passing through are called opposing beams. When data obtained by such opposing beams is added to the above scanogram 22 and arranged, the result is shown in Fig. 6(a).
(A dotted line 23 in the figure indicates the additional data portion), and when this is further subjected to interpolation processing, a scanogram 24 as shown in FIG. 2(b) is obtained. The dashed line 25 in the figure is the interpolated data portion. In the central part of this scanogram 24, the spatial resolution is approximately 2 that of the scanogram 22.
It will be doubled.

■When creating a perspective image using parallel beams First, among the data obtained by helical scanning, mutually parallel beams 26a, 2 in the same direction as shown in FIG.
6 b ・-, 27a, 27 b ・-28g,
The data obtained by 28b.=, 29a, 29b-, etc. are arranged side by side along the locus 31 of the X-ray focal point position 30. FIG. 8 shows, for example, the parallel beams 26a, 26b,
... seen from above in FIG. 7. When the data is arranged in this way, it becomes as shown in FIG. 9(a), and when interpolation processing is performed between the arranged data, a scanogram 32 as shown in FIG. 9(b) is obtained.

Furthermore, in the same way as in case ① above, if data obtained by an opposing beam, that is, a parallel beam in the opposite direction to the above-mentioned parallel beam is added to the scanogram shown in FIG. ) (the dashed line 33 in the figure indicates the additional data part), and when further interpolation processing is performed on this, the spatial resolution in the central part is almost twice that of the above scanogram 32, as shown in (b) of the same figure. A scanogram 34 is obtained.

Note that in the interpolation process, calculations are performed so that each data is arranged in an image matrix.

In addition, by appropriately selecting the rotational phase of the fan beam that provides the data used in the above case (■) and the direction of the parallel beam that provides the data used in the above case (■),
A scanogram (perspective image) of the subject P can be created from any direction.

As described above, in this embodiment, a perspective image can be easily obtained from any direction without performing imaging other than helical scanning. As a result, a large amount of information for diagnosis can be obtained, and diagnostic ability can be improved. Further, by using a scanogram obtained by helical scanning, it is possible to easily and accurately determine the position for image reconstruction.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments (various modifications can be made).

[Effects of the Invention] The X-ray CT apparatus of the present invention has the above-described configuration and function, and can easily obtain a fluoroscopic image of a subject from any direction by helical scanning, thereby improving diagnostic performance. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an X-ray CT apparatus according to an embodiment of the present invention, and FIGS. 2 to 10 are explanatory diagrams for explaining the scanogram creation operation in the embodiment. Figure 3 shows a fan beam with the same rotational phase, Figure 3 is a view of the 7 beam shown in Figure 2, viewed from above, and Figure 4 shows a scanogram created only from data from the fan beam shown in Figure 2. Figure 5 is an explanatory diagram for explaining the opposing beam, Figure 6 (a) is a diagram showing a scanogram created by adding data from the opposing beam to the scanogram in Figure 4, and Figure 6 (b) is a diagram showing a scanogram obtained by performing interpolation processing on this scanogram, Figure 7 is a diagram showing mutually parallel beams in the same direction, Figure 8 is a diagram of the parallel beams shown in Figure 7 viewed from above, 9
Figure (a) shows a scanogram created by arranging only the data from the parallel beam shown in Figure 7, Figure (b) shows a scanogram obtained by performing interpolation processing on this scanogram, and Figure 10 (a). ) is a diagram showing a scanogram created by adding data from the opposing beam to the scanogram in FIG. The figure shows the state of the X-ray tube and the detector during helical scanning, and FIG. 12 is a diagram showing the trajectory of the X-ray tube relative to the subject during helical scanning. 2... X-ray tube 3... Detector 13... Data sorting circuit forming means) 14... CPU P... Subject (scanogram creation)

Claims (1)

[Claims] An X-ray tube that irradiates an object with X-rays, and an
In an X-ray CT device that performs a helical scan in which the trajectory of a detector that detects a line relative to a subject draws a spiral shape, and reconstructs an image based on the data obtained by the helical scan, The X-ray is characterized by being provided with scanogram creation means for creating a scanogram based on data obtained by fan beams having the same rotational phase or mutually parallel beams in the same direction among the data obtained by the helical scan. CT device.