JPS6343098B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation tomography apparatus capable of performing medical examinations by measuring the amount of X-ray absorption of various parts of a subject within the same plane.

Computed Tomography (hereinafter referred to as "computed tomography") is one of the radiation tomography devices.
There is a device called a CT device. This CT device uses, for example, an X-ray source that emits X-rays that spread out in a flat fan shape and a detector that detects the X-rays, which are placed facing each other, and are transmitted in the same direction and at the same period through the tomographic plane of the subject. The object is rotated to collect X-ray absorption data in various directions, and after obtaining sufficient data, it is analyzed using a computer to calculate the X-ray absorption rate at each position on the tomographic plane. This system reconstructs the tomographic plane with a gradation level according to the absorption rate, and the composition of each part of the tomographic plane can be analyzed in 2000 gradation levels, ranging from soft tissue to hard tissue. A clear tomographic image can be obtained. This is a third generation CT device, but there are various other methods such as the first generation, which uses a pencil beam to collect data by combining parallel and rotational movement.

Figure 1 shows the schematic configuration of the CT device. In the figure, 1 is a radiation source that emits X-rays, 2 is a detector,
Reference numeral 3 denotes a support device for holding the radiation source 1 and the detector 2 facing each other via the subject P, and rotating or moving them in parallel around the subject P; an arithmetic processing unit which processes the X-ray absorption data and performs image reconstruction processing of the cross section of the subject P to obtain a tomographic image; 5 is an image storage device which stores the tomographic image obtained by the arithmetic processing unit 4; 6 is an image storage device; This is an image display device that displays this stored image.

Such a device emits X-rays from a radiation source 1 while driving a support device 3 to move the radiation source 1 and detector 2 around the subject P, and transmits the transmitted dose to the detector 2. Detect. Then, this detected data is sent to the arithmetic processing unit 4, and after collecting data for various directions of the tomographic plane position of the subject P, this data is computationally processed to calculate the X-ray absorption at each position of the tomographic plane. The ratio is calculated and obtained as a CT number, and image reconstruction is performed based on this CT number. Then, this reconstructed image is sent to the image display device 5 and displayed.

As mentioned above, the reconstructed image that can be obtained by such a CT device is one in which the X-ray absorption amount distribution in the cross-sectional plane of the human body is changed to a bright and dark density distribution, and the distribution of the tissue with isobestion values in the cross-section is changed. You can see it.
In particular, tumors, blood types, etc. exhibit different absorption values (CT numbers) from normal tissues, so they can be distinguished as lesions.

By the way, since the human gradation discrimination ability is limited to only a few dozen gradations, CT numbers within a predetermined range are treated as the same gradation, and the 2000 levels are classified and displayed into several tens of gradations.

At this time, in tomographic planes whose CT numbers are biased toward compositions that are close to each other, the reconstructed images concentrate at relatively similar densities, making it difficult to distinguish between normal and diseased areas.

In such a case, in the density distribution of the reconstructed image, the concentrated parts are dispersed and the dispersed parts are concentrated, that is, the CT number range of the concentrated specific gradation is narrowed. and disperse the range of CT numbers that should fall into the specific gradation into a plurality of other gradations,
Further, the CT number range of the less frequent gradation portion can be easily identified by processing the image so that the CT number range per gradation is widened so that the density distribution becomes uniform as a result.

The present invention has been made in view of the above circumstances, and a histogram regarding the CT number frequency of a reconstructed image is obtained between an image storage device and an image display device, and from that histogram, the frequency of use of all gradations is uniformly determined. We have installed an arithmetic circuit that converts the image by finding the CT number range for each gradation that makes the image An object of the present invention is to provide a radiation tomography apparatus that facilitates the identification of substances present therein.

Hereinafter, one embodiment of the present invention will be explained in Figs. 2 and 3.
This will be explained with reference to the figures.

The configuration of this device is basically the same as that shown in FIG.
In this application, during this configuration, a histogram of each data (CT number of each position) of one reconstructed image is further calculated based on the data of the reconstructed image stored in the image storage device 5, and the histogram is calculated. Based on the frequency distribution status, the CT number range for each of the gradations used is narrower in areas with higher frequency and wider in areas with lower frequency, so that each gradation is matched to the composition of the tomographic plane, and the frequency of use is uniform. In other words, an arithmetic circuit 21 for image conversion processing that allocates gradations such that the density distribution is uniform is provided, and this arithmetic circuit 21
The output of is given to the image display device 6 to make the image easier to see by dispersing the gradation of the concentrated portion of an image in which close CT numbers are concentrated.

In such a configuration, the X-ray absorption rate, that is, the CT number, of each position on the tomographic plane from which data is collected is determined by the image processing device 4, and the data of the determined CT number is stored in the image storage device 5. This stored data is sent to the arithmetic circuit 21 when displaying the reconstructed image, and the data is sent to the arithmetic circuit 21, where the data for one screen to be displayed (of course, if a part of it needs to be displayed, the display area) is sent to the arithmetic circuit 21. A histogram of CT number data is obtained.

Then, from the histogram, for all the gradations to be used for display, a CT number range in which the frequency of use of each gradation is almost uniform is determined. As a result, in the case of a tomographic plane in which substances with similar CT numbers are concentrated and substances with other CT numbers are small, the concentrated area will be divided into many gradations, and this arithmetic circuit 21 output If this is applied to the image display device 6 for display, parts that would normally be displayed at similar gradations will be divided into many different gradations and displayed, making the image easier to see.

For example, when Substance A and Substance B in an image have similar densities as shown in Figure 3, and only Substance C has a different density, to the naked eye, Substance A and Substance B
Since they appear to be the same, it appears that there are only two types of substances in the image.

When this image is subjected to arithmetic processing according to the present invention, substance A, substance B, and substance C are distributed with equal density differences, and substance A and substance B can be clearly distinguished. , it becomes clear that three types of substances exist in the image.

As described in detail above, according to the present invention, the frequency of the CT number at each position of a tomographic image obtained by reconstruction in a CT apparatus is determined, and furthermore, the frequency of CT numbers used for image display is determined in accordance with this frequency. An arithmetic circuit is installed to determine the range of CT numbers assigned to each gradation so that the frequency of use is uniform, and data with frequently used CT numbers that are close to each other is displayed in different gradations to show that they have different compositions. To provide a radiographic tomography device that is diagnostically useful and easy to use, making it easy to diagnose because it can be clearly seen, and in particular, clearly distinguishing between a lesion and normal tissue similar to the composition of the lesion. be able to.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with appropriate modifications within the scope without changing the gist thereof.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a conventional device, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a diagram for explaining the effect in use thereof. 1... Line source, 2... Detector, 4... Image calculation device, 5... Image storage device, 6... Image display device,
21... Arithmetic circuit.

Claims (1)

[Claims] 1 A radiation source and a detector for detecting the radiation dose are placed facing each other, and while moving them in the same direction through the tomographic plane of the subject, radiation absorption data for various directions of the tomographic plane of the subject are collected. In an apparatus that determines the magnitude of the radiation absorption rate at each position of the tomographic plane of the subject based on the collected data and displays an image with a gradation level corresponding to the magnitude of the radiation absorption rate, the determined radiation absorption rate Create a histogram for each image to be displayed, and allocate data to each gradation so that the frequency of use of all gradations used for display is almost uniform for the data of the size of . What is claimed is: 1. A radiation tomography apparatus characterized in that an arithmetic circuit is provided for determining the range of the radiation absorption rate, and the data of the magnitude of each of the radiation absorption rates is displayed as an image at each of the corresponding gradations.