JPH03210243A - X-ray ct device - Google Patents

Abstract

PURPOSE:To select a sensitivity correction value fitted in the quantity of attenuation of a subject by obtaining the sum of the quantity of attenuation of the subject, and selecting a corresponding sensitivity correction value from the sum. CONSTITUTION:A multi-channel X-ray detector 10 rotating confronting with a fan beam X-ray source and which detects a transmission X-ray transmitting the subject, a memory 15 which stores the sensitivity correction value, a means consisting of a CPU 11 and a memory 12 which corrects a measured value obtained by the detector 10 from the subject with the sensitivity correction value of the memory 15, and a CRT 14 which performs the reconstitution of an image with the measured value after correction are provided. At the means 11 and 12, the sum of the quantity of attenuation via all the channels of the subject at an arbitrary confronting position with the X-ray source and the X-ray detector 10 can be obtained from the measured value by the X-ray detector 10, and the sensitivity correction value corresponding to the sum of the quantity of attenuation can be selected from the memory 15. Furthermore, a selected sensitivity correction value is set as a sensitivity correction value for correction on a CRT 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention provides
Regarding CT equipment.

[Conventional technology]

Conventionally, in the XtIACTlj setting, the actual measured value was corrected using a sensitivity correction value due to the presence of scattered X-rays in the measurement space and variations in detection accuracy of the measurement system. When selecting a sensitivity correction value, it is often selected based on the size of the effective field of view.

The effective field of view refers to the photographic field of view of the head, abdomen, etc., and can be defined by the size of the spread of the fan beam. When the effective field of view becomes large, a sensitivity correction value corresponding to a large amount of attenuation is selected, and when the effective field of view becomes small, a sensitivity correction value corresponding to a small amount of attenuation is selected.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, a problem occurs when the effective field of view and the actual amount of attenuation of the subject do not correspond. For example, even if a large effective field of view is selected, if the actual amount of attenuation of the subject is small, the selected sensitivity correction value will be too large. As a result, changes in radiation quality and the influence of scattered radiation occur, making sensitivity correction inaccurate. This causes a ring-shaped pattern (artifact). Further, there is a problem that the CT value may be different from an image obtained by optimal sensitivity correction in a small effective field of view.

On the other hand, a similar problem occurs when measuring a subject with large attenuation in a small effective field of view.

An object of the present invention is to provide an X@CT apparatus that allows sensitivity correction values to be selected based on the actual amount of attenuation of the subject, rather than selecting the sensitivity correction value based on the size of the effective field of view.

[Means to solve the problem]

The present invention provides means for obtaining the sum total of attenuation through all channels of a subject from measurement values of the X-ray detector at any opposing position between an X-ray source and a multi-channel X-ray detector; It consists of means for selecting a corresponding sensitivity correction value, and means for using the selected sensitivity correction value as a sensitivity correction value for correcting the actual measurement value.

[Effect]

According to the present invention, the total amount of attenuation of the subject is obtained, and the corresponding sensitivity correction value is selected from this total. This makes it possible to select a sensitivity correction value that matches the amount of attenuation of the subject.

〔Example〕

FIG. 2 is a diagram showing an example of determining the amount of attenuation from one channel, and FIG. 3 is a diagram showing an example of determining the amount of attenuation for all channels. In Figure 2, subjects 1 and 2 are the same subjects; (a) is a diagram showing the amount of attenuation 3 in a certain channel in a horizontally long state, and (b) is a diagram in a vertically long state. It is a figure showing the amount of attenuation 4 in the same channel. This figure 2 (a), (b)
) to find the amount of attenuation in one channel.

The idea of using this as the amount of attenuation of the subject is not reliable as the amount of attenuation because the amount of attenuation differs between state 1 and state 2 of the subject, 3 and 4.

In this embodiment, the concept shown in FIG. 3 is adopted. Figure 3(a)
is a diagram in which the sum of the attenuation amounts through all channels in state 1 is shown with diagonal lines. On the other hand, FIG. 3(b) is a diagram in which the total amount of attenuation through all channels in state 2 is shown with diagonal lines.

As is clear from FIGS. 3(a) and (b), state 1
, 2, even if the opposing position between the X-ray source and the X-ray detector changes, the total amount of attenuation 5, 6 through all channels through the object does not change. However, this total attenuation amount is the entire value of the attenuation amount of the subject.

In this embodiment, in either of FIG. 3(a) or (b), the total amount of attenuation through all channels at any opposing position is determined, and the corresponding sensitivity correction value is selected from this total. .

FIG. 4 shows the relationship between the detector channel and the amount of attenuation by a phantom (II-like object). This is a diagram for inserting a phantom in place of an actual subject and attempting to obtain measured values from this phantom as the sum of attenuation amounts. Total value? , 8.9 are large, medium, and large as shown in the figure.
This is the sum total value of phantoms that have a small relationship. According to such a phantom, the total amount of attenuation can be obtained without measurement using an actual subject. However, since it is a phantom, if the total attenuation amount is calculated for each phantom in advance and stored in the memory corresponding to the phantom, the actual measurement procedure is not necessary.

FIG. 1 is a processing flow of this embodiment. This embodiment is an embodiment in which the total amount of attenuation is measured and corrected using a subject. First, the sensitivity correction value in the auxiliary memory (not shown) is read and temporarily stored in the correction value memory (which may also be used as the main memory) (F2). Next, any X-ray The subject is irradiated with fan beam X-rays with the source and the X-ray detector facing each other. This transmitted X-ray is detected by an X-ray detector. The X-ray detector is a multi-channel detector, and the computer adds up the measured values of all channels of this multi-channel X-ray detector.In reality, the amount of attenuation is obtained by logarithmically converting the amount of transmitted X-rays, not the amount of transmitted X-rays. is determined, this is used as the measured value, and the total amount of attenuation is determined (F3).

Access the correction value memory from the total attenuation amount and read the corresponding sensitivity correction value (F4, F5), then perform correction calculations (for example, difference or division) (F6), and perform reconstruction calculations from the correction results. (F7), and displays the reconstructed image on the CRT using a video signal (F8). After displaying, exit (F9)
).

FIG. 5 is a processing system diagram. The detector 10 is an input device including a multi-channel probe, an integrator, and an AD converter. The CPU 1 and the main memory 12 are computers that perform the entire process shown in FIG.

The auxiliary memory 15 is a memory that stores correction values and also stores various image data. The CRT 14 displays the reconstructed image. 13 is a common bus.

With this system configuration, the processing shown in FIG. 1 can be realized.

〔Effect of the invention〕

According to the present invention, a sensitivity correction value can be selected according to the actual amount of attenuation of the subject, and appropriate sensitivity correction can be achieved.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of the processing of the present invention, Figure 2 is a diagram showing the amount of attenuation corresponding to channels, Figure 3 is a diagram for calculating the total amount of attenuation of a subject, and Figure 4 is an example diagram of a phantom. , FIG. 5 is a processing system diagram of the present invention. DESCRIPTION OF SYMBOLS 10... Detection system, 11... CPU, 12... Main memory, 13... Common lotus, 14... CRT, 15...
...Auxiliary memory. No. 12, No. 3, No. 40 m→*>#1L&

Claims (1)

[Claims] 1. A fan beam X-ray source, a multi-channel X-ray detector that rotates in opposition to the X-ray source and detects transmitted X-rays transmitted through a subject, and a sensitivity correction value. An X-ray device comprising: a memory for storing a value, a means for correcting an actual measurement value obtained by an X-ray detector from a subject using a sensitivity correction value in the memory, and a means for reconstructing an image using the actual measurement value after the correction. In a ray CT apparatus, means for obtaining the sum total of attenuation through all channels of a subject at any opposing position between an X-ray source and an X-ray detector, from the measurement value of the X-ray detector, and a means corresponding to the sum total of attenuation. an X-ray C comprising means for selecting a sensitivity correction value from the memory, and means for using the selected sensitivity correction value as a sensitivity correction value for correcting the actual measurement value.
T device.