JPH06142095A - X-ray ct apparatus - Google Patents

Abstract

PURPOSE:To facilitate the realization of continuous measurement in the cost of a memory in particular by reducing the capacity of a buffer memory for storing a measuring data temporarily to achieve a lower cost in an image processor. CONSTITUTION:An image processor 15 is made up of a data compression means 21 to reduce the amount of a data by compression when a measuring data is stored into a buffer memory 22, an image reconstruction computing means 25 which reads the measuring data compressed from the buffer memory 22 to perform an image reconstruction computation using the compressed data as intact and a data extension means 25 to apply a reconstruction image data obtained by the means 25 to an image display device 20 and an external storage device 27 after the data is subjected to a processing for releasing the compression thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus in which the capacity of a buffer memory for temporarily storing measurement data is reduced.

[0002]

2. Description of the Related Art A conventional X-ray CT apparatus is shown in FIG. In FIG. 2, the X-rays from the X-ray tube 11 pass through the subject 12, and the transmitted X-rays are detected by the X-ray detector 13 consisting of 700 to 1000 channels and converted into electric signals.
Further, A / D converter 14 performs A / D conversion to obtain measurement data.

This measurement data is taken into the image processing device 15 and temporarily stored in the buffer memory 16. The measurement data stored in the buffer memory 16 is subjected to correction processing calculation by the correction processing calculator 17, and is then supplied to the image reconstruction calculator 19 via the buffer memory 18 to be subjected to image reconstruction calculation. The image data after the reconstruction calculation is sent to the image display device 20,
It is displayed as an image.

[0004] By the way, in principle, one measurement in the X-ray CT apparatus is basically performed around the subject 12 in 360 degrees.
700-1000 angle samples must be measured over the angle. Therefore, the amount of data generated by one measurement is (the number of channels) × (the number of angle sampling points), which is 0.5 × 10 ⁶ to 1 × 10 ⁶ . Normally, one data is expressed as 2 bytes of digital data,
The data amount is 1 to 2 megabytes.

[0005]

In the conventional apparatus, the image reconstructing process takes 3 to 5 seconds after the end of the measurement even if it is started at the same time as the start of the measurement, which is longer than one measurement time. On the other hand, in a recent X-ray CT system, which uses a slip ring and a brush between the rotating part of the scanner and the stationary part to transmit signals to each other, continuous measurement of 50 times is possible at one time. Has become.

When such a large number of measurements are continuously performed, the image reconstruction processing takes longer than one measurement time as described above, and thus the acquired measurement data are not processed but accumulated one after another. I will go. Therefore, in the conventional apparatus, as shown in FIG. 2, the buffer memory 16 is provided immediately after the measurement data capturing section of the image processing apparatus 15, or the buffer memory 18 is provided at the location after the correction processing operation is performed by the correction processing operation unit 17. It is provided to store data temporarily. However, if the measurement is continuously performed 50 times, the capacity of the buffer memory 16 (18) needs to be 30 megabytes or more.

As described above, in the conventional apparatus, the X-ray detector 1 is required in order to realize the continuous measurement technique and to improve the accuracy.
Since the number of channels and the number of angle sampling points are increasing, the amount of measurement data to be generated further increases, so that the capacity of the buffer memory 16 (18) also increases and there is a problem that it becomes expensive.

An object of the present invention is to suppress this increasing amount of data and reduce the capacity of the buffer memory,
It is to provide an X-ray CT apparatus capable of suppressing an increase in price.

[0009]

The above object is to provide a data compression means for compressing the measurement data when the measurement data is stored in a buffer memory to reduce the data amount, and a data compression means for compressing the data. An image reconstruction calculating means for reading the measured data thus obtained from the buffer memory and performing an image reconstruction operation with the compressed data as it is, and a process for uncompressing the reconstructed image data obtained by the image reconstruction calculating means. This is achieved by configuring the image processing apparatus with the data decompressing means for performing.

[0010]

The data compression means compresses the measured data when storing the measured data in the buffer memory to reduce the amount of the data. As a result, the capacity of the buffer memory can be reduced and the price can be reduced. On the other hand, if the same buffer memory capacity as that of the conventional device is maintained, the number of times of continuous measurement can be increased, and the performance of the device can be improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an X-ray CT apparatus according to the present invention.

In FIG. 1, 11 to 14 and 20 are the same as in FIG. Reference numeral 15 shows an image processing apparatus as in FIG. 2, but here it is configured as follows. That is, it is provided with a compression calculator 21, a buffer memory 22, a controller 23, a correction processing calculator 24, an image reconstruction calculator / data expander 25, and an interface 26 for an external storage device. In this case, the compression calculator 21 compresses the measurement data when storing the measurement data in the buffer memory 22 to reduce the amount of the data.
The correction processing calculator 24 performs correction processing calculation on the measurement data as it is as compressed data. The image reconstruction calculation / data decompressor 25 performs image reconstruction calculation on the measured data from the correction processing calculator 24 as compressed data, and decompresses the obtained reconstructed image data (data expansion processing). It is applied to the image display device 20 or the external storage device (magnetic disk or the like) 27.

Next, the operation of the device of the present invention will be described. The X-rays from the X-ray tube 11 pass through the subject 12, and the transmitted X-rays are detected by the X-ray detector 13 and converted into electric signals, and further A / D converted by the A / D converter 14. Measured data.

This measurement data is taken into the image processing device 15. The captured measurement data is stored in the buffer memory 22 after being compressed by the compression calculator 21 to reduce the data amount.

The compressed data (compressed measurement data) stored in the buffer memory 22 is fetched by the correction processing calculator 24, and the offset correction of the X-ray detector 13 and the fluctuation correction of the X-ray tube 11 are performed as the compressed data. The correction processing calculation such as is performed.

The data (compressed data) after the correction processing calculation is subjected to the image reconstruction calculation by the image reconstruction calculation / data decompressor 25 as it is as the compressed data, and the obtained reconstruction image data is uncompressed ( Data decompression processing) is applied to the image display device 20 or the external storage device 27.

The image display device 20 thereby displays the reconstructed image. The external storage device 27 can record both the image data after the reconstruction and the data expansion processing and the data (compressed data) after the correction processing calculation.

The controller 23 controls the compression calculator 21 and the buffer memory 22 when the measurement data is compressed, and may be either dedicated hardware or a general-purpose CPU. When a general-purpose CPU is used, the compression calculator 21 may be replaced with a simple interface with the A / D converter 14, and the measurement data compression calculation may be executed by the general-purpose CPU.

The measurement data compression is lossless compression because the data to be handled is raw measurement data. Any method may be used as long as it is lossless compression, and as an example of a simple method, it is conceivable to use a compression method by a difference operation between two data.

[0020]

The present invention has the following effects. Generally, the measurement data in the X-ray CT apparatus can be compressed by a data amount of about 40 to 50% even when the compression processing by the difference calculation is performed, and therefore the capacity of the buffer memory of the measurement data is reduced to about half. It is possible,
The price of the device can be reduced. On the other hand, assuming that it has a memory capacity equivalent to that of the conventional device, it will be possible to perform approximately twice as many continuous measurements, and if it is now possible to make approximately 50 continuous measurements, it will be possible to make continuous measurements up to approximately 100 times. Therefore, the performance of the device can be improved. Furthermore, in the image processing device, since the measurement data is compressed from the beginning, it is possible to increase the number of measurement times that the measurement data can be stored in the external storage device.
Further, when storing the data, a new compression process is not required, so that the cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a device of the present invention.

FIG. 2 is a block diagram of a conventional device.

[Explanation of symbols]

 11 X-ray tube 12 Subject 13 X-ray detector 14 A / D converter 15 Image processing device 20 Image display device 21 Compression calculator 22 Buffer memory 23 Controller 24 Correction processing calculator 25 Image reconstruction calculation / data expander 26 External storage interface 27 External storage device

Claims (1)

[Claims] 1. A buffer memory for temporarily storing measurement data obtained by A / D conversion of a signal from an X-ray detector is provided immediately after the measurement data capturing section of an image processing apparatus for performing image reconstruction calculation. In the X-ray CT apparatus, the image processing apparatus compresses the measurement data when the measurement data is stored in the buffer memory to reduce the data amount, and the data compression unit. The image reconstruction calculation means for reading the measurement data compressed by the means from the buffer memory and performing the image reconstruction calculation with the compressed data as it is, and for compressing the reconstructed image data obtained by the image reconstruction calculation means. An X-ray CT apparatus, comprising: a data decompression means for performing a solving process.