JPH04261650A - X-ray ct apparatus - Google Patents

Abstract

PURPOSE:To achieve a higher rotational speed of a rotary plate as advantage of a slip ring device by allowing the using of the slip ring device for a data transmission means for a static system without increase in a cut off frequency of the slip ring itself regardless of increase in the amount of data to be outputted from an X-ray detector. CONSTITUTION:A data compressing device 9 for compressing a data to a slip ring device 8 is provided on the side of a rotation system and a data restoring device 10 is provided on the side of a static system to restore the compressed data to be inputted into the static system from the data compressing device 9 through the slip ring device 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an X-ray CT apparatus that uses a slip ring device for data transmission from a rotating system to a stationary system.

0002

[Prior Art] An X-ray CT apparatus (third generation) is equipped with a rotating plate, a rotating system including an X-ray tube and an X-ray detector disposed on the rotating plate, and an image processing device. It mainly consists of a stationary system and a stationary system.

FIG. 3 is a schematic diagram of the configuration. As shown in this figure, an X-ray tube 2 and an X-ray detector 3 are arranged facing each other on a rotary plate 1, with a central portion between them. With the subject 4 positioned, the rotary plate 1 is rotated 360 degrees while emitting X-rays from the X-ray tube 2. Also, during the rotation, X-ray projection data is measured at every fixed angle.

[0004] This X-ray projection data is transmitted to the X-ray detector 3.
The minute analog signal is amplified by a preamplifier 5, digitized by an A/D converter 6, and the data is transmitted from the rotary plate 1 to an image processing device 7, where image reconstruction calculations are performed.

At this time, it is necessary to transmit data at point A in FIG. 3, that is, the boundary between the rotating system and the stationary system, but the amount of data passing through this point is usually 10 Mbit/s.
~12 Mbit/s.

As data transmission means at this time, there are two methods: a method using a cable directly connected to a predetermined location on the rotary plate 1 and routed around the rotary plate 1, and a method using a slip ring device. The slip ring device includes a slip ring having the same center as the rotating plate 1, and
A contact point that slides into this slip ring is provided on the stationary system side,
These devices transmit data between each other, and are being used more frequently as the rotation speed of the rotary plate 1 increases.

[0007]

In the above prior art, the method of using the slip ring device as a means of data transmission from the rotating system to the stationary system at point A is advantageous in increasing the rotational speed of the rotating plate 1 itself. It is.

However, when transmitting data using this slip ring device, the slip ring has a large diameter (about 1 m in diameter) and a long circumference. Therefore, considering the cutoff frequency determined by the signal propagation time on the slip ring (approximately 20 MHz here, see U.S. Pat. No. 4,139,251 regarding the cutoff frequency), the amount of data that can be reliably transmitted is several Mbit/ It will be about s. In other words, the amount of data (10 Mbit/s to 12 Mbit/s) when passing through point A during the aforementioned X-ray projection data measurement.
There was a problem that the slip ring device could not be used as it was because the number of slip rings was considerably less than that of s.s.

An object of the present invention is to reduce the amount of data sent from the rotating system to the stationary system even if the amount of data output from the X-ray detector increases (the amount of data (bit/s) that should be sent from the rotating system to the stationary system in conventional equipment). The object of the present invention is to provide an X-ray CT apparatus that can use a slip ring device as a data transmission means without any problems and can sufficiently achieve the high rotational speed of a rotary plate, which is an advantage of a slip ring device.

0010

[Means for Solving the Problems] The above object is to provide a rotating system including at least a rotating plate, an X-ray tube and an X-ray detector disposed on the rotating plate, and a rotating system including at least an image processing device. A third generation X-ray CT apparatus that uses a slip ring device for data transmission to a stationary system includes a data compressor that is provided on the rotating system side and compresses data to be sent to the slip ring device; This is achieved by providing a data restorer provided on the stationary system side to restore compressed data input from the data compressor to the stationary system via a slip ring device.

[0011]

[Operation] The data compressor is provided on the rotating system side and compresses data to be sent to the slip ring device. This results in
The amount of data transmitted (bit/s) from the rotating system to the stationary system is small, and the slip ring device can be used below the cutoff frequency on the slip ring. In other words, even if the amount of data output from the X-ray detector is large (the amount of data (bit/s) that should be sent from the rotating system to the stationary system in conventional equipment), there are no problems as a means of transmitting data from the rotating system to the stationary system. A slip ring device can be used instead.

The data restorer is provided on the stationary system side and restores compressed data input from the data compressor to the stationary system via a slip ring device. Therefore, the subsequent circuit configuration, such as an image processing device, can be the same as that of the conventional device.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described 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 this FIG. 1, 1 to 7 are the same as those in FIG. 3, respectively. In addition, point A also represents the boundary between the rotating system and the stationary system, as in Figure 3 (the left side of point A in the figure is the rotating system,
The right side represents the stationary system), but here it is assumed that the slip ring device 8 is located at the boundary between the rotating system and the stationary system.

A data compressor 9 is provided on the rotary plate 1 and compresses data (X-ray projection data) from the A/D converter 6 to the slip ring device 8.

Further, 10 is provided on the stationary system side, usually at the same location as the image processing device 7, and restores the compressed data input from the data compressor 9 to the stationary system via the slip ring device 8. Original X output from A/D converter 6
This is a data restorer that restores line projection data.

That is, in the conventional device, the output data of the A/D converter 6 is directly input to the image processing device 7 on the stationary side, whereas in the device of the present invention, the output data of the A/D converter 6 After compressing the data with the data compressor 9,
Data is transmitted from a point, that is, a rotating system to a stationary system, and the amount of data passing through point A is reduced by the amount compressed by the data compressor 9.

Further, after this compressed data passes through point A, it is restored to the original data by a data restorer 7 and sent to the image processing device 7. As a result, the image processing device 7 It becomes possible to handle data in the same way as devices.

As the data compression method used in the data compressor 9, a conventionally known method is used (for data compression, see, for example, "Computer Image Processing" by Takeshi Agoin and Masayuki Nakajima, Sanpo Publishing Co., Ltd., 1979, June 1979). Published on May 11th, see pages 129-136).

As shown in FIG. 2, in the normal X-ray projection data of the subject 4, the values (X-ray intensities) of adjacent data in the channel direction of the X-ray detector 3 do not differ greatly. Therefore, as a data compression method, if a differential data compression method is used in which the difference between adjacent data is used as the transmission data value rather than the absolute value of the data itself, the compression ratio will be high and the amount of data passing through point A can be reduced. can be further reduced.

[0020]

As explained above, according to the present invention, data transmitted from the rotating system side to the slip ring device is compressed to reduce the amount of data transmitted via the slip ring device. The slip ring device can be used without increasing the cutoff frequency of the ring itself or reducing the reliability of transmitted data, and the advantage of the slip ring device, which is the high speed of rotation of the rotating plate, can be fully achieved. It has the effect of gaining.

[0021] Since the data restorer is provided on the stationary system side and the compressed data input from the data compressor to the stationary system via the slip ring device is restored, the subsequent circuit configuration, for example, image processing The equipment can be the same as conventional equipment.

[Brief explanation of the drawing]

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

FIG. 2 is a diagram showing the relationship between the X-ray intensity detected by the X-ray detector and the channel direction during normal object measurement.

FIG. 3 is a block diagram showing a conventional device.

[Explanation of symbols]

1 Rotating plate 2 X-ray tube 3. X-ray detector 4 Subject 5 Preamplifier 6 A/D converter 7 Image processing device 8 Slip ring device 9 Data compressor 10 Data recovery device

Claims (1)

[Claims] Claim 1: Data transmission from a rotating system comprising at least a rotating plate and an X-ray tube and an X-ray detector disposed on the rotating plate to a stationary system comprising at least an image processing device. In an X-ray CT apparatus that uses a slip ring device for transmission, a data compressor is provided on the rotating system side and compresses data to the slip ring device, and a data compressor is provided on the stationary system side and compresses data from the data compressor to the slip ring device. An X-ray CT apparatus comprising: a data restorer for restoring compressed data input to a stationary system via a slip ring device.