JPH0630924A - X-ray ct apparatus - Google Patents

Abstract

PURPOSE:To enable to simplify a frame construction with a smaller package capacity of a data collection part by selecting signals from a plurality of channels of a detector sequentially to obtain a difference of a plurality of digital signals adjacent or close to each other. CONSTITUTION:A frame package part A has a surface detector in which light- voltage transducers are arranged two-dimensionally to convert an X-ray dose from an X-ray bulb 1 into a voltage and an amplification part 2 to amplify outputs a1M-aNM of NXM pieces of X-ray detector. Signals b1M-bNM amplified are selected with M pieces of mutiplexer selected in sequence at each channel and a signal (c) thereof is converted into a digital signal (d) with an A/D converter 5. A differential compressor 6 determines a difference of a plurality of digital signals (d) from a channel adjacent or close thereto and digital signals (e) compressed with a parallel-serial converter 7 undergo a parallel-series conversion. A serial signal (p) obtained is transferred with a slip ring 8.

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, and more particularly to a data acquisition unit (DAS) of an X-ray two-dimensional detector of the X-ray CT apparatus.

[0002]

2. Description of the Related Art Conventionally, in an X-ray CT apparatus, detectors for detecting X-rays emitted from a tube and transmitted through an object have been arranged in a line in the channel direction. Further, a plane detector in which N detectors arranged in the channel direction are arranged in M columns and arranged two-dimensionally (N, M) is being developed (see FIG. 2).

[0003]

However, if the above-mentioned surface detector is constructed by arranging N detectors which were conventionally arranged in a line in the channel direction, the data collector is mounted and the data is transferred from the data collector. Was almost N times, which was not practical. For example, there is a problem that analog filters are required for the number of detection elements by simply combining the filter of the data acquisition unit and the surface detector, and it cannot be mounted on the rotary mount, and the data transfer from the mount to the console is N channels. 800 views / s in × M columns,
16 Mbit / CH, 200 Mbit / sec
It becomes a large amount of data of s. To transfer this, about 100 slip rings are required, which is not practical.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an X-ray CT apparatus having a mounting section capable of reducing the mounting capacity of a data acquisition section in an X-ray two-dimensional detector. .

[0005]

In order to achieve the above object, the X-ray CT apparatus of the present invention has a two-dimensional array of X-ray CT devices.
A plurality of X-ray detection elements for electrically converting dose, an amplification means for amplifying signals from a plurality of channels consisting of a one-dimensional array of the X-ray detection elements, and a signal amplified by the amplification means are sequentially selected. Selecting means, a converter for converting the signal selected by the selecting means into a digital signal, a compressing means for taking a difference between a plurality of digital signals from adjacent or adjacent channels, and a digital compressed by the compressing means It is characterized by comprising a gantry mounting section having a transfer means for transferring a signal. Further, in the above X-ray CT apparatus, it is desirable that the selecting means is a multiplexer, and has means for making one round of the multiplexer at an integer multiple of the cutoff frequency of the filter.

Further, the X-ray CT apparatus selects the gantry mounting section, the restoring means for restoring the compressed digital signal transferred via the transferring means, and the output of the restoring means as the digital output for each channel. It is desirable to have a selective distribution means for distributing and distributing, and a filter means for filtering the distributed digital output of each channel, and further, a data collecting section having a setting means capable of arbitrarily converting a filter constant. It is characterized by being provided.

[0007]

With the above construction, in the data collecting section of the X-ray CT apparatus of the present invention, the two-dimensionally arranged X-ray detecting elements electrically convert the received X-ray capacitance, and the amplifying means makes each X-ray. The signal from the detection element is amplified, the selecting means sequentially selects the signals amplified by the amplifying means, the converter converts the signal selected by the selecting means into a digital signal, and the compressing means from adjacent or adjacent channels. Then, the transfer means transfers the digital signal compressed by the compression means by taking the difference between the plurality of digital signals. Further, the decompression means decompresses the compressed digital signal transferred through the transfer means, the selective distribution means selects and distributes the output of the decompression means as the output for each channel, and the filter means receives the input from the setting means. The output signal of each distributed channel is filtered according to the filter constant.

[0008]

1 is a block diagram showing the configuration of an embodiment of a data acquisition unit of an X-ray CT apparatus of the present invention, and FIG. 2 is an explanatory diagram showing an example of connection between a surface detector and a surface detector and an amplifier. is there.
In FIG. 1, a data collection unit including a gantry mounting unit A and other portions B of the X-ray CT apparatus, an image reconstruction unit C, and a display unit 1
6 is shown.

The gantry mounting section A of the data collecting section is a two-dimensional photo-current conversion element that receives an X-ray dose from the X-ray tube 1 and converts it into an electric current (a row consisting of N elements is M Row; N
Surface detectors 2 (see FIG. 2) arranged in a channel × M array, and outputs a of N × M X-ray detection elements of the surface detector 2.
An amplification unit 3 composed of M × N amplifiers for amplifying 1M to aNM respectively and converting them into a voltage, and the amplified M × N signals b1M to bNM are sequentially arranged for each channel from b.1 to b.N. The M number of multiplexers 4 as selecting means for selecting, the A / D converter 5 for converting the signal c selected by the multiplexer 4 into a digital signal d, and the difference between a plurality of digital signals d from adjacent or adjacent channels. , A parallel-serial converter (PSC) 7 for converting the digital signal e compressed by the differential compressor 6 from parallel to serial, and a slip ring for transferring the converted serial signal f. It is composed of 8 and. The parallel-serial converter 7 and the slip ring 8 form a transfer means.

The other part B of the data collecting section is
A serial-parallel converter (SPC) 9 that reconverts the serial signal f transferred from the slip ring 8 into a compressed digital signal e, and a differential restoration that restores the digital signal d from the output signal e of the serial-parallel converter 9. 10, a buffer 11 as a selective distribution means for temporarily storing and sequentially outputting the output signal d of the difference restoring device 10, and a digital output (j11 for each X-ray detecting element stored in the buffer 11 and sequentially output). .About.jMN), the digital filter 12 as a filter means.
The serial-parallel converter 9 and the difference restorer 10 constitute a restorer.

Further, the data collecting unit, as shown in FIG. 1, is a filter constant setting unit 15 for setting the filter constant of the digital filter 12, and a controller 16 for controlling the multiplexer 4, the difference restoring unit 10 and the buffer 11.
And have.

As shown in FIG. 2, the surface detector 2 has an X on its upper surface.
An X-ray detection element 27, which is composed of a scintillator 25 arranged to face the ray tube and a photodiode 26 provided on the lower surface of the scintillator 25, is arranged in a plane. Each scintillator is shielded from light in all four directions so that light from an adjacent scintillator does not enter. The surface detector 2 is a two-dimensional (Mx) matrix of X-ray detection elements (channels) in which M rows of N-dimensionally arranged X-ray detection elements 27 are arranged.
N) consists of arrays. Then, the X-rays incident on the scintillator 25 are photo-current converted by the photodiode 26. The electrical conversion of light is not limited to the photoelectric conversion, and for example, the photoelectric conversion may be performed using a charge conversion element, and may be the result of the electrical conversion of light.

As shown in FIG. 2, the amplifying section 3 is composed of MxN amplifiers for converting the outputs from the MxN photodiodes 26 into voltages, and the output side of the amplifiers is for removing noise. A low pass filter (not shown) is provided.

The multiplexer 4 sequentially selects the X-ray detection signals b.1 to b.N of channels 1 to N by switching based on the control signal from the controller 16. The selection is performed from 1 to N in a cycle that is an integral multiple of the cutoff frequency of the filter, and the selection is not repeated after one cycle. Since M multiplexers 4 are provided, M-row X-ray detection signals b11 to bMN of 1 to N channels are sequentially selected. When a plurality of A / D converters are used, the signal b
Selection does not have to follow the above procedure.

The differential compressor 6 calculates the difference between b11 and b12, outputs the result as b12 ', then calculates the difference between b12 and b13, and outputs the result as b13', Similarly, the difference between bN-1 and b1N is calculated, and the result is output as bN-1N '. The difference may be calculated by calculating the difference between b11 and b21, and setting the result to b21 'and repeating the following.
Since there is no difference in the outputs (voltage levels) of the elements slightly apart, the difference between the outputs of the elements slightly apart may be calculated so that the difference between b11 and b51 is calculated and the result is b51 '. Data (digital signal) in which the difference output by the difference calculation is compressed e
Is output as.

The present invention makes use of the fact that the voltage level difference between adjacent or adjacent channels is small, and the data is reversibly compressed by the difference. Since the differential circuit has a simple circuit configuration, it can be made compact.

The parallel-serial converter 7 converts the compressed digital data e from 8-bit parallel data to serial data. By using the parallel-serial converter 7, the number of slip rings 8
Compared with the case where the parallel-serial converter 7 is not used, it is 1/8, which is smaller.

The differential decompressor 10 outputs the output of the differential compressor 6, which is transferred and decompressed into a digital signal by the serial-parallel converter 9, for example, b11 ', b12', ... bMN '.
From the formula; bij '= bij-1'; (i = 1 to N, j = 2 to N) and synchronized with the controller 16] in the M × N buffers 11 for each X-ray detection element. Store data temporarily. ●

The filter 12 is a digital filter,
The filter constant depends on the instruction from the filter constant setter 15. Conventionally, an analog filter was used as the filter means, but the buffer 1 by the controller 16 was used.
By synchronizing the output timings of 2 and making the cycle an integral multiple of the cutoff frequency of the filter, a digital filter can be used instead of the analog filter.
Then, by using the digital filter, the mounting capacitance of the circuit can be reduced. In addition, the filter constant setter 15
Input the cutoff linkage and the elements of the filter curve such as gain and phase, etc.
The switching of the 4th cutoff frequency can be set. Also,
With this setting, an optimum reconstructed image can be obtained.
Further, the filter constant setter 15 can specify a preset filter constant according to the site of the subject. In this case, since it is not necessary to manually set, the operator's operation can be simplified. Although one embodiment of the present invention has been described above, it is needless to say that the present invention is not limited to the above embodiment and various modifications can be made.

[0020]

As described above, according to the present invention,
Since the mounting capacity of the data collecting unit is reduced, the structure of the gantry is simplified. Further, since the amount of data is reduced, the speed of data transfer is increased. Furthermore, since there is no limitation from data transfer or mounting, the resolution and resolution of scanning are improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a data acquisition unit of an X-ray CT apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a connection example of a surface detector and a surface detector and an amplifier.

[Explanation of symbols]

 2 surface detector 3 amplification part (amplification means) 4 multiplexer (selection means) 5 A / D converter (converter) 6 differential compressor (compression means) 8 slip ring (transfer means) 10 difference restoration device (restoration means) 11 Buffer (selective distribution means) 12 Digital filter (filter means) 15 Filter constant setting device (setting means) 16 Controller A mounting section

Claims (5)

[Claims] 1. A plurality of X-ray detection elements arranged two-dimensionally for electrically converting an X-ray dose, amplification means for amplifying a signal from each X-ray detection element, and each amplified by the amplification means. Selecting means for sequentially selecting signals from the X-ray detecting element,
A converter for converting the signal selected by the selecting means into a digital signal, a compressing means for taking a difference between a plurality of digital signals from adjacent or adjacent X-ray detecting elements, and a digital signal compressed by the compressing means. An X-ray CT apparatus comprising: a gantry mounting unit having a transfer unit for transferring. 2. The X-ray CT apparatus according to claim 1,
An X-ray CT apparatus, wherein the selection means is a multiplexer. 3. The X-ray CT apparatus according to claim 2, wherein
An X-ray CT apparatus having means for making one round of a multiplexer at an integer multiple of a cutoff frequency of a filter. 4. The X-ray CT apparatus according to claim 1,
A gantry mounting unit, a decompression unit that decompresses the compressed digital signal transferred via the transfer unit of the gantry mounting unit, and a distribution unit that sequentially distributes the output of the decompression unit as a digital output for each X-ray detection element. An X-ray CT apparatus, comprising: a data collection unit having: a filter unit for filtering a distributed digital output of each X-ray detection element. 5. The X-ray CT apparatus according to claim 4,
Further, the X-ray CT apparatus is characterized by having setting means capable of arbitrarily converting a filter constant.