JPH0865658A - Method and device for compressing row data - Google Patents

Abstract

PURPOSE: To compress the row data of an X-ray CT device with high compressibility. CONSTITUTION: A row data compressor 200 is provided with an interpolator 7 for calculating interpolated row data D (k,i+0.5) from the row data of one correspondent channel for the counter view of row data in the parallel view system of the CT device and the row data of a channel adjacent to that channel, correspondent channel difference computing element 5 for calculating the difference between the interpolated row data D (k,i+0.5) and row data D (k+m/2, n+1-i) of the other correspondent channel, and adjacent channel difference computing element 4 for calculating the difference between row data D (k, i) of the adjacent channel for any one view and the row data D (k, i+1). Thus, data transfer capacity can be reduced and high-seed data transfer or a low-speed storage device can be effectively utilized. Further, data storage capacity can be reduced and the number of row data to be saved can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention is applicable to raw data (raw data).
ta) a compression method and apparatus, more specifically, CT
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw data compression method and apparatus capable of reducing the number of bits by compressing parallel view type raw data in a (Computer Tomography) apparatus.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of an example of a conventional raw data compression apparatus. This raw data compression device 500
Is a data collection device 1, a buffer 52 for one data,
The adjacent channel difference calculator 4 is provided. The data collector 1 collects raw data acquired by the detector S of the X-ray CT apparatus, and sets a set of raw data of parallel X-ray transmission paths as a raw data set of one view, and the raw data is arranged in a predetermined order. Is output serially. Such raw data is called parallel view type raw data. From the output of the data acquisition device 1, as shown in FIG. 3, the X-ray transmission path a of the channel [i] and the X-ray transmission path of the channel [i + 1] are shown.
The line transmission path b is a parallel path separated by one channel. Note that 1 ≦ k ≦ m and 1 ≦ i ≦ (n−1). The one-data buffer 52 outputs the raw data D (k, i) one channel before the raw data D (k, i + 1) output from the data collection device 1. The adjacent channel difference calculator 4 outputs adjacent difference raw data E ′ (k, i), which is E ′ (k, i) = D (k, i) −D (k, i + 1) (1). As described above, although the X-ray transmission paths a and b are separated by one channel, they are the paths that transmit almost the same portion of the subject H. Therefore, the raw data D (k, i) and D (k, i)
i + 1) has a correlation with the adjacent difference raw data E ′.
(K, i) is raw data D (k, i) or D (k, i)
The number of bits is compressed more than i + 1). When the number of bits of the raw data D (k, i) is d and the number of bits of the adjacent difference raw data E '(k, i) is e', the compression rate r'is r '= e' / d ... (2) 0 <r '<1.

All raw data are raw data (k, 1) for k = 1 to m and adjacent differential raw data E '(k,
1) to E '(k, n-1) are set, the required number of bits C'of all raw data is C' = m * {d + e '(n-1)} (3) . On the other hand, all raw data without the compression is raw data (k, 1) for k = 1 to m.
.About.D (k, n), the required number of bits Z of all raw data is Z = m.times.d.times.n (4). Therefore, the compression ratio R ′ for all raw data
Is R ′ = C ′ / Z = r ′ + 1 / n−r ′ / n (5) To give numerical examples, m = 64, n = 128, d
= 8, Z = 65536, e '= 6, r' = 0.75
C '= 49280 and R' = 0.75195.

[0004]

In the above-mentioned conventional raw data compression apparatus 500, the adjacent X-ray transmission paths a and b are 1 or less.
Since the channels are separated, the raw data D (k,
The correlation between i) and D (k, i + 1) was small, and the compression ratios r ′ and R ′ were limited. Therefore, it is an object of the present invention to provide a raw data compression method and apparatus that can obtain a higher compression rate.

[0005]

According to a first aspect of the present invention, as a whole, a difference between raw data of a parallel view method in a CT apparatus and raw data of a corresponding channel of an opposite view is obtained. A raw data compression method for compressing the amount of data is provided.

According to a second aspect, the present invention takes the difference between the raw data of the parallel view method in the CT apparatus and the raw data of the corresponding channel of the opposite view, and the raw data of the adjacent channel of one view. A raw data compression method characterized by compressing the data amount as a whole by taking the difference between them.

[0007] In a third aspect, the present invention relates to parallel view type raw data in a CT apparatus by interpolating raw data from one raw data of a corresponding channel of an opposite view and raw data of a channel adjacent to that channel. There is provided a raw data compression method characterized in that data is calculated and the difference between the interpolated raw data and the other raw data of the corresponding channel is calculated to compress the entire data amount.

[0008] In a fourth aspect, the present invention relates to parallel view type raw data in a CT apparatus by using an interpolated raw data from one raw data of a corresponding channel of an opposite view and raw data of a channel adjacent to the corresponding channel. Calculate the data, take the difference between the interpolated raw data and the other raw data of the corresponding channel, and also take the difference between the raw data of the adjacent channels of one of the views to compress the total data amount. A raw data compression method is provided.

According to a fifth aspect, the present invention comprises a corresponding channel difference calculating means for calculating the difference between the raw data of the parallel view system in the CT apparatus and the raw data of the corresponding channel of the opposite view. A raw data compression device for performing the same is provided.

According to a sixth aspect of the present invention, the present invention provides a corresponding channel difference calculating means for calculating a difference between raw data of a corresponding view channel and raw data of a parallel view method in a CT apparatus, and adjoining one view. And a adjacent channel difference calculating means for calculating the difference between the raw data of the channels.

In a seventh aspect, the present invention is based on parallel view type raw data in a CT apparatus, and interpolates raw data from raw data of one channel corresponding to an opposite view and raw data of a channel adjacent to the channel. And a corresponding channel difference calculating means for calculating a difference between the interpolated raw data and the other raw data of the corresponding channel.

[0012] In an eighth aspect, the present invention is based on parallel view type raw data in a CT apparatus, and interpolates raw data from raw data of one channel corresponding to an opposite view and raw data of a channel adjacent to the channel. And a corresponding channel difference calculating means for calculating the difference between the interpolated raw data and the other raw data of the corresponding channel, and an adjacency for obtaining the difference between the raw data of the adjacent channels of either one of the views. There is provided a raw data compression device comprising a channel difference calculation means.

[0013]

In the raw data compression method according to the first aspect and the raw data compression apparatus according to the fifth aspect, the CT
The difference between the raw data of the parallel view method in the device and the raw data of the corresponding channel of the opposite view is calculated. Each X of the corresponding channel of the opposite view
The line transmission paths are separated by 0.5 channel. Therefore, the correlation between the raw data of the corresponding channel is stronger than the correlation between the raw data of the adjacent channels separated by one channel, and a compression ratio r higher than the compression ratio r ′ is obtained. That is, when the bit number of the difference between the raw data of the corresponding channels of the opposite view is e, r = e / d (6) e <e '0 <r <r'<1.

In the raw data compression method according to the second aspect and the raw data compression apparatus according to the sixth aspect,
For the parallel view type raw data in the CT apparatus, the difference between the raw data of the corresponding channel of the opposite view and the difference between the raw data of the adjacent channels of one view are calculated. Therefore, the required number of bits C of all raw data is C = (m / 2) × {d + e ′ (n−1) + e × n} (7), and the compression ratio R for all raw data is R = C / Z = (r '+ 1 / n-r' / n + r) / 2 (8) = (R '+ r) / 2. To give numerical examples, m = 64, n = 128, d
= 8, Z = 65536, e '= 6, r' = 0.75, e
= 5, r = 0.625, C = 45120, R = 0.68
848.

In the raw data compression method according to the third aspect and the raw data compression apparatus according to the seventh aspect,
For parallel view type raw data in a CT apparatus, interpolated raw data is calculated from one raw data of a corresponding channel of an opposite view and raw data of a channel adjacent to that channel, and the interpolated raw data and the corresponding channel are calculated. The difference from the other raw data of is taken. The X-ray transmission path associated with the interpolated raw data matches the X-ray transmission path of the corresponding channel. Therefore, the correlation between the interpolated raw data and the raw data of the corresponding channel becomes particularly strong, and a compression ratio r ″ higher than the compression ratio r ′ or r is obtained. When the number of bits of the data difference is e ″, r ″ = e ″ / d (9) e ″ <e <e ′ 0 <r ″ <r <r ′ <1.

In the raw data compression method according to the fourth aspect and the raw data compression apparatus according to the eighth aspect,
For parallel view type raw data in a CT apparatus, interpolated raw data is calculated from one raw data of a corresponding channel of an opposite view and raw data of a channel adjacent to that channel, and the interpolated raw data and the corresponding channel are calculated. The difference between the raw data of the other channel and the raw data of the adjacent channel of one of the views is obtained. Therefore, the required number of bits C ″ of all raw data is C ″ = (m / 2) × {d + e ′ (n−1) + e ″ (n−1) + e} (10) The compression ratio R ″ is about R ″ = C / Z = (r ′ + 1 / n−r ′ / n + r ″ −r ″ / n + r / n) / 2 (11) = (R ′ + r ″ −r ″) / N + r / n) / 2 Numerical examples are: m = 64, n = 128, d
= 8, Z = 65536, e '= 6, r' = 0.75, e
= 5, r = 0.625, e ″ = 4, r ″ = 0.5, C ″
= 41056, R ″ = 0.62646.

[0017]

The present invention will be described in more detail with reference to the embodiments shown in the drawings. The present invention is not limited to this.

[First Embodiment] FIG. 1 is a block diagram showing a raw data compression apparatus according to a first embodiment of the present invention. This raw data compression device 100
Is a data collection device 1, a buffer 2 for one view, and F
It comprises an IFO buffer 3, an adjacent channel difference calculator 4, a corresponding channel difference calculator 5, and an address generator 6.

The data collecting apparatus 1 collects raw data acquired by the detector S of the X-ray CT apparatus, and sets a set of raw data of parallel X-ray transmission paths as a raw data set of one view, in a predetermined order. To output raw data serially. Such raw data is called parallel view type raw data. From the output of the data collection device 1,
As shown in FIG. 1, X of channel [i] in [k] view
The line transmission path a and its adjacent channel [i +
The X-ray transmission path b of 1] is a parallel path separated by one channel. In addition, channel [i] of [k] view
Of the channel [n + 1-i] of the [k + m / 2] view that is the corresponding channel of the X-ray transmission path a of
The line transmission path c is a parallel path separated by 0.5 channel. Note that 1 ≦ k ≦ m. Also, 1 ≦ i ≦ (n−1) for adjacent channels and 1 ≦ i ≦ n for corresponding channels.

The one-view buffer 2 holds the one-view raw data output from the data collection device 1. For example, channels [1] to [k + m / 2] view
Raw data D (k + m / 2,1) to D of channel [n]
Hold (k + m / 2, n). The FIFO buffer 3 holds from the raw data of the previous view of the raw data held in the one-view buffer 2 to the raw data of the opposite view of the raw data held in the one-view buffer 2 and is old. Output in order. For example, the above 1
When the raw data of the [k + m / 2] view is stored in the view buffer 2, the raw data of the [k + m / 2−1] view to the raw data of the [k] view are stored, and the raw data of the [k] view is stored. Output raw data.

The adjacent channel difference calculator 4 operates in the F
A difference operation of E ′ (k, i) = D (k, i) −D (k, i + 1) (12) is performed on the output of the IFO buffer 3 to obtain adjacent difference raw data E ′ (k,
i) is output. However, 1 ≦ k ≦ m / 2, 1 ≦ i ≦ (n
-1). As described above, the X-ray transmission paths a and b are
Although it is separated by one channel, it is a path that passes through almost the same portion of the subject H. Therefore, the raw data D
There is a correlation between (k, i) and D (k, i + 1), and the adjacent difference raw data E ′ (k, i) is the raw data D (k, i).
The number of bits is compressed more than i) or D (k, i + 1). Let the number of bits of raw data D (k, i) be d,
When the number of bits of the adjacent difference raw data E ′ (k, i) is e ′, the compression rate r ′ is r ′ = e ′ / d (13) 0 <r ′ <1.

The corresponding channel difference calculator 5 has the above 1
A difference operation of E (k, i) = D (k, i) -D (k + m / 2, n + 1-i) (14) is performed on the outputs of the view buffer 2 and the FIFO buffer 3 to obtain the corresponding difference. Raw data E (k, i)
Is output. However, (m / 2 + 1) ≦ k ≦ m, 1 ≦ i ≦
n. As described above, the X-ray transmission paths a and c are 0.
It is a path that passes through almost the same part of the subject H, although it is separated by 5 channels. Therefore, the raw data D
There is a stronger correlation between (k, i) and D (k + m / 2, n + 1-i), and the corresponding difference raw data E (k, i) is the raw data D (k, i) or D (k + m / 2). , N + 1-
The number of bits is compressed more than i). Raw data D
Let d be the number of bits of (k, i), and the corresponding difference raw data E
When the number of bits of (k, i) is e, the compression ratio r is r = e / d (15) 0 <r <r '<1.

The address generator 6 generates i = 1 to n each time output of raw data for one view from the data collection device 1 to the buffer for one view 2 is completed.
I = 1 to (n-1) to the adjacent channel difference calculator 4
Is input to the corresponding channel difference calculator 5 from i = 1 to
Enter n.

All raw data are raw data (k, 1) for k = 1 to m / 2 and adjacent differential raw data E '.
A set of (k, 1) to E '(k, n-1) and k = (m /
Corresponding differential raw data E (k,
1) to E (k, n), the required number of bits C of all raw data is C = (m / 2) × {d + e ′ (n−1) + e × n} (16) Is. On the other hand, all raw data without the compression is raw data (k, 1) for k = 1 to m.
.About.D (k, n), the required number of bits Z of all raw data is Z = m.times.d.times. (17). Therefore, the compression ratio R for all raw data is R = C / Z = (r '+ 1 / n-r' / n + r) / 2 (18) = (R '+ r) / 2. To give numerical examples, m = 64, n = 128, d
= 8, Z = 65536, e '= 6, r' = 0.75, e
= 5, r = 0.625, C = 45120, R = 0.68
848.

-Second Embodiment- FIG. 2 is a block diagram showing a raw data compression apparatus according to a second embodiment of the present invention. This raw data compression device 200
The configuration of is the same as the raw data compression apparatus 100 of the first embodiment.
2 is different from that of FIG. 2 in that an interpolator 7 is added, and the corresponding channel difference calculator 5 calculates the difference between the output of the interpolator 7 and the output from the buffer 2 for one view. . The interpolator 7 uses the raw data D (k, i) of the channel [i] of the [k] view and the channel [i + 1].
Interpolation raw data D (k, i + 0.5) is calculated from the raw data D (k, i + 1) of No. The interpolated raw data D (k, i + 0.5) is calculated raw data for an X-ray transmission path c intermediate between the X-ray transmission path a and the X-ray transmission path b, as shown in FIG. However, 1
≦ k ≦ m / 2 and 1 ≦ i ≦ (n−1). And i
= N, the interpolator 7 outputs the raw data D (k, n) of the channel [n] as it is. Corresponding channel difference calculator 5 outputs 1 ≦ k ≦ m / 2 and 1 ≦ i ≦ (n−1) to the outputs of the one-view buffer 2 and the interpolator 7.
In the case of, E (k, i) = D (k, i + 0.5) -D (k + m / 2, n + 1-i) (19) The difference calculation is performed and 1 ≦ k ≦ m / 2, i = n Then, the difference calculation of E (k, i) = D (k, n) -D (k + m / 2,1) (20) is performed, and the corresponding difference raw data E (k, i) is obtained.
Is output. As described above, the raw data D (k, i +
Since 0.5) and D (k + m / 2, n + 1-i) are the same X-ray transmission path c, there is a particularly strong correlation, and
The corresponding difference raw data E (k, i) according to the equation (9) is the raw data D (k, i) or D (k + m / 2, n + 1−).
The number of bits is compressed more than i). Raw data D
When the number of bits of (k, i) is d and the number of bits of the corresponding difference raw data E (k, i) according to the above equation (19) is e ″, the compression ratio r ″ is r ″ = e ″ / d ... (21) 0 <r ″ <r <r ′ <1.

All raw data are raw data (k, 1) for k = 1 to m / 2 and adjacent differential raw data E '.
A set of (k, 1) to E '(k, n-1) and k = (m /
Corresponding differential raw data E (k,
1) to E (k, n), the required number of bits C ″ of all raw data is C ″ = (m / 2) × {d + e ′ (n−1) + e ″ × (n− 1) + e} (22) Therefore, the compression ratio R ″ for all raw data is
Is R ″ = C / Z = (r ′ + 1 / n−r ′ / n + r ″ −r ″ / n + r / n) / 2 (23) = (R ′ + r ″ −r ″ / n + r / n) / It becomes 2. To give a numerical example, m = 64, n = 128, d
= 8, Z = 65536, e '= 6, r' = 0.75, e
= 5, r = 0.625, e ″ = 4, r ″ = 0.5, C ″
= 41056, R ″ = 0.62646.

[0027]

According to the raw data compression method and apparatus of the present invention, it is possible to reduce the number of bits by compressing parallel view type raw data in a CT apparatus at a high compression rate. Therefore, the data transfer capacity can be reduced, and high-speed data transfer and slow storage device can be utilized. Also, because the amount of data as a whole can be reduced,
The number of raw data to be stored can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a raw data compression apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a raw data compression apparatus according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a conventional raw data compression apparatus.

[Explanation of symbols]

 100,200 Raw data compression device 1 Data collection device 2 1 view buffer 3 FIFO buffer 4 Adjacent channel difference calculator 5 Corresponding channel difference calculator 6 Address generator 7 Interpolator S X-ray CT device detector H Subject a , B, c X-ray transmission path

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H03M 7/36 9382-5K H04N 7/32

Claims (8)

[Claims] 1. A raw data compression method for compressing a total data amount by calculating a difference between raw data of a corresponding channel of an opposite view and raw data of a parallel view method in a CT apparatus. . 2. The whole of the parallel view type raw data in the CT apparatus is calculated by taking the difference between the raw data of the corresponding channel of the opposite view and the difference between the raw data of the adjacent channels of one view. A method for compressing raw data, characterized by compressing the amount of data. 3. Interpolation raw data is calculated from the raw data of one of the corresponding channels of the opposite view and the raw data of the channel adjacent to the channel with respect to the raw data of the parallel view method in the CT apparatus. A raw data compression method, wherein the difference between the data and the other raw data of the corresponding channel is calculated to compress the entire data amount. 4. Interpolation raw data is calculated from the raw data of one of the corresponding channels of the opposite view and the raw data of the channel adjacent to the corresponding channel of the parallel view type raw data in the CT apparatus, and the interpolated raw data is calculated. The raw data is characterized by taking the difference between the data and the other raw data of the corresponding channel, and taking the difference between the raw data of the adjacent channels of either one of the views to compress the overall data amount. Compression method. 5. A raw data compression apparatus comprising a corresponding channel difference calculation means for calculating a difference between raw data of a corresponding channel of an opposite view with respect to raw data of a parallel view system in a CT apparatus. 6. A corresponding channel difference calculating means for calculating a difference between raw data of a corresponding channel of an opposite view with respect to raw data of a parallel view method in a CT device, and a difference between raw data of adjacent channels of one view. And an adjoining channel difference calculating means for obtaining the raw data compression device. 7. Interpolation means for calculating interpolated raw data from raw data of one of corresponding channels of an opposite view and raw data of a channel adjacent to the channel for parallel view type raw data in a CT apparatus, A raw data compression apparatus comprising: a corresponding channel difference calculating means for calculating a difference between the interpolated raw data and the other raw data of the corresponding channel. 8. Interpolation means for calculating interpolated raw data from raw data of one of corresponding channels of an opposite view and raw data of a channel adjacent to the channel for parallel view type raw data in a CT apparatus, A corresponding channel difference calculating means for calculating a difference between the interpolated raw data and the other raw data of the corresponding channel, and an adjacent channel difference calculating means for calculating a difference between raw data of adjacent channels of either one of the views are provided. A raw data compression device characterized in that