JPS59141936A - Image treating apparatus for electrocardiograph synchronous type ct - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention collects a large amount of projection data by performing X-ray projection from multiple directions on a specific cross section of a subject, and performs reconstruction calculation processing based on this data. The so-called CT (Comput
Regarding image processing devices for erized tomographs (X-ray tomography devices), especially electrocardiogram-gated C
Regarding both image processing devices for T.

[Prior art]

Figure 1 shows an overview of the scanner section of the fan beam method 〇T. The data collection in this device is based on the inspection area 3.
The X-ray tube 1 that covers the area and the detector row 4 placed opposite the X-ray tube 1 rotate 360° around the subject along a circular locus 2 centered on the point 5 at regular angle intervals. This is done by measuring the transmitted dose of X-rays irradiated to the area.

The projection gator obtained as described above is normally processed according to the procedure shown in FIG. 2 during OCT reconstruction.

(1) Step 7: Data preprocessing The measurement data obtained in step 6 is subjected to processes such as sensor correction and logarithmic transformation.

(2) Step 8: Convolution calculation with a reference function is performed to prevent blurring during filtering backprojection.

(3) Step 9: Back projection calculation [4] Step 10: Back projection Note that it usually takes 4.5 to 9 seconds to measure the projection data, and approximately 30 seconds to reconstruct the image (dedicated). ).

By the way, when reconstructing a cross section that includes the heart using only one hand, it is not possible to capture the movement of the four internal organs, which beat approximately once per second, and the reconstructed image is blurry. It becomes a thing. Therefore, as shown in FIG.
Reconstruction (DJ) is a method that captures each phase of the heart's movement using an electrocardiogram-gated CT device.
This is commonly done.

However, in the above method, if the number of phases to be divided is n, the number of projection data that can be used for 'fFU for each phase is l/n, so it is necessary to increase the number of scans, use neighboring projection data, etc. Countermeasure d! It becomes necessary. Also, since approximately 30 seconds is required for image reconstruction for each phase, if the number of phases to be divided is 8, the number of scans will be 8, and even if the time required for l scan is 4.5 seconds, the scan time will be is 4.5 x 8 = 36 (seconds) In addition, the image reconstruction calculation time is 30 x 8 = 240 (seconds) In the end, the total time required is about 4 minutes, and there was a strong desire to shorten the processing time. .

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide an electrocardiogram-gated CT system that can quickly obtain CT images of all phases of the heart without waiting time after the scan is completed. An object of the present invention is to provide an image processing device.

[Summary of the invention]

The main point of the present invention is that an electrocardiogram-gated CT image processing device consisting of a CT device and an electrocardiograph connected to the CT device performs image processing for each phase of the electrocardiogram on the basis of information obtained from the electrocardiogram waveform. By assigning processors to each phase, processing can be parallelized and contention between memories can be eliminated.

[Embodiments of the invention]

Hereinafter, the principle and embodiments of the present invention will be explained in detail based on the drawings.

In Figure 4, the angle at which projection data whose phase is synchronized with the R wave (a) of the electrocardiogram (A) is obtained in one cycle of projection data collection is indicated by diagonal lines (B). 4.5 seconds/rotation, and the heartbeat cycle is about 1 second. Due to the periodicity of heart beats, in-phase projection data obtained by one scan results in data in a certain angular range being spatially scattered.

Due to the nature of the CTT construction algorithm, image reconstruction of a certain phase does not require any projection data of other phases;
When focusing on the phase synchronized with the R wave, the only data required is the shaded portion in the diagram. The amount of data in this case is 1/n for one scan, where n is the number of phase divisions. Therefore, the number of phase divisions is set to 8. If the reconstruction time is 30 seconds, the reconstruction time for a certain phase using one scan of projection data is ! The scan time can be set to a value smaller than 4.5 seconds. That is, if attention is focused on only one phase, by performing scan processing and reconstruction processing at the same time, a CT image can be obtained whose reconstruction is completed almost simultaneously with the end of scanning.

Therefore, in the present invention, a dedicated processor is assigned to each of the above phases to perform parallel processing, thereby making it possible to obtain images of multiple phases simultaneously. What is important here is to prevent memory contention between multiple processors. In the present invention, by allocating tasks to processors as shown below, contention between memories does not occur.

FIG. 5 is a block diagram showing an embodiment of the present invention. In the figure, 11 is a CT scanner unit that measures projection data, 12 is an electrocardiograph that measures the electrocardiogram of a subject, and 13 measurement signals will be described later. 14. ．． 14
2,...14. is a processing device (proc) that reconstructs each phase OCT image from projection data at each phase of the heart.
(hereinafter referred to as "PE"),
15 is a shared memo of the reconstructed image 'J M+, M2,
. . . bus for sending to Ml, and 16 is a function for editing the image that is the processing result and outputting it to the display, and the above-mentioned P.
E l 4+ + 1421... This is an operation console that has 14 management functions.

The above P E 141 H142+...14. The configuration is shown in FIG. In the figure, 17 is a CPU that performs preprocessing and filtering of projection data, and 18 is an image processing device that performs back projection calculations.
(hereinafter referred to as rIPJ), 19 is an image local memory IJ for storing projection raw data, projection data after calculation, reconstruction results, etc., and 20 is the shared memory Ml from the local memory 19.

A memory interface (I/F) is used to transfer data at high speed to M2, . . . M, and 21 is a pass line that connects these.

FIG. 7 shows a configuration diagram of the console 16. In the figure, 22
is the CPU that controls the device.

23 is a program storage memo IJ (RAM), 24 is a display memo IJ (FLAMI,
25 is a CFLT, and 26 is a pass line connecting these.

The operation of the present example device configured as described above is described in the fifth example above.
This will be explained using the flowcharts shown in FIGS. 7 and 8.

(1) Step 81: Measure projection data of the subject using the CT scanner 11,
Sequentially send data to the bus 13 via the input/output interface (I/Fl).

(2) Step 82: Simultaneously with the electrocardiogram measurement step 81, the electrocardiogram of the subject is measured by the electrocardiograph 12 and sequentially sent to the bus 13 via the input/output interface (I/F). When sending this data, the electrocardiogram value at the time of measurement of the data is added to the beginning of each projection data in synchronization with step 81 described above.

(3) Step 831+832+...83. : Projection data selection PE14+, 142,...14. is the above bus 13
All of the projection data sent to the computer is sequentially imported into each person's local memo I719. PE 14+ for reconstructing the phase 1 image will be described below.

The CPU 17 discards data other than the projection data corresponding to the phase to be reconstructed, based on the electrocardiogram data attached to the beginning of each projection data.

(4) Step 841: Data preprocessing Step 8 above
3. The remaining projection data is subjected to pre-processing such as sensor correction and logarithmic conversion by f: cPU 17.

(5) Step 85I: Filtering CPU1
7 performs a convolution operation on the preprocessed projection data p(kΔφ, βj) with the following reference function g(k〃Δφ). Regarding the meanings of symbols in formula (1), Section 9
Let me explain using a diagram.

In the figure, S is the position of the X-ray source, βj is its angular direction,
φ is the angle at which the sensor array is viewed (2φ=m·Δφ).

(q) pl (kΔφ, βj) (1) Here, Δφ: sensor interval m: number of sensors. Note that the functions cos and g(k"Δφ) are made into a table and stored in the local memory 19 in advance.

(6) Step 861: Back projection calculation The data in the CPU 17U local memory 19 is sequentially sent to the IP 18 via the bus 21, and the IP 18 performs a back projection calculation according to the following equation.

(10) Here, n2 projection data number IPI 8 is the value of projection data I) + (φ, β,) corresponding to each pixel f (x, y), interpolated from the projection data calculated in step 851 above. Then, the calculation of equation (2) is performed.

The results are saved in memory within IPI8.

After transmitting the final projection data, the CPUI 7 sends the reconstructed image obtained in the IPI 8 to the bus 21. The data is sent to the input/output interface (I/F) via bus 15 (see FIG. 5).

Signals passed through the input/output interface (I/F) are stored in the display RAM 24 via the bus 26 (see FIG. 7) in the console 16. CP in the operation console 16
U22 edits the image and displays it on CR, T25 according to the control program stored in RAM23.

The processing itself in steps 841, 851 and 861 is the same as the reconstruction processing in conventional electrocardiogram-gated CT. In addition, in the above explanation, PE1 of phase l
Although the operation of Pg.41 has been described, as described above, the same applies to Pg that performs other phase reconstructions. Note that step 83
+ + 83” '...83.: Projection data selection is
It goes without saying that each PE may take in only the projection data required.

〔Effect of the invention〕

As described above, according to the present invention, in an electrocardiogram-gated CT image processing device consisting of a CT device and an electrocardiograph connected to the CT device, information obtained from the electrocardiogram waveform is used to Image processing is assigned to a separate processor for each phase, and the data used by each processor is temporarily stored in the local memory of each processor, so there is no conflict between memories. This has the remarkable effect of making it possible to perform parallel processing and realizing high-speed image processing.In addition, if reconstruction operations are performed in parallel with scanning processing, images can be displayed immediately after completion of scan processing. It also becomes possible to display the movement of the heart between phases.

[Brief explanation of the drawing]

(12) Figure 1 is a diagram showing an overview of the scanner section of a CT device, Figure 2 is an example of a flowchart for CT image reconstruction, Figure 3 is a conceptual diagram of electrocardiogram-gated CT, and Figure 4 is a synchronized phase diagram. FIG. 5 is a block diagram of an embodiment of the present invention, FIGS. 6 and 7 are block diagrams showing the main parts thereof, and FIG. 8 shows the processing procedure of the embodiment. flowchart,
FIG. 9 is a symbol explanatory diagram of the reconfiguration formula. 11...CT scanner, 12...electrocardiograph, 13,1
5゜21.26...Bass, 14+, 142...1
4. ...PE, 16 river operation console, 17,22...CP
U, 18...IP, 19...Local memo! 7.2
3.24...1'LAM, 25...CRT, M...
M,...M,...Shared memory. (13) Fig. 1 ￥ JZ 舅 3I21 x 4 Fig. S mouth Fig. 6 Fig. 1 Fig. 3 Fig. I standing 1st bow j Jusai day 2 --
-m-positionpnclosed9figψ223-1-14 Uchikanda-chome, Chiyoda-ku, Tokyo

Claims (1)

[Claims] A CT device that obtains an image corresponding to the X-ray absorption rate inside the subject through reconstruction processing based on projection data collected by performing X-ray projection on the subject from multiple directions, and an electrocardiograph connected to the CT device. An electrocardiogram-gated CT image processing device comprising a plurality of processors, and configured to have the plurality of processors share image processing in each phase of the electrocardiogram for each phase based on information obtained from the electrocardiogram waveform. An electrocardiogram-gated CT image processing device characterized by