JP2002034950A - Magnetic resonance imaging apparatus and method for transmitting data thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit image data from a data collecting device to a host computer at high speed even when the display frame rate is controlled by the data transmission, and to increase the number of images displayed per unit time. SOLUTION: Data are collected and restructured as an image in a data collecting/restructuring device 11, and the post-treatment is applied to the image data. Then the post-treated image data are compressed and transmitted to the host computer 12 via a data bus 14. The compressed data transmitted via the data bus 14 are depressed in the host computer 12, and the pre-treatment before display is applied to the depressed image data to be displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a magnetic resonance imaging (MRI) apparatus for imaging the inside of a subject and a data transfer method thereof, and particularly to data for collecting and reconstructing data (raw data) generated by scanning. The present invention relates to a magnetic resonance imaging apparatus in which an acquisition reconstruction apparatus and a host computer for displaying images are separated from each other as separate components, and both are connected via a data bus, and a data transfer method thereof.

[0002]

2. Description of the Related Art In magnetic resonance imaging, a nuclear spin of a subject placed in a uniform static magnetic field is magnetically excited by a high frequency signal of the Larmor frequency, and an MR signal generated by the excitation (so-called raw signal) is generated. This is an imaging method for obtaining an image from data).

Conventionally, in this imaging method, a method has been generally adopted in which after collecting data by scanning, the collected raw data is transferred to a host computer without any modification. In this case, the host computer has performed all necessary processes from reconstruction of the transferred raw data, filtering, brightness adjustment, and image display. Therefore, in many cases, high-speed processing cannot be supported.

As one of them, there is an increase in data amount due to data collection using a plurality of receiving coils. In addition, digital processing technology has advanced rapidly, and high-speed digital processing is possible.
There is a system that performs reconstruction processing while collecting raw data in the data collection system. Thus, the reconstruction can be completed immediately after the raw data is collected, so that the processing time of the reconstruction is greatly reduced. Since the brightness of the reconstructed image data has not been adjusted yet, it is transferred from the data collection system to the host computer. In the host computer, the transferred image data is subjected to luminance adjustment and size conversion, and is then displayed.

[0005]

However, in the case of the above-described magnetic resonance imaging in which the collected raw data is reconstructed in the data acquisition system, the amount of data processing is reduced by using a plurality of receiving coils. Although it is possible to cope with the increase, on the other hand, the data transfer for transferring the reconstructed image data to the host computer becomes a rate-determining stage for the entire system, and it is not possible to increase the number of image displays per unit time. Problems have arisen.

SUMMARY OF THE INVENTION The present invention has been made to overcome the current situation encountered in the prior art. The data processing amount is increased, and the data transfer is displayed by reconstructing the raw data in the data collection system. It is an object of the present invention to enable image data to be transferred from a data collection system to a host computer at high speed even when the frame rate is rate-determined, thereby enabling the number of images to be displayed per unit time to be improved.

[0007]

In order to achieve the above object, according to the magnetic resonance imaging apparatus of the present invention,
A first apparatus having a reconstructing unit for reconstructing data collected from the subject along with the spin excitation into an image, and a post-processing unit for subjecting the reconstructed image data to a predetermined post-processing; A second device having display pre-processing means for applying the reconstructed image data to display pre-processing, and display means for displaying the image data subjected to the display pre-processing, between the first and second devices; And transfer means for transferring data. Further, the first device includes a compression unit that compresses the image data post-processed by the post-processing unit and passes the image data to the transfer unit, and the second device is transferred through the transfer unit. Decompressing means for decompressing the compressed image data and transferring the decompressed image data to the display preprocessing means.

Thus, the image data reconstructed by the first device undergoes necessary processing, is compressed, and is then transferred to the second device. In response, in the second device, the transferred image data is decompressed and thereafter subjected to display processing. For this reason, even in the case of continuous shooting, even when the image data processing amount increases, it is possible to reliably avoid a state in which the entire system is limited by the data transfer, and the number of images that can be processed and displayed per unit time,
That is, the frame rate can be improved.

Preferably, the post-processing means performs predetermined filtering and brightness adjustment on the reconstructed image data. The collected data is, for example, raw data collected by performing fluoroscopy (continuous imaging).

Preferably, the second device includes means for generating window width and window level information of a pixel value and transferring the information to the first device via the transfer means. The post-processing means provided in the first device includes:
It may be a means for adjusting the brightness according to the information sent via the transfer means.

Further, in each of the above structures, the compression means may be means for performing image compression based on a correlation of the data in a frame time axis direction.

Further, as an example, each of the reconstruction means, the post-processing means, the compression means, the transfer means, the decompression means, and the pre-display processing means is constituted as means driven by pipeline processing. Is also good.

On the other hand, according to the data transfer method of the magnetic resonance imaging apparatus according to the present invention, in the first apparatus,
The data collected from the subject along with the spin excitation is reconstructed into an image, the reconstructed image data is subjected to predetermined post-processing, and the post-processed image data is compressed. The compressed image data is transferred to the second device by the transfer unit, and the compressed image data transferred via the transfer unit is decompressed in the second device, and the image data is subjected to display preprocessing. The display-processed image data is displayed.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) A magnetic resonance imaging apparatus according to a first embodiment will be described with reference to FIG.

This magnetic resonance imaging apparatus collects and reconstructs MR data (raw data) generated by scanning, which is a so-called data acquisition system (a data acquisition apparatus, a data acquisition / reconstruction apparatus, or a data processing apparatus). And a host computer that performs various functions including an interface function and an image display function accompanying a dialogue with a user. It is configured to transfer data to a host computer.

More specifically, as shown in FIG. 1, the magnetic resonance imaging apparatus includes a data acquisition / reconstruction apparatus 11 as a first apparatus, a host computer 12 which forms a second apparatus together with a display, which will be described later, It comprises a display 13 connected to the host computer 12, and a data bus 14 serving as a transfer means for interconnecting the data acquisition / reconstruction device 11 and the host computer 12.

Although not shown, the magnetic resonance imaging apparatus includes a static magnetic field magnet, a static magnetic field power supply, a gradient magnetic field coil, a gradient magnetic field power supply, an RF coil, a transmitter, a receiver,
A component such as a sequencer is provided, and scanning is performed by a command based on desired pulse sequence information from the sequencer. The echo signal collected by this scan is detected by an RF coil and sent to a receiver. In the receiver, the echo signal undergoes processing such as preamplification, intermediate frequency conversion, phase detection, low frequency amplification, a low-pass filter, and A / D conversion, and is converted into echo data (raw data). Sent to

The data collection and reconstruction device 11 shown in FIG.
A modularized image reconstruction process 22, a post-processing & filtering process 23, and a data compression process comprising a main memory 21 for storing echo data (raw data) and image data, and performing processing using the main memory 21. It has 24 functions. This process 22-24 is a CP
Although U is functionally implemented by executing a predetermined software program, U may be equipped with a module based on hardware corresponding to the function of each process.

The host computer 12 includes, as its hardware, a file system 31 and a shared memory 32 that can be used by a plurality of processes, and has a data decompression process 33, a preprocessing process 34, and a display process 35, which are modularized as software. , Receiving a user request.

The preprocessing process 34 is a preprocessing (display format or the like) for simply displaying the image data stored in the shared memory 31. The processes 33 to 36 are functionally realized by the CPU executing a predetermined software program, but may be provided with a module based on hardware corresponding to the function of each process.

The host computer 12 is provided with hardware for performing the scan, and various control programs for the hardware are installed. However, the description thereof is omitted here.

The data collection / reconstruction device 11 and the host computer 12 can mutually transfer data via a data bus such as Ethernet (trademark of Fuji Xerox Co., Ltd.). The data transfer speed itself is set to a sufficiently high value.

However, for the following reasons, the data transfer time, which should be sufficiently high, may reach the rate-determining stage in which the data transfer time exceeds the reconstruction time.

As one imaging method of magnetic resonance imaging, there is continuous imaging (fluoroscopy) in which imaging is continuously performed while changing imaging conditions. In order to implement this continuous imaging method, a frame rate of more than ten frames per second is required.
Therefore, in order to obtain an image from the collected raw data, a reconstruction based on the fast Fourier transform (FFT) must be performed. Therefore, the reconstruction process 22 (or the like) for reconstructing the raw data in the data acquisition and reconstruction device 11. A reconfiguration unit is interposed to enable reconfiguration while collecting data. Since the reading direction in the reconstruction is the same as the data acquisition, and the data can be read at the same time as the data acquisition during the reconstruction, the processing time after the last read line of the 2D image is acquired is actually the phase time. A short time equivalent to the time required for one-dimensional FFT in the encoding direction is sufficient.
In other words, if the time required for the one-dimensional FFT elapses after the data collection, the reconstruction of the two-dimensional image is completed.

As described above, especially when performing continuous shooting,
The apparent shortening of the reconstruction time may lead to a situation where the data transfer time, which is supposed to be sufficiently high, is longer than the reconstruction time, leading to a rate-determining stage.

Therefore, in order to avoid such a situation leading to the rate-determining step, the data collection / reconstruction device 11 is provided with a data compression process 24 for compressing image data to reduce the data amount. Image data can be transferred via the data bus 14. As described above, the data compression process 24 may be implemented by hardware elements.

In response, the host computer 12
Is provided with a data decompression process 33. By this process 33, the compressed image data transferred via the data bus 14 is decompressed, and the image data is stored in the shared memory 32. As described above, the data decompression process 33 may be implemented by hardware elements.

On the other hand, the user inputs a window width and a window level of a desired pixel value to the user interface 36 of the host computer 12. The information on the window width and the window level is passed from the user interface 36 to the post-processing & filtering process 23 of the data acquisition / reconstruction device 11 via the data bus 14. The post-processing & filtering process 23 adjusts the brightness of the pixel value of the window width and window level specified by this information.

The main memory 21 and the shared memory 32 of the data collection / reconstruction device 11 and the host computer 12
Has an access check function such as a semaphore. As a result, even when image data stored in the same memory is used in multiple processes, data conflict is prevented, and high speed is ensured.

Next, the overall operation and effect of this embodiment will be described. Now, this magnetic resonance imaging apparatus performs continuous imaging (fluoroscopy) using multiple receiving coils.

In the data acquisition and reconstruction device 11, the acquired data (raw data) stored in the main memory 21 is reconstructed almost in parallel with the acquisition as described above via the reconstruction process 22. The reconstructed image data is subjected to an addition process for the multiplex receiving coil by the post-processing & filtering process 23, and the window width and the window level of the pixel value are designated to generate image data of 256 gradations. You.

The image data is further compressed by a data compression process 24 into image data of a minimum necessary size based on an image compression method such as the JPEG method. The compressed image data is transferred to the host computer 12 via the data bus 14.

In the host computer 12, the compressed image data transferred via the data bus 14 is decompressed and restored to the original size. This image data is temporarily stored in the shared memory 32. After that, the stored data is displayed in the display format by the preprocessing process 34 and displayed on the display 13 by the display process 35.

Further, image data can be stored in a low-speed file system. In this case, the image data before decompression is stored from the data decompression process 33 without performing the decompression processing. Therefore, since the image size is small, the overall transfer performance is not reduced.

As described above, according to the present embodiment, reconstruction is performed almost in parallel with data collection, and after this reconstruction, necessary processing such as brightness adjustment is performed. After being compressed, it is transferred to the host computer. In response, the host computer decompresses the transferred image data and then performs display processing. For this reason, even in the case of continuous shooting, even when the amount of image data processing increases, it is possible to reliably avoid a state in which the entire system is limited by data transfer. Therefore, image data can be transferred from the data collection and reconstruction device to the host computer at a higher speed. For this reason, the time required for compression / decompression can be made shorter than the reduced transfer time, and the number of images that can be processed and displayed per unit time, that is, the frame rate can be improved. As a result, the high-speed shooting performance of continuous shooting is not reduced.

(Second Embodiment) Referring to FIG.
An embodiment will be described. This embodiment relates to another example of the image compression method. Note that, in this embodiment and a third embodiment described later, the same or equivalent components as those in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted or simplified.

As shown in FIG. 2, in the data acquisition / reconstruction device 11 of the magnetic resonance imaging apparatus according to the second embodiment, compression is performed on each frame of image data using the frame correlation in the time direction. It has become. This improves the efficiency of image compression.

It is assumed that the current image is n, and that
If the images n-1, n-2, and n-3 are traced back by a few time phases, the inter-frame correlation of the image data may be calculated for each pixel, and the compressed image data based on the correlation image is obtained. The data is transferred to the host computer 12 via the data bus 14.

Similarly, the host computer 12 forms an image of the current time phase from the compressed image data newly transferred via the data bus 14 and the past image while storing the decompressed past image. .

In general, in the case of continuous imaging (fluoroscopy), once an imaging slice is designated, a portion where the pixel value of an image obtained thereafter changes for each frame remains in a small area in the entire image. . Therefore, the data amount of the difference image obtained by calculating the inter-frame difference between the image at the current time phase and the image at the past time phase is usually a small value. That is, since the amount of data to be compressed is reduced, the efficiency of data compression is improved, and transfer can be performed at high speed. For this compression method, various methods such as MPEG, which is widely used, can be used.

(Third Embodiment) Referring to FIG.
An embodiment will be described. This embodiment relates to the application of pipeline processing.

As shown in FIG. 3, the magnetic resonance imaging apparatus according to this embodiment has a data acquisition / reconstruction apparatus 1.
The pipeline processing is performed in the image reconstruction process 22, the post-processing & filtering process 23, the data compression process 24, the data bus 14, and the data decompression process 33 and the pre-processing process 34 in the host computer 12 in FIG. It has become. As a result, a series of processing from image reconstruction to pre-display processing is parallelized, and the processing speed is increased. The images thus processed at high speed are sequentially displayed on the display 13 by the display process 35.

Therefore, similarly to the first embodiment, the number of displayed images per unit time can be increased, and resources can be effectively used.

It should be noted that the present invention is not limited to the configuration described in each of the above-described embodiments, and those skilled in the art can appropriately interpret the present invention within the scope of the claims. The present invention can be modified or modified, and configurations involving such modifications or modifications are also included in the present invention.

[0046]

As described above, according to the magnetic resonance imaging apparatus and the data transfer method thereof according to the present invention, the apparatus for collecting and reconstructing raw data and the computer apparatus for performing the user interface and display are separated. By performing compression and decompression of image data by hardware or software before and after the transfer of the image data, the performance of the image data transfer at the rate-determining stage can be improved. The display frame rate per unit time at the time of high-speed shooting such as scopy can be greatly improved, and a situation in which the high-speed shooting is impaired can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a partial block diagram illustrating a schematic configuration of a magnetic resonance imaging apparatus according to a first embodiment of the present invention.

FIG. 2 is a partial block diagram illustrating a schematic configuration of a magnetic resonance imaging apparatus according to a second embodiment of the present invention.

FIG. 3 is a partial block diagram illustrating a schematic configuration of a magnetic resonance imaging apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 data acquisition and reconstruction device (first device) 12 host computer (second device) 13 display (second device) 14 data bus (transfer means) 21 main memory 22 image reconstruction process 23 post-processing & filtering Process 24 Data compression process 32 Shared memory 33 Data decompression process 34 Pre-processing process 35 Display process 36 User interface

Claims (7)

[Claims] A first means for reconstructing data collected from the subject along with the spin excitation into an image, and a post-processing means for subjecting the reconstructed image data to predetermined post-processing. A second apparatus including: a display pre-processing unit that applies the reconstructed image data to display pre-processing; and a display unit that displays the display pre-processed image data; 2. A magnetic resonance imaging apparatus comprising: a transfer unit that transfers data between two devices, wherein the first device compresses image data post-processed by the post-processing unit and passes the image data to the transfer unit. And a decompression means for decompressing the compressed image data transferred via the transfer means and passing the decompressed image data to the display preprocessing means. Grayed apparatus. 2. The magnetic resonance imaging apparatus according to claim 1, wherein the post-processing unit is a unit that performs predetermined filtering and brightness adjustment on the reconstructed image data. 3. The magnetic resonance imaging apparatus according to claim 1, wherein the acquired data is raw data acquired by performing fluoroscopy (continuous imaging). 4. The magnetic resonance imaging apparatus according to claim 2, wherein the second device generates information on a window width and a window level of a pixel value, and transmits the information to the first device via the transfer unit. A magnetic resonance imaging apparatus, comprising: means for causing a device to transfer the data; and the post-processing means provided for the first device is a means for adjusting the brightness in accordance with information transmitted via the transfer means. 5. The magnetic resonance imaging apparatus according to claim 1, wherein the compression unit is a unit that performs image compression based on a correlation of the data in a frame time axis direction. . 6. The magnetic resonance imaging apparatus according to claim 1, wherein the reconstruction unit, the post-processing unit, the compression unit, the transfer unit, the decompression unit, and the pre-display process. A magnetic resonance imaging apparatus wherein each of the means is driven by pipeline processing. 7. A first apparatus, wherein data collected from a subject along with spin excitation is reconstructed into an image, and the reconstructed image data is subjected to predetermined post-processing. The compressed image data is compressed, and then the compressed image data is transferred to a second device by a transfer unit. In the second device, the compressed image data transferred through the transfer unit is decompressed, A data transfer method in a magnetic resonance imaging apparatus, wherein the image data is subjected to pre-display processing, and the pre-display processed image data is displayed.