JP4434447B2 - Magnetic resonance imaging system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic resonance imaging (MRI) apparatus that images the inside of a subject, and in particular, a data collection / reconstruction apparatus that collects and reconstructs data (raw data) generated by scanning, and a host computer that displays an image. The present invention relates to a magnetic resonance imaging apparatus of a type in which are separated from each other as separate components, and both are connected via a data bus.
[0002]
[Prior art]
In magnetic resonance imaging, a nuclear spin of a subject placed in a uniform static magnetic field is magnetically excited with a high-frequency signal of its Larmor frequency, and an image is obtained from an MR signal (so-called raw data) generated by this excitation. An imaging method to obtain.
[0003]
Conventionally, in this imaging method, after collecting data by scanning, a method of transferring collected raw data to a host computer without any change has been generally adopted. In this case, the host computer performs all necessary processing from reconstruction of the transferred raw data to filtering, brightness adjustment, and image display. For this reason, there were many cases where high-speed processing could not be supported.
[0004]
One of them is an increase in data volume due to data collection using a plurality of receiving coils. Moreover, since digital processing technology has advanced rapidly and high-speed digital processing is possible, there is a system in which reconstruction means is installed in the data collection system and reconstruction processing is performed while collecting raw data in the data collection system. is made of. As a result, the reconstruction can be completed immediately after the raw data is collected, so that the reconstruction processing time is greatly reduced. Since this reconstructed image data has not yet been subjected to brightness adjustment, it is transferred from the data collection system device to the host computer. In the host computer, brightness adjustment and size conversion are performed on the transferred image data, and the image data is displayed.
[0005]
[Problems to be solved by the invention]
However, in the case of magnetic resonance imaging in which the collected raw data is reconstructed in the data collection system device as described above, although it is possible to cope with an increase in data processing amount by using a plurality of receiving coils, On the other hand, the data transfer for transferring the reconstructed image data to the host computer becomes a rate-determining step for the entire system, and a new problem arises that the number of displayed images per unit time cannot be increased.
[0006]
The present invention was made in order to overcome the current situation faced by the prior art. The data processing amount is increased, and the data transfer system reconfigures the raw data to reconstruct the display frame rate. Even in the case of rate control, the object is to enable image data to be transferred from a data collection system device to a host computer at a high speed and to improve the number of displayed images per unit time.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the magnetic resonance imaging apparatus of the present invention, reconstruction means for reconstructing data collected from a subject along with spin excitation into an image, and the reconstructed image data A first apparatus having post-processing means for predetermined post-processing; display pre-processing means for subjecting the reconstructed image data to display pre-processing; and display means for displaying the pre-display processed image data And a transfer means for transferring data between the first and second devices. Further, the first apparatus includes a compression unit that compresses the image data post-processed by the post-processing unit and passes the compressed image data to the transfer unit, and the post-processing unit is sent via the transfer unit. The second device is configured to adjust the luminance according to the window value and window level information of the pixel value, and the second device generates the window width and window level information of the pixel value and transfers the information to the transfer unit. and means for transferring to the first device via, characterized in that a decompression means to pass to the display preprocessing means compressed image data that has been transferred to decompress via the transfer means.
[0008]
As a result, the image data reconstructed by the first device is subjected to necessary processing and then compressed, and then transferred to the second device. In response to this, in the second apparatus, 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 amount of image data processing increases, it is possible to reliably avoid the state where the entire system is rate-limited by data transfer, and the number of images that can be processed and displayed per unit time, That is, the frame rate can be improved.
[0009]
Preferably, the post-processing means is means for performing predetermined filtering and brightness adjustment on the reconstructed image data. The collected data is, for example, raw data collected by performing fluoroscopy (continuous shooting).
[0011]
Further, in each configuration described above, the compression unit may be a unit that performs image compression based on a correlation of the data in the frame time axis direction.
[0012]
Further, as an example, each of the reconstruction unit, the post-processing unit, the compression unit, the transfer unit, the decompression unit, and the display pre-processing unit may be configured as a unit driven by pipeline processing.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0015]
(First embodiment)
A magnetic resonance imaging apparatus according to the first embodiment will be described with reference to FIG.
[0016]
This magnetic resonance imaging apparatus collects and reconstructs MR data (raw data) generated along with scanning, and is a so-called data collection system apparatus (data collection apparatus, data collection reconstruction apparatus, data processing apparatus, etc.) Is often separated from the host computer responsible for various functions including the interface function and image display function associated with the user's interaction, and the image data collected and reconstructed by the data collection system device is hosted. It is configured to transfer to a computer.
[0017]
Specifically, as shown in FIG. 1, the magnetic resonance imaging apparatus includes a data collection / reconstruction apparatus 11 as a first apparatus, a host computer 12 that forms a second apparatus together with a display unit to be described later, and the host computer 12 And a data bus 14 constituting transfer means for connecting the data collection / reconstruction apparatus 11 and the host computer 12 to each other.
[0018]
Although not shown, this magnetic resonance imaging apparatus includes components such as 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, and a sequencer. The scanning is performed by a command based on the desired pulse sequence information. The echo signal collected by this scan is detected by the RF coil and sent to the receiver. In the receiver, the echo signal is processed as pre-amplification, intermediate frequency conversion, phase detection, low-frequency amplification, low-pass filter, A / D conversion, and the like as echo data (raw data), and the data collection reconstruction apparatus 11 Sent to.
[0019]
A data collection / reconstruction apparatus 11 shown in FIG. 1 includes a main memory 21 for storing echo data (raw data) and image data, and a modularized image reconstruction process 22 that performs processing using the main memory. , A post-processing & filtering process 23 and a data compression process 24. The processes 22 to 24 are functionally realized by the CPU executing a predetermined software program. However, hardware-based modules corresponding to the functions of the individual processes may be provided.
[0020]
The host computer 12 includes, as hardware, a file system 31 and a shared memory 32 that can be used by a plurality of processes, and is modularized as software, a data decompression process 33, a preprocessing process 34, a display process 35, a user process It has a process 36 that receives the request.
[0021]
The preprocessing process 34 is preprocessing (display format or the like) for simple display of image data placed in the shared memory 31. The processes 33 to 36 are functionally realized by the CPU executing a predetermined software program. However, a module based on hardware corresponding to the function of each process may be provided.
[0022]
The host computer 12 is provided with hardware for performing scanning, and various control programs for the hardware are installed, but the description thereof is omitted here.
[0023]
The data collection / reconstruction device 11 and the host computer 12 can bidirectionally transfer data to each other via a data bus such as Ethernet (trademark of Fuji Xerox Co., Ltd.). This data transfer rate itself is set to a sufficiently high value.
[0024]
However, due to the following reasons, the data transfer time, which is sufficiently fast, may reach the rate-determining stage, which exceeds the reconstruction time.
[0025]
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 carry out this continuous photographing method, a frame rate of 10 or more frames per second is required. For this reason, in order to obtain an image from the collected raw data, reconstruction based on Fast Fourier Transform (FFT) must be performed. Therefore, a reconstruction process 22 (fork) that reconstructs the raw data in the data collection reconstruction device 11. Can be reconfigured while collecting data. Since the reading direction in reconstruction is the same as in data collection, and data can be read simultaneously with data collection during reconstruction, the processing time after the last read line of the two-dimensional image is collected is actually a phase. A short time equivalent to the time required for the one-dimensional FFT in the encoding direction is sufficient. That is, when the time required for such a one-dimensional FFT elapses after data collection, the reconstruction of the two-dimensional image is completed.
[0026]
In this way, particularly when continuous shooting is performed, due to the apparent shortening of the reconstruction time, the data transfer time, which is sufficiently high, may be longer than the reconstruction time, and the rate-limiting step may be reached.
[0027]
Therefore, in order to avoid such a situation that reaches the rate-determining step, the data collection / reconstruction apparatus 11 is provided with a data compression process 24 for compressing image data to reduce the data amount, and the compressed image data based on this process 24 is received. Data can be transferred via the data bus 14. As described above, the data compression process 24 may be constituted by hardware elements.
[0028]
Correspondingly, a data decompression process 33 is placed in the host computer 12. By this process 33, the compressed image data transferred via the data bus 14 is decompressed, and this image data is placed in the shared memory 32. As described above, the data decompression process 33 may be constituted by hardware elements.
[0029]
On the other hand, the window width and window level of a desired pixel value are input from the user to the user interface 36 of the host computer 12. The window width and window level information is transferred from the user interface 36 to the post-processing & filtering process 23 of the data collection / reconstruction apparatus 11 via the transfer means by the data bus 14. The post-processing & filtering process 23 adjusts the luminance of the pixel value of the window width and window level specified by this information.
[0030]
The main memory 21 and the shared memory 32 of the data collection / reconstruction apparatus 11 and the host computer 12 have an access check function such as a semaphore. Thus, even when image data placed on the same memory is used in multiple processes, data contention is prevented and high speed is ensured.
[0031]
Next, the overall function and effect of this embodiment will be described. Now, it is assumed that this magnetic resonance imaging apparatus performs continuous imaging (fluoroscopic copying) using multiple receiving coils.
[0032]
In the data collection / reconstruction apparatus 11, the collected data (raw data) placed in the main memory 21 is reconstructed almost in parallel with the collection through the reconstruction process 22 as described above. This reconstructed image data is subjected to addition processing for being a multiple receiving coil by a post-processing & filtering process 23, and a window width and a window level of a pixel value are designated to generate 256 gradation image data. The
[0033]
This image data is further compressed by the data compression process 24 into image data of the 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.
[0034]
In the host computer 12, the compressed image data transferred via the data bus 14 is decompressed and restored to the original size image data. This image data is temporarily stored in the shared memory 32. Thereafter, the storage data is adjusted in display format by the preprocessing process 34 and displayed on the display 13 by the display process 35.
[0035]
In addition, 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 decompression processing. Accordingly, since the image size is small, the overall transfer performance is not deteriorated.
[0036]
As described above, according to the present embodiment, reconstruction is performed almost in parallel with data collection, and necessary processing such as brightness adjustment is performed after the reconstruction, and thereafter, the image data is compressed. To the host computer. In response to this, the host computer decompresses the transferred image data and applies it to 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 the state where the entire system is rate-limited by data transfer. Therefore, the image data can be transferred from the data collection / reconstruction device to the host computer at a higher speed. Therefore, it is possible to improve the number of images that can be processed and displayed per unit time, that is, the frame rate, so that the time required for compression / decompression is shorter than the shortened transfer time. As a result, the high-speed shooting performance of continuous shooting is not deteriorated.
[0037]
(Second Embodiment)
A second embodiment will be described with reference to FIG. This embodiment relates to another example of an image compression method. In this embodiment and a third embodiment to be described later, the same reference numerals are given to the same or equivalent components as those in the first embodiment, and the description thereof will be omitted or simplified.
[0038]
As shown in FIG. 2, the data acquisition / reconstruction apparatus 11 of the magnetic resonance imaging apparatus according to the second embodiment performs compression using the frame correlation in the time direction for each frame of the image data. ing. Thereby, the efficiency of image compression is improved.
[0039]
Assuming that the current image is n and the images n-1, n-2, and n-3 that are traced back by 1, 2, and 3 time phases in the past, the inter-frame correlation of these image data is calculated for each pixel. The compressed image data based on the correlation image is transferred to the host computer 12 via the data bus 14.
[0040]
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.
[0041]
In general, in the case of continuous shooting (fluoroscopy), once a shooting 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. For this reason, the data amount of the difference image that can be obtained by calculating the inter-frame difference between the current time phase image and the past time phase image 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 the transfer can be performed at high speed. For this compression method, various methods including MPEG which is widely used can be used.
[0042]
(Third embodiment)
The third embodiment will be described with reference to FIG. This embodiment relates to the application of pipeline processing.
[0043]
As shown in FIG. 3, the magnetic resonance imaging apparatus according to this embodiment includes an image reconstruction process 22, a post-processing & filtering process 23, a data compression process 24, a data bus 14, and a data acquisition / reconstruction apparatus 11, Pipeline processing is executed in the data decompression process 33 and the pre-processing process 34 in the host computer 12. Thereby, a series of processing from image reconstruction to pre-display processing is parallelized, and the processing speed is increased. The images processed in such a high speed are sequentially displayed on the display 13 by the display process 35.
[0044]
Therefore, the number of display images per unit time can be increased as in the first embodiment, and resources can be used effectively.
[0045]
It should be noted that the present invention is not limited to the configurations described in the above-described embodiments, and those skilled in the art will appropriately modify or modify the present invention within the scope of the gist described in the claims. The present invention can be implemented with modifications, and configurations related to these modifications or modifications are also included in the present invention.
[0046]
【The invention's effect】
As described above, according to the magnetic resonance imaging apparatus according to the present invention, in a configuration in which a raw data collection / reconstruction apparatus and a user interface and a computer apparatus responsible for display are separated, an image based on hardware or software By performing data compression and decompression before and after image data transfer, the performance of image data transfer at the rate-determining stage can be improved. Therefore, per unit time during high-speed shooting such as fluoroscopy. The display frame rate can be greatly improved, and it is possible to reliably prevent a situation in which the high-speed shooting performance is impaired.
[Brief description of the drawings]
FIG. 1 is a partial block diagram showing 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 showing 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 showing a schematic configuration of a magnetic resonance imaging apparatus according to a third embodiment of the present invention.
[Explanation of symbols]
11 Data collection 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 (5)

A first apparatus having reconstruction means for reconstructing data collected from a subject with spin excitation into an image, and post-processing means for subjecting the reconstructed image data to predetermined post-processing;
A second device having display preprocessing means for subjecting the reconstructed image data to display preprocessing, and display means for displaying the preprocessed image data;
A magnetic resonance imaging apparatus comprising transfer means for transferring data between the first and second apparatuses;
The first apparatus includes a compression unit that compresses the image data post-processed by the post-processing unit and passes the compressed image data to the transfer unit, and the post-processing unit includes a pixel sent via the transfer unit. It is a means to adjust the brightness according to the value window width and window level information,
The second device generates window width and window level information of the pixel value and transfers the information to the first device via the transfer unit, and is transferred via the transfer unit. and a decompression means to pass to the display preprocessing means compressed image data has been decompress, magnetic resonance imaging apparatus characterized by. The magnetic resonance imaging apparatus according to claim 1.
The magnetic resonance imaging apparatus, wherein the post-processing means is means for performing predetermined filtering and brightness adjustment on the reconstructed image data. The magnetic resonance imaging apparatus according to claim 1 or 2,
The magnetic resonance imaging apparatus, wherein the collected data is raw data collected by performing fluoroscopy (continuous imaging). The magnetic resonance imaging apparatus according to any one of claims 1 to 3 ,
The magnetic resonance imaging apparatus, wherein the compression unit is a unit that performs image compression based on a correlation of the data in the frame time axis direction. The magnetic resonance imaging apparatus according to any one of claims 1 to 4 ,
Each of the reconstruction means, the post-processing means, the compression means, the transfer means, the decompression means, and the display pre-processing means is a magnetic resonance imaging apparatus that is driven by pipeline processing.

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