JPH0430829A - Image reconstruction apparatus and system for magnetic resonance imaging apparatus - Google Patents

Abstract

PURPOSE:To achieve a higher speed of an image reconstruction processing corresponding to a higher speed of photographing time by a method wherein an image memory for storing a measuring data is formed with a plurality of local memories, which are each provided with a local processor and the measuring data undergoes a specified computation to make a tomographic image. CONSTITUTION:An image processor 3 outputs a measuring data from a detector 1 through a pulse sequencer 2 to be stored into a local memory 51 of an image memory 5. On the other hand, a local processor 71 starts a data computation for the reconstruction of an image based on a command of the image memory 3 and thereafter, local processors 72-78 corresponding to local memories 52-58 start their data computations independently. After the end of the computation, when a data is generated for the image reconstruction, it is stored into a corresponding local memory again. The data is transferred to a display processor 6 under specified conditions to show a tomographic image on a display 10 thereby enabling the displaying of an image in real time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image reconstruction device and an image reconstruction method for a magnetic resonance imaging apparatus, and in particular to real-time image reconstruction by realizing high-speed image reconstruction processing. The present invention relates to an image reconstruction device and an image reconstruction method suitable for performing three-dimensional high-speed image reconstruction.

[Conventional technology]

An example of a circuit of a conventional image reconstruction device for a magnetic resonance imaging apparatus is shown in FIG. According to this circuit example, a pulse sequencer 101 of a magnetic resonance imaging apparatus controls a detection device 102 consisting of a coil magnet, a probe, etc.
A predetermined sequence is executed on the detection device 102 to capture data obtained by measurement from the detection device 102. The measurement data taken into the pulse sequencer 101 is sent to the image processor 104 via the bus 103.
The data is transferred to the memory 105 of the arithmetic processing unit 106, which consists of a memory 105 and a memory 105, and is stored there. memory 105
When the amount of measurement data stored in the memory 105 reaches a predetermined two-dimensional or three-dimensional amount, the image processor 104 is activated and starts image reconstruction processing using the data stored in the memory 105. The image-reconstructed data is then transferred to the display device 107 via the memory 105, and an image is displayed on the display device 107 using the data. In this way, conventional magnetic resonance imaging devices are not configured to perform image reconstruction processing in real time because the imaging speed is slow, but only when a predetermined amount of measurement data is stored in memory. It was configured to be executed in a so-called batch format.

[Problem to be solved by the invention]

In conventional magnetic resonance imaging systems, real-time performance is not originally required because the imaging time is longer than the processing time required for image reconstruction processing.
A relatively slow processing time on the order of seconds was sufficient for image reconstruction processing.

However, recently, photographing technology has advanced, and a photographing technique that requires a photographing time of less than Looms is about to be put into practical use in the near future. Using such high-speed photography technology,
Magnetic resonance can be used in real time, for example, to search for an affected area while looking at an image of the affected area of a patient, or even to import three-dimensional measurement data all at once and perform a diagnosis while displaying an arbitrary cross section of it. The uses of imaging devices will expand. However, even if such high-speed imaging becomes possible, as long as image reconstruction processing based on the conventional device configuration is used, the processing time is on the order of seconds as described above, so the image reconstruction processing time becomes a bottleneck. This means that real-time image display and high-speed three-dimensional display cannot be performed.

An object of the present invention is to provide an image reconstruction device for a magnetic resonance imaging apparatus that can speed up image reconstruction processing in response to faster imaging times, and to display images in real time using this device. The object of the present invention is to provide an image reconstruction processing method that enables high-speed three-dimensional image display.

[Means to solve the problem]

An image reconstruction device for a magnetic resonance imaging apparatus according to the present invention is a magnetic resonance imaging apparatus that creates a tomographic image of a subject using magnetic resonance phenomena under the control of an image processor, and uses measurement data handled by an image processor. The image memory to be stored is formed by a plurality of local memories, each of the local memories is provided with a local processor, and each of the plurality of local processors under the management of the image processor applies a predetermined value to the measurement data stored in the corresponding local memory. The feature is that a calculation is performed to form a tomographic image.

A first image reconstruction method of a magnetic resonance imaging apparatus according to the present invention uses the image reconstruction apparatus of the magnetic resonance imaging apparatus described above, and an image processor performs two-dimensional measurement continuously captured by a detection device. Data is periodically transferred to each local memory in a predetermined order, and a signal to start a predetermined operation is given to the local processor corresponding to the local memory where the data transfer has been completed, and the local memory of the local processor where the operation has been completed. A feature of the present invention is that images are displayed periodically on the image display means in order from 1 to 3, and images are displayed in real time equivalent to the measurement cycle of the detection device.

A second image reconstruction method of a magnetic resonance imaging apparatus according to the present invention uses the image reconstruction apparatus of the magnetic resonance imaging apparatus described above, and an image processor performs two-dimensional measurement continuously captured by a detection device. Regarding data, the first
A fast Fourier transform is performed on the data for each dimension, and the transformed data is divided by the number of local processors and transferred to each local memory, and is stored in the corresponding local memory of each local processor in parallel. The feature is that fast Fourier transform is performed on the second and third dimension data to perform high-speed three-dimensional image reconstruction.

[Effect]

In the magnetic resonance imaging apparatus according to the present invention, the memory space of the image memory is divided into a predetermined number of spaces, each of which is set as a local memory, and each local memory has a dedicated memory for processing the measurement data stored therein. Local processors are provided, each local processor is operated at a predetermined timing, and measurement data is calculated in parallel to create a tomographic image. This aims to shorten the processing time for image reconstruction.

In the image reconstruction method of the first magnetic resonance imaging apparatus according to the present invention, since the image reconstruction processing time can be achieved by the magnetic resonance imaging apparatus, real-time image reconstruction can be performed by utilizing this. Similarly, the image reconstruction method of the second magnetic resonance imaging apparatus according to the present invention realizes high-speed three-dimensional image reconstruction.

〔Example〕

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

FIG. 1 is a block diagram showing an image reconstruction device of a magnetic resonance imaging apparatus according to the present invention. In this figure, the block configuration is shown, and the specific configuration of the detection device and the like of the magnetic resonance imaging apparatus is omitted. . In FIG. 1, 1 is a high frequency oscillator, x, y.

2 is a detection device consisting of coil magnets, etc., and 2 is a pulse sequencer that supplies predetermined pulses to each coil of the detection device 1 in a predetermined order. When obtaining image data of a desired part of a subject using a magnetic resonance imaging device,
When the pulse sequencer 2 supplies a predetermined pulse to the detection device 1 in a predetermined measurement cycle, an echo signal is generated, and image data can be obtained from this echo signal.

The pulse sequencer 2 is connected to an image processor 3, and image data obtained by the pulse sequencer 2 is given to the image processor 3. The measurement operation based on the pulse sequence is controlled by the image processor 3. Image processor 3 is connected to system bus 4 . An image memory 5 and a display processor 6 are further connected to the system bus 3.

The image memory 5 is allocated to the memory space of the image processor 3, and this memory space is divided into a plurality of areas, each of which is used as a local memory, and is divided into n local memories. There is.

In FIG. 1, as an example, the image memory 5 is divided into eight equal parts,
Eight local memories 51-58 are included in the image memory 5. These local memories 51 to 58
are each equipped with dedicated local processors 71 to 78 that are given the ability to access only that area. The data processing operations of these local processors 71 to 78 are executed under the control of the image processor 3.

FIG. 2 shows the configuration of one local memory section in detail. This figure shows, for example, the configuration of a local memory 51, which includes a bus buffer 51a and a memory array 51b, and the system bus 4 is gated by the path buffer 51a. path buffer 51
a is connected to the local bus 51c only when the image processor 3 accesses the memory area of the local memory 51.
The memory array 51b operates to connect the system bus 4 and the memory array 51b through the memory array 51b. When the image processor 3 is accessing the local memory 51, an access prohibition signal is given to the local processor 71 from the path buffer 51a, and the local processor 71 cannot access the local memory 51. Otherwise, local processor 71 can access local memory 51.

The configurations of other local memories and local processors are also the same as above.

The display processor 6 is provided with a display memory 8 and a keyboard 9, and the display memory 8 is further provided with a display 10. Display processor 6 operates under the control of image processor 3.

Next, the operation of real-time image reconstruction processing by the image reconstruction device of the magnetic resonance imaging apparatus having the above configuration will be explained with reference to FIGS. 1 and 3.

The image processor 3 receives measurement data from the detection device 1 via the pulse sequencer 2 (this is assumed to be first data).
is input, and this measurement data is first stored in the local memory 51 of the image memory 5. This completed series of operating states is shown as first data acquisition 11 in FIG.

Taking in this first data requires a predetermined time (t,). Regarding the data acquisition operation, based on the operation command of the image processor 3, following the first data acquisition 11, the second data acquisition 1 is performed continuously at the same time t.
2. Third data acquisition 13, . . . , up to eighth data acquisition 13 are performed, and data acquisition is further repeated in this pattern.

On the other hand, when the first measurement data is stored in the local memory 51, the local processor 71 is activated based on a command from the image processor 3, waits for the first data acquisition 11 to be completed, and immediately stores data for image reconstruction. Start calculation. This is shown as the first data calculation 21 in FIG. The time required for the first data calculation 21 by the local processor 71 is preferably 300 to 400, for example.
m5, and the first data operation 21 is generally designed to be completed before the next ninth data acquisition for the local memory 51 is started.

In this way, data acquisition by the image processor 3 and data calculation by the local processor 71 are performed in parallel. Furthermore, when the second data import 12 into the local memory 52 by the image processor 3 is completed,
Local processor 72 begins second data operation 22 on second measurement data stored in local memory 52 .

The second data operation 22 by the local processor 72 is
This is substantially the same as the first data operation 21 by the local processor 71, and the only difference is the data. In this manner, after the third data import 13 and the like are completed, the local processors 73 to 78 corresponding to each local memory 53 to 58 independently start data calculation. The data calculation speed of image reconstruction by the local processors 71 to 78 is usually slower than the measurement cycle described above.

When the calculations are completed in each local processor 71 to 78 and data for reconstructing an image is created, this data is stored again in the corresponding local memory, and then processed in each local processor under predetermined conditions. The images are sequentially transferred from the memory to the display processor 6 and displayed on the display 10 via the display memory 8 to display a predetermined tomographic image. In FIG. 3, the data display items at the bottom indicate the display timing and display order of each data displayed on the display 10, respectively. In this way, images can be displayed in real time on the display 10.

In the device configuration example shown in FIG. 1, the number of local memories and local processors is 8, but if the number is generally n, then n is n×(data acquisition time)>
The integer value is determined to be the data calculation time. In FIG. 3, the data acquisition time is shown as tl, and the data calculation time is shown as t2. If the above integer value is used as n, for example, when the local processor 71 takes in the next (n+1)th measurement data, the calculation has been completed, and the local processor 71 again processes the (n+1)th measurement data. Data operations can be performed. In the above embodiments, n was described as 8, but it is assumed that this number of 8 satisfies the above conditions.

Next, a specific example of real-time image reconstruction of the magnetic resonance imaging apparatus will be described, assuming that the two-dimensional image capturing time is Looms and the two-dimensional image reconstruction time is 700 m5. Fourth
The figure shows an example of a screen displayed on the display 10 during image reconstruction. In this screen 31, a reference image 32 indicating the photographing position is displayed on the left side, and by moving a cursor 33 displayed superimposed on this image up and down using the up and down keys on the keyboard 9, the part where the cursor 33 is located can be adjusted. The tomographic image is displayed on the right side of the screen as a real-time image 34. When the up/down keys that control the position of the cursor 33 are operated to set the cursor 33 at a predetermined part of the reference image 32, the display processor 8 transmits the information to the image processor 3 via the system bus 4, The image processor 3 provides the pulse sequencer 2 with magnetic field control parameters necessary to obtain an image at the cursor position, and the pulse sequencer 2 controls the magnetic field according to the parameters to obtain measurement data of the predetermined region. While the up key on the keyboard 9 is being pressed, the image processor 3 gives control parameters so that the shooting position is one after another as the cursor 33 rises, once every 100 m s. Obtain data from different tomographic planes one after another. The data obtained in this way is stored in the local memory 51 one two-dimensional section at a time.
, 52. . When each local processor completes image reconstruction for one tomographic plane (700 seconds after local processor startup)
m5), sends a message to the display processor 6. After the display processor 6 receives the message, if the up key is still pressed at that time,
The reconstructed data is read from the local memory, transferred to the display memory 8, and displayed on the display 10.

According to the image reconstruction described above, if the operator observes the cross section of the subject while scanning it, and releases the up/down keys when the cross section of the affected area necessary for diagnosis appears on the display, Necessary tomographic images can be obtained interactively.

As described above, according to the above-mentioned image reconstruction device, the tomographic plane of the part of the subject necessary for diagnosis can be obtained in real time and in an interactive manner while viewing the display screen, and as a result, positioning operations during imaging can be greatly simplified. It can be easily performed and the diagnosis can be made accurately.

Next, three-dimensional high-speed image reconstruction using the image reconstruction device of the magnetic resonance imaging apparatus according to the present invention will be explained.

First, a general explanation will be given where the number of local memories and local processors is n. In three-dimensional image reconstruction, measurement data is subjected to fast Fourier transform in three directions, so in order to perform image reconstruction with a resolution of 1xjxk pixels, 1xjXkX (log2iX log2
A butterfly operation of the order of jX log2k) is required. During three-dimensional image reconstruction processing, the image processor 3 receives data for one dimension (one project) from the pulse sequencer 2, immediately performs fast Fourier transform, and converts the transformed data into The data is divided into n equal parts and transferred to each local memory of the image memory. The structure of the data is shown in FIG. Here, regarding three-dimensional data, it is assumed that the X direction is the i point, the X direction is the j point, and the two directions are the points, and the data and the local memories LL, L2 . ~． The correspondence with Ln is shown.

As shown in FIG. 5, n local memories L1 to
Finally, i/n pieces of two-dimensional data are stored in each of Ln, with the fast Fourier transform completed in the X direction. Therefore, local memories L1 to Ln
each of the X direction and 2
Image reconstruction processing is performed by performing fast Fourier transform regarding the direction.

Therefore, the image reconstruction time after capturing all data by the image reconstruction device according to this embodiment is longer than that of conventional image reconstruction in which one image processor performs fast Fourier transform in all directions. It is shortened to 1/n.

Next, three-dimensional high-speed imaging will be explained by giving concrete numerical values to the image reconstruction apparatus having the configuration shown in FIG. Now, assume that the three-dimensional matrix is 256x256x256. Further, it is assumed that the speed of complex fast Fourier transform for 256 points is 1 ms, and the measurement time for one projection (256 points) is 10 m5. At this time, the data measurement time is 0.01 x 256 x 256 = 655 seconds image reconstruction time (in this case, only fast Fourier transform is assumed)
According to the conventional image reconstruction device, D, HI
6×256×3=196 seconds On the other hand, according to the image reconstruction device configured as shown in FIG. 1, the image processor 3 executes the fast Fourier transform in the one-dimensional direction during the measurement operation. In other words, 1 in the measurement time lQms
ms is used. After the measurement is completed, eight local processors 71 to 78 are caused to execute fast Fourier transform for the two dimensions of the ridges and the predetermined data stored in the local memories 51 to 58, respectively. As a result, in the case of the present invention, the image reconstruction time is 0.001 x 256x (256
/8) x 2 = 16 seconds, and a speed increase of more than 10 times can be achieved.

In order to further speed up the process, if a method is adopted in which each local processor performs fast Fourier transform in the y-axis direction every time 256 points are accumulated in the y-axis direction, it will take 2 times after measurement is completed.
Only the directional fast Fourier transform needs to be performed, and the image reconstruction time is halved.

0.001 x 256 can.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in an image reconstruction device of a magnetic resonance imaging apparatus, a predetermined number of local memories and local processors corresponding to each of these are provided to decentralize data processing work. Because it is configured to operate in parallel, it is possible to achieve a faster processing time for image reconstruction processing, and in conjunction with the recent increase in imaging time, it is possible to achieve real-time measurement and high-speed 3. Dimensional measurements can be performed. In addition, since real-time measurement and high-speed three-dimensional measurement can be performed in this way, it is possible to omit the preprocessing required to determine the affected area and imaging area, which was previously required, and it is possible to improve the throughput of the magnetic resonance imaging system. Handling of the magnetic resonance imaging device becomes easier.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the image reconstruction device of the magnetic resonance imaging apparatus according to the present invention, Fig. 2 is a block diagram showing the circuit configuration of the local memory section, and Fig. 3 is a block diagram showing the circuit configuration of the local memory section. Diagram showing the relationship between data and local memory, No. 6
The figure is a block diagram of a conventional image reconstruction device. [Explanation of symbols] l... 2... 3... 4... 5...φ... 51 to 58... Detection device number Pulse sequencer image processor system Bus φ image memory/local memory 6...Display processor 10...
Display 71-78@Local processor

Claims (3)

[Claims] (1) In a magnetic resonance imaging apparatus that creates a tomographic image of a subject using magnetic resonance phenomena under the control of an image processor, an image memory that stores measurement data handled by the image processor is formed from a plurality of local memories. A local processor is provided in each of the local memories, and each of the plurality of local processors performs a predetermined operation on the measurement data stored in the corresponding local memory under the management of the image processor, and the tomographic image is An image reconstruction device for a magnetic resonance imaging apparatus, characterized in that the image reconstruction device is configured to create an image. (2) Using the image reconstruction device of the magnetic resonance imaging apparatus according to claim 1, the image processor:
Two-dimensional measurement data continuously captured by the detection device is periodically transferred to each of the local memories in a predetermined order, and the predetermined calculation is performed on the local processor corresponding to the local memory for which the data transfer has been completed. A starting signal is given to the image display means to periodically display images in the order from the local memory of the local processor where the calculation has been completed, so as to display images in real time equivalent to the measurement cycle of the detection device. An image reconstruction method for a magnetic resonance imaging device characterized by the following. (3) Using the image reconstruction device of the magnetic resonance imaging apparatus according to claim 1, the image processor:
Regarding the two-dimensional measurement data that is continuously captured by the detection device, fast Fourier transform is performed on the data for the first dimension, and the transformed data is divided by the number of the local processors and stored in each of the local memories. At the same time, each local processor performs fast Fourier transform on the second and third dimension data of the data stored in the corresponding local memory, thereby creating a high-speed three-dimensional image. An image reconstruction method for a magnetic resonance imaging apparatus, characterized in that reconstruction is performed.