JPH0623503U - MR device - Google Patents

Abstract

(57) [Abstract] [Purpose] The majority of the full range of the A / D converter is always available. [Configuration] Each time the view is started, the variable gain amplifier 1 is set to a low gain, and the digital value SD output by the A / D converter 2 at that time is read. And the digital value S
From D and the low gain, an appropriate gain is determined so that most of the full range of the A / D converter 2 can be used, and the appropriate gain is set as the gain G of the variable gain amplifier.
After this, the digital value SD output from the A / D converter 2
Is taken into the information processing section 3 as the original data. [Effect] The image quality can be improved. Throughput can be improved.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an MR device, and more particularly to an MR device that can improve image quality and throughput.

[0002]

[Prior art]

 FIG. 6 is a principal block diagram of an example of a conventional MR device. In the MR device 501, the NMR signal SA of the patient K received by the RF coil B is first-stage amplified by the preamplifier P, transmitted through the coaxial cable C, and input to the variable gain amplifier 51. The variable gain amplifier 51 amplifies the signal with the gain G given from the control unit 54 and outputs it to the A / D converter 52. The A / D converter 52 performs analog / digital conversion according to the timing signal Ti from the information processing section 53 and outputs a digital value SD to the information processing section 53. The information processing unit 53 reconstructs the MR image using the digital value SD, and then passes the processing to the image processing unit V. In addition, the timing signal Ti is sent to the A / D converter 52. Further, a preliminary adjustment process described below is performed to determine the gain G of the variable gain amplifier 51, and the control unit 54 is notified.

FIG. 6 is a flow chart of preliminary adjustment processing for determining the gain G of the variable gain amplifier 51. First, in step SU1, scan conditions are set. In step SU2, a view with a warp amount of 0 is activated. In step SU3, the gain of the variable gain amplifier 51 is set to "1 (times)".

In step SU 4, scanning is performed to read the digital value SD, and it is determined whether the digital value SD is 70% or more of the full range of the A / D converter 52. If less than 70%, the process proceeds to step SU5. If 70% or more, the process proceeds to step SU6. At first, it is always less than 70%, and the process proceeds to step SU5. In step SU5, the gain of the variable gain amplifier 51 is increased by one step. Then, the process returns to step SU4. In step SU6, the gain of the variable gain amplifier 51 is lowered by one step, and it is determined as the gain G. Then, the process ends.

Through the preliminary adjustment process, the gain G of the variable gain amplifier 51 is set so that the digital value SD is about 70% of the full range of the A / D converter 52 in the view with the warp amount of 0.

[0006]

[Problems to be solved by the device]

 In the conventional MR device 501, when the gain G is determined by the preliminary adjustment process, the gain G is used for any of the warp amounts. Therefore, in the region where the NMR signal is small except for the vicinity of the warp amount 0, only a small part of the full range of the A / D converter 52 is used. For example, in the case of the NMR signal shown by the solid line in FIG. 7, with the warp amount a, only 20% of the full range of the A / D converter 52 is used. The NMR signal shown by the solid line in FIG. 7 is the maximum NMR signal when the warp amount is 0, and is the NMR signal assumed by the preliminary adjustment process.

However, when only a small part of the full range of the A / D converter 52 is used, the influence of a quantification error becomes large, which causes a problem that image quality is deteriorated. Further, due to the non-uniformity of the magnet and the characteristics of the RF coil, the NMR signal may be as shown by the broken line in FIG. 7, but in this case, in the region L near the warp amount a, the There is a problem that it becomes a range. Furthermore, the preparatory adjustment process requires several tens of seconds, which causes a problem of reducing the throughput.

Therefore, the object of the present invention is to always use most of the full range of the A / D converter regardless of the warp amount, thereby improving the image quality, and preventing the overrange from occurring. It is an object of the present invention to provide an MR device that does not require adjustment time and can improve throughput.

[0009]

[Means for Solving the Problems]

 The MR device of this invention activates a series of views in order, amplifies the received NMR signal with a variable gain amplifier for each view, converts it into a digital value with an A / D converter, and captures the digital value as data. In the MR device, each time a certain view is activated, the variable gain amplifier is set to a low gain to read the digital value output from the A / D converter, the proper gain is determined based on the digital value, and the proper gain is changed. The constitutional feature is that it is provided with a gain adjusting means for giving to the gain amplifier, and the digital value output from the A / D converter after giving an appropriate gain to the variable gain amplifier is taken as data. In the above configuration, the predetermined view may be all views or may be discrete views.

[0010]

[Action]

 In the MR device according to the present invention, the variable gain amplifier is set to a low gain each time a predetermined view is activated, and the digital value output from the A / D converter at that time is read. Then, the signal level is estimated from the digital value and the low gain, an appropriate gain is determined for the signal level so that most of the full range of the A / D converter can be used, and the appropriate gain is set in the variable gain amplifier. To do. After this, the original data is imported. In this way, since the gain of the variable gain amplifier is optimized for each predetermined view, most of the full range of the A / D converter can be used and the image quality can be improved. Also, overrange does not occur. Furthermore, since no preliminary adjustment time is required, the throughput can be improved.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the examples shown in the drawings. However, this does not limit the present invention. FIG. 1 is a block diagram of an essential part of the MR device of the present invention. In the MR device 101, the NMR signal SA of the patient K received by the RF coil B is first-stage amplified by the preamplifier P, transmitted through the coaxial cable C, and input to the variable gain amplifier 51. The variable gain amplifier 51 amplifies the signal with the gain G given from the control unit 4, and outputs it to the A / D converter 2. The A / D converter 2 performs analog / digital conversion according to the timing signal Ti from the control section 4 and outputs a digital value SD to the information processing section 3 and the control section 4. The information processing section 3 takes in the gain G from the control section 4 and the digital value SD output from the A / D converter 2 in response to the timing signal Ti from the control section 4, and obtains the gain G and the digital value SD. The M image is used to reconstruct the MR image, and then the process is passed to the image processing unit V. It also sends a timing signal Ta to the control unit 4.

The control unit 4 determines the gain G of the variable gain amplifier 1 for each view based on the digital value SD from the A / D converter 2 and the appropriate gain table 5, and sets the gain G in the variable gain amplifier 1. The information processing unit 3 is notified. The process of determining the gain G of the variable gain amplifier 1 will be described later. The control unit 4 also sends a timing signal Ti to the A / D converter 2 based on the timing signal Ta from the information processing unit 3.

FIG. 2 is a flowchart showing the operation of the MR device 101 for each view. The steps ST3 to ST6 correspond to the processing of the gain adjusting means according to the present invention. Steps ST1, ST2 and ST7 are the same as the conventional processing. In step ST1, scan conditions (width and intensity of RF pulse, etc.) are set. In step ST2, one of the series of views is activated.

In step ST 3, the control unit 4 sets the gain of the variable gain amplifier 1 to “1 (times)”. In step ST4, the control section 4 sends the timing signal Ti to the A / D converter 2 and reads the upper 4 bits of the output digital value SD. In step ST5, the control section 4 refers to the proper gain table 5 to take out the proper gain corresponding to the upper 4 bits of the digital value SD, and determines the proper gain as the gain G of the variable gain amplifier 1.

FIG. 3 exemplifies the proper gain table 5. The A / D converter 2 has 8 bits. For example, when the gain of the variable gain amplifier 1 is “1 (times)”, the maximum value of the upper 4 bits of the digital value SD is “0000” is “000011111”. Therefore, the full range of the A / D converter 2 is 5 Although less than 0.99% (= 100 × 15/255) or less is used, if the gain of the variable gain amplifier 1 is set to “16 (times)”, almost full range of the A / D converter 2 will be achieved without overrange. Can be used. Therefore, the appropriate gain at this time is “16 (times)”. Further, since the maximum value of the upper 4 bits of the digital value SD when the gain of the variable gain amplifier 1 is “1 (times)” is “000 1” is “00011111”, the full range of the A / D converter 2 is However, if the gain of the variable gain amplifier 1 is set to "8 (times)", it will not be overrange and will be almost equal to that of the A / D converter 2. Full range can be used. The appropriate gain is defined in the same way below.

Returning to FIG. 2, in step ST6, the control unit 4 sets the determined gain G in the variable gain amplifier 1.

At step ST 7, the control section 4 sends a timing signal Ti to the A / D converter 2 and the information processing section 3. The information processing section 3 takes in the digital value SD output from the A / D converter 2 as data. At the same time, the gain G of the variable gain amplifier 1 is also taken in. FIG. 4 shows a timing chart of the above processing.

In the above description, the gain G is expressed by a magnification, but this is merely for convenience of description, and the present invention is not limited to this.

[0019]

[Effect of device]

 According to the MR device of the present invention, since the gain of the variable gain amplifier is optimized for each predetermined view, most of the full range of the A / D converter can always be used and the image quality can be improved. Also, overrange does not occur. Furthermore, since no preconditioning time is required, throughput can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an essential part of an MR device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the MR device shown in FIG.

FIG. 3 is a view showing an example of an appropriate gain table.

FIG. 4 is a timing chart of the operation of FIG.

FIG. 5 is a block diagram of a main part of an example of a conventional MR device.

FIG. 6 is a flowchart showing a conventional gain adjustment method.

FIG. 7 is an explanatory diagram of a conventional gain adjustment method.

[Explanation of symbols]

 101 MR device 1 Variable gain amplifier 2 A / D converter 3 Information processing unit 4 Control unit 5 Appropriate gain table P Preamplifier B RF coil

Claims (1)

[Scope of utility model registration request] 1. A series of views are sequentially activated, and a received NMR signal is amplified by a variable gain amplifier for each view,
In an MR device that converts a digital value with an A / D converter and captures the digital value as data, each time a predetermined view is activated, the variable gain amplifier is set to a low gain to read the digital value output from the A / D converter, The digital value output from the A / D converter after the appropriate gain is determined based on the digital value and the determined gain is provided to the variable gain amplifier, and the determined gain is provided to the variable gain amplifier An MR device characterized in that is captured as data.