JPS6382648A - Magnetic resonance ultrasonic apparatus - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention branches into two systems of MR multiplied signals obtained from a subject, obtains Sin component and Cos component data from each, and performs image processing. This article relates to magnetic resonance diagnostic equipment.

(Prior Art) In a magnetic resonance diagnostic apparatus (hereinafter referred to as an MRI apparatus), an input signal (MR multiplied signal) from a subject obtained by diagnosis is branched into two systems, each of which is sent to a detector.

After passing through an amplifier, filter, etc., it is converted into a digital signal by an A/D converter, and the S1n component and C
Image processing is performed by obtaining OS component data and using a paralysis machine.

Figure 3 shows a block diagram of a conventional MRI device.
The input signal fin applied to the terminal Ti is divided into two systems A,
8 and added to a pair of detectors 1.2. The phase shifter 3 converts the signal fr added from the standard low frequency generator 4 into two reference signals fr having a phase difference of 90' from each other and applies them to the detector 1.2. This allows the detector 1.2
So-called quadrature detection is performed at each detector 1.2.
Detected signal r1n-fr of Sin component and CO8 component from
is output. Each detected signal f'1n-t'r is applied to DC amplifiers 5 and 6 and subjected to desired amplification, and then passed through sample and hold circuits 7 and 8 and AD converters 9 and 10 to have a Sin component and a Cos component, respectively. Under the terminal as data? 31
and is output from T232 and added to the computer.

Timing control means 11 operates to control the operation timing of a pair of sample and hold circuits 7.8 and AD converter 9.10. FIG. 4 shows the sampling operation in the case of AD conversion, and shows the sine component of (a>) and (
Both the Cos components of b) have a constant sampling operation ポPs
This is done by sampling data in the same phase.

By the way, in the conventional MRIH system shown in Fig. 3, a signal over a certain band frequency appears from the DC component O[H2] as the detection output of the detector 1.2, so a C amplifier such as 5 or 6 is used as an amplifier. It is necessary to use it. For this reason, both DCs
Fine adjustment is required to eliminate variations in the gain of the amplifier, and since it is a DC amplifier, it is necessary to adjust the offset between the two. It is necessary to roughly adjust the gain of the AD converters 9 and 10.

Therefore, detailed work is required for each gain adjustment, and there is a drawback that artifacts may occur in the image if variations occur in any of the gains.

In addition, the conventional MHI equipment requires many parts in two circuit systems below the detector, which has the disadvantage that the circuit configuration is complicated and the cost per oil line of the device is high.

(Problems to be Solved by the Invention) As described above, the conventional MRI apparatus has the problem that the circuit configuration is complicated and the adjustment work of the two circuit systems is complicated.

The present invention has been made in response to the above-mentioned problems.
The purpose is to provide an I-device.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a pair of detectors each detecting two systems of input signals, and only one of the pair of detection main power is added. a pair of sample-and-hold circuits that can obtain 7JO amplified outputs, a pair of AD converters that output 3 in component and CO8 component data to which only one of the number-hold outputs is added; It is characterized by comprising a detection output, the operation timing and sample-hold output of a pair of sample-and-hold circuits, and timing control means for controlling the operation timing of an AD converter.

(Function) The pair of detection outputs are switched by the timing control means and applied to the AC amplifier and AD converter, which are provided only for the first system.
O6 component data can be obtained. Since one system of AC amplifiers and AD converters is used in common, there is no need to adjust variations in gain.

(Embodiment) FIG. 1 is a block diagram showing an MRI apparatus according to an embodiment of the present invention, in which 21 and 22 are a pair of detectors, and the input signal fin is branched into two systems A and B and added to each of them. 23 is a phase shifter, 24 is a target? M signal generator. The detectors 21 and 22 output detection signals fi n - f r, respectively. The configuration up to this point is the same as the conventional one. The switch 26 is a first switch and a pair of detection outputs f i n −f
r is switched with a signal "S" of a desired frequency and applied to the AC amplifier 25. As a result, the AC amplifier 25 receives (f
in-fr) is modulated by fs (hiratashin, = fs
±(fin-fr) will be added. The amplified output from the AC amplifier 25 is sent to a pair of sample and hold circuits 2.
Added on 7.28. 30 is a second switch that outputs a pair of sample and hold outputs fs±(fin-fr) to the signal g.
'f' S is switched in synchronization with the first switch and applied to the AD converter 29.

As a result, the AD converter 29 has fs±(fin-i'
signal (f1n-fr) obtained by demodulating r) with fs
will be added.

31 is timing i! The control means includes the first switch 26. A pair of sample and hold circuits 27 and 28 operate to synchronize and control the operation timings of the second switch 30 and the AD converter 29.

Next, the operation of the embodiment of the present invention will be explained.

The first switch 26 is operated by the signal fs controlled by the timing control means 31, and the pair of detection outputs f
By switching in-fr, the detection output f
in-fr is made into a signal fS±(fin-fr) shifted to a higher frequency by f's. As a result, even if the detection output fin-fr contains a DC component, this DC component will be converted to an AC signal of fs, so the DC
0, an AC amplifier can be used as 25 without using an amplifier, and as this AC amplifier 25, the fs
A filter having characteristics that covers a band of ±(fin-fr) is used, thereby eliminating the need for offset adjustment.

Furthermore, the AC amplifier 25 is designed to have the characteristics of a band-pass filter in order to reduce noise. As a result, the power supply frequency is 50 [H2].

60 [T+Z] can be removed.

Assuming that the first switch 26 is now switched to the detector 21 side, the - pair sample and hold circuits 27 and 28 are switched to the 27 side, so the output of the AC amplifier 25 is transferred to the sample and hold circuit. 27
The redata is held (latched) in addition to the data being sampled. Also, at this time, the second switch 30 is switched to the sample and hold circuit 27 side in synchronization with the first switch 26, so this circuit 2
7 data is converted by the AD converter 29 which is switched accordingly, the terminal ? 31 outputs sin component data.

FIG. 2A shows that the sampling of the Sin component is performed at a constant sampling pitch Ps in this way.

Next, when the second switch 26 is switched to the detector 22 side, the sample and hold circuits 27 and 28 are switched to the 28 side, contrary to the above, and the second switch 30 switches to the sample i1-hold. The signal is switched to the circuit 2B side, and the ΔD converter 29 is switched accordingly. Therefore, since the operation opposite to the above is performed, the CO8 component data is output from the terminal TZ32.

FIG. 2(b) shows that the J:SCO5 component is sampled at a constant sampling pitch Ps in this way.

As is clear from FIGS. 2(a) and 2(b), sampling of the Sin component and the COS component is not performed in the same phase, but is performed alternately, resulting in a phase shift. However, if the data is processed using the FFT technique used in a normal MRI apparatus, sufficient waveform reproduction is possible, so there is no problem. In addition, when performing non-bringing by setting three sampling points, which is the same as the conventional method, the timing control means 31 needs to be controlled to double the switching speed, but this is not currently implemented. This can be achieved by using existing hardware technology.

According to this embodiment of the present invention, the following advantages can be obtained.

(1) Since an AC amplifier is used in only one system as an amplifier, there is no variation in gain, so detailed work of gain adjustment is unnecessary, artifact 1 does not occur, and offset adjustment is also unnecessary.

(2) Since the AD converter is used for only one system, gain adjustment is not necessary.

(3) Since the detection output is switched, A
Since signal processing up to the D converter can be handled at relatively high frequencies,
Become more resistant to noise.

(4) Since the circuit configuration is simplified, the number of adjustment points is greatly reduced, improving stability and reducing costs.

[Effects of the Invention] As described above, according to the present invention, the circuit configuration is simplified, so detailed work of gain adjustment is not required, and the cost of the device can be reduced.

[Brief explanation of the drawing]

FIG. 1 shows fVIRII? of the embodiment of the present invention. Fig. 2 is a signal waveform diagram during sampling of the MRI device of the present invention, Fig. 3 is a block diagram of a conventional MRI device, and Fig. 4 is a signal waveform diagram during sampling of the conventional MRI device. . 21.22...Detector, 25...AC amplifier, 26
．． 30...Switch, 27.28...Ripple hold circuit, 29...A
D converter, 30...timing control means.

Claims (1)

[Claims] In a magnetic resonance diagnostic apparatus that branches an MR signal obtained from a subject into two systems and obtains data of a sine component and a cosine component from each system for image processing, a pair of detectors each detecting input signals of the two systems, and a pair of detectors are used. an AC amplifier to which only one of the detected outputs is applied; a pair of sample-hold circuits to which the amplified output is applied; and an AD converter to which only one of the pair of sample-hold outputs is applied and outputs Sin component and Cos component data; A magnetic resonance diagnostic apparatus characterized by comprising a timing control means for controlling the pair of detection outputs, the operation timing and sample hold output of the pair of sample and hold circuits, and the operation timing of the AD converter.