SU1656423A1 - Device for magnetic resonance signal detection - Google Patents

Description

The invention relates to the technical physics and can be used to build radio spectroscopes. The purpose of the invention is to increase expressnet measurements. The measured signal is summed by the amplifier with the signal accumulated in the storage device. An analog-to-digital converter converts the sum signal to a digital form. The noise component is measured as the difference of two successively measured signals and is accumulated in a similar manner in the storage device. An inverting amplifier changes the sign of the signal from the storage device, and the amplifier subtracts it from the measured signal. Accumulation stops when a given noise level is reached, which is measured by the unit. 1 il.

The invention relates to the technical physics and can be used to build radio spectroscopes.

The purpose of the invention is to increase expressnet measurements.

The drawing shows a block diagram of the proposed device.

The device contains an analog-to-digital converter (ADC) 1 and digital-to-analog converter (DAC) 2, first storage device (memory) 3. subtractive 4 and summing 5 amplifiers, controlled voltage divider 6 and control unit 7, second storage device (memory) 8, a switching unit 9, an inverting amplifier 10, a first sampling-storage device 11 (TCC), a second sampling-storage device 12 (TCC), and a calculation unit 13.

The device works as follows.

The selection of weak magnetic resonance signals is as follows.

At the input of the device receives a signal and recorded when a periodic passage of the resonant region of the spectrum:

and, = 5 + y,

where ί is the sequence number of the passage of the resonant region;

5 - magnetic resonance signal; n, is the noise component of the recorded signal.

The channel for the accumulation of the magnetic resonance signal includes a subtractive amplifier 4, a controlled divider 6

voltage summing amplifier 5.

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3

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ADC 1, the first memory 3. DAC 2 and block 9 switching.

The accumulation of the magnetic resonance signal is as follows.

The subtractive amplifier 4 subtracts from the recorded signal 1) ι, arriving at its first input, the signal IR – 1 recorded in the memory of the first memory unit 3 at the previous (I-1) -th passage of the resonant spectral region;

υι-υΡί-ι.

At the first passage of the resonant region of the spectrum, the signal ΙΙι = 5 + ηι is formed at the output of the subtracting amplifier 4, since (1) 3 ¹ = 0) is erased before the information is measured in memory 3.

The difference signal from the output of the detracting amplifier 4 is fed to a controlled voltage divider 6, which normalizes it to a weighting factor inversely proportional to the number of) passes;

1 p 1

4 (υ, -υί-1).

I

The normalized signal is fed to the input of summing amplifier 5, which completes the signal to it and * ¹ : -1 from the memory of memory 3, which is fed to the second input of amplifier 5;

ι п1 п1

W (υι — ι) + υι - ι

A / D converter 1 converts the signal from the output of summing amplifier 5 to digital form to record it in the memory of memory 3, the D / A converter 2 performs the inverse conversion of the signal from memory of memory 3 (from digital to analog). The analog signal from the output of the DAC 2 is supplied through the switching unit 9 to the inputs of the subtractive 4 and summing 5 amplifiers.

After N passes of the resonance region of the spectrum (Ν accumulations), the signal will be recorded in the memory of the first memory unit 3

nd ¹ = 5 + rm Σ p ,,

'H = 1

^one

where tt d y sh - noise component of the accumulation ^Ν Ι = 1

Lennogo signal representing the sum of the noise components ηι of the recorded signals, divided by the number of accumulations.

Noise intensity

In the proposed device in parallel with the accumulation of the magnetic resonance signal, the accumulation of noise components u of the recorded signal is carried out. To do this, at each step of sweeping the resonant parameter, along with the cycle of summation of the magnetic resonance signal, a second cycle is performed — the summation of the differences of successively recorded signals in and 1) ί, which for each even number of accumulations gives a result equivalent to summing only the noise components of the recorded signal.

The channel for the accumulation of noise components includes a subtracting amplifier 4, a controlled voltage divider 6, a summing amplifier 5. ADC I. a second charger 8, a DAC 2, an inverting amplifier 10 and a switching unit 9.

The accumulation of noise components is as follows.

At each step of sweeping the resonant parameter after performing operations on summing the recorded signal and recording the result in the memory of the first memory unit 3, the control unit 7 generates control signals for which information from the memory of the second memory unit 8 is output to the input of the DAC 2. And the switching unit 9 switches the input of the detracting amplifier 4 to the output of an inverting amplifier 10.

Inverting amplifier 10 changes the sign of the signal coming from the memory of the second charger 8 and the input of the subtracting amplifier 4.

As a result, a signal is generated at the output of the subtractive amplifier 4.

ΙΦ + υ ι-ι

As in the accumulation cycle of the recorded magnetic resonance signal, the signal from the output of the subtracting amplifier 4 is fed to the controlled voltage divider 6, which normalizes it to a weighting factor inversely proportional to the number I of the accumulations made:

one

Y (and, + and <, - 1).

The normalized signal is fed to the input of summing amplifier 5, where the signal from the output of inverting amplifier 10 is added to it (i.e., the signal is actually subtracted from the memory of the second memory device 8):

-ι п2 п2

At (and * + 1Л-1) -и, - ι

ADC 1 converts this signal to digital form, after which it is recorded in

second memory 8

Since before the device starts working, the information in the memory 8 is erased

noise components πι, which results in an increase in the signal-to-noise ratio in the accumulated signal.

five

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(5 ^п2 о = 0), then after the first passage of the resonant region of the spectrum, the signal is recorded in the memory of the second memory unit 8

and ⁿ² 1 = 5 + y. after the second - signal

iZ ² + (ig - η 1), after the third - the signal

и9 ² = 5 + ^ (ПЗ-П2 + щ): after the fourth - the signal

iZ ² (P4-PZ + P2-P1).

Thus, after making an even number N of accumulations (N = 2, 4, 6, 8 ...), the signal is recorded in the memory of the first memory unit 3

υΡι ¹ = 5 § η,,

¹⁴ I = 1

where 5 is the magnetic resonance signal;

¹ ·

tg Λ πι = sum of noise components ^Ν ί = 1

Sign u u recorded signals vι.

In the memory of the second memory 8 at the same time, the signal is recorded

'm = 1

representing the sum of only the noise components of the recorded signals, which differs from the similar sum in the first memory 3 only by the signs with which the individual noise components belong to it.

The intensity of the noise component recorded instead of the magnetic resonance signal in the memory of the first memory unit 3, with an even number of accumulations, is equal to the intensity of the noise component recorded without the magnetic resonance signal in the memory of the second memory unit 8.

In the proposed device, the intensity of the noise component in the accumulated magnetic resonance signal is measured by the intensity of the noise component accumulated in the second memory device 8.

UVH II, turned on at the output of the DAC 2, remembers the value of the magnetic resonance signal that is output from the memory of the first memory 3 at the time of switching on the second charger 8 and generates at the output a magnetic resonance signal in analog form.

Similarly, the water chemistry department 12 remembers for the time of switching on the first charger 3 the value of the signal of the noise component output from the memory of the second charger 8 and generates at the output a signal of the noise component in analog form.

The intensity of the noise component is measured in block 13 of the calculation after each passage of the resonant region having an even number: / 2 4. 6, etc. When the intensity of the noise component decreases to a predetermined value (when the specified signal-to-noise ratio is reached), the output of this block is formed a control signal that enters the control unit 7 and stops the accumulation.

The control unit 7 also generates a sweep signal for passing through the resonant region of the spectrum.

Thus, the proposed device allows you to control the signal-to-noise ratio in the process of signal accumulation and stop accumulation when the specified measurement accuracy of the magnetic resonance signal is achieved, which ensures the optimal accumulation time for recorded signals with any signal-to-noise ratio.

In addition, the device does not need to set large amplitudes of the sweep of the resonance parameter to estimate the noise level.

Operation of the developed accumulator showed that, depending on the complexity of the spectrum and the initial signal-to-noise ratio, the achievement of the same measurement accuracy of the magnetic resonance signal is provided with 1 5 2 times less accumulation time than in the prototype

Claims (1)

Claim A device for extracting magnetic resonance signals, containing an analog-digital and digital-analog converter, a memory device, subtracting and summing amplifiers, a controlled voltage divider and a control unit, the subtracting amplifier, a controlled voltage divider, a summing amplifier, and an analog-digital converter. the storage device and the digital-to-analog converter are connected in series, the second input of the summing amplifier is connected to the second input of the subtracting amplifier, and the outputs of the control unit are connected respectively to the control inputs of the controlled voltage divider and storage device, characterized in that additionally introduced a second storage device connected in parallel to the first storage device. switching unit connected between the output of the digital-to-analog converter and the second input of the detracting amplifier, an inverting amplifier and two sampling-storage devices, connecting7 1656423 eight not connected to the output of the D / A converter, and a computing unit whose input is connected to the output of the second sampling-storage device, the inverting amplifier being connected to the second 5 input of the switching unit, and the control inputs of the switching unit and the first sampling-storage device are connected to the second output of the control unit, which is provided with a third output connected to the control inputs of the second storage device and the second sampling-storage device, and an input connected to the output of the computing unit.