SU1455288A1 - Method of obtaining a magnetic signal - Google Patents

Abstract

The invention relates to the field of radio-spectroscopy, and more specifically to the technique of magnetic resonance-based introscopy, and can be used to obtain a signal from a local volume when forming a picture of the spatial distribution of resonant magnetic moments in the sample under study. The aim of the invention is to increase the spatial selectivity in the study of the local volume of the sample. A sample placed in a magnetic uniform field is affected by a sequence of high-frequency pulses 90, 180 and 90. Simultaneously with 180 ° High-frequency impulse of a special form is influenced by a magnetic field gradient Resonant signals are recorded after 90 pulses. After subtracting the recorded signals, an amplitude-doubled magnetic resonance signal from the sample layer is obtained. 4 il. and s /

Description

one

The invention relates to radio spectroscopy, in particular to a magnetic resonance imaging introscopy technique, and can be used to obtain a signal from a local volume when a picture is formed. spatial distribution of resonance magnetic moments in the sample under study.

The purpose of the invention is to increase the spatial selectivity in the study of the local volume of the sample.

Figure 1 shows the sequence

nosti 90 and 180 high-frequency pulses; Figure 2 shows the envelope of the 180 ° pulse as a function of time; Fig. 3 shows the sequence of the effect of the magnetic field gradient; 4 is a block diagram of a device implementing the proposed method (B, B are mutually perpendicular components of the high-frequency field; G is the magnetic field gradient; t is time, C is the time interval between 180 ° and second 90 ° - high frequency pulses).

The device (figure 4) contains an electronic control computing ma. busbar 1, generator 2 high-frequency oscillations, phase modulator 3, amplitude modulator 4, amplifier 5

JV GS GS

00

00

I3u55288

power, power supply 6, magnet 7, gradient coils 8j receive I transmitting coil 9 sample under study 10J receiver 11 resonance signals, analog-to-digital converter 12,

Control computer 1 sets the sequence of impulses;

Re-act 90-hf pulse and record the resonant signal). Signal from the layer

coBj acon amplitude and phase modulus of the sample get subtracted from the signal

| U - real dimensionless

magnitude.

Inversion of spins is carried out in the frequency range / uooUju / J

Re-act 90-hf pulse and record the resonant signal). Signal from the layer

sample get subtracted from signal

signal generator 2, performs the registration and processing of resonant signals with a high-frequency signal from generator 2 is modulated in phase in modulator 3 and in amplitude in gydullator 4 The pulses go to power amplifier 5 and then to fflo-forward coil 9, creating a high-frequency field of the resonance frequency acting on the sample 10. The gradient magnetic field is created by means of coils 8 fed by ISTOCH1-SHKOM b. After the pulses are applied, the resonant signals generated by the IB coil are amplified in the receiver 11, digitized, stored and processed in computational malpages not 1,

The sample containing spin magnetic moments (nuclear or electron I) f is placed in. homogeneous static magnetic field

| N Affect the sample 90 - the

: high frequency

(HF) impulse with

C0 „

ff

But,

where X is the gyromagnetic ratio.

After the pulse, the signal is recorded). Then the sample is simultaneously affected by a 180 ° HF pulse and a magnetic field gradient. The pulse inverts the magnetic moments in the layer practically

rectangular shape with a frequency interval of 2 m (Lm l) fl 1 & that UCO. For this bending around the 180th pulse, depending on the time t, is determined by the ratio

B (t) B, (t) -biB (t) (t-t,) f

t - t. BV and В „- mutual comp frequency time

50 foot

AT,

and B mutually perpendicular ro components of the HF field;

 B2, / y / Bob (i {u.

the amplitude of the high-frequency field, measured in units of magnetic induction; is valid constant, Hz |

S, (t) is the signal S (t), and the signal from the layer is doubled.

The invention provides more. high selectivity due to the inversion of the mass moments in the layer of a practically rectangular edge with a uniform distribution of the phase of the resonance of magnetic moments along the layer thickness and the exclusion of a refasing gradient.

Claims (1)

Invention Formula  -Jq The method of obtaining the magnetic resonance signal, which consists in the fact that the sample, which is in a constant uniform magnetic field, is affected by a high-frequency pulse and a magnetic field, which has a spatial gradient, and a resonant signal is recorded. and with the fact that, in order to improve spatial selectivity in the study of the local volume of 25 samples, the sample is first subjected to a high-frequency pulse, the first resonant signal is recorded, then simultaneously affected by a 180 ° signal sokochastot- 40 momentumQ, Imek CIM envelope B (t) versus time t of the following formula B (t) B, (t) -i-iB (t) Bjsech | 3 (t-t,) 1-I  t 2 (lm l) fl 1 & t - t. BV and В „are mutually perpendicular components of the high-frequency field; 180 hp high frequency exposure time momentum B is the amplitude of the high-frequency field, measured in units of magnetic 5 induction; real constant, Hz; real dimensionless value; 1 (H D) is the gyromagnetic ratio of the studied nuclei; i-lgt and a magnetic field having a national gradient, re-acting w.Gu. and Fi €. one V A 90% high frequency pulse is recorded, a second resonant signal is recorded, and the magnetic resonance signal is determined from the difference between the received signals. and oo t.c Phie, 2 Fig.Z G. Shig,