SU1257485A1 - Method of measuring time of longitudinal and transverse relaxation - Google Patents

Abstract

The invention relates to the field of magnetic resonance and can be used in the technological control of chemical production. The purpose of the invention is to expand the range of measurement of relaxation times. This is achieved by affecting the sample with a sequence of two pulses of a resonant radio frequency field. Spin echo signals are recorded. The repetition period of the pulse sequence is reduced until the echo signals before the second pair of pulses are visible, and with respect to the amplitudes of these signals at different intervals between the pulses and between the pairs of pulses of the pulse sequence, the longitudinal and transverse relaxation times are found. Moreover, the duration of two pulses make the same and equal to 90. 2 Il. i (L 1CE ate 431 00 ate

Description

eleven

The invention relates to methods for measuring nuclear relaxation times and can be used in process control of chemical production.

The purpose of the invention is to expand the measurement range by measuring the transverse relaxation time under conditions of thermodynamic saturation.

Fig. 1 shows the recording of spin echo signals in nuclei / with a repetition period of the pulse sequence of 700 microseconds; Fig. 2 shows the dependence of the pre-echo amplitude M (T (, -2t) on the repetition period of the pulse sequence TO, where T is the interval between pulses (within a pair).

Example. When KRe04 is exposed to the sample at K, the pulse pairs with the repetition period of the pulse sequence of the microsecond are obtained by recording the spin signal

(

the echo on the Re wires presented in FIG. 1, where the main signal 1 is indicated, the secondary signal 2 is spazM (TO -t) 4 (cos / 2 - sin $) exp (- ---)

T

where - the duration of the radio frequency pulse,

(3)

m ()

M () f f- g exp (

  P . t,

M (That-2G)

Figure 2 shows the dependence of the amplitude of the leading echo M (T (i-L) on the repetition period of the pulse sequence on Re cores in KReO + (at K and frequency i 55.651 MHz). From the graph it follows that the echo amplitude reaches at Tf, - 400 µs. When measuring the transverse relaxation time by the usual method (Khanovsky) T2 400 µs. Thus, using the leading echo (Tr -2 G), one can determine the transverse relaxation time of the sample, whose spin system is in saturated thermodynamic disequilibrium574852

of the leading type, leading signals 3 and 4 (before the second pair of pulses). Measurement of Tg (transverse relaxation time) can be done in two ways: by changing g

  J2 (r: f:) j

M (T, -2Г) I Tg J and when T changes,

-, 0 M (That -2G) f2 (To-Tc;)

M (Tj, -2r)

 exp

Ta

(2)

at

COSCJ TO

one

COSLO TO

where M is the sign of the amplitude function of the spin echo signal:

t-L is the modified time interval between two pulses; TO is the modified repetition period of impulse sequences;

W is the resonant transition frequency. Measurement T) (time of longitudinal relaxation).

When you change t get:

Mr. state. Therefore, the relaxation constant is always the same and does not depend on the mode of excitation. 40 In order to determine it correctly, it is necessary to take into account various additives, which depend on the method of exciting echo signals.

45

The longitudinal relaxation time, measured by the proposed method, is 0 ms, which roughly corresponds to the value obtained by the zero method and the stimulated echo method (within the limits of the measurement error of 5–10).

Claims (1)

Invention Formula A method for measuring longitudinal and transverse relaxation times, which includes exposing a sample to a sequence of two pairs of pulses of a resonant radio frequency field, recording spin echo signals and determining relaxation times on the envelope of the signals received, which are different in order to extend the measurement range by measurements of transverse relaxation time under conditions of thermodynamic saturation, affect the sample by a series consisting of pairs of equal-duration ninth-degree im- RF field pulses, reducing the repetition period of the pulse sequence until the echo signals before the second pair of pulses are visible, and with respect to the amplitudes of these signals at different intervals between pulses and Ti # between pairs of pulses, longitudinal and transverse relaxation times are found: , 1 MfTo-2t) 900 650 Compiled by A. Kondratiev Editor A. Ogar Tehred L. Oliynyk Proofreader d.Zimokosov Order 4909/40 Circulation 778 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab, 4/5 Production and printing company, Uzhgorod, st. Project, 4 WD FIG. 2 150 That, ISS