Nuclear magnetic resonance system-based substance measurement method and system

A substance measurement method based on a nuclear magnetic resonance (NMR) system, comprising:

• (a) acquiring a plurality of echo signals of an NMR pulse sequence varying in echo spacing from a substance to be measured, and processing the plurality of echo signals to obtain a plurality of signals varying in transverse relaxation and diffusion attenuation;
• and
• (b) in combination with prior knowledge, fitting the plurality of signals with transverse relaxation and diffusion attenuation to obtain diffusion coefficient, transverse relaxation time or/and content weight of components in the substance to be measured;
• wherein the NMR pulse sequence is a Carr-Purcell-Meiboom-Gill (CPMG) sequence;
• a gradient system of the NMR system comprises a unilateral magnet, and a gradient magnetic field formed by the unilateral magnet is configured to perform diffusion encoding on the plurality of signals varying in transverse relaxation and diffusion attenuation;
• and the echo spacing and b satisfy:
• b
• =
• -
• 1
• 12
• ⁢
• γ
• 2
• ⁢
• G
• 0
• 2
• ⁢
• t
• E
• 2
• ;
• (
• 4
• )
• wherein G0 is a magnetic field intensity of the gradient magnetic field;
• γ is a spin-magnetic ratio;
• tE is the echo spacing;
• and b is defined as b-value in NMR;
• step (a) comprises:
• defining each of the plurality of echo signals as a four-dimensional array s (b′, m, x, p), wherein a first dimension b′ indexes an echo signal corresponding to the b-value in formula (4);
• a second dimension m indexes echo train length (ETL);
• a third dimension x indexes signal average of the plurality of echo signals;
• a fourth dimension p indexes sampling points of data in a single readout;
• and b′, m, x and p are positive integers;
• and
• performing Fourier transform on fourth dimensions p in all four-dimensional arrays s (b′, m, x, p);
• taking a low-frequency part as an average value;
• and averaging third dimensions x of the four-dimensional arrays s (b′, m, x, p) to obtain the plurality of signals varying in transverse relaxation and diffusion attenuation.