Correcting and measuring method and device for transverse magnetization vector decay time constant, computer equipment and non-uniform field magnetic resonance system

Abstract

The invention relates to the technical field of nuclear magnetic resonance imaging, and discloses a correction measurement method and device for a transverse magnetization vector decay time constant,computer equipment and a non-uniform field magnetic resonance system. In an extremely non-uniform magnetic field or a nuclear magnetic resonance system which cannot realize extremely short echo time,an ADC-T2 two-dimensional atlas is fitted firstly through the acquired echo signals acquired by applying the SE-CPMG sequences with different b values, and then a transverse magnetization vector decaytime constant T2 is corrected so that the problem of a small T2 measurement value caused by diffusion can be avoided. Besides, an accurate ADC-T2 two-dimensional atlas can be further obtained based on the corrected T2 measurement value, T2 value measurement is ensured not to be affected by echo time and molecular diffusion, the requirement for the system is low, and system cost can be reduced.

Description

technical field [0001] 本发明属于核磁共振成像技术领域,具体而言,涉及磁共振频谱仪技术,特别地涉及一种横向磁化矢量衰减时间常数的校正测量方法、装置、计算机设备及非均匀场磁共振系统。 Background technique [0002] 核磁共振技术是利用氢质子的核磁共振现象进行成像或者检测物质成分和结构的一种技术。人体内包含单数质子的原子核,例如氢原子核,其质子具有自旋运动。带电原子核的自旋运动,在物理上类似于单独的小磁体,在没有外部条件影响下这些小磁体的方向性分布是随机的。当人体置于外部磁场中时,这些小磁体将按照外部磁场的磁力线重新排列。这时,用特定频率的射频脉冲激发原子核,使这些原子核的自旋(小磁铁)发生偏转,产生共振,这就是核磁共振现象。停止发射射频脉冲后,被激发的原子核(共振的小磁体)会逐渐恢复到激发前的状态,在恢复的过程中会释放电磁波信号,通过专用设备接收并处理核磁共振信号后即获得磁共振图像或者物质的成分和结构信息。 [0003] 原子核横向磁化矢量趋于零的速度取决于自旋-自旋相互作用的强度,用横向磁化矢量衰减时间常数T2(也称为自旋-自旋弛豫时间T2)来描述。在磁共振技术中,一般使用自旋回波序列(Spin Echo,SE)来测量T2,如CPMG核磁共振序列(aNMR pulsesequencenamed by several scientists Carr,Purcell,Meiboom and Gill,即由Carr,Purcell,Meiboom和Gill等人命名的核磁共振序列),即在x轴施加90度射频脉冲,之后在t=τ,3τ,5τ,…,(2n-1)τ时在y轴施加180度射频脉冲,于是在t=2τ,4τ,6τ,…,2nτ时可得到回波信号,如 figure 1 shown. CPMG序列时间短,且可以避免由于180度射频脉冲不准确(由于射频场均匀性有限)而造成的误差累积。 在非均匀场磁共振系统中,通常也使用CPMG序列采集信号。 一般的,固体中T2比液体中T2短得多。 典型的生物组织中的T2位于20-150ms范围,自由水T2比束缚水T2要长得多。 临床上,在病灶处观察到T2延长被解释为自由水比例增高。 [0004] 物质中的分子都存在一定程度的扩散运动,其方向是随机的,称为分子的热运动或布朗...

AI Technical Summary

Problems solved by technology

[0007] In order to solve the problem that in NMR systems with extremely inhomogeneous magnetic fields or where extremely short echo times cannot be achieved, the measured transverse magnetization vector decay time constant T2 is too small, resulting in the inability to accurately measure the two-dimensional spectrum of T2 and ADC coefficients The problem of distribution, the object of the present invention is to provide a kind of correction measurement method, device, computer equipment, inhomogeneous field magnetic resonance system and computer-readable storage medium of transverse magnetization vector decay time constant

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