Magnetic resonance imaging method for measuring R2, R2* and R2' parameter image of tissue in noninvasive and dynamic manner

Abstract

The invention discloses a magnetic resonance imaging method which utilizes the fact that a tissue with different deoxygenated hemoglobin content has magnetic sensitive chatacteristics of different degrees, uses an asymmetric spin echo magnetic resonance imaging sequence, adopts a strategy of moving a 180-degree echo refocusing RF pulse position periodically, allows 180-degree echo refocusing pulses to distribute on both sides of a TE / 2 time position in each period, and obtains a high-time-resolution multiple-echo image. Further, aiming at acquired multiple-echo signals, the magnetic resonance imaging method performs mobile estimation by taking length of a corresponding 180-degree echo refocusing pulse mobile period as a window width, adopts least square estimation, and obtains dynamic parameter images of R2, R2* and R2' simultaneously according to a signal attenuation index model. By adopting the magnetic resonance imaging method, the high-time-resolution dynamic R2, R2* and R2' parameter images can be obtained, and a dynamic curves in an arbitrary region of interest can be displayed.

Description

technical field [0001] The invention belongs to the technical field of magnetic resonance imaging (MRI), in particular to a set of methods for dynamically and noninvasively and quantitatively measuring the intrinsic relaxation times R2, R2* and R2' of different tissues based on the magnetic resonance imaging technology. Background technique [0002] Susceptibility, as an important contrast mechanism, has a wide range of applications in magnetic resonance techniques. For example, blood oxygen level-dependent imaging (BOLD) is an imaging method developed based on the paramagnetic properties of deoxygenated hemoglobin. Blood) functional evaluation. [0003] In magnetic resonance imaging, susceptibility effects affect the R2* parameter, and R2* is the free decay rate of the tissue signal, usually fitted using a single-exponential decay model. And R2* contains two components: (1) one is the irreversible component R2, and (2) the other is the reversible R2', which reflects the d...

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Problems solved by technology

However, in this sequence, non-ideal slice-selection profiles caused by short radio frequency (RF) pulse times lead to a mismatch of image slice profiles acquired before and after the 180° refocusing pulse, which will be discussed later in R2 Larger estimation errors in the quantitative calculation of R2*

[0005] As mentioned above, the existing methods have the disadvantages of low time resolution or large estimation error

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