使用乘法、加法、减法和/或拟合(MASTIR)脉冲序列提高协同对比磁共振成像(scMRI)的灵敏度、特异性和范围的新选项。
New options for increasing the sensitivity, specificity and scope of synergistic contrast magnetic resonance imaging (scMRI) using Multiplied, Added, Subtracted and/or FiTted (MASTIR) pulse sequences.
作者信息
Ma Ya-Jun, Shao Hongda, Fan Shujuan, Lu Xing, Du Jiang, Young Ian R, Bydder Graeme M
机构信息
Department of Radiology, University of California, San Diego, CA, USA.
Formerly Department of Electrical Engineering, Imperial College, London, UK.
出版信息
Quant Imaging Med Surg. 2020 Oct;10(10):2030-2065. doi: 10.21037/qims-20-795.
This paper reviews magnetic resonance (MR) pulse sequences in which the same or different tissue properties (TPs) such as T and T are used to contribute synergistically to lesion contrast. It also shows how synergistic contrast can be created with Multiplied, Added, Subtracted and/or fiTted Inversion Recovery (MASTIR) sequences, and be used to improve the sensitivity, specificity and scope of clinical magnetic resonance imaging (MRI) protocols. Synergistic contrast can be created from: (i) the same TP, e.g., T used twice or more in a pulse sequence; (ii) different TPs such as ρ, T, T, and D* used once or more within a sequence, and (iii) additional suppression or reduction of signals from tissues and/or fluids such as fat, long T tissues and cerebrospinal fluid (CSF). The short inversion time (TI) inversion recovery (IR) (STIR) and double IR (DIR) sequences usually show synergistic positive contrast for lesions which have increases in both T and T. The diffusion weighted pulsed gradient spin echo (PGSE) sequence shows synergistic contrast for lesions which have an increase in T and a decrease in D*; the sequence is both positively weighted for T and negatively weighted for D*. In the brain, when an IR sequence nulling white matter has subtracted from it an IR sequence nulling gray matter to form the subtracted IR (SIR) sequence, increases in the single TP T between the two nulling points of the original two sequences generate high synergistic positive contrast. In addition, the subtraction to produce the SIR sequence reduces fat and CSF signals. To provide high sensitivity to changes in TPs in disease the SIR sequence can be used (i) alone to provide synergistic T contrast as above; (ii) with T-weighting to provide synergistic T and T contrast, and (iii) with T- and D*-weighting to provide synergistic T, T, and D* contrast. The SIR sequence can also be used in reversed form (longer TI form minus shorter TI form) to produce very high positive synergistic T contrast for reductions in T, and so increase the positive contrast enhancement produced by clinical gadolinium-based contrast agents (GBCAs) when they reduce T. The specificity of MRI examinations can be improved by using the reversed SIR sequence with a long echo time (TE) gradient echo as well as echo subtraction to show synergistic high contrast from T and T* shortening produced by organic iron. Other added and subtracted forms of the MASTIR sequence can be used synergistically to selectively show myelin, myelin water and fluids including blood and CSF. Protocols using MASTIR sequences to provide synergistic contrast in MRI of the brain, prostate and articular cartilage are included as illustrative examples, and the features of synergistic contrast MRI (scMRI) are compared to those of multiparametric MRI (mpMRI) and functional MRI (fMRI).
本文回顾了磁共振(MR)脉冲序列,其中相同或不同的组织特性(TPs),如T1和T2,被协同用于增强病变对比度。本文还展示了如何利用相乘、相加、相减和/或拟合反转恢复(MASTIR)序列来创建协同对比度,并将其用于提高临床磁共振成像(MRI)协议的敏感性、特异性和范围。协同对比度可通过以下方式创建:(i)相同的TP,例如在脉冲序列中使用两次或更多次的T1;(ii)不同的TP,如ρ、T1、T2和D*,在序列中使用一次或更多次;以及(iii)额外抑制或减少来自组织和/或液体(如脂肪、长T1组织和脑脊液(CSF))的信号。短反转时间(TI)反转恢复(IR)(STIR)和双重IR(DIR)序列通常对T1和T2均增加的病变显示协同正性对比度。扩散加权脉冲梯度自旋回波(PGSE)序列对T1增加而D降低的病变显示协同对比度;该序列对T1为正加权,对D为负加权。在脑部,当一个使白质信号抑制的IR序列减去一个使灰质信号抑制的IR序列以形成相减IR(SIR)序列时,在原始两个序列的两个抑制点之间单一TP T1的增加会产生高协同正性对比度。此外,相减以产生SIR序列可减少脂肪和CSF信号。为了对疾病中TPs的变化具有高敏感性,SIR序列可用于:(i)单独使用以提供如上所述的协同T1对比度;(ii)与T2加权一起使用以提供协同T1和T2对比度;以及(iii)与T1和D加权一起使用以提供协同T1、T2和D对比度。SIR序列也可以以相反的形式(较长TI形式减去较短TI形式)使用,以对T1降低产生非常高的正协同T1对比度,从而增加基于钆的临床造影剂(GBCAs)降低T1时产生的正性对比增强。通过使用具有长回波时间(TE)梯度回波的反向SIR序列以及回波相减来显示由有机铁产生的T1和T2*缩短所产生的协同高对比度,可以提高MRI检查的特异性。MASTIR序列的其他相加和相减形式可以协同使用,以选择性地显示髓磷脂、髓磷脂水以及包括血液和CSF在内的液体。作为示例,包括了使用MASTIR序列在脑部、前列腺和关节软骨的MRI中提供协同对比度的协议,并将协同对比度MRI(scMRI)的特征与多参数MRI(mpMRI)和功能MRI(fMRI)进行了比较。