MR GluCEST Study of Neuroinflammation

Chen Yanzi¹, Dai Zhuozhi¹, Shen Zhiwei¹, Chen Miaomiao¹, Ma Xilun¹, and Wu Renhua¹

¹2nd Affilicated Hospital, Shantou University Medical College, Shantou, China, People's Republic of

Synopsis

Glutamate (Glu) plays a crucial role in the early stage of neuroinflammation, which requires early diagnosis and treatment. This study aimed to explore Glu concentration changes in rats brain abscess model and patients with neuroinflammation using chemical exchange saturation transfer (CEST) MRI.

Synopsis

Glutamate(Glu) plays a crucial role in the early stage of neuroinflammation, which requires early diagnosis and treatment. This study aimed to explore Glu concentration changes of the brain in SD rats and patients with neuroinflammation using chemical exchange saturation transfer (CEST) MRI.

Background

Imaging Glutamate (Glu) has shown great prospective in scientific and can help people diagnosis neuroinflammation incipiently and precisely. The conventional approach such as Proton Magnetic Resonance Spectroscopy (1H-MRS) require long acquisition times and have poor spatial resolution. Glu chemical exchange saturation transfer (GluCEST) MRI opens up new possibilities for imaging Glu efficiently and accurately.

Materlals and Methods

First, the sensitivity of GluCEST was validated in phantoms under a variety of different concentrations. GluCEST imaging was acquired in both rats brain abscess model at 7T and human patients at 3T. The association between physiologic and GluCEST MRI was explored, along with the progression of rats brain abscess model.

Results

The GluCEST signal increases along with rising of Glu concentration in vitro. Besides, it rises progressively in the lesion of brain abscess after bacterial injection, reaches its zenith at 7th day and sets (p<0.01). High Glu concentration lesion in patients with the clinical diagnosis of neuroinflammation displayed high signal on T2 weighted imaging, Diffusion Weighted Imaging (DWI) and CE-T1 weighted imaging.

Conclusion

Glu concentration changes in the early stages of neuroinflammation. GluCEST MRI may provide new insight into neuroinflammation physiology.

Acknowledgements

This work was supported in part by the National Natural Science Foundation of China (Grant No. 81471730), the National High Technology Research and Development Program (863 Program) of China (Program No. 2014AA021101).

References

1. Takaki J, Fujimori K, Miura M, et al. L-glutamate released from activated microglia downregulates astrocytic L-glutamate transporter expression in neuroinflammation: the 'collusion' hypothesis for increased extracellular L-glutamate concentration in neuroinflammation [J]. Neuroinflammation. 2012; 9: 275

2.Ciccarelli O, Barkhof F, Bodini B, et al. Pathogenesis of multiple sclerosis: insights from molecular and metabolic imaging[J].Lancet Neurol 2014; 13: 807–22

3. Dai ZZ, Jim Ji, Gang Xiao, et al.Magnetization transfer prepared gradient echo MRI for CEST imaging [J]. PloS One 2014; 9(11): e112219

4. Cai K, Haris M, Singh A, et al.Magnetic resonance imaging of glutamate [J]. Nat Med. 2012 Jan 22; 18(2): 302–306

Figures

Figure 1. (a)CEST z-spectra of different Glu concentration at pH 7.0 and 37°C at 7T. (b) The GluCEST effect is in linear relationship with the concentration. (c) Shows the GluCEST contrast color-coded on the original CEST image (3 p.p.m.), acquired with application of saturation pulse train with B1rms = 155 Hz for 2 s. (d) CEST images of a phantom consisting of test tubes with solution of different metabolites at their physiological concentrations and pH 7 immersed in a beakercontaining PBS.

Figure 2. T2WI and GluCEST images images obtained from normal and abscess rats brain.

Figure 3.Z spectra from normal and brain abscess rats for the voxels shown.

Figure 4. Statistics of GluCESTR with a 4 × 4 voxel at the field of the lesion center of 27 SD rats in different periods of brain abscess.

Figure 5.A patient diagnosed neuroinflammation clinically underwent 3.0T MRI with T2WI (a), CE-T1WI (b) and DWI (c) scans. In addition, GluCEST imaging was acquired by a MT-prepared GRE MRI sequence.

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)

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