Glutamate Chemical Exchange Saturation Transfer (GluCEST) Magnetic Resonance Imaging in Pre-clinical and Clinical Applications for Encephalitis

Yanlong Jia; Yanzi Chen; Kuan Geng; Yan Cheng; Yan Li; Jinming Qiu; Huaidong Huang; Runrun Wang; Yunping Zhang; Renhua Wu

doi:10.3389/fnins.2020.00750

Glutamate Chemical Exchange Saturation Transfer (GluCEST) Magnetic Resonance Imaging in Pre-clinical and Clinical Applications for Encephalitis

Front Neurosci. 2020 Jul 28:14:750. doi: 10.3389/fnins.2020.00750. eCollection 2020.

Authors

Yanlong Jia¹, Yanzi Chen², Kuan Geng³, Yan Cheng¹, Yan Li¹, Jinming Qiu¹, Huaidong Huang¹, Runrun Wang¹, Yunping Zhang⁴, Renhua Wu¹

Affiliations

¹ Department of Radiology, The Second Affiliated Hospital of Shantou University Medical College, Shantou, China.
² Department of Radiology, Affiliated Longhua People's Hospital, Southern Medical University, Shenzhen, China.
³ Department of Radiology, The First People's Hospital of Honghe Prefecture, Mengzi, China.
⁴ Department of Nuclear Medicine, Shenzhen Luohu District People's Hospital, Shenzhen, China.

Abstract

Background: Encephalitis is a common central nervous system inflammatory disease that seriously endangers human health owing to the lack of effective diagnostic methods, which leads to a high rate of misdiagnosis and mortality. Glutamate is implicated closely in microglial activation, and activated microglia are key players in encephalitis. Hence, using glutamate chemical exchange saturation transfer (GluCEST) imaging for the early diagnosis of encephalitis holds promise.

Methods: The sensitivity of GluCEST imaging with different concentrations of glutamate and other major metabolites in the brain was validated in phantoms. Twenty-seven Sprague-Dawley (SD) rats with encephalitis induced by Staphylococcus aureus infection were used for preclinical research of GluCEST imaging in a 7.0-Tesla scanner. For the clinical study, six patients with encephalitis, six patients with lacunar infarction, and six healthy volunteers underwent GluCEST imaging in a 3.0-Tesla scanner.

Results: The number of amine protons on glutamate that had a chemical shift of 3.0 ppm away from bulk water and the signal intensity of GluCEST were concentration-dependent. Under physiological conditions, glutamate is the main contributor to the GluCEST signal. Compared with normal tissue, in both rats and patients with encephalitis, the encephalitis areas demonstrated a hyper-intense GluCEST signal, while the lacunar infarction had a decreased GluCEST signal intensity. After intravenous immunoglobulin therapy, patients with encephalitis lesions showed a decrease in GluCEST signal, and the results were significantly different from the pre-treatment signal (1.34 ± 0.31 vs 5.0 ± 0.27%, respectively; p = 0.000).

Conclusion: Glutamate plays a role in encephalitis, and the GluCEST imaging signal has potential as an in vivo imaging biomarker for the early diagnosis of encephalitis. GluCEST will provide new insight into encephalitis and help improve the differential diagnosis of brain disorders.

Keywords: Staphylococcus aureus; chemical exchange saturation transfer; encephalitis; glutamate; magnetic resonance imaging.