Abstract
BackgroundEncephalitis 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.MethodsThe 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.ResultsThe 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).ConclusionGlutamate 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.
Highlights
Encephalitis is serious inflammatory disease of the central nervous system (CNS) that is caused by many physiological or pathological factors (Kumar, 2020)
The results show that Glu is the main contributor to the glutamate chemical exchange saturation transfer (GluCEST) signal, GABA and Cr provide a small contribution to the GluCEST effect, while the contribution of other metabolites (NAA, MI, and Gln) to the GluCEST effect was negligible (Figure 1D)
The results show that the mean MTRasym (3.0 ppm) in the encephalitis areas was elevated 3 days after infection with S. aureus compared with the healthy control (HC) group (20.24 ± 1.71% vs 14.09 ± 0.79%, t = -16.985, p = 0.000), indicating that Glu was involved in the occurrence of encephalitis and that GluCEST imaging could be used for the diagnosis of encephalitis (Figure 2B)
Summary
Encephalitis is serious inflammatory disease of the central nervous system (CNS) that is caused by many physiological or pathological factors (Kumar, 2020). Owing to a lack of well-defined clinical characteristics, it is easy to misdiagnose the condition and delay treatment, resulting in a higher disability and death rate, which can cause a serious burden to patients, families, and society (Dong et al, 2019). 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. Using glutamate chemical exchange saturation transfer (GluCEST) imaging for the early diagnosis of encephalitis holds promise
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