RETURN TO ABSTRACT LISTING


Objective:
Chemical exchange saturation transfer (CEST) imaging is a promising tool to evaluate epilepsy patients for seizure focus lateralization. It has the potential to produce a major paradigm shift in epilepsy evaluation and improve the prognosis of a large medical-refractory epilepsy population. Routine epilepsy diagnosis includes multimodal imaging used to localize the source of seizures and is necessary for successful surgical intervention in drug-resistant cases. Unfortunately, up to one-third of epilepsy evaluations have no clear anatomical source of seizures and have non-lesional, normal brain MRIs. Glutamate levels in the brain are known to be increased in anatomical seizure foci. Conventional MR spectroscopy (MRS) is limited in accurately detecting glutamate levels, but glutamate CEST (GluCEST) imaging has demonstrated higher sensitivity and spatial resolution. GluCEST has already demonstrated promising results in epilepsy evaluation on research 7T MRI scanners for patients. It is feasible that GluCEST can accurately lateralize the epileptogenic hippocampal foci in patients with non-lesional imaging on 3-T MRI scanners.

Materials and Methods:
We performed phantom studies using the investigation CEST sequence on the 3-T PET/MRI scanner (Signa PET/MRI, GE Health Systems) to demonstrate the feasibility of our study. A phantom containing two compartments of L-carnosine solution at different pH were imaged at 57 offset frequencies ranging from 7 to -7 ppm with intervals of 0.25 and at three saturation powers (0.75, 1.0 and 1.25 µT).

Results:
We were able to successfully generate Z-spectrum from the data and produce MTR-asymmetry maps at 3.1 ppm which shows pH-dependent contrast between the compartments. GluCEST parameters and postprocessing were optimized on the newly installed GE PET/MRI scanner. Next we will proceed with healthy controls (n = 5) then assess GluCEST in epilepsy patients (n = 10). Patients will be recruited from the Emory Epilepsy Center and GluCEST imaging will be analyzed using routine multimodal comprehensive epilepsy evaluation as the gold standard.

Conclusion:
This work has the potential to make a significant, positive impact on millions of patients in the epilepsy community. GluCEST would capture drug-resistant, non-lesional epilepsy patients, guide their surgical intervention, and thus greatly improve their prognosis. Additionally, this work would facilitate transition of this advanced imaging technique to a clinical environment suitable for the standard hospital setting. This lays the foundation for future multicenter trials and will subsequently make a new profound diagnostic technique widely available to the benefit of patients with epilepsy in need.