Using magnetic resonance fingerprinting to characterize periventricular nodular heterotopias in pharmacoresistant epilepsy

Abstract

Objective: We aimed to use a novel magnetic resonance fingerprinting (MRF) technique to examine in vivo tissue property characteristics of periventricular nodular heterotopia (PVNH). These characteristics were further correlated with stereotactic-electroencephalographic (SEEG) ictal onset findings.

Methods: We included five patients with PVNH who had SEEG-guided surgery and at least 1 year of seizure freedom or substantial seizure reduction. High-resolution MRF scans were acquired at 3 T, generating three-dimensional quantitative T₁ and T₂ maps. We assessed the differences between T₁ and T₂ values from the voxels in the nodules located in the SEEG-defined seizure onset zone (SOZ) and non-SOZ, on -individual and group levels. Receiver operating characteristic analyses were performed to obtain the optimal classification performance. Quantification of SEEG ictal onset signals from the nodules was performed by calculating power spectrum density (PSD). The association between PSD and T₁ /T₂ values was further assessed at different frequency bands.

Results: Individual-level analysis showed T₁ was significantly higher in SOZ voxels than non-SOZ voxels (p < .05), with an average 73% classification accuracy. Group-level analysis also showed higher T₁ was significantly associated with SOZ voxels (p < .001). At the optimal cutoff (normalized T₁ of 1.1), a 76% accuracy for classifying SOZ nodules from non-SOZ nodules was achieved. T₁ values were significantly associated with ictal onset PSD at the ultraslow, θ, β, γ, and ripple bands (p < .05). T₂ values were significantly associated with PSD only at the ultraslow band (p < .05).

Significance: Quantitative MRF measures, especially T₁ , can provide additional noninvasive information to separate nodules in SOZ and non-SOZ. The T₁ and T₂ tissue property changes carry electrophysiological underpinnings relevant to the epilepsy, as shown by their significant positive associations with power changes during the SEEG seizure onset. The use of MRF as a supplementary noninvasive tool may improve presurgical evaluation for patients with PVNH and pharmacoresistant epilepsy.

Keywords: MR fingerprinting; T1 relaxation time; magnetic resonance imaging; periventricular nodular heterotopia; stereotactic electroencephalography.