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.

Magnetic Resonance Fingerprinting

“…60 In addition, in these patients, MRF T1 values have been shown to be associated with ictal-onset electroencephalogram waveforms, suggesting potential associations between tissue relaxometry and electrophysiological changes. 60 In patients with medically intractable focal epilepsy, 3D MRF T1 and T2 maps combined with machine learning have shown potential in lateralizing seizure onset zones in patients with visually normal basal ganglia and thalami. 64 Research has also been done in using brain MRF for assessment of pediatric brain myelination and evaluation of neurodevelopmental disorders.…”

“…Furthermore, 3D MRF-detected epileptogenic lesions were concordant with stereotactic electroencephalogram localization. In patients with multifocal lesions such as in periventricular nodular heterotopias, voxels within stereotactic electroencephalogram-localized seizure onset zones have shown higher T1 values compared with voxels outside these zones 60 . In addition, in these patients, MRF T1 values have been shown to be associated with ictal-onset electroencephalogram waveforms, suggesting potential associations between tissue relaxometry and electrophysiological changes 60 .…”

“…However, many pathologically proven epileptogenic lesions can be “MRI invisible” on visual assessment of conventional images, and quantitative analysis has the potential to improve detection 58 . Magnetic resonance fingerprinting has been explored in both temporal lobe epilepsy (TLE) 59 and extratemporal lobe epilepsy 60 . When MRF was added to a clinical protocol in 33 patients with mesial TLE, Liao et al 59 found that MRF increased correct diagnosis rate (correct diagnosis on MRF: 32/33 [96.9%] vs on conventional MRI: 23/33 [69.7%]) of TLE.…”

“…In patients with multifocal lesions such as in periventricular nodular heterotopias, voxels within stereotactic electroencephalogram-localized seizure onset zones have shown higher T1 values compared with voxels outside these zones 60 . In addition, in these patients, MRF T1 values have been shown to be associated with ictal-onset electroencephalogram waveforms, suggesting potential associations between tissue relaxometry and electrophysiological changes 60 . In patients with medically intractable focal epilepsy, 3D MRF T1 and T2 maps combined with machine learning have shown potential in lateralizing seizure onset zones in patients with visually normal basal ganglia and thalami 64 …”

“…58 Magnetic resonance fingerprinting has been explored in both temporal lobe epilepsy (TLE) 59 and extratemporal lobe epilepsy. 60 When MRF was added to a clinical protocol in 33 patients with mesial TLE, Liao et al 59 found that MRF increased correct diagnosis rate (correct diagnosis on MRF: 32/33 [96.9%] vs on conventional MRI: 23/33 [69.7%]) of TLE. The MRF T1 and T2 values were significantly higher in hippocampal sclerosis compared with normal hippocampus in healthy controls.…”