Fluid and White Matter Suppression Imaging and Voxel-Based Morphometric Analysis in Conventional Magnetic Resonance Imaging-Negative Epilepsy

Abstract

Purpose: Delineation of subtle lesions in magnetic resonance imaging (MRI)-negative patients is of great importance in preoperative epilepsy evaluation. The aim of our study was to explore the diagnostic value of the novel fluid and white matter suppression (FLAWS) sequence in comparison with a voxel-based MRI postprocessing morphometric analysis program (MAP) in a consecutive cohort of non-lesional patients.Methods: Surgical candidates with a negative finding on an official neuroradiology report were enrolled. High-resolution FLAWS image and MAP maps generated based on high-resolution three-dimensional (3D) T1 image were visually inspected for each patient. The findings of FLAWS or MAP-positive (FLAWS/MAP+) regions were compared with the surgical resection cavity in correlation with surgical outcome and pathology.Results: Forty-five patients were enrolled; the pathological examination revealed focal cortical dysplasia (FCD) in 32 patients and other findings in 13 patients. The positive rate, sensitivity, and specificity were 48.9%, 0.43, and 0.87, respectively, for FLAWS and 64.4%, 0.57, and 0.8, respectively, for MAP. Concordance between surgical resection and FLAWS+ or MAP+ regions was significantly associated with a seizure-free outcome (FLAWS: p = 0.002; MAP: p = 0.0003). A positive finding in FLAWS and MAP together with abnormalities in the same gyrus (FLAWS–MAP gyral+) was detected in 31.1% of patients. FLAWS+ only and MAP+ only were found in 7 (15.5%) and 14 (31.1%) patients, respectively.Conclusions: FLAWS showed a promising value for identifying subtle epileptogenic lesions and can be used as a complement to current MAP in patients with MRI-negative epilepsy.

MRI of focal cortical dysplasia

“…Two 3D sets with isotropic 1 mm 3 voxel are acquired in an interleaved acquisition scheme with two different inversion times (TI): TI 1 suppresses the white matter signal and TI 2 suppresses the CSF signal. From both data sets, a set of synthetic minimum FLAWS contrast images is calculated which can be regarded as a gray matter specific image [ 41 , 42 ] (Fig. 1 ).…”

Fully automated detection of focal cortical dysplasia: Comparison of MPRAGE and MP2RAGE sequences

“…The evaluation of ipsilateral clusters remains a matter of debate, as the extent of an FCD can ultimately be defined only to a limited extent even employing current morphometric postprocessing. Previous studies using MAP have reported a sensitivity/specificity of 90%/67% based on MPRAGE sequences 9 and 43%/87% based on the FLAWS sequence 25 . In another study comparing MAP based on MPRAGE and MP2RAGE sequences, 10% of FCDs were visible only on MAP junction maps based on MP2RAGE sequence 11 .…”

“…Previous studies using MAP have reported a sensitivity/specificity of 90%/67% based on MPRAGE sequences 9 and 43%/87% based on the FLAWS sequence. 25 In another study comparing MAP based on MPRAGE and MP2RAGE sequences, 10% of FCDs were visible only on MAP junction maps based on MP2RAGE sequence. 11 In a study by Wang et al examining a 7-T MAP based on the MP2RAGE sequence, 25% more lesions were detected compared to a 3-T MRI MAP based on the MPRAGE sequence.…”

Making the Invisible Visible: Advanced Neuroimaging Techniques in Focal Epilepsy

“…Figure 5 describes a case of conventionally MRI-negative PET-positive unilateral TLE, in which increased DIR signals can be found in the focus side, while it was difficult to detect on FLAIR, T1WI, and T2WI. More recently, fluid and white matter suppression (FLAWS) has been reported for better visualization of focal cortical dysplasia even in conventionally MRI-negative cases ( Chen et al, 2018a ; Sun et al, 2021 ). FLAWS suppresses the white matter and cerebrospinal fluid signals and then generate gray matter-specific images ( Tanner et al, 2012 ; Chen et al, 2018a ).…”