Automated quantitative FLAIR analysis in hippocampal sclerosis
Introduction
Hippocampal sclerosis (HS) is the most frequent cause of pharmaocoresistant temporal lobe epilepsy (TLE) and the most common histopathologic diagnosis in patients with TLE undergoing epilepsy surgery (Urbach et al., 2004, Wiebe et al., 2001). The primary features of HS in magnetic resonance imaging (MRI) are atrophy of the hippocampus and hyperintense signal in fluid-attenuated inversion-recovery (FLAIR) and T2-weighted sequences (Jack et al., 1996, Jackson et al., 1990, Jackson et al., 1993a). Visual detection of clear unilateral HS in good-quality MR images by experienced radiologists is considered unproblematic (Van Paesschen, 2004), but the recognition can be difficult for subtle sclerosis or cases of bilateral HS where a side comparison is hampered. In addition, subtle changes of T2 signal intensity over time, e.g. during potential progression of limbic encephalitis to HS, are difficult to assess by pure visual analysis. Focke et al., 2008, Focke et al., 2009 have recently described a new method for quantitative analysis of FLAIR scans, i.e. images with T2-weighted contrast but complete suppression of high signal intensity of cerebrospinal fluid (CSF). Their approach avoids difficulties due to partial volume effects with CSF which are to consider for other quantitative methods like T2 relaxometry. Compared to T2 mapping with FLAIR CSF suppression (Rugg-Gunn et al., 2005) it does not require a special FLAIR T2 map which has a long acquisition time and is often not available but takes a standard clinical FLAIR spin echo sequence as input. Essentially, the voxel-based method performs both a spatial and intensity normalization of FLAIR images by using internal reference regions and spatial normalization parameters derived from combined normalization and segmentation of a coregistered T1-weighted image (Focke et al., 2008, Focke et al., 2009). The normalized and rescaled FLAIR images are the starting point for a whole brain FLAIR analysis which has been shown to be successful in the detection of focal cortical dysplasia. In the present study, we describe a further development of this method for regional quantitative FLAIR analysis of the hippocampus and present first results in patients with HS compared to controls.
Section snippets
Patients and controls
At the Swiss Epilepsy Centre in Zürich, a register has been maintained for all patients receiving an MRI since January 2006. The majority of these patients had a high-resolution MRI at a Philips Achieva 3T scanner (Philips, Amsterdam, The Netherlands) according to a dedicated epilepsy protocol which comprised the following sequences: an unenhanced T1-weighted volume data set (3D Turbo Field Echo sequence with 1 mm3 voxel; TR 8.1 ms; TE 3.7 ms; flip angle 8°; field of view 256 mm × 256 mm, slab
Results
Between January 2006 and April 2011, 1640 patients of the Swiss Epilepsy Centre received an MRI at the local Philips 3T scanner according to the protocol described above. Based on clinical history, seizure semiology, and EEG findings, 998 of these patients (=61%) were classified as suffering from focal epilepsy (i.e. having seizures which originate from and at least at the beginning are limited to a part of one hemisphere). HS was diagnosed in 115 of these patients. One patient had to be
Interpretation of results
In the present study, a novel method for automated quantitative FLAIR analysis of the hippocampus has been evaluated in patients with HS and controls, with the following main findings:
- -
Separation of HS patients and controls by this method was in high agreement with prior classification according to visual assessment. This was especially true for the subgroup of histologically confirmed HS patients (i.e. sensitivity of 100%).
- -
The method allowed to separate right and left HS without overlap.
- -
The
Conclusion
The method of automated quantitative FLAIR analysis of the hippocampus presented here appears to be a valuable additional diagnostic tool in the evaluation of epilepsy patients which may assist in the detection of HS and in monitoring the temporal evolution of the disease. Due to spatial and intensity normalization of the FLAIR images, signal changes in the hippocampus can be quantified and directly compared to the results of healthy controls and other HS patients. The automated image
Acknowledgements
The development of the MRI post-processing technique presented here was kindly supported by the Swiss National Foundation. Dr. Bernd Weber was supported by a Heisenberg Grant of the DFG (WE 4427/3-1) and by the SFB TR3 projects A1 and A8.
The authors are grateful to Dr. Dominik Huber, MRI Institute, Schulthess Clinic, Zürich, for providing and conducting the MRI measurements.
References (39)
- et al.
Voxel-based iterative sensitivity (VBIS) analysis: methods and a validation of intensity scaling for T2-weighted imaging of hippocampal sclerosis
Neuroimage
(2009) - et al.
Unified segmentation
Neuroimage
(2005) - et al.
MRI evidence of mesial temporal sclerosis in subjects without seizures
Seizure
(2002) - et al.
Multi-site voxel-based morphometry—not quite there yet
Neuroimage
(2011) - et al.
Enhanced visualization of blurred gray-white matter junctions in focal cortical dysplasia by voxel-based 3D MRI analysis
Epilepsy Res.
(2005) - et al.
FLAIR signal and texture analysis for lateralizing mesial temporal lobe epilepsy
Neuroimage
(2010) - et al.
Evaluation of MRI criteria (1.5 T) for the diagnosis of hippocampal sclerosis in healthy subjects
Epilepsy Res.
(2010) - et al.
Voxel-based relaxometry: a new approach for analysis of T2 relaxometry changes in epilepsy
Neuroimage
(2004) Qualitative and quantitative imaging of the hippocampus in mesial temporal lobe epilepsy with hippocampal sclerosis
Neuroimag. Clin. N. Am.
(2004)- et al.
A grading system for mesial temporal pathology (hippocampal sclerosis) from anterior temporal lobectomy
J. Epilepsy
(1992)
Automated MRI analysis for identification of hippocampal atrophy in temporal lobe epilepsy
Epilepsia
Hippocampal pathology in refractory temporal lobe epilepsy: T2-weighted signal change reflects dentate gliosis
Neurology
Voxel-based analysis of whole brain FLAIR at 3T detects focal cortical dysplasia
Epilepsia
Automated normalized FLAIR imaging in MRI-negative patients with refractory focal epilepsy
Epilepsia
Three-dimensional maximum probability atlas of the human brain, with particular reference to the temporal lobe
Hum. Brain Mapp.
Automatic striatal volumetry allows for identification of patients with chorea-acanthocytosis at single subject level
J. Neural. Transm.
Voxel-based 3D MRI analysis helps to detect subtle forms of subcortical band heterotopia
Epilepsia
Mesial temporal sclerosis: diagnosis with fluid-attenuated inversion-recovery versus spin-echo MR imaging
Radiology
Optimizing the diagnosis of hippocampal sclerosis using MR imaging
AJNR Am. J. Neuroradiol.
Cited by (36)
Automatic segmentation of white matter hyperintensities from brain magnetic resonance images in the era of deep learning and big data – A systematic review
2021, Computerized Medical Imaging and GraphicsBrain MRI post-processing with MAP07 in the preoperative evaluation of patients with pharmacoresistant epilepsy – Croatian single centre experience
2021, Clinical Neurology and NeurosurgeryEffect of MR Field Strength on the Texture Features of Cerebral T2-FLAIR Images: A Pilot Study
2020, Chinese Medical Sciences JournalQuantitative volume-based morphometry in focal cortical dysplasia: A pilot study for lesion localization at the individual level
2018, European Journal of Radiology
- 1
Tel.: +49 228 6885 262; fax: +49 228 6885 261.
- 2
Tel.: +49 40 5077 3345.
- 3
Tel.: +49 228 287 16507; fax: +49 228 287 16093.