Didato, G

Maccagnano, C

malagoli, M

Meletti, S

Palesi, F

Summers, P

Vitali, P

Wheeler-Kingshott, CAM

Zucca, I

UCL Discovery

11/8/2017 https://submissions.mirasmart.com/ISMRM2018/ViewSubmission.aspx?sbmID=4096https://submissions.mirasmart.com/ISMRM2018/ViewSubmission.aspx?sbmID=4096 1/2Setting up a Multi-centric Multiparametric hMRI Protocol for the Investigation of TemporalLobe EpilepsyPaul Summers , Fulvia Palesi , Francesco Padelli , Ileana Zucca , Marcella Malagoli , Carmelo Maccagnano , StefanoMeletti , Giuseppe Didato , Claudia Wheeler-Kingshott , and Paolo VitaliC. Mondino National Neurological Institute, Pavia, Italy, University of Pavia, Pavia, Italy, IRCCS Foundation, C. Besta Neurological Institute, Milan, Italy,Civile Aziende Ospedaliera-Universitaria, Modena, Italy, University of Modena and Reggio Emilia, Modena, Italy, University College London, London,United KingdomSynopsisQuantitative characterization of MT, R1, R2*, and PD may aid in providing more consistent readings of alterations in temporal lobe epilepsy. Aspart of a multi-centric study we have set up a hMRI protocol for use at 3T across two manufactures of MR scanners. Because of diﬀerences inMT pulses and SAR calculations, near matching was achieved only through use of commercial or research options. Initial results from onescanner show excellent reproducibility within and between subjects for MT and R1. A cross-scanner evaluation is in course.INTRODUCTIONTemporal lobe epilepsy can be associated with hippocampal sclerosis, focal cortical dysplasia, low grade tumours and other focal lesions that canfrequently, but not always be appreciated on conventional MR imaging at 1.5 or 3T.  Quantitative characterization of MR tissue properties (including MT,R1, R2*, and PD) that can be associated with histopathological substrates (hMRI) has the potential to provide more consistent readings of alterations tothe brain.  As part of an Italian multi-centric study of temporal lobe epilepsy, we have set up a hMRI protocol for use at 3T across two manufactures ofMR scanners.METHODSResolution and timing parameters of 3D multi-echo PD, R1 and MT-weighted gradient-echo scans and B1 mapping based on prior publications wereiteratively adapted to provide a common parameter set across 3T scanners from two manufacturers (Philips Achieva, Siemens Skyra). Constraintsincluded: acquisition time below 20 minutes, and acquisition resolutions within 15% of the target 1mm isotropic resolution to avoid loss of grey-whiteboundary sharpness.Software for hMRI analysis was used to generate MT, PD, R1 and R2* maps.  Visual inspection of the source images and resulting maps was performed toidentify artifacts. After uniﬁed registration and segmentation using the ICBM atlas into grey and white matter probabilities, a threshold of 50% was used tobinarize each class against the Harvard-Oxford Atlas to produce ROIs of the hippocampi and temporal lobes. For each ROI, the mean and standarddeviation of MT, R1, R2* and PD were extracted. We report here one center’s results with the protocol as mean and standard deviation of these values over16 volunteers as well as the test-retest variability from three scans of two subjects on a single scanner.RESULTSThe ﬁnal imaging parameters are detailed in Table 1. Notable diﬀerences between manufacturers involved the default MT pre-pulses and SAR estimation.A research agreement with one manufacturer allowed matching of MT pre-pulse angle and duration.As the product of number of slices and echoes proved a limiting factor for one manufacturer, a sagittal acquisition was adopted to limit the number ofslices required for whole brain coverage. Persistent ghosting from the eyes was noted propagating over the temporal lobes and hippocampus (Figure 1a),leading us to adopt a rotated sagittal geometry to ensure this artifact remains below the temporal poles (Figure 1b). The hMRI maps provide gooddepiction of anatomy, and although elevated R2* values are seen in the orbito-frontal cortex and the inferior temporal lobes the other maps appearrelatively unaﬀected (Figure 1c).Averaged over the entire temporal lobe or hippocampus, hMRI values were very consistent across subjects with the variation in grey and white mattervalues generally being less 3% for MT, R1 and R2*; roughly a third the intrasubject variation (Table 2). Intra-subject reproducibility of mean values waswithin 1% for MT and R1, 10% for R2* and 15% for PD.DISCUSSIONUsing a liberal threshold for grey and white matter segmentation we observed a relatively large variability in properties within the temporal lobes andhippocampi of individual subjects. Despite this, the inter- and intra-subject reproducibility for whole lobe (hippocampus) values was below 3% and 1%respectively for both MT and R1. Greater variability in R2* values likely reﬂects the eﬀects of magnetic ﬁeld inhomogeneity in areas adjacent to largesusceptibility diﬀerences, to which the other values appear relatively immune during map generation. Incorporating correction for imperfect spoiling andhead coil sensitivity proﬁles into the workﬂow should further improve performance.To allow study of the hippocampus we favored spatial resolution over speed of acquisition. In other applications, slight reductions of spatial resolution,combined with parallel imaging should permit signiﬁcant reductions in scan time without substantial reductions in SNR. A strongly rotated sagittalacquisition visibly reduced the artifacts aﬀecting images of the temporal lobes and hippocampus. Greater spoiling may help to reduce eye-movementrelated artifact, but would likely require increased scanning time. Inter-site variability is currently under investigation with volunteers undergoing hMRIscans on both models of MR scanner. This will aid in assessing the importance of some sequence characteristics (e.g. RF pulse shape, degree of gradientspoiling, and SAR models) that remain beyond user control.CONCLUSIONWe have demonstrated a hMRI mapping protocol for the study of temporal lobe epilepsy with isotropic 1mm resolution that yields good anatomicaldepiction and reproducibility of values across subjects in under 20 minutes on 3T scanners from two diﬀerent manufacturers. It must be noted however,that this required the use of commercial or research options, which may limit use outside of the research context.Acknowledgements1 2 3 3 4 34,5 3 1,2,6 11 2 34 5 612,32,3 411/8/2017 https://submissions.mirasmart.com/ISMRM2018/ViewSubmission.aspx?sbmID=4096https://submissions.mirasmart.com/ISMRM2018/ViewSubmission.aspx?sbmID=4096 2/2We thank our colleagues who have supported our eﬀorts: Emilio Perucca, Carlo Andrea Galimberti, Elena Tartara, Valentina De Giorigis (NeurologicalInstitute C. Mondino, Pavia), Valeria Mariani, Alberto Citterio, Laura Tassi, (Epilepsy Surgery Center “C.Munari” Niguarda Hospital) Milano, and LauraMirandola (University of Modena and Reggio Emilia); Rebecca Samson (University College London) for early suggestions of hMRI processing andscanning; and the contributors to the hMRI toolbox: Karsten Tabelow, Evelyne Balteau, Martina F. Callaghan, Bogdan Draganski, Tobias Leutritz, AntoineLutti, Christophe Phillips, Enrico Reimer, Lars Ruthotto, Maryam Seif , Nikolaus Weiskopf, Gabriel Ziegler and Siawoosh Mohammadi. Funding support forthis work was provided by the Italian Ministry of Health grant: NET2013-02355313.References1. Tassi L, Meroni A, Deleo F, et al. Temporal lobe epilepsy: neuropathological and clinical correlations in 243 surgically treated patients. EpilepticDisord. 2009;11(4):281-292.2. Weiskopf N, Suckling J, Williams G, et al. Quantitative multi-parameter mapping of R1, PD*, MT, and R2* at 3T: a multi-center validation. FrontNeurosci. 2013;7:9.3. Callaghan MF, Helms G, Lutti A, Mohammadi S, Weiskopf N. A General Linear Relaxometry Model of R1 Using Imaging Data. Magn Res Med.2015;73:1309–1314.4. https://hMRI.infoFiguresTable 1. hMRI acquisition parameters. In brackets are the values for Siemens Skyra where these diﬀer from the Philips settings. Table 2. Mean MT, T1, R2* and relative PD values and volumes for temporal lobes with their standard deviation across subject. In parentheses are theaverage of the standard deviations obtained in the single subject ROIs, followed by the standard deviation of whole ROI average values in test-retest (3repetitions) evaluation of 2 subjects.Figure 1. Evolution of hMRI maps with change of the protocol from a) initial to b) ﬁnal parameter choices - from left to right: MT, R1, R2*, and PD maps.Amelioration is seen of eye ghosting that propagates over the temporal lobes and produces artifactual values in (compare area indicated by blackarrowheads in a. with similar location in b). c) Axial reformat of ﬁnal protocol hMRI maps illustrate anatomical consistency of MT, R1 and PD maps despitesusceptibility induced alterations in R2* in proximity to nasal sinuses and acoustic canal (white arrowheads).

Setting up a multi-centric multiparametric hMRI protocol for the investigation of temporal lobe epilepsy

http://discovery.ucl.ac.uk/10045185/1/summer%20et%20al_ISMRM2018_hMRI%20%283%29.pdf

Setting up a multi-centric multiparametric hMRI protocol for the investigation of temporal lobe epilepsy

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