P3‐422: PROTOCOL HARMONISATION AND IN‐VIVO COMPARISON OF ARTERIAL SPIN LABELLING PERFUSION MRI FOR MULTICENTER CLINICAL TRIALS (2018)

Arterial Spin Labelling (ASL) is a technique for measuring cerebral blood flow (CBF)1,2 and has shown promising results for discriminating Alzheimer's disease patients from mild cognitive impairment and controls1. ASL is commercially available on all major MRI vendors; however, it has been shown that CBF values are sequence and scanner-dependent, due to variability of the acquisition methods used by each vendor. In this study, we compare the latest generation of pseudo-continuous ASL (pCASL) vendor-provided sequences to quantify between-vendor variability of whole-brain and regional CBF estimation. Eight healthy volunteers (4/4 M/F; mean/SD/median age=47/12/48 years) were scanned on three 3T MR systems with pCASL matched acquisition parameters (Table 1) and ADNI-2 3D-T1weighted (MPRAGE). CBF quantification and post-processing was performed using ExploreASL3 in conjunction with SPM124. Post-processing included registration of the T1-MPRAGE and ASL to MNI space, parcellation of the T1-MPRAGE to grey matter (GM), white matter (WM), and regions affected in dementia (ROI_dem). Quantification was performed according to the ASL consensus paper5. Mean-CBF was calculated in ROI_dem and in the whole-brain within a standard (GM+WM>70%) and expanded (GM+WM>5%) mask. Spatial coefficient of variation (sCoV)6 was calculated for GM(>70%) and whole-brain (GM+WM>70%). Statistical significances were calculated using repeated measure ANOVA (P<0.05). Whole-brain CBF values using the expanded mask showed better agreement between three vendors than the standard mask (Figure 1). There was no significant difference in mean-CBF of ROI_dem for Philips and Siemens, while GE showed significantly lower mean-CBF in these regions (Figure 2). sCoV also showed a similar trend, with GE having the lowest sCoV relative to Philips and Siemens for both whole-brain and GM (Figure 3). Mean CBF of whole brain using standard brain mask and expanded brain mask. Average CBF in main regions affected by dementia (for pGM>0.70) sCoV calculated in Grey Matter and Whole brain with expanded mask, showing significant differences in sCoV in GE compared with Philips and Siemens. Whole-brain CBF was similar across vendors when an expanded mask was applied. However, there was a difference between GE and Philips/Siemens in CBF and sCoV in grey matter regions. We hypothesize that the differences are related to between-scanner differences in effective spatial resolution, in particular the lower effective resolution of GE's spiral readout7. Future work will investigate whether smoothness equalization8 can account for this. We anticipate that this work will increase the utility of ASL as a perfusion biomarker in multi-center dementia studies. References: 1. J.-C. Ferré, E. Bannier, H. Raoult, G. Mineur, B. Carsin-NicoL J.-Y. Gauvrit Arterial spin labeling (ASL) perfusion: Techniques and clinical use, Journal de Radiologic Diagnostique et Interventionnelle, Volume 94, Issue 12, December 2013, Pages 1208-1221. 2. Binnewijzend MA, Kuijer JP, Benedictus MR, van der Flier WM, Wink AM, Wattjes MP et al (2013) Cerebral blood flow measured with 3D pseudocontinuous arterial spin-labeling MR imaging in Alzheimer disease and mild cognitive impairment: a marker for disease severity. Radiology 267:221–230. 3. Mutsaerts H., et al. Comparison of arterial spin labeling registration strategies in the multi-center GENetic frontotemporal dementia initiative (GENFI). Journal of Magnetic Resonance Imaging: JMRI, 2017 https://doi.org/10.1002/jmri.25751. 4. Statistical Parametric Mapping, Wellcome Trust Centre for Neuroimaging, London, UK. 5. Alsop DC. et al., Recommended implementation of arterial spin-labeled perfusion MRI for clinical applications: A consensus of the ISMRM perfusion study group and the European consortium for ASL in dementia. Magn Reson Med, 2015.73(1): p. 102-16. 6. Mutsaerts H, Petr J, Václavů L, Van Dalen JW, Robertson AD, Caan MWA, Masellis M, Nederveen AJ, Richard E, Macintosh BJ. The spatial coefficient of variation in arterial spin labeling cerebral blood flow images. Journal of cerebral blood flow and metabolism 2017; 37: 3184-3192. 7. Petr J, Mutsaerts HJMM, E DV, Maus J, van den Hoff J, Asllani I. Deformation and resolution issues in partial volume correction of 2D and 3D arterial spin labeling data. Proc. Int. Soc. Magn. Reson. Med. 2016; 24. 8. Friedman L, Glover GH, The FBIRN Consortium. Reducing inter-scanner variability of activation in a multicenter fMRI study: Role of smoothness equalization Neurolmage 2006; 33:471-481. 9. Mutsaerts HJMM, Steketee RME, Heijtel DFR, Kuijer JPA, Van Osch MJPMJP, Majoie CBLM, Smits M, Nederveen AJ. Inter- vendor reproducibility of pseudo-continuous arterial spin labeling at 3 Tesla. PLoS ONE 2014; 9. doi:10.1371/journal.pone.0104108.