Comparison between regional cerebral blood flow estimates using different MR arterial spin labelling approaches and early-phase amyloid PET on a simultaneous PET/MR
Rodriguez, Jose Antonio Matthews, J. C. Scott, L. Lohezic, M. Herholz, K. Parkes, L. M.
Rodriguez, Jose Antonio
Matthews, J. C.
Scott, L.
Lohezic, M.
Herholz, K.
Parkes, L. M.
Citations
Altmetric:
Abstract
Aim/Introduction: Amyloid-PET can be used as dualphase
biomarker enabling differential diagnosis between
dementias by providing images of amyloid load (late-phase)
and functional estimates of regional cerebral blood flow
(rCBF) (early-phase) [1]. MRI arterial spin labelling (ASL) can
quantify CBF and can provide similar patient classification
information as [18F]FDG PET [2]. Here, we compare rCBF
obtained with ASL with the early-phase distribution of
amyloid-PET using [18F]flutemetamol (FLUT). Materials
and Methods: Twenty participants, 70(60-80) years old, 14
cognitively normal/6 mild cognitive impairment, were
scanned on a SIGNA PET/MR (GE-Healthcare). PET list-mode
data were acquired for 30 minutes following the injection
of ~185MBq of FLUT. PET images were reconstructed
using GE Q.Clear (β=250) for two separate time frames
corresponding to 20s-80s and 120s-300s post-arrival of
tracer in the brain. Enhanced-ASL with pCASL labelling and
3D spiral FSE acquisition was acquired with 6 post-labelling
delays to obtain voxel-wise arrival-time-corrected CBF
maps [3] (scan duration: 9min). CBF maps were calculated
using either global (CBFglobal) or local (CBFlocal) correction
for equilibrium magnetisation and also using a single time
point post-labelling of 2.2s (CBF2.2) (scan duration: ~3min).
FreeSurfer brain segmentation on each participant’s T1w
MPRAGE image (1mm isotropic resolution) was used to
estimate median CBF values for 12 ‘meta-regions’. Linear
regression was used to compare intensity normalised early
phase PET and ASL. Results: For PET20-80 vs CBFglobal, CBFlocal,
CBF2.2 the r (median(range)) values across the 20 participants
were 0.56(0.26-0.65), 0.67(0.33-0.82) and 0.59(0.27-0.82)
respectively. Removing subcortical ROIs caudate and
striatum (clear outliers on the scatter-plots) improved the
r values to 0.63(0.36-0.81), 0.82(0.48-0.96), 0.85(0.42-0.96).
Lower r values for PET120-300 were observed. Conclusion: For
cortical regions, there is a good proportional relationship
between ASL and PET measurements (improved using
earlier PET (PET20-80) to PET120-300 proposed in [1]) with this
proportion not holding for the subcortical ROIs with
values underestimated for ASL. ASL CBF maps with local
magnetisation correction have a closer association with PET
suggesting that spatial inhomogeneity in coil sensitivities
cause significant errors if uncorrected. Good association
is maintained with single time point ASL suggesting that
2.2s is sufficient delay for complete transit of labelled blood;
enabling faster ASL acquisition. These close associations
suggest that simultaneous ASL with late-phase amyloid-
PET and injection of FLUT off the bed could provide
excellent classification of dementia patients in a single scan.
Affiliation
Description
Date
2020
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Rodriguez JA, Matthews JC, Scott L, Lohezic M, Herholz K, Parkes LM. Comparison between regional cerebral blood flow estimates using different MR arterial spin labelling approaches and early-phase amyloid PET on a simultaneous PET/MR. European Journal of Nuclear Medicine and Molecular Imaging. 2020;47(SUPPL 1):S498-S9