Test-retest reliability of myelin imaging in the human spinal cord: Measurement errors versus region- and aging-induced variations
January
Test-retest reliability of myelin imaging in the human spinal cord: Measurement errors versus region- and aging-induced variations
Simon Le vy 1 2 3 4
Marie-Claude Guertin 0 1 4
Ali Khatibi 1 2 4
Aviv Mezer 1 4
Kristina Martinu 1 2 4
Jen-I Chen 1 2 4
Nikola Stikov 1 3 4
Pierre Rainville 1 2 4
Julien Cohen-Adad 1 3 4
0 Montreal Health Innovations Coordinating Center (MHICC), Montreal Heart Institute , Montreal, QC , Canada , 4 Psychology Department, Bilkent University , Ankara , Turkey , 5 Interdisciplinary program in Neuroscience, Bilkent University , Ankara , Turkey , 6 National Magnetic Resonance Research Center (UMRAM), Bilkent University , Ankara , Turkey , 7 The Edmond and Lily Safra Center for Brain Sciences (ELSC), The Hebrew University of Jerusalem , Jerusalem , Israel , 8 Department of Stomatology, Faculty of Dentistry, Universit e de Montr eÂal , Montreal, QC , Canada , 9 Montreal Heart Institute , Montreal, QC , Canada
1 Current address: Centre d'Exploration M eÂtabolique par Re sonance Magn eÂtique (CEMEREM), AP-HM, H oÃpital de la Timone, Poà le d'imagerie meÂdicale , Marseille , France
2 Centre de Recherche de l'Institut Universitaire de Ge riatrie de Montre al (CRIUGM) , Montr eÂal, QC , Canada
3 0 Functional Neuroimaging Unit, CRIUGM, Universite de Montre al , Montreal, QC , Canada
4 Editor: Fernando de Castro, Instituto Cajal-CSIC , SPAIN
Volume (MTV).
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Data Availability Statement: The current Quebec
law on the protection of private data prevents us
from sharing all the MRI datasets this work is
based on, even though they are de-identified,
because they contain potentially sensitive
information. This restriction has been imposed by
the ethical review board of the Research Center of
Montreal University Geriatric Institute (ComiteÂ
mixte d'eÂthique de la recherche du RNQ, approval
number CMER-RNQ_14-15-010). To contact the
research ethics board of the RNQ, please refer to
Purpose
Methods
To implement a statistical framework for assessing the precision of several quantitative MRI
metrics sensitive to myelin in the human spinal cord: T1, Magnetization Transfer Ratio
(MTR), saturation imposed by an off-resonance pulse (MTsat) and Macromolecular Tissue
Thirty-three healthy subjects within two age groups (young, elderly) were scanned at 3T.
Among them, 16 underwent the protocol twice to assess repeatability. Statistical reliability
indexes such as the Minimal Detectable Change (MDC) were compared across metrics
quantified within different cervical levels and white matter (WM) sub-regions. The
differences between pathways and age groups were quantified and interpreted in context of the
test-retest repeatability of the measurements.
Results
The MDC was respectively 105.7ms, 2.77%, 0.37% and 4.08% for T1, MTR, MTsat and MTV
when quantified over all WM, while the standard-deviation across subjects was 70.5ms,
1.34%, 0.20% and 2.44%. Even though particular WM regions did exhibit significant differences, these differences were on the same order as test-retest errors. No significant difference was found between age groups for all metrics.
Mrs Karima Bekhiti (phone: +1 514 527-9565
#3223; email: .
ca). Notwithstanding this limitation, we are willing
to share the MRI data from four members of the
lab, from which we have obtained explicit approval.
Furthermore, we are also sharing the processing
scripts used in this work, which will enable other
researchers to re-run the analyses on the shared
datasets. The data and scripts have now been
uploaded to https://osf.io/ezmrj/.
Funding: This study was funded by the Canada
Research Chair in Quantitative Magnetic
Resonance Imaging (JCA), the Canadian Institutes
of Health Research [CIHR FDN-143263] (JCA), the
Canadian Institutes of Health Research [CIHR
MOP-130341] (JCA and PR), the Fonds de
Recherche du QueÂbecÐSante [FRQS-28826]
(JCA), the Fonds de Recherche du QueÂbecÐ
Nature et Technologies [2015-PR-182754] (JCA),
the Natural Sciences and Engineering Research
Council of Canada [NSERC-435897-2013] (JCA),
the Natural Sciences and Engineering Research
Council of Canada [NSERC 2016-06774] (NS), the
Quebec BioImaging Network (JCA) and the
Montreal Heart Institute Foundation (NS). Those
funds were used for MRI data acquisition,
computer and software resources and authors'
funding.
Competing interests: The authors have declared
that no competing interests exist.
Conclusion
While T1-based metrics (T1 and MTV) exhibited better reliability than MT-based
measurements (MTR and MTsat), the observed differences between subjects or WM regions were
comparable to (and often smaller than) the MDC. This makes it difficult to determine if
observed changes are due to variations in myelin content, or simply due to measurement
error. Measurement error remains a challenge in spinal cord myelin imaging, but this study
provides statistical guidelines to standardize the field and make it possible to conduct
largescale multi-center studies. (...truncated)