The Canadian Dementia Imaging Protocol: Harmonizing National Cohorts

Abstract

Background: Harmonized protocols to collect imaging data must be devised, employed, and maintained in multicentric studies to reduce interscanner variability in subsequent analyses.

Purpose: To present a standardized protocol for multicentric research on dementia linked to neurodegeneration in aging, harmonized on all three major vendor platforms. The protocol includes a common procedure for qualification, quality control, and quality assurance and feasibility in large-scale studies.

Study type: Prospective.

Subjects: The study involved a geometric phantom, a single individual volunteer, and 143 cognitively healthy, mild cognitively impaired, and Alzheimer's disease participants in a large-scale, multicentric study.

Field strength/sequences: MRI was perform with 3T scanners (GE, Philips, Siemens) and included 3D T₁ w, PD/T₂ w, $T_2^{*}$ , T₂ w-FLAIR, diffusion, and BOLD resting state acquisitions.

Assessment: Measures included signal- and contrast-to-noise ratios (SNR and CNR, respectively), total brain volumes, and total scan time.

Statistical tests: SNR, CNR, and scan time were compared between scanner vendors using analysis of variance (ANOVA) and Tukey tests, while brain volumes were tested using linear mixed models.

Results: Geometric phantom T₁ w SNR was significantly (P < 0.001) higher in Philips (mean: 71.4) than Siemens (29.5), while no significant difference was observed between vendors for T₂ w (32.0 and 37.2, respectively, P = 0.243). Single individual volunteer T₁ w CNR was higher in subcortical regions for Siemens (P < 0.001), while Philips had higher cortical CNR (P = 0.044). No significant difference in brain volumes was observed between vendors (P = 0.310/0.582/0.055). The average scan time was 41.0 minutes (SD: 2.8) and was not significantly different between sites (P = 0.071) and cognitive groups (P = 0.853).

Data conclusion: The harmonized Canadian Dementia Imaging Protocol suits the needs of studies that need to ensure quality MRI data acquisition for the measurement of brain changes across adulthood, due to aging, neurodegeneration, and other etiologies. A detailed description, exam cards, and operators' manual are freely available at the following site: www.cdip-pcid.ca.

Level of evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:456-465.

Keywords: diffusion tensor imaging; magnetic resonance imaging; morphometry; neuroimaging; resting state functional MRI; standardization.