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The Centiloid (CL) scale represents an attempt to standardize amyloid positron emission tomography (PET) imaging to create a measure of amyloid-β (Aβ) deposition in the brain. CL converts the standard uptake value ratio (SUVR) from brain PET into values from 0 to 100 using paired magnetic resonance (MR) images in the processing pipeline. This study aims to evaluate the CL variability with processing pipelines without MR (MR-less). Image data of 79 individuals (34 young controls; 45 Alzheimer's disease patients) from the GAAIN database were processed with three pipelines: one MRbased, and two MR-less, using an MR template smoothed with Gaussian filters (4 mm/8 mm). Using the whole cerebellum as a reference, we used PMOD - PNEURO tool to convert SUVR from the global cortical target region. We find a strong agreement between the MR-based pipeline and previous studies (R2 = 0.997), exceeding the minimum acceptance criteria (slope = 0.99; intercept = 0.92). For the 4 mm Gaussian filter MR-less pipeline, we reach a strong agreement (R2 = 0.981) and minimum acceptance criteria (slope = 0.98; intercept = 1.29). However, results for the 8 mm filter Gaussian MR-less pipeline are below the acceptance criteria (R2 = 0.969, slope = 0.97; intercept = 1.52), mainly for higher CL values. No statistical differences were found comparing MR-based vs. MR-less and GAAIN vs. MR-less for both filters. Concluding, CL implementation using 4 mm Gaussian filter MR-less pipeline is comparable to the paired MR-based, simplifying the clinical practice to quantify Aβ deposition in the brain. However, MR-based processing for brain quantification is indicated mainly for clinical research in aging studies.
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