Biomarkers.

Background: Phase four of the Alzheimer's Disease Neuroimaging Initiative (ADNI4) began in 2023. This time-period corresponded to MRI vendors introducing product sequences with compressed sensing (CS), cross-vendor adoption of arterial spin-labelling (ASL) and multi-band slice excitation, and hardware improvements (head-coils, increased gradient amplitudes). These advances enabled the acquisition of new imaging measures and reduced scan times.

Alzheimer's Imaging Consortium.

Background: Phase four of the Alzheimer's Disease Neuroimaging Initiative (ADNI4) began in 2023. This time-period corresponded to MRI vendors introducing product sequences with compressed sensing (CS), cross-vendor adoption of arterial spin-labelling (ASL) and multi-band slice excitation, and hardware improvements (head-coils, increased gradient amplitudes). These advances enabled the acquisition of new imaging measures and reduced scan times.

Overview of ADNI MRI.

The magnetic resonance imaging (MRI) Core has been operating since Alzheimer's Disease Neuroimaging Initiative's (ADNI) inception, providing 20 years of data including reliable, multi-platform standardized protocols, carefully curated image data, and quantitative measures provided by expert investigators. The overarching purposes of the MRI Core include: (1) optimizing and standardizing MRI acquisition methods, which have been adopted by many multicenter studies and trials worldwide and (2) providing curated images and numeric summary values from relevant MRI sequences/contrasts to the scientific community. Over time, ADNI MRI has become increasingly complex.

Design and validation of the ADNI MR protocol.

Phase four of the Alzheimer's Disease Neuroimaging Initiative (ADNI4) magnetic resonance imaging (MRI) protocols aim to maintain longitudinal consistency across two decades of data acquisition, while adopting new technologies. Here we describe and justify the study's design and targeted biomarkers. The ADNI4 MRI protocol includes nine MRI sequences.