TABLE 2.

Main changes from ADNI3 to ADNI4.

Series	Changes from ADNI3 to ADNI4
MP‐RAGE	Kept the same for continuity.
CS‐MP‐RAGE	New added sequence. Will test the diagnostic potential of an under 2‐minute acquisition using advanced compressed sensing reconstructions on data with 4.8‐ and 6‐fold acceleration.
3D T2w FLAIR	Reduced slice thickness from 1.2 to 1 mm to produce isotropic voxels that match T1w and T2w structural images. Also, reduced echo time from 119 to 104 ms to compensate for SNR loss.
Structural 3D isotropic T2w	New isotropic resolution structural T2w sequence with matched T1w and 3D T2w FLAIR coverage.
Multi‐PLD 3D ASL	Went from single PLD in ADNI3 to a new multiple PLD ASL and proton density volumes to enable quantitative cerebral blood flow and arterial transit time mapping across all three vendors.
T2* weighted GRE	Went from three echoes in ADNI3 to five echoes in ADNI4 to improve QSM estimates.
Diffusion	Added multi‐band slice excitation acquisition on vendors where it recently became product. Added an additional short anterior–posterior acquisition to improve distortion correction.
TF‐EPI‐BOLD	Used multi‐band slice excitation to improve the basic acquisitions sampling rate from 3 seconds to 1.5 seconds. Due to overall protocol duration, the total acquisition time was reduced from 10 minutes to 5 minutes.
High‐resolution hippo	Kept the same for continuity.

Abbreviations: ADNI, Alzheimer's Disease Neuroimaging Initiative; ASL, arterial spin labeling; CS, compressed sensing; FLAIR, fluid‐attenuated inversion recovery; GRE, gradient recalled echo; MP‐RAGE, magnetization‐prepared rapid acquisition gradient echo; PLD, post‐labeling delay; QSM, quantitative susceptibility mapping; SNR, signal‐to‐noise ratio; T1w, T1‐weighted; T2w, T2‐weighted; Task‐Free‐EPI‐BOLD, XXXXXXXX echo‐planar imaging blood‐oxygen level dependent.