1. A method for determining the efficacy of a prospective prevention therapy for Alzheimer's disease (AD) in persons having no clinical symptoms of AD, the method comprising: receiving at a computing device a plurality of brain imaging measurements from one or more positron emission tomography (PET) scanners, the brain imaging measurements indicating a concentration of amyloid plaques or neurofibrillary tangles deposited in a brain of each of a plurality of subjects in an AD prevention therapy study, each subject having no clinical symptoms of AD and at least one of Down syndrome or a concentration of amyloid plaques or neurofibrillary tangles deposited in the brain, wherein the concentration is at least equal to a threshold concentration of amyloid plaques or neurofibrillary tangles deposited in the brain, and wherein a first portion of the measurements were obtained by the PET scanner from a first group of the subjects who first received a prospective prevention therapy for AD, a second portion of the measurements were obtained by the PET scanner from a second group of the subjects who did not first receive the prospective prevention therapy for AD; and executing instructions stored in memory of the computing device, wherein execution of the instructions by a processor of the computing device: determines a correlation between the brain imaging measurements and a plurality of coordinates of a brain atlas, extracts from the brain imaging measurements data corresponding to a region of interest identified by at least a portion of the brain atlas coordinates, the data indicating the concentration of amyloid plaques or neurofibrillary tangles deposited in the region of interest, calculates based on a predetermined interval a rate of change in the concentration of amyloid plaques or neurofibrillary tangles deposited in the region of interest for each of the plurality of subjects, compares the rates of change in the concentration of amyloid plaques or neurofibrillary tangles deposited in the region of interest calculated for the first group of the subjects to the rates of change in the concentration of amyloid plaques or neurofibrillary tangles deposited in the region of interest calculated for the second group of the subjects, determines that a difference between the rates of change in the concentration of amyloid plaques or neurofibrillary tangles deposited in the region of interest between the first group of the subjects and the second group of the subjects is statistically significant, and reports to a user of the computing device by way of a user interface that based on the statistically significant difference the prospective prevention therapy for AD is efficacious in persons having no clinical symptoms of AD and at least one of Down syndrome or at least the threshold concentration of amyloid plaques or neurofibrillary tangles deposited in the brain.