1. A method for determining the efficacy of a prospective prevention therapy for a neurodegenerative disease in persons having no clinical symptoms of the neurodegenerative disease, the method comprising: receiving at a computing device a plurality of brain imaging measurements from one or more imaging systems, 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 a disease prevention therapy study, each subject having no clinical symptoms of the disease 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 one or more imaging systems from a first group of the subjects who first received an amount of a prospective prevention therapy for the disease, and a second portion of the measurements were obtained by the one or more imaging systems from a second group of the subjects who either did not first receive the prospective prevention therapy or who received a lesser amount of the prospective prevention therapy than the first group of subjects; and executing instructions stored in memory of the computing device, wherein execution of the instructions by a processor of the computing device: extracts from the brain imaging measurements data corresponding to a region of interest identified within a brain atlas, the data indicating the concentration of amyloid plaques or neurofibrillary tangles deposited in the region of interest, compares a plurality of 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 a plurality of 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 is efficacious in persons having no clinical symptoms of the disease and at least one of Down syndrome or at least the threshold concentration of amyloid plaques or neurofibrillary tangles deposited in the brain.