For generations, peering into the brain's hidden pathology required costly imaging machines and specialized centers — barriers that quietly narrowed who could access early Alzheimer's detection. Now, researchers analyzing data from 419 participants have found that a blood protein called p-tau217 can approximate what a PET scan reveals about tau tangles, the disease's defining signature. The work does not promise a perfect test, but it opens a quieter, more democratic door: a blood draw as the first question asked, with imaging reserved for those who need a deeper answer.