This is a prospective, multi-center, single-arm study to evaluate the safety and efficacy of BBB disruption using the ExAblate Model 4000 Type 2.0 (220 kHz) system. Patients with diagnosis of Probable Alzheimer's Disease may qualify for a clinical trial to have three serial ExAblate BBB disruption procedures in specific areas in the brain. This study will be conducted at up to 8 sites in the United States and will enroll up to 30 patients.