Blood-Brain-Barrier Opening Using Focused Ultrasound With IV Contrast Agents in Patients With Early Alzheimer's Disease

Inclusion Criteria: 1. Probable AD consistent with NIA/AA criteria (McKhann, Alzheimer \& Dementia 2011) 2. Modified Hachinski Ischemia Scale (MHIS) score of \<= 4. 3. Mini Mental State Exam (MMSE) scores 18-28 4. Short form Geriatric Depression Scale (GDS) score of \<= 6 5. Has a Florbetaben PET scan consistent with the presence of amyloid pathology in the proposed target region (right frontal lobe) 6. Able to communicate sensations during the ExAblate® MRgFUS procedure. Exclusion Criteria: 1. MRI findings: * Active infection/inflammation * Acute or chronic hemorrhages, specifically \> 4 lobar microbleeds, and no siderosis or macrohemorrhages * Tumor/space occupying lesion * Meningeal enhancement 2. More than 30% of the skull area traversed by the sonication pathway is covered by scars, scalp disorders (e.g., eczema), or atrophy of the scalp 3. Clips or other metallic implanted objects in the skull or the brain, except shunts; other metallic objects implanted in body 4. Significant cardiac disease or unstable hemodynamic status including: 5. Uncontrolled hypertension on medication or abnormal ECG 6. Medications known to increase risk of hemorrhage, (e.g.: patients should be off of aspirin or another anticoagulants for at least 7 days prior to treatment) or anticoagulants (class I and III) or off Avastin for 30 days 7. History of a bleeding disorder, coagulopathy or a history of spontaneous hemorrhage or use of anticoagulants 8. Abnormal coagulation profile (PLT \< 100,00/μl), PT (\>14 sec) or PTT (\>36 sec), and INR \> 1.3 9. No more than 1 non-strategic lacune \<1.5 cm 10. Known cerebral or systemic vasculopathy 11. Significant depression and at potential risk of suicide 12. Known sensitivity/allergy to gadolinium (an alternative product may be used), Definity or any of its components. 13. Any contraindications to MRI scanning such as metallic implants, claustrophibia or too large for MRI scanner 14. Untreated, uncontrolled sleep apnea 15. Impaired renal function with estimated glomerular filtration rate \<30 mL/min/1.73m2 16. Does not have a reliable caregiver in frequent contact with the patient and can accompany the patient to the clinic and treatment or be available by telephone at designated times. Participants living in retirement homes may be included. Caregiver not willing to sign the Informed Consent Form 17. Respiratory: chronic pulmonary disorders e.g. severe emphysema, pulmonary vasculitis, or other causes of reduced pulmonary vascular cross-sectional area, patients with a history of drug allergies, asthma or hay fever, and multiple allergies where the benefit/risk of administering Definity® is considered unfavorable by the study physicians in relation to the product monograph for Definity. 18. Currently in a clinical teial involving investigational product.