Feasibility Study to Evaluate Renal Denervation Using Focused Ultrasound

Inclusion Criteria: * Subject is at least 18 years of age. * Subject has systolic blood pressure of 160 mmHg in average or greater. * Subject has refractory, stable hypertension despite being treated with at least three hypertensive drugs. * Subject has two functioning kidneys, defined as eGFR ≥ 45 ml/min. * Subject has at least one renal artery on each side which is greater than 4mm. Exclusion Criteria: * Subject has hydronephrosis as seen on MRA or ultrasound. * Subject has renal stenosis greater than 50% based on baseline MRA. * Subject has a renal stent or other implant in the region. * Subject has kidney stones which are symptomatic and/or greater than 1cm or in the discretion of the investigator may interfere with treatment. * Subject has a history of abdominal surgery within the past six months. * Subject has heterogeneities in the kidney such as large cysts or tumors which in the discretion of the investigator may interfere with treatment. * Subject has active pyelonephritis or a history of pyelonephritis which in the discretion of the investigator may interfere with treatment. * Subject has a history of myocardial infarction, unstable angina pectoris, or cerebrovascular accident within the last six months. * Subject has hemodynamically significant valvular heart disease. * Subject has an implantable cardioverter defibrillator, pacemaker, neurostimulator or other device incompatible with MRI. * Subject has a body weight \> 150 kilograms. * Subject has a target treatment depth \> 14 cm. * Subject is pregnant, nursing or intends to become pregnant during the trial period. * Subject is currently enrolled in other potentially confounding research. * Subject has any condition that, at the discretion of the investigator, would preclude participation in the trial.