A method of treating hypertension in a mammal is described, including: by focused sound energy, heating at least one nerve at a surface of a renal artery in a mammal during the heating and by magnetic resonance imaging, repeatedly determining thermal levels in each of first and second volumetric zones of a region that includes at least a portion of the surface, the second zone being adjacent to the first zone after determining that an indicium of a thermal level in the first zone exceeds a first threshold, and upon determining that an indicium of a thermal level in the second zone exceeds a second threshold, ceasing the heating of the at least one nerve for at least three months and as a result of the heating, lowering a blood pressure in the mammal.
