Abstract: Ultrasound methods and apparatus for reducing tissue damage from ischemia by means of insonation through intact skin and/or bone, the insonation preferably promoting thrombolysis, reducing edema and promoting microcirculation, recanalization, increased collateraled interstitial flow and delivery of lytic agents to clots located in supplying arteries as well as nutrients or therapeutic agent to the ischemic tissue. A portion of an organ affected by ischemia or the entire organ is exposed to low frequency low power ultrasound generated by multiple transducers of variable power limits which at least partially surround an organ, preferably at least 90% of a skull surface, for instance. Studies indicate the approach maintains biological tissue function or viability in the setting of reduced perfusion by exposing the tissue or organ to ultrasound energy transmission.