A method for treating a desired volume of tissue using HIFU or other energy modality to ablate a pattern of elemental treatment volumes each having a volume that is greater than that of the focal zone of the HIFU transducer but smaller than the overall volume of the desired treatment volume. In one embodiment, the pattern of elemental treatment volumes are arranged to form a shell which partially or wholly encapsulates the desired volume of tissue, which then necroses in situ due to effects other than direct HIFU damage (including some combination of ischemia, thermal conduction, inflammation, apoptosis, etc.). The necrosed tissue remains in the body and is subsequently resorbed and/or healed via normal body mechanisms.