Human leg heating using a mini-annular phased array

The energy deposition pattern within an isolated human leg heated with a mini-annular phased array (MAPA) hyperthermia applicator has been determined. The non-tumor-bearing lower portion of a human leg amputated at the hip due to the presence of a large tumor in the thigh was "fixed" in a 50% ethanol in 0.9% saline solution. Subsequent to this fixation process, the leg was rehydrated in 0.9% saline and heated four times using a MAPA operating at 122 MHz. Specific absorption rates and electric field strengths were calculated from the rates of change of temperature with time measured at 143 different anatomical locations within the leg. When the leg was coaxial with the MAPA and the MAPA was axially positioned midway between the knee and the ankle, the points of maximum heating were skewed away from the center of the MAPA, towards the ankle of the leg and along the central axis of the MAPA. Significant temperature rise was measured inside the bone and the fat as well as inside the muscle of the leg. Bone heating was reduced when the leg was shifted away from the MAPA axis.