Apparatuses and methods are disclosed for applying radio frequency (RF) energy to an object in an energy application zone. At least one processor may be configured to cause RF energy to be applied at a plurality of electromagnetic field patterns to the object in the energy application zone. The processor may be further configured to determine an amount of power dissipated in the energy application zone, for each of the plurality of field patterns. The processor may also be configured to determine a spatial distribution of energy absorption characteristics across at least a portion of the energy application zone based on the amounts of power dissipated when the plurality of field patterns are applied to the energy application zone.