Treatment envelopes based on 2D MRTI. Three orthogonal views of the treatment envelopes based only on the focal spot heating for the phantom (a) and lamb (b) studies. Near-field temperatures are not considered for this type of envelope. Temperature rises of at least 10°C can be seen in large parts of the intracranial volume in both cases. This is the type of envelope that can be derived from 2D MRTI. In both (a) and (b), the temperature maps are overlayed on magnitude images. In (a) and (b), the three views are color coded, with the colored frame and arrows indicating each view’s position in the other two views.