Treatment of malignant tumors or other lesions by localized transfer of 
radio frequency electromagnetic energy into a portion of the body may be achieved by means of spatially localized magnetic 
resonance (MR). A 
magnetic field with appropriate 
spatial distribution and 
radio frequency tuned to the resonant frequency unique to the tumor treatment volume will cause selective therapeutic energy deposition or heating within the tumor (
hyperthermia). The desired 
magnetic field distribution for the MR treatment volume may be achieved by means of a main static 
magnetic field with a superimposed magnetic field to define the treatment volume size and shape, positioned by a gradient magnetic field. Treatment may be enhanced by 
MR contrast agents (such as 
gadolinium) and pharmacologic agents. The therapy may be achieved by simultaneous 
resonance throughout an entire selected therapy volume, or successively point by point, or by 
superimposition of small volumes, including by successively excited points, lines or planes as practiced in prior art 
magnetic resonance imaging systems, facilitating simultaneous imaging and therapy. In a preferred embodiment, the invention is incorporated in a 
magnetic resonance imaging (MRI) 
scanner wherein the imager modified by the addition of a localizing 
magnet is used visually or by automated or semi-automated 
computer image processing to define and localize the treatment volume and the main magnetic field and positioning gradient fields are created by the same magnets used for imaging and the 
radio frequency apparatus used for Magnetic 
Resonance Therapy uses the same 
electronics and probe coil used for MRI.