Field-focusing hyperthermia and magnetic resonance imaging (MRI) with a grounded probe and a commercial MRI scanner.

A method for performing magnetic resonance imaging (MRI) and producing field-focusing hyperthermia sequentially in phantoms and rat tissues with a grounded hyperthermic probe and a commercial MRI scanner was demonstrated. In the treatment mode the MRI scanner was used as a radiofrequency (RF) power source, and an invasive, electrically grounded, tuned probe was used to produce hyperthermia in phantoms via induced eddy current convergence. Temperature increases of 4.5 degrees C/5 minutes in a dielectrically uniform phantom and 5.0 degrees C/6 minutes in the peritoneum of a rat were measured in the vicinity (3-5 mm) of the grounded probe with the transmitter of the MRI scanner working at 2 per cent duty cycle. The advantage of this combined diagnostic and therapeutic approach is that the position of the hyperthermic probe can be monitored before each treatment, with observation of the tumor during and after treatment, if desired. In addition, the total cost is significantly less than that of both an MRI scanner and an RF hyperthermia treatment system.