The development of PdNi thermoseeds for interstitial hyperthermia.

Magnetic induction heating of thermoseed implants can be used to produce highly localized hyperthermia in deep-seated tumors. Automatic temperature control throughout the tumor can be achieved by the self-regulating character of ferromagnetic seeds, which corrects for local variations in heat loss due to blood perfusion. An increased sharpness of the ferromagnetic transition at the Curie temperature, Tc, improves the performance of self-regulating control. This was realized for palladium-nickel alloys by a "cold working" procedure preceded and followed by annealing. Palladium-nickel seeds with a predetermined Tc were produced, showing a sharp decrease at Tc of the magnetic susceptibility and the heat production.