Core-excited nanoparticle thermotherapy (CENT) represents a new paradigm in thermotherapy. The CENT method employs core-shell nanoparticles. The core of the nanoparticles is formed from one or more core-exciting, energy absorbing materials which absorbs core-exciting energy, either from an external energy source or from an energy source within the nanoparticle core (e.g., one or more radionuclides which undergo decay). Upon excitation by the core-exciting energy, the one or more core-exciting, energy absorbing materials reemit energy. A shell surrounds the particle nanoparticle core. The energy reemitted by the one or more core-exciting, energy absorbing materials is absorbed by the nanoparticle shell, so as to heat the shell of the nanoparticle. The heated nanoparticle then heats the surrounding region, to a temperature sufficient to detect, affect, damage or destroy the targeted cell or material. These core-shell nanoparticles can be administered to a patient in need thereof to treat diseases or disorders, including cancer. CENT nanoparticles can be optionally be bound to targeting agents that deliver them to the region of the diseased cell.