Enhancement of radiation effects by gold nanoparticles for superficial radiation therapy

Radiation therapy aims to deliver a high therapeutic dose of ionizing radiation to the tumor volume without exceeding normal tissue tolerance. Preferential tumor uptake of contrast agents has been used to improve this therapeutic ratio by changing the lower energy photon interaction cross-sections in the immediate vicinity of the tumor, thereby delivering a highly localized dose boost to the tumor [1, 2]. This is normally done by loading the target volume with contrast agents and irradiating the target with kilovoltage x-rays where photoelectric effects are dominant. High-atomic-number (Z ) contrast agents such as iodine (Z = 53) and gadolinium (Z = 64) provide a high probability for photon interaction by photoelectric effect [2, 3]. The high linear energy transfer and short range of photoelectric interaction products (photoelectrons, characteristic xrays, Auger electrons) produce localized dose enhancement at the tumor [2].