ABSTRACT
Therapeutic radiation is typically delivered locally at a low-dose rate (brachytherapy) or high-dose rate through megavoltage devices (external beam or tele-therapy). In either case, radiation administered is measured as the radiation absorbed dose (rad) or more recendy, the Gray (Gy) unit. 1 Gray equals 100 rads. Each type of radiation has a characteristic depth of penetration that is used to estab lish its effect on a lesion. The following treatment parameters therefore have influ ence on the overall radiadon-induced damage: (1) total dose; (2) dose ffaction size; (3) total volume of tissue treated; (4) elapsed time during irradiation. Dose fraction ation regimens have been created by radiation therapists to minimize injury to nor mal tissue. Standard dose regimens in practice today occur at a rate of 100-200 cGy per minute.
