The process of delivering pulsed-dose-rate (PDR) brachytherapy is similar to HDR, but radiation is delivered in short 'pulses' over several hours. The principle behind PDR is that it is biologically similar to traditional low dose rate (LDR) techniques where sources are manually loaded into catheters and applicators. The source is left in place for a number of hours or days. Because PDR uses a remote controlled afterloader, it promotes radiation safety, prospective planning, and precise dose shaping.
In contrast to the HDR technique, PDR treatments are delivered on an in-patient basis and require a dedicated shielded treatment room where a patient can stay for up to a day. Controlling applicator movement during that time adds another level of challenge. In order to allow visitors and staff to interact with the patient, PDR equipment typically has a treatment an interrupt capability which allows the source to automatically be returned to the afterloader while nurses, hospital staff, and visiting family members are in the room.
Outside the United States, Varian supports PDR techniques with the GammaMedPlus™ HDR/PDR afterloader, BrachyVision™ treatment planning system, and applicators & accessories.