HDR brachytherapy involves placing a single high-strength radioactive source next to or inside the tumor for a short period of time, usually a few minutes, and then removing it. Typically, doctors use catheters or needles — usually called "applicators" - to direct the radioactive source to the tumor, though it depends on the area of the body being treated; in some instances, catheters may not be necessary.
HDR brachytherapy is often used to treat gynecological, lung, breast, prostate, and head and neck cancers. It is usually performed on an outpatient basis, meaning the patient does not need an overnight stay in hospital. Only a few outpatient sessions of treatment are typically needed (1 to 5), which can take place over a period of a few hours, days or weeks.
LDR brachytherapy requires that sources of radiation are placed inside the tumor permanently. This type of brachytherapy is mostly used in the treatment of prostate cancer — sometimes known as "seed therapy." For prostate treatments, the radiation sources look like tiny seeds, about the size of a grain of rice. The level of radiation given out by the seeds gradually decreases over time to almost nothing. Most of the radiation is released over 3 months, and by 9 months, the seeds are practically inactive.
In addition to LDR and HDR brachytherapy, radiation can also be delivered in short pulses of radiation (e.g. once an hour) over a total period of up to 24 hours. This is termed "pulsed dose rate" or PDR brachytherapy. PDR brachytherapy is often used to treat gynecological and head and neck cancers.