Prostate Permanent Seed Implants
Radioactive seed implants, sometimes called low dose rate brachytherapy,
are a form of radiation therapy for prostate cancer. The radiation oncologist
implants radioactive seeds into the prostate gland using an ultrasound
for guidance. The number of seeds and where they are placed is determined
by a computer-generated treatment plan tailored for each patient. Anywhere
from 40 to 100 seeds are commonly implanted.
Patients who pursue low dose rate brachytherapy as their prostate cancer
treatment will undergo an important planning stage. A radiation oncologist,
urologist, and physics team plan and map the prostate gland to ensure
the seeds are implanted in the correct locations. During the mapping process,
a radiation oncologist and a physics team use a transrectal ultrasound
(TRUS) to take pictures of the prostate and surrounding organs every five
millimeters. This imaging takes about 15 minutes.
After drawing the area that needs to be treated, the oncologist writes
a prescription indicating the amount of radiation needed and gives the
prescription and images to the physics team. This planning process takes
place either in the weeks before the minimally invasive surgery or as
part of the surgical procedure. Your doctor will explain which approach
will be right for you.
The implants remain in place permanently, and become biologically inert
(no longer useful) after a period of months. This technique allows a high
dose of radiation to be delivered to the prostate with limited damage
to surrounding tissues.