IGRT and IMRT
External radiation delivered from a high energy X-ray
machine called a linear accelerator has been effectively used to treat prostate cancer for more than 30 years. In recent years,
there have been several major technological advances allowing cure rates that typically exceed those of surgery and proton
beam therapy, with far fewer side effects.
With intensity modulated radiation therapy (IMRT), sophisticated computers modulate the intensity of the radiation
beam, increasing it to areas where cancer cells reside, and decreasing it to areas that need to be protected. This allows
for maximum radiation to be delivered to the prostate and areas potentially harboring cancer cells, while minimizing radiation
to the bladder and rectum. Patients with intermediate to advanced stage prostate cancer have a high risk of having cancer
outside the prostate, beyond the surgeon's reach. Unlike surgery, IMRT can treat this area.
Image Guided Radiation Therapy (IGRT) takes IMRT one step further. Various imaging technologies such as Cone-beam
® CT scan and tracking of implanted gold fiducial markers are utilized before each daily treatment, to acquire a 3-dimensional
image of the prostate and surrounding anatomy. Computers detect any slight change in position of the prostate gland that may
result from movement or variations in filling of the bladder or rectum. Using this information, the computer adjusts the radiation
beam accordingly in order to precisely target the treatment to the prostate's exact position that day. Changes as small as
1 millimeter are made to provide the greatest precision available. IGRT is the newest and most advanced system for the delivery
of radiation, allowing much greater precision than proton therapy.