As an equally effective, non-surgical treatment of all stages of prostate cancer, radiation therapy remains a mainstay of prostate cancer treatment today. As technology has evolved, so has the field of radiation oncology. Perhaps the most important advancement have been the development of Intensity Modulated Radiation Therapy (IMRT) and Image Guided Radiation Therapy (IGRT).

Intensity Modulated Radiation Therapy
IMRT is an advanced, computer driven method of delivering radiation. Historically, each of the beams used to treat the prostate would encompass the prostate entirely. And though this technique, termed 3D conformal radiation therapy (3D CRT), worked well, IMRT has proven to be better. With IMRT, each beam treats different parts of the prostate and with varying amounts of radiation, as determined by a computer. And though this may seem counterintuitive, this technique results in the ability to deliver more dose to the prostate while reducing the dose to the normal surrounding structures, such as the bladder and rectum.

Imaged Guided Radiation Therapy
Through a number of clinical studies, we have learned that despite immobilization of the patient, the prostate moves. And as we deliver higher doses of radiation to the prostate with IMRT, it is crucial that the prostate remain in the correct location so that it, and not the adjacent bladder or rectum, receive these high doses.

There are a number of methods that, on a daily basis, allows one to verify the position of the prostate, just prior to the beginning of the treatment. This includes Tomotherapy, which utilizes a CT image, or On Board Imaging (OBI) which utilizes an x-ray image, of the prostate. In both cases, the location of the prostate is verified, and corrected if necessary, before the treatment starts. However, neither method is able to monitor the location of the prostate during treatment, which may last up to 10 minutes. In addition, each method inherently exposes the patient to additional, albeit minimal, radiation. Finally, each method relies on a subjective interpretation of the images obtained, one that may vary from physician to therapist.

Calypso 4D Localization System
With Calypso, better known as "GPS for the Body", we are able to monitor the location of the prostate at all times. It is not uncommon for the prostate to move during treatment (also known as intrafraction motion) as a result of changes in the bladder or rectum or simply because the patient relaxes, becomes tense, or coughs. And this movement, which can range from a few millimeters to over a centimeter, results in the prostate being out of position. Thus, with the Calypso System, we can ensure the prostate remains exactly where it needs to; and if it moves, we can bring the prostate back into position! Even more impressive is that all of this is accomplished without the need for x-rays or CTs, thus limiting the exposure to additional radiation. In addition, foregoing CTs and x-rays and the subjective interpretation of them allows the treatment to be delivered more quickly and efficiently.

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