About Calypso GPS

Virginia Hospital Center in Arlington was the first cancer program in the region to offer the Calypso™ 4D Localization System for treating cancer. This unique radiation targeting technology, developed with the help of our radiation oncologists and urologists, works like a GPS system. It determines the exact position and movement of the prostate during radiation therapy treatment – optimizing radiation targeting and minimizing side effects.

Why Organ Motion During Radiation Therapy Matters

Your organs move naturally during therapy and the prostate occasionally moves outside of the intended radiation field during treatment. Since your doctor can’t predict which way – or how much – your organs will move, the tumor may not get the right amount of radiation. In addition, other nearby tissue and organs may receive radiation they shouldn’t receive.

The Calypso System offered at Virginia Hospital Center, uses radiofrequency waves that allow very accurate alignment of your prostate before each treatment session. This technology now makes it possible to determine the position of the prostate at all times during treatment delivery and make adjustments, as needed, to optimize external beam treatment delivery.


Calypso allows your doctor to know exactly where the tumor is at all times. This means your radiation therapy is more precise – making sure all the necessary radiation gets to your tumor and minimizing side effects, such as impotence, incontinence and rectal bleeding. Currently, no other realtime method for precisely tracking tumor location during radiation therapy exists.

Virginia Hospital Center is ranked one of America’s top 100 Hospitals, including our top rankings and national accreditation in Radiation Oncology by the American Board of Radiology and American Society of Radiation Oncology. Drs. Hong and Nasr are also one of the few Radiation Oncologists in the region who are skilled to place the GPS Beacons themselves in their dedicated outpatient procedure room.  To meet with one of our physicians and learn if the Calypso 4D Localization System is right for you, call 703-558-6284.

How it Works

  1. Three tiny Beacon® electromagnetic transponders are implanted into your prostate in an outpatient procedure, similar to a biopsy, by either Dr. Hong or Dr. Nasr. Each transponder is about as small as a grain of rice.
  2. The Beacon transponders communicate with the Calypso 4D Localization System™ using safe radiofrequency waves.
  3. Your prostate is monitored during treatment by the Calypso System, showing exactly where the target is at all times. This allows your doctor to make quick, important decisions about your care.

More information can be found here.