Continuous Nonionizing Localization

The Calypso 4D Localization System uses implanted markers and an AC electromagnetic system to track a tumor?s movement within the patient?s body.

The Calypso 4D also called GPS for the Body, is the only continuous tumor-localization system for radiation therapy that does not use ionizing radiation. It was given 501(k) clearance by the US Food and Drug Administration on July 28, 2006. The system, made by Calypso Medical Technologies Inc (Seattle), uses implanted markers and an AC electromagnetic system that tracks their positions to provide monitoring of a tumor’s movement within the patient’s body.

The patient’s overall radiation dose for a course of therapy will probably be lower if ionizing forms of localization are used less often. The Calypso system generates no image; instead, it tracks, with submillimeter accuracy, transponders permanently implanted in the tumor. Unlike the several forms of pretreatment and post-treatment imaging in common use for radiation therapy, Calypso also provides localization data during treatment. This provides reassurance that the radiation beams are reaching their therapeutic target but are not damaging the surrounding tissue.

The manufacturer has identified applications for Calypso in treating cancers of the head and neck, abdomen, breast, lung, and prostate. Eventually, the system is expected to be useful for tracking the movement of tumors throughout the body.

Because Calypso uses no radiation, a technologist can remain with the patient throughout pretreatment preparations. The Calypso data on tumor location can be understood clearly by those who have no experience in interpreting images, potentially making more radiologist time available. Workflow within the radiation-therapy department is likely to improve because this technology’s use reduces patient-setup times significantly. This, in turn, also can allow more efficient use and scheduling for the radiation-therapy equipment/room.

The Spec Sheet

  1. Transponders: wireless Beacon transponders, detected by Calypso, are small resonant circuits implanted in or near the target tumor.
  2. Console: in the treatment room, the console (processor, power source, control panel, and AC electromagnetic array) sends target data to the tracking station.
  3. AC electromagnetic array: this energy source detects transponder coordinates by exciting the Beacons.
  4. Infrared optical system: ceiling-mounted infrared cameras in the treatment room are signaled by the AC electromagnetic array?s optical targets to verify the array?s position in the room.
  5. Tracking station: produces daily tumor-motion reports in addition to displaying tumor position continuously.

The Visible DIfference

The constant availability of precise target data allows the expansion of treatment options for radiation-therapy patients, possibly reducing the total number of treatment days. Real-time information also can help Calypso users minimize the adverse effects of radiation therapy for their patients, since healthy tissues are more likely to be spared when the tumor’s exact location is known before and during treatment. Because the system shortens patient-setup time by about 5 minutes, busy radiation-therapy departments may experience gains in efficiency.