What does satellite navigation and prostates have in common? First, they can both be manipulated with one’s finger, and now satnav technology is being used to guide radiotherapy for prostate cancer.
Using a form of global positioning software, the technique pinpoints cancer cells rather than healthy surrounding tissue.
The radiotherapy could spare men the damaging effects of radiation zapping vital organs such as the colon or bladder, which can leave patients with side-effects such as bowel problems and bleeding.
The new “sat nav” radiotherapy device, called Calypso, has already been approved for use in the U.S. by the Food and Drug Administration, and can direct X-rays to within a fraction of a millimetre of their target.
To begin with, surgeons insert a probe through the rectum and implant three tiny transmitters into the prostate. These are placed in a triangle formation around the site of the cancer.
As the treatment gets under way, the Calypso is moved into position. It has an extending arm with a large square plate on the end which is lowered over the body.
As this plate delivers the X-rays, it monitors the signals from the tiny transmitters at a rate of 60 times a second.
By tracking the signals, the device is able to target the harmful rays to the space between the three transmitters – ensuring only the cancerous cells are affected.
The radiotherapist, meanwhile, sits in another room a safe distance from the harmful rays and tracks the progress of the treatment on a computer screen.
If the patient moves even a few millimetres, the signals are lost and the machine sounds an alert to the operator to stop treatment.
Although the Calypso device is only approved for prostate cancer so far, it could eventually be used for any kind of solid tumour that needs radiotherapy.
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