Doctors using Iowa’s first “Cyber-Knife” machine say it’s a valuable tool for some kinds of cancer and other medical problems. Doctor Richard Deming is medical director at the Radio Surgery Center at Mercy Iowa Clinic in Des Moines, and has been using the new machine. The generic term in today’s medicine is stereo-tactic radio-surgery, using 3-dimensional techniques to give a high dose of radiation precisely to a tumor while giving a low dose to surrounding structures. The normal tissue the X-ray beam passes through, he explains, receives a very low dose, but where the beams converge in the tumor, it gets a very high dose. In more conventional radiation therapy, a beam of X-rays may help kill a cancerous tumor but often exposes nearby parts of the body to the deadly radiation also. He explains it could be a case where a tumor’s pressing on the spinal cord, or a brain tumor very close to where nerves to the eyes pass by. Dr. Deming says the “Cyber-Knife” allows doctors to aim a dose of radiation right at the tumor and avoid those delicate structures nearby. The device, developed at Stanford University, is different in some ways from other stereo-tactic radio surgery systems. It’s a miniature linear accelerator mounted on a robotic arm. A computer directs that arm into any of 1,200 different positions around the patient so the doctors can focus it from many different directions. More than 30 patients have been treated with the CyberKnife since early April when they got the machine, and Dr Deming says while it’s still only one of the tools available to doctors, for some cases it offers options they never had before.