The use of computed tomography, or CT scans, has increased more than 20 times since 1980. They are used in every hospital, every day. The doctors we spoke with say they are overused.
"I believe I've been exposed to too much radiation," Bryan Cross said.
Cross, a 44-year-old San Jose resident, was diagnosed with colon cancer in 2009. He had surgery to remove it, but not before the cancer spread to his liver. In the course of his treatment, he says he's received 17 CT scans, about four per year.
Depending on the type of CT scan, the radiation dose can be 100-500 times more than an X-ray.
"I used to joke around and say that, you know, that I would glow in the dark," Cross said.
Cross is concerned that each of the 17 times he was exposed to radiation, makes it more likely he'll get a new cancer.
"I know that I have cancer but I don't look forward to an additional cancer," he said.
Studies have linked CT scans to higher risks of cancer. A study in The Lancet medical journal last June suggests kids who receive 2-3 head CT scans before the age of 15 might have triple the risk of brain tumors.
Cross says he was never told about a cumulative risk from CT scan radiation.
"I'm the patient and I go there for help and I go there to get well, I don't go there to get more problems," he said.
The I-Team showed some of Cross' CT scan results to Dr. Rebecca Smith-Bindman, a specialist on radiology and biomedical imaging at the University of California, San Francisco. She has never treated Cross, but has been a critic of the overuse of CT scans.
"Some of them looked reasonable and some of them didn't look like it was going to help very much," Smith-Bindman said.
Smith-Bindman says multiple CT scans are common and sometimes needed. But she says doctors and patients need to know the risks before any test is done.
"The risk of any one test is relatively low, so not a big risk, but the risks are additive," she said. "So if you've had 17 CT Scans the risk is getting up there to a place where it's a real possibility that the patient can develop cancer directly in response to the DNA changes from that CT scan."
A study published in the New England Journal of Medicine in 2007 estimated CT scans accounted for up to 2 percent of all cancers in the United States. Smith-Bindman says that number could now be 5 percent.
"Somehow we have blown out of proportion and out of context the radiation risk from CT scans," Dr. Michael Brant-Zawadzki said.
Dr. Michael Brant-Zawadzki is a radiologist and executive director of neurosciences at Hoag Memorial Hospital in Newport Beach. He points out that the cancer rate is down slightly and says there is no evidence CT scan radiation has a cumulative effect, that radiation from multiple CTs shouldn't be added up to one big dose -- each event is separate, done at different times, allowing the body to heal between tests.
He uses a sunburn analogy.
"If you stood there for an hour, one dose, you get red blistered skin, whereas if every week or so you go out for five minutes twelve weeks, an hour's worth of exposure, nothing happenings," Brant-Zawadzki said.
Brant-Zawadzki adds that even if there is a small cancer risk with CT scans, the benefit outweighs the risk.
"The need to destroy the cancer is much greater than the slight concern from a CT scan being used to monitor whether or not the treatments being effective," he said.
"That's my dilemma," Cross said. "I don't know how to weigh saving somebody's life and then potentially them dying later."
Cross has one more problem. In a letter last month, his oncologist told him to find someone else, writing, "There had been a breakdown in our therapeutic relationship," "I recommended that you find another oncologist," and "You will need to do so within 30 days."
That's leaving Cross without a physician and the worry more cancer is in his future.
"I can't help but think about how many CT Scans I've had," Cross said. "It scares me but, all you can do is have hope. It's the last thing to go."
Both doctors the I-Team spoke with said CT scans save lives but are over-used and the radiation dose needs to be low. A patient can always ask if other tests that don't use radiation, like MRI or ultrasound, that can be used instead of a CT scan.