CT Scan vs. MRI: Which is safer for those with cancer?

When I learned in January 2017 that my colon cancer had metastasized to my liver, my oncologist, Dr. G, suggested (in addition to 4 rounds of chemo, surgery, and up to 8 more rounds of chemo) a series of scans to monitor the status of my cancer. CT scans of my abdomen and lungs were immediately taken to determine the location of any tumor(s). One tumor was detected on my liver; no other tumors were seen.

Dr. G then referred me for a PET Scan. I'd never had a PET scan and knew nothing about the procedure or possible risks. I was still in a state of shock over my Stage IV-A metastatic diagnosis (and end-of-year death sentence if I did not submit to the chemo / surgery regimen). So, I compliantly agreed to the PET scan. There was a caveat, through. Badger Care (my insurance) would have to approve the scan. A week later I was told that Badger Care refused to pay for the scan because of its cost.

That's when I decided to do some research. What I discovered shocked and upset me!

We are constantly exposed to radiation from natural sources. This exposure is known as "naturally-occurring 'background' radiation exposure" ("background radiation exposure"). It is estimated that the average U.S. resident receives an effective radiation dose of about 3 mSv per year. This radiation occurs naturally in our environment, and varies in amount throughout the county.

A medical physicist at Johns Hopkins Hospital in Baltimore, Maryland, has created a chart of the approximate amounts of effective radiation doses for adults and compared that with the background radiation exposure received from X-ray, CT scans and PET scans. In other words, how long would it take an adult to receive the same amount of radiation from naturally-occurring radiation exposure as they would from a scan?

For example, a dental intraoral x-ray is 0.005 mSv, which is comparable to 1 day of natural background radiation. Not so bad, eh?

Here's where it gets not only bad, but downright scary!

• For a CT of the abdomen and pelvis (standard for colon cancer) is 10 mSV, comparable to 3 years natural background radiation.

• Repeat the CT of the abdomen and pelvis and the numbers jump to 20 mSv, comparable to 7 years natural background radiation!

• A CT scan of the chest (required after metastasis to make sure the cancer has not also spread to the lungs), 7 mSv, comparable to 2 years natural background radiation.

• A PET scan's effective radiation dose is 25 mSv, comparable to 8 years natural background radiation!

I presented for a CT scan of the abdomen on January 5th -- exposing me to the equivalent of 3 years of natural background radiation.

I presented for a CT scan of the chest on 12th (just one week later) -- exposing me to the equivalent of 7 more years of natural background radiation

And Dr. G wanted me to have a PET scan to follow-up with the two CT scans -- exposing me to the equivalent of 8 years of natural background radiation.

That's the equivalent of 18 years of natural background radiation in less than a month!!!!! How could that be good for me!?

I also learned that radiation from CT scans is harmful and repeated scans can even cause cancer. In a February 2014 New York Times OP-ED article entitled, We Are Giving Ourselves Cancer, it was reported that:

The radiation doses of CT scans (a series of X-ray images from multiple angles) are 100 to 1,000 times higher than conventional X-rays.

A single CT scan exposes a patient to the amount of radiation that epidemiologic evidence shows can be cancer-causing. The risks have been demonstrated directly in two large clinical studies in Britain and Australia. In the British study, children exposed to multiple CT scans were found to be three times more likely to develop leukemia and brain cancer. In a 2011 report sponsored by Susan G. Komen, the Institute of Medicine concluded that radiation from medical imaging, and hormone therapy, the use of which has substantially declined in the last decade, were the leading environmental causes of breast cancer, and advised that women reduce their exposure to unnecessary CT scans.

(emphasis added)

Did you see that? The Susan G. Komen Foundation determined that radiation from medical imaging and hormone therapy were the leading environmental causes of breast cancer!

I knew this 25 years ago, when I was in my 30's. My health insurance company began insisting I start getting mammograms. My father, with a Ph.D. in organic chemistry and who had worked in cancer research in the early 1960's, told me not to get a mammogram because it would cause me to get breast cancer. I did not have a mammogram until two years ago (at age 58) -- as follow up to the 2011 colon cancer diagnosis.

Back to our original topic . . . 

Radiation doses of CT and PET scans are 100-1,000 times higher than conventional x-rays, and exposure to large amounts of radiation can cause cancer!!!!! So then why are procedures using high amounts of radiation being used to diagnose cancer?????

This is the kind of withheld information that really pissed me off!!! Dr. G never had a conversation with me about levels of radiation and the inherent risks. In fact, when we did have a chance to discuss what I had uncovered in my research, he assured me not properly diagnosing my cancer was a far greater risk than the radiation in the scans.

Turns out, that's not exactly correct. For a patient like me with Stage IV-A metastatic colon cancer, the MRI has many advantages over the CT scan.

• First and foremost, the CT scan uses x-ray, plus the patient is given . The MRI uses  a magnetic field to capture the pictures.

• There can be side effects from the CT scan radiation and iodine contrast (injected into the patient via IV); there are no known side effects from an MRI, which is completely non-invasive.

• When detecting and identifying a tumor, the MRI is generally superior to a CT scan. While an MRI can be more expensive (up to $4,000) than a CT scan ($1,2000-$3,200), it's not by much, especially when considering the risk factors to cancer patients.

• The MRI provides a more-detailed look at soft tissue because the MRI has the ability to produce images "in any plane" without moving the patient.

This is a great video from Bellevue Medical Center that explains the difference between the CT scan and the MRI.

Sadly, the new oncology facility I go to does not have the 1.5 Tesla MRI scanner with the larger, less-claustrophobic MRI machine. I was crammed into a tiny tunnel, found the MRI very uncomfortable, and did not like it. But, I'd also developed a crush on my radiologist with a Scottish brogue, and that made the experience more palatable. Plus, I knew I wasn't subjecting my cancer to a cancer-causing scan, and that gave me peace of mind.

I'm on a new diagnostic schedule with my new oncologist, Dr. Y. I had an MRI on March 14th. The MRI shows very different measurements of the tumor than what was diagnosed from the CT scan. Two of the measurements are much smaller, one is .2 larger! But, comparing the CT scan and the MRI, because the MRI provides a different look -- a more detailed look, a superior look -- at the tumor, the only way to really know whether or not the tumor is shrinking is to have another MRI in 6-8 weeks.