Radiation from medical imaging

Plagued by shoulder pain, especially at night, Jack was not happy with his orthopedist nor improved by physical therapy. Being a tightly wound sort, he'd come to the conclusion that the pain must be from cancer. I was happy to reassure him, as I'd done many times in the past, that he did NOT have cancer. Soothing the worried well (there's actually an ICD-9 diagnostic code for 'worried well') is one of the easiest parts of my day.

But Jack came back the following week, yet again shouldering grave doubts. A second opinion from another orthopedist confirmed the original diagnosis of a torn rotator cuff. So what was on Jack's mind? He was agonizing over the fact that Dr. Two took a repeat set of shoulder films. Not the unwarranted expense that now worried Jack, however, he was near tears over the possibility that this extra radiation would significantly increase his future risk of cancer.

So what's the scoop on medical imaging and cancer risk? Radiation from any source is not only a cancer inducer, turning healthy cells into pre-malignant ones, but also a cancer promoter which can push these compromised cells into a more abnormal state. Radiation danger is compounded through a lifetime of ionizing destruction; years of exposure compounding today's CT with yesterday's tan. If you'd like an estimate on your annual irradiation, check out the interactive quiz at American Nuclear Society's website.

If you're not an internet quiz type, let me inform you that a single CT scan can deliver a radiation dose equal to dozens of shoulder films. And there's no particular standardization here; radiologists can adjust their sets to enhance detail, and the higher the dose, the crisper the image. As a result, concerned specialists have banded together in various self-policing initiatives to rein in the rads, among them Image Gently setting guidelines for testing children and Image Wisely for adults. Nevertheless, the estimated annual number of CT scans in the US rose from 3 million in 1980 to 67 million in 2006 and the numbers continue to climb. Scarcely an ER visit goes by for one of my patients without an accompanying CT procedure. And one CT begets another when "incidentalomas" are found (unexpected abnormal findings of unclear significance) that require future scans to clarify their nature.

Based on data from survivors of the atomic bombings in war-time Japan, biophysicist David Brenner estimated the lifetime risk of cancer for a child undergoing a single abdominal CT as one in 1000. While other experts take issue with both his calculations and his conclusions, all agree that rads must be reduced.

One of the most innovative approaches comes from Mass General Hospital. Docs there created a rather complex program that scores the appropriateness of the choice of a diagnostic CT as compared to other imaging techniques for any particular clinical situation. The software shares this info with the ordering physician who is then offered the opportunity to change their minds and their orders. This software replaces the aggravating insurance pre-authorization procedures that Dr. James Thrall has dubbed "1- 800- may- I- do- a scan." Once this process was in place, CT use at MGH dropped considerably.

There is no doubt that CT technology has been critical to the accuracy of diagnosis since its inception. Pre-CT scanning (back when I was a doc-lette in training), diagnosing brain tumors involved a horrendous procedure wherein air was introduced into the spaces around the brain (as demoed graphically in "The Exorcist"). CT scans are perfectly appropriate even while over-ordered. Ask your doctor, however, what your other choices might be when offered such tests.

A rare complication of MRIs

I had an MRI last year as a screening test for breast cancer. MRI scanning with a contrast material called gadolinium is the best screen currently available for the cancer, and I received my negative results with a deep sense of satisfaction that, for the moment, I was free and clear.

While I have an internist's enthusiasm for ingested substances*, I have an abiding distaste for things injected. I will think long and hard about getting another MRI--I didn't mind the noise, no problem with the confined space, and I don't really mind IVs, it's the thought of another IV injection that stops me cold. And now, here's news of a new disease, rare but icky, we've created with gadolinium imaging technology.

Nephrogenic systemic fibrosis (NSF) was first described in 1997. Case series confirmed that NSF was confined to patients with renal insufficiency (diminished kidney function), and later determined to affect only those kidney patients who had undergone radiological imaging with gadolinium in the several months prior to developing hardened leathery skin. The fibrosis or connective tissue thickening and scarring associated with NSF binds up joints, lungs, heart, and diaphragm as well as the skin. The systemic involvement can be fatal.

By the time your kidney function is low enough to be at risk for NSF, you have already come to the attention of a specialist. Hopefully, no cases of NSF will appear in people not known to be at risk. This emerging syndrome reminds me, however, that there's no such thing as diagnoses for nothing' and MRIs for free**.
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*Coupled with a coming-of-age-in-the-'60s mentality
**Sorry Dire Straits!