Focus on CT Effectiveness, Not Its Theoretical Risk

CHICAGO - Every so often, a sudden flurry of articles proclaiming the dangers of radiation dose from CT hits newspapers and magazines, warning patients to resist when their doctors recommend the study. It’s now time for radiologists to start pushing back and having conversations with patients about what CT actually does, industry experts said.

The problem, Michael McNitt-Gray, PhD, a radiological sciences professor at the David Geffen School of Medicine at UCLA, said at this year’s RSNA annual meeting, is that patients - and many providers - don’t understand what CT dose actually means. Consequently, many are vastly overestimating levels of radiation exposure.

That’s why open communication between physician and patient is so critical, said Cynthia McCollough, PhD, biomedical engineering and medical physics professor at the Mayo Clinic in Minneapolis. If providers don’t discuss the significant benefits of CT weighed against its relatively minor, and unverified, radiation risk, patients could forgo studies that might help them avoid a fatal disease.

In fact, McCollough said, her practice sees a substantial number of canceled CT appointments when media reports about radiation risk appear.

“Referring physicians and patients need to know that reducing the use of CT will delay care - our modalities will be clogged, trying to handle the additional volume of studies,” she said. “They won’t know why CT is important if we don’t tell them.”

Education is key to reducing the public’s fear about radiation exposure. And, McCollough recommended having one-on-one conversations when possible and disseminating specialty-specific brochures about the benefits of CT to patients.

It’s also important to reassure patients that radiologists are adhering to the ALARA principle for dosing levels - As Low As Reasonably Achievable. But providers should be wary of swinging the dose pendulum too far. Extremely low doses will negate the test’s efficacy, she said.

For some patients and providers, however, demonstrating low-dose fidelity won’t be enough. In those cases, it can be beneficial to discuss the American College of Radiology (ACR) Appropriateness Criteria that regard CT as an optimal modality for several studies in many disciplines, including neurology, cardiothoracic, vascular, gastroenterology, and urology. In fact, 30 percent to 60 percent of the time, ACR deems CT to be one of the most appropriate for studies, and 10 percent to 40 percent of the time, the ACR considers it the most appropriate study.

It’s also important for patients to understand that multiple CT scans do not increase their cumulative risk of developing cancer, said Robert Dixon, PhD, owner of Radiological Physics Consultants in Winston-Salem, NC.

“Repeated CT scans are not at all like chopping down a tree,” he said. “Each axe blow weakens the tree until it topples with the last blow. That doesn’t happen with CT.”

For example, a patient who undergoes an abdominal CT scan has a 1 in 3,000 chance of developing cancer from that scan within the next 20 to 40 years. And, contrary to what many patients believe, those odds remain the same with each subsequent exam, Dixon said.

“Cumulative dose history is not useful at all as a basis for clinical decisions about whether to order a CT scan for the patient,” he said. “It can only bias patient care negatively.”

Even though the profession will continue to debate CT’s actual radiation risk, McNitt, McCollough, and Dixon all agreed it is incumbent upon radiologists to consistently advocate for the clinical effectiveness of CT scans and debunk the misconceptions that plague the modality.

“The evidence of any risk associated with CT exposure is and will remain controversial and will be debated for a long time,” McCollough said. “But we can’t continue to discuss small, hypothetical risks without emphasizing the large set of documentation that outlines CT’s benefits.”