From the Chief Medical Officer's Desk
by Dr. David Edwards
“If ignorance is bliss, then I am the happiest man in the world.” ~Written on the board at Jefferson Medical College 1978 just prior to the Anatomy Final Exam.
Recent articles in the literature have highlighted an area of potential ignorance of the medical profession in recent years: radiation exposure to patients from diagnostic testing.
We have always been concerned about radiation, especially with children and pregnant women but we didn’t really think about this too much in other groups. A year ago, articles appeared in the news about excessive radiation exposure due to errors in CT scan programming and maintenance. We tried to take solace as these were isolated events and our machines checked out fine. But an article in the Archives of Internal Medicine calculated 29,000 future cancers attributable to CT scanning in 2007 alone (Arch Intern Med. 2009;169(22):2071-2077).
The Dartmouth Atlas and other works have documented significant regional variation in the delivery of healthcare and use of healthcare resources. As they say, all medicine is local and we learn from one another in our contacts with colleagues in the hospital but not from those in another state or across the country. Banner has been using the Premier database to look at variation occurring in our hospitals compared other areas in the United States. We found that we have a higher rate of CT scan use for simple pneumonia yet our outcomes and readmissions are no better. Sharing the data with physicians has had a powerful effect as our CT usage has decreased, with no change in outcomes.
But the CT issue is not isolated to just simple pneumonias because it is a commonly used diagnostic test. It is hard to quantify risk for radiation exposure as it varies with the time, type of radiation and other factors. However, according to the BEIR subcommittee, they recommend using an additive and linear model with no minimum risk threshold in calculation of radiation exposure and subsequent risk.
To put things in perspective:
- Background exposure (radon) ~ 3.6 mSv/year
- 6 hour commercial airline flight ~ 0.03 mSv
- Pregnancy Exposure: < 5mSv recommended
- Bone marrow suppression ~ 50 mSv
- Chernobyl LD 50 ~ 1.4 Gy = 1400 mSv
|Dose Range |
|CXR, PA & Lat||0.1||0.05 – 0.24|
|CT Chest||7||4 – 18|
|CT Angio||15||12 – 18|
|Ventilation/Perfusion Lung Scan||37||30 - 45|
|Pulmonary Angiogram||50||40 – 60|
|CT Abd||8||4 - 25|
|CT Pelvis||6||3 - 10|
|Coronary CT Angio||16||5 -32|
|PET/CT||25||20 - 30|
|Barium Enema||7||6 - 10|
|Fluoroscopy||8.3 /hr avg|
Having been educated prior to the CT scan, I appreciate the improved diagnostic accuracy that CTs afford. But now, just as we do for other procedures and therapies, we need to weigh the risks and benefits of CT scanning, especially for those patients who have had multiple CTs in a narrow time window with no significant changes. We must understand that we all have a contribution. “No snowflake blames itself for the avalanche.”