Radiation Exposure from CT Imaging

Position Statement from Cooper Aerobics Center

Topic: In the September 2004 issue of the journal Radiology is an article by David Brenner, Ph.D., DSc, and Carl Elliston titled "Estimated Radiation Risks Potentially Associated with Full-Body CT Screening." This article has received much publicity, and has raised concerns regarding the safety of CT scanning. It is important to interpret this report in the context of safe and appropriate medical imaging.

Dr. Kenneth Cooper and colleagues respond to this claim with the following comments:

• The scanners listed in the report are multi-detector row CT scanners. Cooper Clinic uses a different technology, electron beam tomography (EBT), which delivers a lower-absorbed dose to patients. Also, the radiation that is used passes through the patient from back to front, so that the critical organs on the front side of the patient (eyes, thyroid glands, breasts) have a lower absorbed radiation dosage than with CT scanners in which the X-ray tube circles the patient.
  
  
• The article compares the radiation dose from an atomic explosion with the controlled dosage from a limited spectrum used in medical radiography. There is only a limited comparison that can be made concerning qualitatively different spectra of radiation. The comparison is only theoretical and involves assumptions which may not be accurate. There are other theoretical constructs that disagree strongly with the assumptions in this article. For instance, the conclusion from the review article "Cancer Risk from Low-Level Radiation" (American Journal of Roentgenology 2002;179:1137-43) states:
  
  "The evidence presented in this review leads to the conclusion that the linear no-threshold theory fails badly in the low-dose region because it grossly overestimates the risk from low-level radiation. This means, for example, that the cancer risk from diagnostic radiography is much lower than is given by usual estimates, and may well be zero."
  
  
• A very important factor missing in the article is that there is abundant evidence that EBT saves lives and changes medical management, when included appropriately as part of comprehensive medical evaluations. EBT detects not only coronary artery disease and cancers, but also identifies many other potentially hazardous conditions which benefit from early detection. Taking cancers alone, we found 58 confirmed cancers among 15,651 Cooper Clinic patients scanned in 1999 and 2000. This is approximately three to four cases per 1,000 scans, which is comparable to the breast cancer detection rate with screening mammography. We believe this early detection has saved many lives.
  
  
• The article used the assumption that full body CT scans would be performed yearly, and this is seldom the case. Our provisional protocols do not include yearly studies, except in unusual circumstances where risk for abnormalities is greater. Even in these cases, often only limited scans are done of the area of interest.
  
  

For these and other reasons, we are confident that EBT as used at Cooper Clinic presents very small risks to patients. In our experience, this small theoretical risk is greatly outweighed by the diagnostic and therapeutic benefits to our patients.