Letter by Bardo Regarding Article, “Cumulative Radiation Exposure and Cancer Risk Estimation in Children With Heart Disease”
To the Editor:
It was with great interest that I read the article by Johnson et al1 that was published recently in Circulation. As a board-certified pediatric and cardiac radiologist, I thank them for highlighting the importance of cumulative radiation dose in children with congenital heart disease. However, the computed tomography (CT) data presented do not reflect best practices currently available, and the emphasis on lifetime attributable risk of cancer from medical radiation exposure is possibly misleading.
The recent literature shows cardiac CT performed on current-generation scanners with aggressive dose reduction techniques to be 1/10th of catheterization dose and <5% of the dose listed in this article, even when size and age are adjusted.2 With new technology and a scan technique tailored to the patient, the effective dose and risk of cardiac CT are far less than what is reported by Johnson et al1 and should be the goal for all programs going forward with increased awareness to decrease cumulative diagnostic risk.
Table 3 in the article by Johnson et al1 shows that average effective dose attributed to cardiac CT was 18.28 mSv in 21 exams performed in their population of 337 children <6 years of age. To attain this effective dose it is likely that the retrospective scan technique, with adult kV, mA, and other settings, was performed on an outdated scanner. Indeed, Table I in the online-only Data Supplement in the article by Johnson et al1 lists references from which dose estimates were culled, including the retrospective technique performed on a 16-multiple detector CT scanner by Hollingsworth et al3 and exclusively adult patients by Einstein et al.4
The concept of lifetime attributable risk of cancer from radiation exposure is based on data from studies of 4 populations, including atomic bomb survivors, patients undergoing radiation cancer treatment, workers exposed to occupational radiation, and people exposed to high levels of environmental radiation by virtue of living near a nuclear energy facility or atomic bomb testing site. Conclusions regarding lifetime attributable risk in the Biological Effects of Ionizing Radiation VII document5 are partially based on assumed modifying parameters that were decided by committee rather than fact or absolute truth, use various risk models for different organs, and are based on having received a single 1-time dose of 100 mGy (1 Gy).
None of these assumptions fit or model any patient undergoing diagnostic levels of medical radiation. Therefore, outdated CT effective dose data, which implies that cardiac CT is a high-dose examination and is a major contributor to lifetime attributable risk in young children with congenital heart disease, may in combination only serve to perpetuate fear of an imaging modality that has become an important contributor to the diagnosis and care of patients with complex congenital heart disease.
Benefits of an indicated cardiac CT examination to define anatomy or even to assess function far outweigh the very small risk of malignancy when appropriate dose management techniques are used, on modern CT scanners, by imaging physicians who are experts in both the imaging modality and the intricacies of complex congenital heart disease.
Dianna M. E. Bardo, MD
Radia Inc., PS
Swedish Medical Center
Seattle, WA and Chicago, IL
- © 2015 American Heart Association, Inc.
- Johnson JN,
- Hornik CP,
- Li JS,
- Benjamin DK Jr.,
- Yoshizumi TT,
- Reiman RE,
- Frush DP,
- Hill KD.
- Einstein AJ,
- Moser KW,
- Thompson RC,
- Cerqueira MD,
- Henzlova MJ.
- 5.↵Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation; Nuclear and Radiation Studies Board, Division on Earth and Life Studies, National Research Council of the National Academies. Health Risks From Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2. Washington, DC: The National Academies Press; 2006.