Individualized Assessment of Radiation Dose in Patients Undergoing Coronary Computed Tomographic Angiography With 256-Slice Scanning

OBJECTIVES: Available data on the radiation burden from coronary computed tomography (CT) angiography (CCTA) are mostly limited to effective dose estimates. This study provides individualized estimates of doses and associated life attributable risks of radiation-induced cancer in a clinical patient population undergoing 256-slice CCTA.

 METHODS: Typical retrospectively and prospectively ECG-gated CCTA exposures in a 256-slice CT scanner were simulated on 52 patient-specific voxelized phantoms. Dose images depicting the dose deposition on the exposed region were generated, and normalized organ doses for all primarily irradiated radiosensitive organs were derived and correlated to patient body habitus. Lung, breast, and esophagus absorbed doses were then determined in 136 consecutive patients subjected to CCTA. Projected life attributable risks of radiation-induced cancer were estimated through the use of appropriate sex-, age- and organ-specific cancer risk factors and compared with corresponding nominal cancer risks. The total projected life attributable risk of radiogenic cancer after CCTA decreases steeply with age at exposure, and lung cancer constitutes the most probable detriment for both sexes.

RESULTS: The relative risks of lung cancer associated with prospectively ECG-gated CCTA were 1.0032 and 1.0008 for women and men, respectively. The mean total projected life attributable risks were estimated to be 24.9±7.4 and 71.5±30.0 per 100 000 women undergoing prospectively and retrospectively ECG-gated CCTA, respectively. The corresponding values for men were 7.3±1.3 and 31.4±5.0 per 100 000 patients.

CONCLUSIONS: The mean projected life attributable risks of radiation-induced cancer in a typical clinical patient cohort undergoing standard prospectively ECG-gated CCTA with a 256-slice scanner were found to inconsequentially increase the natural cancer incidence rates.

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PMID:

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4 Comments

  1. Elegant study, from bench to bedside, and showing the relatively low risk of radiation exposure with modern scanners.
    However, how low is “relatively low”?

    I once discussed the risk of CT radiation with one of my patients who’s an aeronautics engineer prior to CT exam. He told me that in his view, and according to aviation safety standards, anything that may cause harm to humans in a frequency of less than 1 to a million is considered unsafe…

  2. This study reminds me of a negligent study published in December 2009 in the Archives of Internal Medicine about CT radiation exposure and its link to cancer that made headlines in the mainstream media-and brought unwarranted concerns to the public. According to the study entitled, Projected Cancer Risks from Computed Tomographic Scans Performed in the United States in 2007; the use of CT scans in the United States, has increased to approximately 70 million scans per year, as compared with 3 million in 1980 and may cause 29,000 new cancers a year.

    The reason I use the word negligent the authors used 95% uncertainty limits (UL). The Uncertainty Limits Principle, explains, the more precisely one property is known, the less precisely the other is known. As it relates to their study, it’s a 95% chance a patient with cancer, did not receive cancer from CT; or in other words, only a 5% chance that they did. Meanwhile, that 5% does not take into account the patient’s exposure to natural background radiation and other factors such as occupation, family history, etc.

  3. Important study, which addresses issues related to dose measurements in modern wide z-coverage, volume scanners.

  4. Great article!

    One comment in the conclusions caught my attention: “Given that CCTA-related LARs of radiogenic cancer depend significantly on patient age, sex, and body habitus, individualized risk assessment based on organ dose calculations should be preferred against risk evaluation based on DLP-derived patient effective dose.

    Clinical studies recommend CCTA as a tool to exclude disease in low risk patients…. like younger patients. Females are also at a lower risk than males… Thin patients have a lower risk than obese patients… Quite the Catch-22 we find ourselves in; isn’t it. What are we supposed to do?

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