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Medical Physics / Volume 38 / Issue 12 / MEDICAL PHYSICS LETTERS

Med. Phys. 38, 6654 (2011); http://dx.doi.org/10.1118/1.3660592 (5 pages)

An approach to assessing stochastic radiogenic risk in medical imaging

Anthony B. Wolbarst

Department of Radiology, College of Medicine and Division of Radiation Sciences, College of Health Sciences, University of Kentucky, Lexington, Kentucky 40536

William R. Hendee

Department of Radiology, Mayo Clinic, Rochester, Minnesota 55901

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(Received 29 August 2011; accepted 25 October 2011; revised 25 October 2011; published online 28 November 2011)

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Purpose: This letter suggests a formalism, the medical effective dose (MED), that is suitable for assessing stochastic radiogenic risks in diagnostic medical procedures.
Methods: The MED is derived from radiobiological and probabilistic first principals, including: (1) The independence of radiation-induced biological effects in neighboring voxels at low doses; (2) the linear no-threshold assumption for stochastic radiation injury (although other dose-response relationships could be incorporated, instead); (3) the best human radiation dose-response data currently available; and (4) the built-in possibility that the carcinogenic risk to an irradiated organ may depend on its volume. The MED involves a dose-risk summation over irradiated voxels at high spatial resolution; it reduces to the traditional effective dose when every organ is irradiated uniformly and when the dependence of risk on organ volumes is ignored. Standard relative-risk tissue weighting factors can be used with the MED approach until more refined data become available.
Results: The MED is intended for clinical and phantom dosimetry, and it provides an estimate of overall relative radiogenic stochastic risk for any given dose distribution. A result of the MED derivation is that the stochastic risk may increase with the volume of tissue (i.e., the number of cells) irradiated, a feature that can be activated when forthcoming radiobiological research warrants it. In this regard, the MED resembles neither the standard effective dose (E) nor the CT dose index (CTDI), but it is somewhat like the CT dose-length product (DLP).
Conclusions: The MED is a novel, probabilistically and biologically based means of estimating stochastic-risk-weighted doses associated with medical imaging. Built in, ab initio, is the ability to link radiogenic risk to organ volume and other clinical factors. It is straightforward to implement when medical dose distributions are available, provided that one is content, for the time being, to accept the relative tissue weighting factors published by the International Commission of Radiological Protection (ICRP). It requires no new radiobiological data and avoids major problems encountered by the E, CTDI, and CT-E formalisms. It makes possible relative inter-patient dosimetry, and also realistic intercomparisons of stochastic risks from different protocols that yield images of comparable quality.

© 2011 American Association of Physicists in Medicine

ACKNOWLEDGMENTS

The authors wish to thank Patrizio Capasso, MD, DSc, for suggesting the quantification by CT of the relative volumes of breast glandular and other tissues. The authors also thank our two referees for their very helpful comments.

Article Outline

  1. INTRODUCTION
  2. METHODS AND THEORY
  3. DISCUSSION
  4. CONCLUSION
Digital Object Identifier
http://dx.doi.org/10.1118/1.3660592

KEYWORDS and PACS

Keywords

ab initio calculations, biological effects of ionising radiation, biological organs, biological tissues, cellular biophysics, computerised tomography, diagnostic radiography, dosimetry, phantoms, stochastic processes, probabilistic risk assessment, stochastic risk, dose distribution, effective dose, CTDI

PACS

PUBLICATION DATA

ISSN

0094-2405 (print)  

Publisher

$abstract.society.value is a Member of CrossRef American Association of Physicists in Medicine

  1. AAPM, “The measurement, reporting, and management of radiation dose in CT,” Report No. 96 (2008), http://www.aapm.org/pubs/reports/rpt_96.pdf.
  2. “The CTDI paradigm: A practical explanation for medical physicists” (2010), http://www.imagewisely.org/~/media/ImageWisely/20Files/Medical/20 Physicist/20Articles/IW/20Dixon/20Boone/20CTDI/20Paradigm/202.pdf.
  3. CT Users Group, “Practical investigations into using a small ion chamber and realistic phantom length for CT dosimetry” (2006), http://www.ctug.org.uk/meet10-10-14/dunn_abstract.html.
  4. “The 2007 Recommendations of the International Commission on Radiological Protection. ICRP publication 103,” Ann ICRP, 37, 1–332 (2007), http://www.icrp.org/docs/ICRP_Publication_103-Annals_of_the_ICRP_37(2-4)-Free_extract.pdf.
  5. “FDA safety investigation of CT brain perfusion scans,” Food and Drug Administration. Update 11/9/2010, http://www.fda.gov/medicaldevices/safety/alertsandnotices/ucm185898.htm.
  6. E. J. Hall and A. J. Giaccia, Radiobiology for the Radiologist, 7th ed. (Lippincott Williams & Wilkins, Philadelphia, PA, 2011).
  7. BEIR VII, “Health risks from exposure to low levels of ionizing radiation” (2005). The National Academies. http://dels-old.nas.edu/dels/rpt_briefs/beir_vii_final.pdf (2005).
  8. “ACR CT accreditation program requirement,” American College of Radiology. http://www.acr.org/accreditation/computed/ct_reqs.aspx. Update 10/4/2011.
  9. UNSCEAR 2010 Report: “Summary of low-dose radiation effects on health.” Report of the United Nations Scientific Committee on the Effects of Atomic Radiation 2010. United Nations, New York (2011).
  10. “The 1960 Recommendations of the International Commission on Radiological Protection.” ICRP Publication 60; Ann. ICRP 21 (1-3) (1991). http://www.icrp.org/publication.asp?id=ICRP Publication 60.


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