CONCISE REVIEW FOR CLINICIANSRadiation Risk From Medical Imaging
Section snippets
Radiation Dose
Absorbed dose, measured in grays (Gy), quantifies the energy deposited per unit mass. The energy deposition of 1 J/kg of tissue is the equivalent of 1 Gy. Because not all types of radiation produce the same biological effect, the dose equivalent is often used instead of the absorbed dose. The dose equivalent is the product of the absorbed dose and a radiation weighting factor and is expressed in sieverts (Sv). Because the radiation weighting factor for x-rays and gamma rays is 1.0, 1 Gy is
Excess Cancer Risk From Radiation: The Evidence
The relevant biological effect of x-rays and gamma rays is secondary to ionization. Ionization of water molecules can create hydroxyl radicals that may interact with DNA to cause strand breaks or base damage; DNA can also be ionized directly. Although most radiation-induced damage is rapidly repaired, misrepair can lead to point mutations, chromosome translocations, and gene fusions that are linked to cancer induction.1 This effect is typically thought to be stochastic, ie, it can occur at any
Radiation Dose From Imaging Examinations
A useful way to understand radiation doses from diagnostic examinations is to compare them to average natural background radiation (3 mSv per year) (Table).2, 6, 17
Radiation doses are sometimes expressed as entrance skin doses. Entrance skin doses are used in conventional radiography: a dose estimate at 1 point in the beam allows estimates of organ doses and effective dose. To assess the health risks of low doses of ionizing radiation, the International Commission on Radiation Protection uses
Reducing Patient Radiation Dose
Radiation dose from an imaging study can be reduced by 3 methods. First, one can decide not to perform the study at all. Such a decision should be based on proper understanding of the indications of the study, review of any previous imaging that might have already reasonably answered a clinical question, and an assessment of any special patient considerations that increase or decrease risk. Second, an alternative study that does not use ionizing radiation can be selected. Third, less radiation
CONCLUSION
A basic knowledge of radiation risk is useful in counseling patients who express concern about this issue. In most cases, the benefits of indicated medical imaging will outweigh the relatively small excess cancer risk, and patient management should not be altered on the basis of radiation risk. However, for certain subsets of patients, radiation risk should be of greater concern to the clinician. In addition, clinicians can play a role in minimizing radiation risk to their patients by referring
CME Questions About Radiation Risk
- 1.
Which one of the following is the average annual background radiation dose?
- a.
0.001 mSv
- b.
0.7 mSv
- c.
3 mSv
- d.
10 mSv
- e.
50 mSv
- a.
- 2.
Which one of the following is an average effective radiation dose from single-phase computed tomography (CT) of the abdomen and pelvis?
- a.
0.001 mSv
- b.
0.7 mSv
- c.
3 mSv
- d.
10 mSv
- e.
50 mSv
- a.
- 3.
Which one of the following is the average effective radiation dose from screening mammography (2 views)?
- a.
0.001 mSv
- b.
0.7 mSv
- c.
3 mSv
- d.
10 mSv
- e.
50 mSv
- a.
- 4.
Which one of the following statements is false?
- a.
The
- a.
REFERENCES (29)
- et al.
American College of Radiology white paper on radiation dose in medicine
J Am Coll Radiol
(2007) The ACR appropriateness criteria: translation to practice and research
J Am Coll Radiol
(2005)- et al.
Analysis of appropriateness of outpatient CT and MRI referred from primary care clinics at an academic medical center: how critical is the need for improved decision support [published correction appears in J Am Coll Radiol. 2010;7(6):466]?
J Am Coll Radiol
(2010) - et al.
Radiation exposure from medical imaging in patients with chronic and recurrent conditions
J Am Coll Radiol
(2010) - et al.
Obesity is a major determinant of radiation dose in patients undergoing pulmonary vein isolation for atrial fibrillation
J Am Coll Cardiol
(2007) - et al.
Submillisievert coronary computed tomography angiography using adaptive statistical iterative reconstruction: a new reality
Can J Cardiol
(2010) - et al.
Computed tomography:an increasing source of radiation exposure
N Engl J Med
(2007) - et al.
Radiation dose associated with common computed tomography exams and the associated lifetime attributed risk of cancer
Arch Intern Med
(2009) - et al.
Projected cancer risks from computed tomography scans performed in the United States in 2007
Arch Intern Med
(2009) Safety Investigation of CT brain perfusion scans: update 12/8/2009
Radiation risk: what you should know to tell your patient
Radiographics
Risks associated with low doses and low dose rates of ionizing radiation: why linearity may be (almost) the best we can do
Radiology
Radiation-induced cancer risks at low doses among atomic bomb survivors
Radiat Res
Cited by (376)
Advances in Imaging (Intraop Cone-Beam Computed Tomography, Synthetic Computed Tomography, Bone Scan, Low-Dose Protocols)
2024, Neurosurgery Clinics of North AmericaLiquid Biopsy Response Evaluation Criteria in Solid Tumors (LB-RECIST)
2024, Annals of OncologyAnalysis and establishment of adult diagnostic reference level for whole-body <sup>18</sup>F-FDG PET/CT imaging: A single institutional study
2023, Radiation Physics and Chemistry
On completion of this article, you should be able to (1) recognize the doses of common medical imaging studies, (2) recognize which patients may be at increased risk from radiation, and (3) be familiar with the evidentiary base for determining excess cancer risks from low-dose radiation.