Chest
Volume 142, Issue 3, September 2012, Pages 750-760
Journal home page for Chest

Special Features
Chest Imaging
Radiation and Chest CT Scan Examinations: What Do We Know?

https://doi.org/10.1378/chest.11-2863Get rights and content

In the past 3 decades, the total number of CT scans performed has grown exponentially. In 2007, > 70 million CT scans were performed in the United States. CT scan studies of the chest comprise a large portion of the CT scans performed today because the technology has transformed the management of common chest diseases, including pulmonary embolism and coronary artery disease. As the number of studies performed yearly increases, a growing fraction of the population is exposed to low-dose ionizing radiation from CT scan. Data extrapolated from atomic bomb survivors and other populations exposed to low-dose ionizing radiation suggest that CT scan-associated radiation may increase an individual's lifetime risk of developing cancer. This finding, however, is not incontrovertible. Because this topic has recently attracted the attention of both the scientific community and the general public, it has become increasingly important for physicians to understand the cancer risk associated with CT scan and be capable of engaging in productive dialogue with patients. This article reviews the current literature on the public health debate surrounding CT scan and cancer risk, quantifies radiation doses associated with specific studies, and describes efforts to reduce population-wide CT scan-associated radiation exposure. CT scan examinations of the chest, including CT scan pulmonary and coronary angiography, high-resolution CT scan, low-dose lung cancer screening, and triple rule-out CT scan, are specifically considered.

Section snippets

Radiation Effects of Chest CT Scans on the Individual Patient

Pioneers of radiation science discovered that ionizing radiation from x-rays causes damaging physical effects.13 Electrons are liberated when x-rays traverse living cells. Free electrons may mutate DNA directly or ionize water molecules to form harmful reactive oxygen species. Most damage is readily repaired, though persistent DNA damage may lead to cellular loss of function, necrosis, or malignancy.8, 12, 14

The term stochastic effect refers to tissue damage from low doses of radiation that is

Discussing Risks With Patients

Given the complex nature of the subject, it can be challenging to discuss the radiation risks of CT scanning with patients. It may be important to avoid citing numeric values for which patients have no frame of reference. A comparison with natural background radiation exposure may be better understood. In 1 year, individuals receive slightly less than one-half the dose associated with a routine chest CT scan from background sources, including cosmic radiation and radon gas (3 mSv).19 Another

Public Health Effects of Chest CT Scans

CT scanning has revolutionized the management of many diseases.5, 11 Its cost, availability, convenience, and versatility have made it one of the most used and fastest growing imaging technologies.11, 15 In 1993, about 18 million CT scans were performed in the United States, and in 2007, this number had increased to > 70 million.5, 7 During this period, CT scan utilization grew at 10 times the rate of US population growth.14

Diseases of the chest are major public health concerns, and advances in

Efforts to Reduce Radiation Dose

Efforts have been made to decrease CT scan-related radiation dose on the population and individual levels.9, 11, 28 Dose reduction strategies are summarized in Table 2.

Population-Wide Dose Reduction Initiatives

In the United States, medical radiation has replaced background radiation as the primary source of population-wide exposure.18, 29 The threshold for ordering CT scan has lowered even in younger, healthier patients for whom risks may outweigh benefits.5, 15, 30 Risk-benefit analyses are difficult to perform, and available decision aids often are underused in practice.11

It has been estimated that 26% to 44% of CT scans are ordered inappropriately.5, 11,15, 37 To counter this, appropriateness

Reducing Radiation Dose From Individual Studies

Reducing the dose administered during each study decreases individual radiation burden from CT scan. Evidence-based decision-making identifies patients for whom a CT scan study would provide clear net benefit and situations in which imaging tools that do not deliver radiation (eg, MRI, ultrasonography) are appropriate.5, 15 Once the decision for a CT scan has been made, it is important to optimize technical parameters to minimize risk and maximize diagnostic utility. Dose reduction strategies

Radiation, Cancer Risk, and Specific Chest CT Scan Modalities

Dose estimates from various chest CT scan studies are summarized in Table 4.

Conclusions

Even if single CT scans increase the individual risk of malignancy minutely, expanding use amplifies population-wide risk.5, 8,14, 15 There is still scientific uncertainty surrounding the risk and likelihood of developing a radiation-induced malignancy from CT scan. However, at our current level of understanding, it appears unwise to assume that there is no increased risk and, thereby, to expose patients to doses that future study may reveal to be critical.26 Chest physicians can minimize

Acknowledgments

Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Other contributions: Jana Johnson provided additional editorial and formatting assistance. We thank Julie Felice, CPM, and Ulrich Rassner, MD, for their advice on the topic of medical physics.

References (76)

  • EM Caoili et al.

    Medical decision making regarding computed tomographic radiation dose and associated risk: the patient's perspective

    Arch Intern Med

    (2009)
  • RT Griffey et al.

    Cumulative radiation exposure and cancer risk estimates in emergency department patients undergoing repeat or multiple CT

    AJR Am J Roentgenol

    (2009)
  • CI Lee et al.

    Diagnostic CT scans: assessment of patient, physician, and radiologist awareness of radiation dose and possible risks

    Radiology

    (2004)
  • R Smith-Bindman et al.

    Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer

    Arch Intern Med

    (2009)
  • KM Takakuwa et al.

    Knowledge and attitudes of emergency department patients regarding radiation risk of CT: effects of age, sex, race, education, insurance, body mass index, pain, and seriousness of illness

    AJR Am J Roentgenol

    (2010)
  • A Berrington de González et al.

    Projected cancer risks from computed tomographic scans performed in the United States in 2007

    Arch Intern Med

    (2009)
  • DJ Brenner et al.

    Computed tomography—an increasing source of radiation exposure

    N Engl J Med

    (2007)
  • A Sodickson et al.

    Recurrent CT, cumulative radiation exposure, and associated radiation-induced cancer risks from CT of adults

    Radiology

    (2009)
  • DJ Brenner

    Slowing the increase in the population dose resulting from CT scans

    Radiat Res

    (2010)
  • H Hricak et al.

    Managing radiation use in medical imaging: a multifaceted challenge

    Radiology

    (2011)
  • DJ DiSantis

    Early American Radiology: the pioneer years

    AJR Am J Roentgenol

    (1986)
  • EJ Hall et al.

    Cancer risks from diagnostic radiology

    Br J Radiol

    (2008)
  • MP Little

    Risks associated with ionizing radiation

    Br Med Bull

    (2003)
  • DJ Brenner et al.

    Cancer risks attributable to low doses of ionizing radiation: assessing what we really know

    Proc Natl Acad Sci U S A

    (2003)
  • Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation et al.

    Health Risks From Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2

    (2006)
  • FA Mettler et al.

    Effective doses in radiology and diagnostic nuclear medicine: a catalog

    Radiology

    (2008)
  • M Mahesh

    MDCT Physics: The Basics-Technology, Image Quality and Radiation Dose

    (2009)
  • M Hofer
  • PA de Jong et al.

    Estimation of cancer mortality associated with repetitive computed tomography scanning

    Am J Respir Crit Care Med

    (2006)
  • PET/CT Scanning

    (2011)
  • W Huda

    Radiation doses and risks in chest computed tomography examinations

    Proc Am Thorac Soc

    (2007)
  • M Brant-Zawadzki

    CT screening: why I do it

    AJR Am J Roentgenol

    (2002)
  • M Tubiana et al.

    A new method of assessing the dose-carcinogenic effect relationship in patients exposed to ionizing radiation. A concise presentation of preliminary data

    Health Phys

    (2011)
  • M Tubiana et al.

    The linear no-threshold relationship is inconsistent with radiation biologic and experimental data

    Radiology

    (2009)
  • FR Verdun et al.

    Quality initiatives radiation risk: what you should know to tell your patient

    Radiographics

    (2008)
  • DL Preston et al.

    Solid cancer incidence in atomic bomb survivors: 1958–1998

    Radiat Res

    (2007)
  • M Mascalchi et al.

    Risk-benefit analysis of X-ray exposure associated with lung cancer screening in the Italung-CT trial

    AJR Am J Roentgenol

    (2006)
  • DL Preston et al.

    Dose response and temporal patterns of radiation-associated solid cancer risks

    Health Phys

    (2003)
  • Cited by (0)

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.

    View full text