J Korean Med Assoc.  2015 Jun;58(6):534-541. 10.5124/jkma.2015.58.6.534.

Strategies of computed tomography radiation dose reduction: justification and optimization

• Do KH
• Sung DW

• KMID: 2137560
• DOI: http://doi.org/10.5124/jkma.2015.58.6.534

Abstract

Medical imaging is an indispensible diagnostic tool in modern medicine enabling fast and accurate diagnosis. Recent technological advances in medical equipment and increased utilization of the imaging modality have resulted in a significant increase in the exposure to ionizing radiation. After the rapid adoption of multi-detector computed tomography, computed tomography (CT) is now the single largest source of diagnostic radiation exposure to patients. The risks and benefits from radiation must be carefully considered in all examinations using ionizing radiation, and the principles of justification and optimization should be considered in the proper use of CT examination. Justification means that the examination must be medically indicated and useful. Optimization means that the imaging should be performed using doses that are ALARA (as low as reasonably achievable), consistent with the diagnostic task. This includes understanding and changing CT protocols to perform the same diagnostic task with the minimal amount of radiation exposure while maintaining diagnostic accuracy. Protocols and guidelines are important tools for radiation dose reduction. Understanding the parameters and dose information for CT examination is essential for optimization. If the exam is justified, then the parameters must be optimized to the imaging indication, scan area, body size, age, and weight of the patients. The physician should always assess the radiation risk-benefit ratio for each patient before ordering an examination that uses radiation. Continuing education is essential for the implementation of the principles of patient radiation dose reduction. Physicians and radiologists must be aware of the radiation risks associated with CT exams.

Keyword

Computed tomography; Radiation protection; Justification; Optimization

MeSH Terms

Body Size
Diagnosis
Diagnostic Imaging
Education, Continuing
History, Modern 1601-
Humans
Radiation Protection
Radiation, Ionizing
Risk Assessment

Figure

• 

  Figure 1 This dose report was generated on a SOMATOM Sensation 16 (Siemens Healthcare, Forchheim, Germany) computed tomography (CT) scanner during a 4 phase dynamic liver CT. Note the volume CT dose index (CTDIvol) and dose length product (DLP). Dose reports from this scanner include kV, mAs/reference mAs, CTDIvol, DLP, and tube rotation time. This dose report shows separate premonitoring and monitoring radiation doses in regard to bolus tracking. In this exam, a topogram was taken, followed by nonenhanced imaging, bolus tracking, arterial, portal, and delayed phase imaging with a total 4 phases. For nonenhanced liver CT, tube current modulation using CareDose 4D was used at 120 kVP with a reference mAs of 200. In this case, the portal phase scan range included the pelvis, which explains the relatively larger scan range and higher DLP. Total DLP was 723 mGy × cm. TI, time per rotation; cSL, collimated slice.

• 

  Figure 2 This dose report was generated on a LightSpeed VCT scanner (GE Healthcare, Milwaukee, WI, USA) during a 4 phase dynamic liver computed tomography (CT) in a 44-year-old woman. Note the volume CT dose index (CTDIvol) and dose length product (DLP). Dose reports from this GE scanner include scanning type, scan range, CTDIvol, and DLP. Series 200 shows the radiation dose occurring during contrast bolus tracking. In this exam, a scout image was taken, followed by nonenhanced imaging, bolus tracking, arterial, portal, and delayed phase imaging with a total 4 phases. In this case, the portal phase scan range included the pelvis, which explains the relatively larger scan range and higher DLP. The total DLP for this patient is estimated as 850.89 mGy × cm.

Reference

1. National Council on Radiation Protection and Measurements. Ionizing radiation exposure of the population of the United States. Bethesda: National Council on Radiation Protection and Measurements;2009.

2. Brenner DJ, Hall EJ. Computed tomography: an increasing source of radiation exposure. N Engl J Med. 2007; 357:2277–2284.

3. United Nations, Scientific Committee on the Effects of Atomic Radiation. Effects of ionizing radiation: UNSCEAR 2006 report to the General Assembly with scientific annexes. New York: United Nations;2008.

4. International Commission on Radiological Protection. Recommendations of the International Commission on Radiological Protection: ICRP publication 26. Oxford: Pergamon Press;1977.

5. International Commission on Radiological Protection. The 2007 recommendations of the International Commission on Radiological Protection: ICRP publication 103. place unknown: Elsevier;2007.

6. International Commission on Radiological Protection. 1990 Recommendations of the International Commission on Radiological Protection: ICRP publication 60. Oxford: Pergamon Press;1991.

7. You JJ, Levinson W, Laupacis A. Attitudes of family physicians, specialists and radiologists about the use of computed tomography and magnetic resonance imaging in Ontario. Healthc Policy. 2009; 5:54–65.

8. Korley FK, Pham JC, Kirsch TD. Use of advanced radiology during visits to US emergency departments for injury-related conditions, 1998-2007. JAMA. 2010; 304:1465–1471.

9. Kim JH. Appropriate management method for high cost advanced imaging. Seoul: Health Insurance Review and Assessment Service;2013.

10. World Health Organization. Bonn call-for-action: joint position statement by IAEA and WHO [Internet]. Geneva: World Health Organization;2013. cited 2015 May 31. Available from: http://www.who.int/ionizing_radiation/medical_exposure/Bonn_call_action.pdf.

11. Park MY, Jung SE. CT radiation dose and radiation reduction strategies. J Korean Med Assoc. 2011; 54:1262–1268.

12. Jung SE. Research for national medical exposure reduction infrastructure. Cheongju: National Institute of Food and Drug Safety Evaluation;2012.

13. Lee CI, Haims AH, Monico EP, Brink JA, Forman HP. Diagnostic CT scans: assessment of patient, physician, and radiologist awareness of radiation dose and possible risks. Radiology. 2004; 231:393–398.

14. Krille L, Hammer GP, Merzenich H, Zeeb H. Systematic review on physician's knowledge about radiation doses and radiation risks of computed tomography. Eur J Radiol. 2010; 76:36–41.

15. Borgen L, Stranden E, Espeland A. Clinicians' justification of imaging: do radiation issues play a role? Insights Imaging. 2010; 1:193–200.

16. Broder J, Fordham LA, Warshauer DM. Increasing utilization of computed tomography in the pediatric emergency department, 2000-2006. Emerg Radiol. 2007; 14:227–232.

17. Jung AY. Medical radiation exposure in children and dose reduction. J Korean Med Assoc. 2011; 54:1277–1283.

18. Image Gently. The alliance for radiation safety in pediatric imaging [Internet]. Cincinnati: Image Gently;cited 2015 May 31. Available from: http://www.imagegently.org/.