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Radiation Dose and Safety: Mammography and Tomosynthesis
Michael P. Andre, PhD
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Terminology

  • Abbreviations

    • Full-field digital mammography (FFDM)
    • Conventional FFDM: 2-dimensional (2D) projection
    • Digital breast tomosynthesis (DBT)
    • Mean glandular dose (MGD), also average glandular dose
    • Mammography Quality Standards Act (MQSA)
    • Picture archiving and communications system (PACS)
    • Automatic exposure control (AEC)
    • As low as reasonably achievable (ALARA), in reference to patient and staff exposures
  • Definitions

    • Conventional FFDM: 2D single-exposure acquisition
    • DBT acquisition: Multiple exposures acquired rapidly as tube sweeps through arc
    • DBT combination mode: Tomosynthesis followed by conventional 2D image, acquired sequentially under same compression
    • MQSA: Law passed in 1992 and enforced by FDA; reauthorization passed in 1998
    • Absorbed dose: Energy imparted to tissue by ionizing radiation
      • MGD is mean absorbed dose in glandular tissue for "standard breast": 50% glandular, 50% fatty
      • Computed by medical physicist from air kerma measurements
    • Air kerma: kinetic energy released in matter (air) per unit mass by interaction with ionizing radiation
      • Measured by medical physicist with calibrated instruments
      • Value at reference point displayed on most x-ray systems after exposure
      • Not equal to patient dose
    • Gray (Gy): Unit of absorbed dose; 1 Gy = 1 Joule/kg tissue = 1,000 mGy
      • Amount of radiation energy deposited in tissue
      • Replaces unit rad: 1 Gy = 100 rad, 1 mGy = 100 mrad
    • Effective dose: Accounts for potential of radiation to cause biological effects, primarily cancer
      • Radiation has not been shown to induce heritable genetic damage in humans
      • Effective dose = Gy x tissue weighting factor
      • Relative weighting factors reflect differing tissue sensitivities to radiation effects
        • Breast, bone marrow, colon, lung, stomach, other tissues: 0.12 each
        • Gonads: 0.08
        • Thyroid, bladder, liver, esophagus: 0.04 each
        • Bone cortex, brain, salivary gland, skin: 0.01 each
        • If entire body irradiated uniformly by 1 Gy, sum of weighted doses to tissue = 1 Gy
    • Sievert (Sv): Unit of effective dose
      • Replaces historical unit rem: 1 Sv = 100 rem = 1,000 mSv
    • Controlled area: Occupied by radiation workers (e.g., x-ray room, control room)
      • Maximum dose < 0.1 mGy per week, < 5 mGy per year
    • Uncontrolled area: Open to general public, nonradiation workers (e.g., hallway, waiting room, office, toilet)
      • Maximum dose < 0.02 mGy per week, < 1 mGy per year
    • Natural background radiation: Unavoidable dose from all environmental sources
      • Varies by geography, ↑ with ↑ elevation: Average effective dose = 3 mSv per year in USA
    • Radioactivity: 1 disintegration/sec = 1 Becquerel (Bq); 1 Curie (Ci) = 3.7x10¹⁰ Bq; 1 mCi = 37 MBq

Mammography Imaging Technology

  • Digital Mammography

    • Digital Breast Tomosynthesis

      Radiation Safety

      • Patient Dose Considerations

        • Radiation Safety in Examination Room

          • Radiation Shielding Requirements

            Potential Risk of Mammography

            • Risk vs. Benefit: Complex Subject

              • Potential Effects of Radiation Exposure

                • Radiation Risk to Patients

                  Selected References

                  1. Gennaro G et al: Radiation dose with digital breast tomosynthesis compared to digital mammography: per-view analysis. Eur Radiol. 28(2):573-581, 2018
                  2. Phillips J et al: Comparative dose of contrast-enhanced spectral mammography (CESM), digital mammography, and digital breast tomosynthesis. AJR Am J Roentgenol. 1-8, 2018
                  3. Conant EF et al: Agreement between breast percentage density estimations from standard-dose versus synthetic digital mammograms: Results from a large screening cohort using automated measures. Radiology. 283(3):673-680, 2017
                  4. Maldera A et al: Digital breast tomosynthesis: Dose and image quality assessment. Phys Med. 33:56-67, 2017
                  5. Ratanaprasatporn L et al: Strengths and weaknesses of synthetic mammography in screening. radiographics. 37(7):1913-1927, 2017
                  6. Zuckerman SP et al: Imaging with synthesized 2D mammography: Differences, advantages, and pitfalls compared with digital mammography. AJR Am J Roentgenol. 209(1):222-229, 2017
                  7. Dance DR et al: Dosimetry in x-ray-based breast imaging. Phys Med Biol. 61(19):R271-R304, 2016
                  8. Mainiero MB et al: ACR Appropriateness Criteria Breast Cancer Screening. J Am Coll Radiol. 13(11S):R45-R49, 2016
                  9. Bouwman RW et al: Average glandular dose in digital mammography and digital breast tomosynthesis: comparison of phantom and patient data. Phys Med Biol. 60(20):7893-907, 2015
                  10. Hruska CB et al: Curies, and grays, and Sieverts, oh my: a guide for discussing radiation dose and risk of molecular breast imaging. J Am Coll Radiol. 12(10):1103-5, 2015
                  11. Svahn TM et al: Review of radiation dose estimates in digital breast tomosynthesis relative to those in two-view full-field digital mammography. Breast. 24(2):93-9, 2015
                  12. Sechopoulos I et al: Radiation dosimetry in digital breast tomosynthesis: report of AAPM Tomosynthesis Subcommittee Task Group 223. Med Phys. 41(9):091501, 2014
                  13. Skaane P et al: Two-view digital breast tomosynthesis screening with synthetically reconstructed projection images: comparison with digital breast tomosynthesis with full-field digital mammographic images. Radiology. 271(3):655-63, 2014
                  14. Feng SS et al: Clinical digital breast tomosynthesis system: dosimetric characterization. Radiology. 263(1):35-42, 2012
                  15. Hendrick RE. Radiation doses and cancer risks from breast imaging studies. Radiology. 257(1):246-53, 2010
                  16. Mettler FA Jr et al: Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 248(1):254-63, 2008
                  17. Sechopoulos I et al: Computation of the glandular radiation dose in digital tomosynthesis of the breast. Med Phys. 34(1):221-32, 2007
                  18. US FDA MQSA National Statistics
                  19. Structural Shielding Design for Medical X-Ray Imaging Facilities, NCRP Report No. 147, National Council on Radiation Protection and Measurements, 2007
                  20. Image Wisely, ACR
                  21. National Academy of Sciences. Health risks from exposure to low levels of ionizing radiation: BEIR VII Phase 2. (2006) Washington DC: The National Academies Press.
                  22. National Cancer Institute -- Breast Cancer
                  23. DD Cody, et al., ACR Appropriateness Criteria® Radiation Dose Assessment Introduction. Accessed 04/12/2018.
                  Related Anatomy
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                  References
                  Tables

                  Tables

                  Terminology

                  • Abbreviations

                    • Full-field digital mammography (FFDM)
                    • Conventional FFDM: 2-dimensional (2D) projection
                    • Digital breast tomosynthesis (DBT)
                    • Mean glandular dose (MGD), also average glandular dose
                    • Mammography Quality Standards Act (MQSA)
                    • Picture archiving and communications system (PACS)
                    • Automatic exposure control (AEC)
                    • As low as reasonably achievable (ALARA), in reference to patient and staff exposures
                  • Definitions

                    • Conventional FFDM: 2D single-exposure acquisition
                    • DBT acquisition: Multiple exposures acquired rapidly as tube sweeps through arc
                    • DBT combination mode: Tomosynthesis followed by conventional 2D image, acquired sequentially under same compression
                    • MQSA: Law passed in 1992 and enforced by FDA; reauthorization passed in 1998
                    • Absorbed dose: Energy imparted to tissue by ionizing radiation
                      • MGD is mean absorbed dose in glandular tissue for "standard breast": 50% glandular, 50% fatty
                      • Computed by medical physicist from air kerma measurements
                    • Air kerma: kinetic energy released in matter (air) per unit mass by interaction with ionizing radiation
                      • Measured by medical physicist with calibrated instruments
                      • Value at reference point displayed on most x-ray systems after exposure
                      • Not equal to patient dose
                    • Gray (Gy): Unit of absorbed dose; 1 Gy = 1 Joule/kg tissue = 1,000 mGy
                      • Amount of radiation energy deposited in tissue
                      • Replaces unit rad: 1 Gy = 100 rad, 1 mGy = 100 mrad
                    • Effective dose: Accounts for potential of radiation to cause biological effects, primarily cancer
                      • Radiation has not been shown to induce heritable genetic damage in humans
                      • Effective dose = Gy x tissue weighting factor
                      • Relative weighting factors reflect differing tissue sensitivities to radiation effects
                        • Breast, bone marrow, colon, lung, stomach, other tissues: 0.12 each
                        • Gonads: 0.08
                        • Thyroid, bladder, liver, esophagus: 0.04 each
                        • Bone cortex, brain, salivary gland, skin: 0.01 each
                        • If entire body irradiated uniformly by 1 Gy, sum of weighted doses to tissue = 1 Gy
                    • Sievert (Sv): Unit of effective dose
                      • Replaces historical unit rem: 1 Sv = 100 rem = 1,000 mSv
                    • Controlled area: Occupied by radiation workers (e.g., x-ray room, control room)
                      • Maximum dose < 0.1 mGy per week, < 5 mGy per year
                    • Uncontrolled area: Open to general public, nonradiation workers (e.g., hallway, waiting room, office, toilet)
                      • Maximum dose < 0.02 mGy per week, < 1 mGy per year
                    • Natural background radiation: Unavoidable dose from all environmental sources
                      • Varies by geography, ↑ with ↑ elevation: Average effective dose = 3 mSv per year in USA
                    • Radioactivity: 1 disintegration/sec = 1 Becquerel (Bq); 1 Curie (Ci) = 3.7x10¹⁰ Bq; 1 mCi = 37 MBq

                  Mammography Imaging Technology

                  • Digital Mammography

                    • Digital Breast Tomosynthesis

                      Radiation Safety

                      • Patient Dose Considerations

                        • Radiation Safety in Examination Room

                          • Radiation Shielding Requirements

                            Potential Risk of Mammography

                            • Risk vs. Benefit: Complex Subject

                              • Potential Effects of Radiation Exposure

                                • Radiation Risk to Patients

                                  Selected References

                                  1. Gennaro G et al: Radiation dose with digital breast tomosynthesis compared to digital mammography: per-view analysis. Eur Radiol. 28(2):573-581, 2018
                                  2. Phillips J et al: Comparative dose of contrast-enhanced spectral mammography (CESM), digital mammography, and digital breast tomosynthesis. AJR Am J Roentgenol. 1-8, 2018
                                  3. Conant EF et al: Agreement between breast percentage density estimations from standard-dose versus synthetic digital mammograms: Results from a large screening cohort using automated measures. Radiology. 283(3):673-680, 2017
                                  4. Maldera A et al: Digital breast tomosynthesis: Dose and image quality assessment. Phys Med. 33:56-67, 2017
                                  5. Ratanaprasatporn L et al: Strengths and weaknesses of synthetic mammography in screening. radiographics. 37(7):1913-1927, 2017
                                  6. Zuckerman SP et al: Imaging with synthesized 2D mammography: Differences, advantages, and pitfalls compared with digital mammography. AJR Am J Roentgenol. 209(1):222-229, 2017
                                  7. Dance DR et al: Dosimetry in x-ray-based breast imaging. Phys Med Biol. 61(19):R271-R304, 2016
                                  8. Mainiero MB et al: ACR Appropriateness Criteria Breast Cancer Screening. J Am Coll Radiol. 13(11S):R45-R49, 2016
                                  9. Bouwman RW et al: Average glandular dose in digital mammography and digital breast tomosynthesis: comparison of phantom and patient data. Phys Med Biol. 60(20):7893-907, 2015
                                  10. Hruska CB et al: Curies, and grays, and Sieverts, oh my: a guide for discussing radiation dose and risk of molecular breast imaging. J Am Coll Radiol. 12(10):1103-5, 2015
                                  11. Svahn TM et al: Review of radiation dose estimates in digital breast tomosynthesis relative to those in two-view full-field digital mammography. Breast. 24(2):93-9, 2015
                                  12. Sechopoulos I et al: Radiation dosimetry in digital breast tomosynthesis: report of AAPM Tomosynthesis Subcommittee Task Group 223. Med Phys. 41(9):091501, 2014
                                  13. Skaane P et al: Two-view digital breast tomosynthesis screening with synthetically reconstructed projection images: comparison with digital breast tomosynthesis with full-field digital mammographic images. Radiology. 271(3):655-63, 2014
                                  14. Feng SS et al: Clinical digital breast tomosynthesis system: dosimetric characterization. Radiology. 263(1):35-42, 2012
                                  15. Hendrick RE. Radiation doses and cancer risks from breast imaging studies. Radiology. 257(1):246-53, 2010
                                  16. Mettler FA Jr et al: Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 248(1):254-63, 2008
                                  17. Sechopoulos I et al: Computation of the glandular radiation dose in digital tomosynthesis of the breast. Med Phys. 34(1):221-32, 2007
                                  18. US FDA MQSA National Statistics
                                  19. Structural Shielding Design for Medical X-Ray Imaging Facilities, NCRP Report No. 147, National Council on Radiation Protection and Measurements, 2007
                                  20. Image Wisely, ACR
                                  21. National Academy of Sciences. Health risks from exposure to low levels of ionizing radiation: BEIR VII Phase 2. (2006) Washington DC: The National Academies Press.
                                  22. National Cancer Institute -- Breast Cancer
                                  23. DD Cody, et al., ACR Appropriateness Criteria® Radiation Dose Assessment Introduction. Accessed 04/12/2018.