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
Radiation Safety
Potential Risk of Mammography
Selected References
- Gennaro G et al: Radiation dose with digital breast tomosynthesis compared to digital mammography: per-view analysis. Eur Radiol. 28(2):573-581, 2018
- 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
- 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
- Maldera A et al: Digital breast tomosynthesis: Dose and image quality assessment. Phys Med. 33:56-67, 2017
- Ratanaprasatporn L et al: Strengths and weaknesses of synthetic mammography in screening. radiographics. 37(7):1913-1927, 2017
- 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
- Dance DR et al: Dosimetry in x-ray-based breast imaging. Phys Med Biol. 61(19):R271-R304, 2016
- Mainiero MB et al: ACR Appropriateness Criteria Breast Cancer Screening. J Am Coll Radiol. 13(11S):R45-R49, 2016
- 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
- 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
- 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
- Sechopoulos I et al: Radiation dosimetry in digital breast tomosynthesis: report of AAPM Tomosynthesis Subcommittee Task Group 223. Med Phys. 41(9):091501, 2014
- 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
- Feng SS et al: Clinical digital breast tomosynthesis system: dosimetric characterization. Radiology. 263(1):35-42, 2012
- Hendrick RE. Radiation doses and cancer risks from breast imaging studies. Radiology. 257(1):246-53, 2010
- Mettler FA Jr et al: Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 248(1):254-63, 2008
- Sechopoulos I et al: Computation of the glandular radiation dose in digital tomosynthesis of the breast. Med Phys. 34(1):221-32, 2007
- US FDA MQSA National Statistics
- Structural Shielding Design for Medical X-Ray Imaging Facilities, NCRP Report No. 147, National Council on Radiation Protection and Measurements, 2007
- Image Wisely, ACR
- 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.
- National Cancer Institute -- Breast Cancer
- DD Cody, et al., ACR Appropriateness Criteria® Radiation Dose Assessment Introduction. Accessed 04/12/2018.
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