Radiation Dose in Mammography
A standard two-view screening mammogram delivers an average mean glandular dose (MGD) of approximately 2.5-3.7 mGy per breast, or about 5-7.4 mGy for a complete bilateral examination.
Specific Dose Information
Standard Digital Mammography
- Per view: 1.8-2.5 mGy mean glandular dose 1, 2
- Complete bilateral exam (4 views): 3.7 mGy for digital mammography, 4.7 mGy for older screen-film mammography 2
- Population average: Studies show mean doses ranging from 6.11-6.53 mGy for bilateral screening 3
The dose varies based on:
- Breast thickness: Thicker breasts require higher doses
- Breast density: Denser tissue may require additional views
- Equipment type: Digital systems typically use slightly less radiation than older film systems
Radiation Risk Context
The lifetime cancer risk from mammography screening is extremely small compared to its benefits. For biennial screening from ages 50-74 years, simulation models estimate 4:
- 3 radiation-induced breast cancers per 10,000 women screened
- 0.5 radiation-induced breast cancer deaths per 10,000 women screened
- Lives saved to deaths from induced cancer ratio: 62:1 1
Special Considerations
Women requiring extra views (5-6% of screened women with large breasts):
- Mean lifetime attributable risk increases to 6 cases per 10,000 (vs. 2 per 10,000 for standard exams) 4
- Breast cancer death risk: 1 per 10,000 (vs. 0.4 per 10,000) 4
Starting screening at age 40 vs. 50:
- Increases lifetime attributable risk to 4 cases per 10,000 women
- Increases breast cancer deaths to 1 per 10,000 women 4
Comparative Perspective
To put this in context 5:
- 50 annual mammograms (ages 25-74) contribute less than 1% additional radiation exposure for women previously treated with chest radiation for childhood cancer
- The dose is equivalent to approximately 3-6 months of natural background radiation
Digital Breast Tomosynthesis (DBT)
DBT combined with standard mammography essentially doubles radiation exposure 4. However:
- Synthetic 2D reconstructions from DBT data eliminate the need for separate standard views, reducing total dose back to single-exam levels 6
- DBT alone delivers approximately 0.037-7.253 μGy depending on protocol 7
Clinical Bottom Line
The radiation dose from screening mammography is minimal and the associated cancer risk is negligible compared to the mortality reduction achieved through early breast cancer detection. The benefit-to-risk ratio strongly favors screening mammography for appropriate age groups, with 497 deaths prevented per 100,000 screened women versus 8 deaths from radiation-induced cancer 1.