What is Light Compression Mammography?
Light compression mammography refers to the application of reduced compression force (typically <10 daN) during mammographic imaging, which is generally inadequate for optimal image quality and should be avoided except in rare circumstances where patient tolerance is severely limited.
Standard Compression Parameters
Current mammographic practice utilizes force-based compression protocols rather than "light" compression approaches:
- Standard compression force ranges from 10-18 daN (decanewtons), with most facilities targeting 15-18 daN to achieve adequate breast flattening 1, 2
- Pressure-based approaches (measuring force per contact area in kPa) are emerging as potentially superior to force-alone protocols, with target pressures around 10-21 kPa showing promise for standardization 2, 3
- Compression below 9 daN is associated with inadequate breast thickness reduction and suboptimal imaging, with more than 50% of such compressions terminated early due to pain rather than achieving adequate compression 4
Why Adequate Compression Matters
Proper compression is essential for three critical outcomes:
- Image quality improvement: Adequate compression separates overlapping breast tissue, reducing the tissue-masking effect that can obscure lesions 1, 5
- Radiation dose reduction: Increasing compression force from 10 to 15 daN reduces average glandular dose (AGD) by approximately 17% 4
- Diagnostic accuracy: Insufficient compression compromises lesion detection and characterization, potentially missing early cancers 1, 3
When Reduced Compression May Be Considered
Light compression is not a recommended protocol but may occur in specific clinical scenarios:
- Severe pain intolerance: Women with pre-existing breast pain or heightened pain sensitivity may terminate compression early, though this compromises image quality 3, 4
- Post-surgical breasts: Recent breast surgery may temporarily limit compression tolerance, though diagnostic quality must still be maintained 1
- Inflammatory conditions: Suspected breast abscess or inflammatory breast cancer requires imaging, but compression should not delay tissue diagnosis if infection fails to respond to antibiotics within 7-10 days 6
Critical Pitfalls to Avoid
Never accept inadequate compression as routine practice. The evidence demonstrates:
- Compression force below 10 daN results in 9% greater breast thickness in small breasts and 2% in large breasts, significantly degrading image quality 3
- Women with smaller breasts experience higher pressures at standard forces (21.3 kPa for CC views vs 14.2 kPa for MLO views), but this does not justify reducing compression below diagnostic thresholds 3
- Pain location is often extra-mammary: More than 50% of women identify the axilla or chest wall as the primary pain source during MLO compression, not the breast tissue itself 4
Optimal Compression Strategy
Rather than "light compression," modern practice should focus on:
- Pressure standardization targeting 10 kPa (equivalent to normal arterial blood pressure) rather than fixed force protocols, which improves standardization across breast sizes 3
- Self-compression techniques allow patients to control compression rate and may achieve stronger compression (114.5 vs 102.5 daN) with comparable pain scores, though without significant dose reduction 7
- Digital breast tomosynthesis (DBT) can partially compensate for suboptimal compression by reducing tissue overlap effects through thin-section reconstruction, though adequate compression remains preferable 1
The term "light compression mammography" should not be used as a clinical protocol designation—all mammography requires adequate compression for diagnostic quality, with individualization based on pressure rather than arbitrarily reduced force.