[Syllabus]: Diagnostic Breast Imaging and Interventions in the age of Digital Breast Tomosynthesis

Introduction

This course synthesizes contemporary principles and practical workflows for Diagnostic Breast Imaging and image-guided interventions in the era of Digital Breast Tomosynthesis (DBT). It emphasizes DBT’s quasi three-dimensional acquisition of planes (not true 3D “slices”), its demonstrated impact on cancer detection and recall reduction, incorporation into diagnostic algorithms, interpretation strategies, and its role in guiding biopsies and localizations. Operational aspects—including equipment, accreditation, training, radiation dose, and IT infrastructure—are integrated to support safe, efficient adoption in clinical practice.

Digital Breast Tomosynthesis: Fundamentals and Nomenclature

DBT acquires multiple low-dose projections over an arc and reconstructs them into a stack of planes that can be scrolled, mitigating tissue superimposition inherent to 2D mammography. The modality is quasi-3D and should be described in planes, not slices, to reflect its reconstruction geometry.

Key Points

• Quasi-3D tomographic planes generated from multiple low-dose projections
• Reduces tissue overlap; improves lesion conspicuity versus 2D
• Use precise terminology: “tomosynthesis,” “DBT,” “tomo”; avoid “3D mammography”

Clinical Rationale and Performance Benefits

DBT increases invasive cancer detection (notably for architectural distortion) and decreases screening recall rates across all breast densities, with pronounced benefits in heterogeneously and extremely dense breasts.

Key Points

• Higher sensitivity for subtle findings, especially architectural distortion
• Fewer call-backs by resolving superimposition
• Better margin assessment and localization of one-view findings
• Radiation dose acceptable; may be reduced with synthetic 2D use

Historical and Technical Evolution

Tomographic concepts date to the 1930s; practical clinical DBT required advances in reconstruction algorithms (1980s) and flat-panel digital detectors (1990s) to achieve low-noise, low-dose imaging with robust image quality.

Key Points

• Early limitations: blurring and computational constraints
• Modern DBT enabled by digital detectors and advanced reconstruction
• Initial development paralleled lung and breast applications

Implementing DBT in Practice: Equipment, Accreditation, Training, and IT

Transitioning requires capital investment, accreditation for both 2D and DBT components, vendor-specific clinician training, technologist hands-on instruction, physicist QA/QC, and substantial PACS storage and network capacity.

Key Points

• Equipment: upgrade kits vs new units; vendor differences in arc angle and acquisition (step-and-shoot vs continuous)
• Accreditation: separate for 2D and DBT components
• Training: radiologists (FDA-required 8 hours vendor-specific), technologists (~6 hours hands-on), physicists (QA/QC and FDA metrics)
• IT readiness: significant storage and bandwidth expansion; plan with PACS/enterprise imaging teams

Image Acquisition and Reconstruction Mechanics

An x-ray tube traverses an arc to acquire low-dose projections (e.g., nine exposures on some systems) that are reconstructed into a plane stack. Plane count approximates posterior breast thickness, with occasional additional algorithm-generated planes.

Key Points

• Projection number and arc angle vary by vendor; trade-offs in sharpness/noise
• Plane index relates to posterior thickness; anterior thickness is less
• Reconstruction can introduce extra planes beyond measured thickness

Synthetic 2D Views: Role, Dose, and Trade-offs

Synthetic 2D images can replace directly acquired 2D views on FDA-approved systems, reducing dose while preserving cancer detection, PPV, and recall metrics comparable to full-field 2D mammography.

Key Points

• Advantages: dose reduction; conspicuous margins/spiculations; bright calcifications
• Pitfalls: pseudocalcifications; blurring in subcutaneous/axillary regions; reduced biopsy marker conspicuity
• Overall comparable performance to 2D; vendor advances continue to narrow differences

Screening Interpretation Workflow with DBT

A structured approach improves efficiency and consistency: review synthetic 2D, correlate with tomo planes, compare to priors, and then inspect CAD outputs. Divide each view into regions to manage visual load.

Key Points

• Read synthetic views first, then tomo planes side-by-side
• Systematically scan in thirds (lateral/middle/medial on CC; superior/middle/inferior on MLO)
• Review priors and CAD last; expect longer interpretation times than 2D
• Implants: full implant views in 2D; implant-displaced views with DBT increase workload

Navigation and Triangulation with Scroll Tools

DBT navigation tools display plane position and orientation (e.g., CC head-to-feet; MLO medial-to-lateral). First/last planes correspond to skin, aiding differentiation of skin vs parenchymal findings.

Key Points

• Plane sliders orient location in breast; plane count influenced by posterior thickness
• Skin signs: first/last-plane lesions, mole air halo, fat “caves and clefts” in dermis
• Accurate localization of one-view asymmetries for ultrasound targeting

Diagnostic Applications: Asymmetries, Pseudolesions, and Skin Findings

DBT discriminates true lesions from overlap and identifies skin-based findings, markedly reducing unnecessary recalls and supplemental views (e.g., tangential views for skin calcifications).

Key Points

• Resolve pseudomasses due to overlap; confirm true masses via in-plane persistence
• Identify skin lesions at surface planes; classic mole halo/air lucencies
• Skin calcifications localized on first plane obviate tangential imaging

Architectural Distortion: Detection and Management

DBT is highly sensitive to architectural distortion—an abnormality commonly missed on 2D. Detection has increased recognition of radial scars, some with atypia requiring surgery.

Key Points

• DBT reveals lines converging to a focal point, “blinking” in and out of plane
• Common causes: postsurgical scars; radial scars (with/without atypia)
• If ultrasound is negative, proceed to DBT-guided biopsy rather than MRI detours

Mass Evaluation with DBT: Margins, Density, and Fat-Containing Lesions

DBT offers superior margin analysis, shape characterization, and density assessment compared to 2D, decreasing reliance on spot compression views.

Key Points

• Margins/spiculations better seen on tomo planes than on 2D spots
• Density assessment aids in recognizing fat necrosis and benign fat-containing lesions
• Classic benign fat-containing entities: lipoma, hamartoma, fat necrosis, lymph node, galactocele
• Caution: malignancies can engulf fat; prioritize suspicious shape/margins over fat content

Calcifications: Strengths, Pitfalls, and When to Use Magnification

While synthetic 2D makes calcifications conspicuous, DBT planes are suboptimal for grouping and morphology. Magnification views remain the standard for definitive calcification assessment.

Key Points

• Synthetic views can create pseudocalcifications; verify with magnification 2D
• DBT excels at identifying skin calcifications; tangential views largely obsolete
• Use magnification for morphology, distribution, and extent analysis

Supplemental Imaging Landscape

DBT outperforms 2D but may be less sensitive than ultrasound in some contexts; MRI remains the most sensitive modality for detection and staging.

Key Points

• MRI: highest sensitivity for detection and extent of disease
• Ultrasound: may detect additional lesions but with higher false-positive burden; recent evidence questions net benefit of routine whole-breast screening ultrasound
• DBT is a strong adjunct to 2D, improving detection while restraining recalls

Extent of Disease Assessment

DBT can assist when MRI is contraindicated or unavailable, though MRI is preferred for mapping multifocal/multicentric disease and invasive lobular carcinoma.

Key Points

• DBT demonstrates multifocal lesions and architectural distortion well
• Consider DBT for extent assessment in patients unable to undergo MRI
• Use multimodality correlation to plan biopsy and surgery

Operational Considerations: Efficiency, Workload, and Costs

DBT interpretation requires more time; adoption entails significant capital and training, but patients increasingly expect access to DBT due to demonstrated benefits.

Key Points

• Increased reading time for screening and diagnostic exams
• High equipment costs; broad team training required
• Substantial PACS storage and IT planning necessary
• Patient demand influenced by public awareness and vendor marketing

Spot Compression and Magnification with DBT

DBT supports spot compression but not magnification on tomo planes; the need for supplemental views is often reduced due to superior intrinsic margin visualization.

Key Points

• Use spot compression selectively; tomo planes usually suffice
• Maintain magnification 2D for calcification characterization
• Fewer tangential and lateral views required with DBT

Tomosynthesis-Guided Interventions: Core Biopsy and Localization

DBT enables precise targeting of lesions visible only on tomo (e.g., architectural distortion without ultrasound correlate), streamlining diagnosis and avoiding MRI-first pathways.

Key Points

• Ensure biopsy tables and attachments support DBT-guided procedures
• Use DBT guidance for AD-only lesions and subtle masses without sonographic correlate
• Post-biopsy clip verification benefits from scrolling through tomo planes

Diagnostic Algorithms Using DBT

Structured DBT-first pathways reduce unnecessary imaging and expedite definitive diagnosis.

Key Points

• Masses: evaluate on tomo for shape/margins; proceed directly to ultrasound or DBT-guided biopsy if no ultrasound correlate
• Calcifications: confirm skin location on tomo; otherwise obtain 2D magnification; biopsy as indicated
• Architectural distortion: prioritize DBT evaluation; seek ultrasound correlate; if absent, perform DBT-guided biopsy
• Asymmetries/one-view findings: localize with DBT; distinguish overlap from true lesions; reduce supplemental views and ultrasound use

Radiation Dose Considerations

Total dose depends on whether synthetic 2D replaces directly acquired 2D; even combined DBT+2D remains within regulatory limits, and synthetic strategies can reduce exposure.

Key Points

• Synthetic 2D substitution reduces dose while maintaining performance metrics
• Combined acquisitions generally remain below per-view dose limits
• Vendor-specific protocols and QC are essential for dose optimization

Conclusion

Digital Breast Tomosynthesis has transformed breast imaging by improving lesion conspicuity, localizing one-view findings, and reducing recalls, particularly in dense breasts. A careful implementation plan—covering equipment, accreditation, team training, and IT infrastructure—supports safe adoption. In daily practice, DBT refines diagnostic workflows, minimizes supplemental views, and enables image-guided interventions for tomo-only lesions. While magnification 2D remains indispensable for calcifications and MRI remains the most sensitive modality for extent of disease, DBT serves as a powerful diagnostic and interventional platform that enhances reader confidence and patient care.