Introduction
This presentation provides a comprehensive, case-driven overview of digital breast tomosynthesis (DBT) in contemporary breast imaging practice. It covers the rationale for DBT, technical acquisition and reconstruction, workflow and implementation issues, artifact recognition, reading strategies, and evidence supporting its clinical impact. Applications for both screening and diagnostic evaluation are highlighted, with emphasis on improved cancer detection, reduced recall rates, and key limitations such as calcification assessment and the high prevalence of benign sclerosing lesions that mimic malignancy.
Historical Background and Rationale for DBT
DBT evolved to overcome the fundamental limitation of 2D mammography—parenchymal overlap—particularly problematic in dense breasts. While full-field digital mammography (FFDM) improved performance versus screen-film in specific subgroups, DBT further reduces masking and false-positive summation artifacts by depicting the breast in thin, pseudo-tomographic sections.
Key Points
- Eight randomized trials established mortality reduction from mammographic screening; FFDM replaced screen-film in most U.S. practices.
- The DMIST trial showed FFDM superiority in younger, pre/perimenopausal, and dense-breasted women.
- 2D planar imaging suffers from tissue overlap, leading to obscured lesions and pseudomasses.
- DBT addresses overlap by reconstructing thin slices through the breast volume, improving conspicuity and margin analysis.
DBT Acquisition and Reconstruction Technique
DBT acquires multiple low-dose projection images as the x-ray tube sweeps an arc; these are reconstructed into a stack of slices in which out-of-plane tissue is blurred. Synthetic 2D images can be generated from the DBT dataset to reduce dose and aid navigation.
Key Points
- Moving x‑ray source (step-and-shoot or continuous) captures a series of low‑dose projections across an angular range.
- Reconstruction yields thin “slices” and thicker “slabs,” enhancing visualization of lesion margins and internal architecture.
- Out-of-plane blurring reduces summation artifacts and clarifies spiculation and distortion.
- Synthetic 2D images (vendor-specific naming) are created from the DBT data to approximate a 2D projection.
Equipment, Vendors, and Protocols
Multiple FDA‑cleared DBT systems exist with differences in tube motion, detector configuration, angular span, and number of projections. Protocols should be tailored to institutional needs, legacy data, and CAD compatibility.
Key Points
- Systems vary: step‑and‑shoot vs continuous tube motion; rotating vs static detectors; differing angular ranges and projection counts.
- Wider angular ranges and more projections can enhance depth resolution but impact acquisition time and dose.
- Common screening protocol: 2D CC/MLO plus DBT CC/MLO, with synthetic 2D views available for navigation/comparison.
- Protocol selection should consider compatibility with prior imaging, CAD availability, and reading preferences.
Radiation Dose and Safety Considerations
DBT adds modest dose when performed as a “combo” with 2D; dose remains below MQSA limits and can be reduced with synthetic 2D adoption. DBT has limited feasibility in specific patient scenarios.
Key Points
- Combo (2D + DBT) exams remain within MQSA limits per view; DBT projections are individually very low dose.
- Transition to synthetic 2D can further reduce overall dose.
- Limitations: difficulty positioning patients with kyphosis/limited range to clear the rotating tube; full-implant views produce artifacts (implant-displaced DBT is feasible).
- No absolute contraindications; safety profile is acceptable.
Implementation, Training, and Workflow
Successful deployment requires capital investment, personnel training, IT infrastructure upgrades, and revised reading workflows. Recall reduction and streamlined diagnostics offset longer interpretation time.
Key Points
- Costs include DBT-capable units, dedicated workstations, PACS upgrades, and substantial storage for large datasets.
- Radiologists, technologists, and physicists require dedicated training (e.g., 8 hours).
- Reading time increases; reduced recalls and fewer additional mammographic views help rebalance workflow.
- Reimbursement has improved over time but may vary; institutional policies should address coverage and self-pay contingencies.
Reading Strategy and Workstation Navigation
Effective DBT interpretation requires a deliberate, plane-focused approach and use of workstation tools to localize findings across views and within the breast volume.
Key Points
- Read slice-by-slice, focusing at one depth before advancing; segment the breast into regions to ensure complete review.
- Use thin “slices” for margin analysis and thicker “slabs” for faster overview.
- Navigation tools show slice location and depth, facilitating cross-referencing between CC and MLO views.
- DBT excels at localizing skin findings on the first/last slices and at determining intramammary position for targeted ultrasound.
Artifacts and Normal Findings to Recognize
Recognition of DBT-specific artifacts and common normal variants prevents unnecessary callbacks and misinterpretation.
Key Points
- Zipper artifact: linear “string” from high-density objects (e.g., clips, calcifications) due to reconstruction—benign and recognizable.
- Skin-fold artifacts can create distracting rings; meticulous positioning reduces impact.
- Cutaneous moles and skin calcifications are confined to the most superficial slices with characteristic appearance (e.g., halo of air for moles).
- Subcutaneous fat “columns” at the skin surface are normal lucencies, not pores or air.
Evidence for Clinical Effectiveness
DBT improves diagnostic performance metrics in both screening and diagnostic settings, particularly for dense breasts.
Key Points
- Randomized comparisons show 2D+DBT detects additional cancers beyond 2D alone.
- TOMMY study: adding DBT improved specificity and overall accuracy for multiple reader types.
- Recall rates decrease by up to ~30% with DBT; cancer detection rate increases by approximately 40–50%.
- Gains are especially notable in women with dense breasts and those under 50; DBT may lessen the need for supplemental ultrasound in dense breasts (pending further trials).
DBT in Screening Practice
DBT reduces recalls for summation artifacts, better depicts benign patterns, and enhances detection of small invasive cancers with spiculation and distortion, even in dense parenchyma.
Key Points
- Benign patterns confidently assessed: multiple bilateral circumscribed masses (benign), lipomas, hamartomas (“breast-within-a-breast”), simple cysts.
- Vascular calcifications are easily tracked within vessels on slices, avoiding unnecessary magnification views.
- Small invasive cancers (e.g., 5–6 mm IDC/ILC) show crisp spiculation and irregular margins on DBT that may be occult or equivocal on 2D.
- DBT-guided localization streamlines targeted ultrasound and biopsy planning.
DBT in Diagnostic Problem-Solving
DBT is valuable in callbacks for asymmetry or distortion, palpable masses, post-treatment breasts, and in evaluating skin findings and multifocal/multicentric disease.
Key Points
- Distinguishes real lesions from summation by demonstrating persistent spiculation/distortion across slices.
- Precisely localizes lesions for targeted ultrasound; can obviate repeated 2D diagnostic views.
- Detects skin-based calcifications/lesions without tangential views.
- Aids in identifying additional sites of disease (e.g., multicentric lesions) and small recurrences in post-lumpectomy breasts.
Limitations, Pitfalls, and Benign Mimics
Despite its advantages, DBT presents challenges—especially in calcification analysis and the high detection rate of benign sclerosing lesions that mimic cancer.
Key Points
- Microcalcifications: clustering is less apparent on DBT slices; 2D (and magnification views) may better convey morphology and distribution.
- Architectural distortion is exquisitely visible on DBT; benign sclerosing lesions (e.g., radial scars, sclerosing papillomas) often mimic invasive cancer.
- Management of radial scars varies; many centers recommend surgical excision, especially with atypia.
- Increased interpretation time, implant-related limitations, and occasional artifacts remain practical constraints.
Practice Algorithms and Operational Considerations
Standardized algorithms enhance efficiency, accuracy, and patient experience when integrating DBT across screening and diagnostic workflows.
Key Points
- Callback workflow: repeat/special views as needed; if asymmetry persists or localization is uncertain, perform DBT to confirm lesion and direct targeted ultrasound.
- If no sonographic correlate to a DBT-detected lesion, consider DBT-guided biopsy when available.
- Screening deployment across units maximizes recall reduction and incident cancer detection; anticipate an initial uptick in detected cancers when DBT is introduced.
- Align vendor selection, service, and IT support (PACS, CAD compatibility, storage) with institutional strategy.
Conclusion
Digital breast tomosynthesis is a superior mammographic technique that mitigates tissue overlap, reduces recalls, and increases detection of clinically significant, often smaller invasive cancers—particularly in dense breasts. Successful implementation requires attention to equipment, training, workflow, and IT infrastructure, alongside an adapted reading strategy and awareness of artifacts and benign mimics. While calcification assessment and the prevalence of sclerosing benign lesions remain challenges, the overall diagnostic advantages firmly support integrating DBT into both screening and diagnostic breast imaging practice.
