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AUTOMATED BREAST VOLUME SCANNER (ABVS)

Comprehensive Exam Notes

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1. DEFINITION

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2. HISTORICAL BACKGROUND

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3. INDICATIONS

Primary Indications

1. Supplemental screening in women with dense breast tissue (ACR BI-RADS density C or D) — most important indication
2. Characterization of breast lesions detected on mammography or HHUS
3. Preoperative assessment — accurate lesion extent measurement for surgical planning
4. Monitoring response to neoadjuvant chemotherapy
5. Post-treatment follow-up after breast-conserving surgery (BCS)
6. High-risk screening — BRCA mutation carriers, family history, prior chest radiation
7. Difficult-to-examine breasts — large breasts where HHUS coverage is incomplete

Additional/Extended Indications

1. Evaluation of multi-focal/multi-centric disease
2. Screening in younger women (<40 years) where radiation exposure from mammography is a concern
3. Novel application: soft tissue tumor evaluation beyond the breast (Chen et al., 2015)

Contraindications / Limitations

• Open wounds or skin lesions over the breast
• Patients unable to maintain prone position
• Very small breasts (may not achieve adequate coupling)
• Not suitable as a standalone diagnostic tool — requires correlation with mammography/HHUS

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4. INSTRUMENTATION

System Components (Siemens ACUSON S2000 ABVS)

A. Transducer

• Type: Wide-aperture (15.4 cm footprint), linear array transducer
• Frequency range: 5–14 MHz (high-frequency, broad bandwidth)
• Footprint: ~15 cm × 17 cm — much wider than HHUS transducers
• Contains hundreds of piezoelectric elements arranged in a linear array

B. Motorized Scanning Unit

• A flexible robotic arm holds the transducer
• Automated, motorized sweep mechanism moves the transducer across the breast at a constant, controlled speed
• Eliminates operator-dependent variability in angulation and pressure

C. Coupling Pad / Membrane

• A soft silicon membrane (coupling pad) is pre-filled with aqueous gel
• Conforms to breast contour, providing uniform acoustic coupling
• Ensures consistent stand-off distance across the entire breast surface

D. Touchscreen Interface

• Controls scan parameters, breast size selection, scan position
• Allows marking of breast position (LCC, LML, LMLO equivalent orientations)

E. 3D Workstation

• High-performance workstation with dedicated post-processing software
• Reconstructs 3D volume from raw data
• Generates multiplanar reconstructions (MPR) in all three planes
• Allows scrolling through volumetric dataset slice by slice
• Integrated with PACS for image storage and reporting

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5. TECHNICAL PARAMETERS

Presettings Based on Breast Size

• Scan depth
• Focus zones
• Gain curves
• Number of scan positions required

Coupling Medium

• Aqueous gel inside a flexible silicon membrane pad
• Alternative: direct gel application + membrane

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6. PATIENT POSITIONING TECHNIQUES

Standard Prone Position Protocol

1. Patient lies prone on a dedicated examination table with a breast aperture (hole in the table through which the breast hangs freely)
2. The affected breast hangs dependently through the aperture
3. The ABVS transducer (with coupling pad) is applied to the inferior surface of the breast from below
4. The motorized arm performs the automated sweep

This prone position ensures the breast is pendulous, maximally uncompressed, and well-separated from the chest wall — unlike the supine position used in HHUS.

Standard Scan Positions (3 scans per breast for complete coverage)

• For large breasts, 4–5 acquisitions may be needed
• The axilla/tail of Spence may require an additional dedicated scan
• Each scan takes ~90 seconds; total examination = ~10–15 minutes per breast

Positioning Variants

• Some protocols allow supine/semi-supine positioning with modified transducer application (used in certain commercial ABUS systems)
• Nipple must be marked to serve as an anatomical reference for MPR alignment

Patient Preparation

• No special preparation required
• Inform patient about prone positioning and mild transducer pressure
• Gel application to membrane or breast surface

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7. MODES OF DISPLAY (Multiplanar Reconstruction — MPR)

A. Transverse (Axial) Plane

• Standard 2D cross-sectional view (equivalent to HHUS B-mode)
• Shows lesion shape, echogenicity, margins in the horizontal plane
• Familiar to sonographers accustomed to HHUS

B. Sagittal Plane

• Vertical cross-section from superior to inferior
• Complements the transverse plane for lesion characterization

C. Coronal Plane ⭐ (UNIQUE to ABVS — Most Important)

• En face view of the breast from front to back
• Cannot be obtained by HHUS
• Shows the entire breast parenchymal architecture in one plane
• Allows visualization of lesion relationship to entire breast and chest wall
• Shows Cooper's ligaments converging toward the nipple ("convergence sign")

Key Coronal Plane Signs:

D. Volume Rendering / 3D Rendering Mode

• Produces a rendered 3D image of the breast volume
• Useful for surgical planning and lesion localization
• Less used in routine diagnosis

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8. ANALYSIS — LESION CHARACTERIZATION

BI-RADS Descriptors Used with ABVS

Key Sonographic Features Assessed

Shape

• Oval / Round → Benign
• Irregular → Suspicious

Margins

• Circumscribed → Benign
• Spiculated / Angular / Microlobulated → Malignant
• Spiculated + stellate margin in coronal plane → High specificity for malignancy (Wang et al., 2012)

Orientation

• Parallel (wider-than-tall) → Benign
• Non-parallel (taller-than-wide) → Suspicious

Echogenicity

• Hyperechoic → Benign (lipoma, fat necrosis)
• Hypoechoic → Requires evaluation
• Anechoic → Cyst (if with posterior enhancement)
• Complex / Heterogeneous → Worrisome

Posterior Acoustic Features

• Enhancement → Cysts, high-grade tumors
• Shadowing → Fibrosis, malignancy
• No change → Indeterminate

Coronal Plane Specific Analysis

• Presence/absence of retraction phenomenon — single most important ABVS-specific feature
• Assessment of architectural distortion in the en face view
• Relationship of lesion to nipple, skin, chest wall

Measurement

• ABVS allows 3D volumetric measurement of lesion in all three planes simultaneously
• More accurate than 2D HHUS for preoperative extent assessment (Tozaki & Fukuma, 2010)

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9. COMPARISON: ABVS vs. HAND-HELD ULTRASOUND (HHUS)

Wang et al. (2012): Detection rate and diagnostic accuracy were similar between ABVS and HHUS, but both were significantly superior to mammography in dense breasts.

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10. PERFORMANCE METRICS (Evidence-Based)

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11. ADVANTAGES OF ABVS

1. Operator independence — results are not dependent on sonographer skill/experience
2. Standardized, reproducible images — ideal for serial monitoring
3. Coronal plane — unique en face visualization unavailable with HHUS
4. 3D volumetric assessment — accurate lesion size/extent measurement
5. Complete breast coverage — standardized full-volume acquisition
6. No ionizing radiation — safer than mammography/CT for repeated use
7. Shorter per-patient time than HHUS for screening large populations
8. Better documentation — complete archived volume for retrospective review
9. Surgical planning — coronal view aids localization relative to Cooper's ligaments, chest wall
10. Telemedicine compatibility — stored volumes can be read remotely

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12. LIMITATIONS / DISADVANTAGES

1. No real-time imaging — cannot perform dynamic maneuvers (compression, color Doppler during scan)
2. No Doppler during acquisition — vascular information not captured in automated sweep
3. Nipple shadowing artifact in coronal plane — can mimic architectural distortion (false positive)
4. Acoustic shadowing from ribs/chest wall — limits posterior visualization
5. Learning curve for coronal plane interpretation — radiologists unfamiliar with en face view
6. High initial cost of equipment and workstation
7. Longer reading time — large volumetric datasets take more time to review
8. Not real-time — cannot guide biopsies directly (biopsy still requires HHUS)
9. Positioning challenges for patients unable to lie prone
10. Limited axillary coverage — tail of Spence may need additional scan position
11. Inter-rater reliability — published studies show heterogeneous quality; more standardization needed

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13. ARTIFACTS IN ABVS

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14. CLINICAL APPLICATIONS

A. Breast Cancer Screening

• Primary role: Supplemental screening in dense breasts (BI-RADS C/D)
• Detects mammographically occult cancers — especially in dense glandular tissue
• Particularly valuable for invasive lobular carcinoma (ILC) — which is notoriously difficult to detect on mammography

B. Lesion Characterization

• Distinguishes benign vs malignant based on BI-RADS descriptors
• Retraction phenomenon in coronal plane → highly specific for malignancy
• Cysts: white-wall sign in coronal plane

C. Preoperative Staging

• Accurate 3D measurement of tumor extent
• Assessment of multifocality/multicentricity
• Tumor-to-nipple distance measurement for surgical planning

D. Neoadjuvant Chemotherapy Monitoring

• Serial volumetric measurements for treatment response assessment
• Standardized, reproducible follow-up scans

E. Post-Treatment Surveillance

• Follow-up after BCS and radiation
• Detecting local recurrence

F. High-Risk Screening

• Complementary to MRI in BRCA mutation carriers
• Alternative when MRI is contraindicated (pacemaker, claustrophobia)

G. Novel Applications

• Soft tissue tumors outside the breast (Chen et al., 2015)
• Photoacoustic hybrid ABVS (PAUS-ABVS) — experimental, combining optical and acoustic imaging for functional information

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15. REPORTING SYSTEM — BI-RADS INTEGRATION

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16. IMAGES

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17. KEY EXAM POINTS TO REMEMBER

Mnemonic — ABVS = "A Beautiful View of the breast in 3D Space"

1. ABVS uses a 15 cm wide-footprint transducer at 5–14 MHz
2. Patient positioned prone (hanging breast through aperture)
3. 3 scan positions per breast = complete coverage
4. Coronal plane = unique feature, not available with HHUS
5. Retraction phenomenon / Sunburst sign on coronal = specific for malignancy
6. Nipple shadow = most common false positive artifact in coronal plane
7. Meta-analysis sensitivity = 92%, specificity = 84.9%
8. No real-time imaging — cannot guide biopsy directly
9. FDA cleared 2012 for supplemental screening in dense breasts
10. Combined with mammography + HHUS: accuracy reaches 96.4%
11. BI-RADS classification applies as with conventional ultrasound
12. Major advantage: operator independence and reproducibility

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