Breast MRI Recognition Pattern

Systematic approach to interpreting breast MRI with BI-RADS lexicon, kinetic analysis, and diagnostic pitfalls

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1. Essential MRI Protocol

A. Standard Sequences

• • T2-weighted fat-sat:
  - Cystic vs. solid differentiation
  - Edema evaluation
  - Implant integrity assessment
• • T1-weighted non-fat-sat:
  - Native tissue evaluation
  - Hemorrhage detection
  - Pre-contrast baseline
• • Dynamic contrast-enhanced (DCE):
  - Temporal resolution ≤90 sec
  - 1-1.5mm in-plane resolution
  - Minimum 5 minutes acquisition
• • DWI (b=800-1000):
  - ADC values <1.1 x 10⁻³ mm²/s suspicious
  - Improves specificity when combined with DCE

B. Patient Preparation

• • Cycle timing:
  - Days 7-14 (follicular phase) for premenopausal women
  - Any time for postmenopausal
• • Contrast:
  - Gadolinium 0.1 mmol/kg
  - Power injection (2-3 mL/sec)
  - Saline flush

2. BI-RADS MRI Lexicon

A. Morphology

Feature

Benign

Suspicious

Shape

Oval/round

Irregular

Margin

Circumscribed

Spiculated

Internal Enhancement

Homogeneous

Heterogeneous/rim

B. Kinetic Analysis

Pattern

Initial Phase

Delayed Phase

Malignancy Risk

Persistent

Gradual

Continuous ↑

9%

Plateau

Rapid

Stable

64%

Washout

Rapid

Signal ↓ >10%

87%

3. Common Pathological Findings

A. Malignant Lesions

• • Invasive ductal carcinoma:
  - Spiculated margins
  - Washout kinetics
  - Low ADC values
  - Rim enhancement
• • Ductal carcinoma in situ (DCIS):
  - Clustered ring enhancement
  - Ductal or segmental distribution
  - Persistent/plateau kinetics

B. Benign Findings

• • Fibroadenoma:
  - Oval shape
  - Homogeneous enhancement
  - Persistent kinetics
  - "Dark internal septations"
• • Cysts:
  - Round/oval
  - T2 hyperintense
  - No internal enhancement

4. High-Risk Screening

A. Indications

• • BRCA mutation carriers
• • ≥20% lifetime risk (Tyrer-Cuzick model)
• • Prior chest radiation (age 10-30)

B. Screening Protocol

• • Annual MRI + mammography
• • Contraindications:
  - Pregnancy
  - GFR <30
  - Prior anaphylaxis

5. Implant Assessment

A. Sequence Requirements

• • Silent sequences:
  - Detect intracapsular rupture
  - "Linguine sign" (pathognomonic)
• • Water-only sequences:
  - Extracapsular rupture
  - Free silicone detection

B. Rupture Signs

Type

Key Features

Intracapsular

Linguine sign, subcapsular line

Extracapsular

"Teardrop" sign, silicone outside capsule

6. Post-Treatment Changes

A. Post-Surgical

• • Seroma:
  - T2 hyperintense
  - Thin rim enhancement
  - Resolves by 12-18 months
• • Fat necrosis:
  - Fat signal on T1
  - Peripheral enhancement
  - May mimic recurrence

B. Neoadjuvant Therapy

• • Response evaluation:
  - Volume reduction
  - Kinetic changes (washout → persistent)
  - ADC increase with treatment

7. BI-RADS Reporting Template

• 1. Indication: High-risk screening/staging/problem-solving
• 2. Background parenchymal enhancement (BPE):
  - Minimal/mild/moderate/marked
  - Symmetric/asymmetric
• 3. Findings:
  - Mass (size/location/morphology/kinetics)
  - Non-mass enhancement (distribution/kinetics)
  - Focus/foci
• 4. Implant evaluation (if applicable)
• 5. BI-RADS assessment:
  - 0: Incomplete
  - 1-6: Standard categories

Always correlate with mammography/ultrasound. For screening studies, schedule during days 7-14 of menstrual cycle when possible. Use kinetic analysis cautiously - some benign lesions show washout, while some DCIS shows persistent enhancement. Document BPE as it affects sensitivity. For implants, always include silicone-specific sequences. In post-treatment cases, compare with preoperative MRI and note therapy dates.

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