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Key Concepts to Memorize
Breast cancer screening context:
- Most common cancer in women
- X-ray mammography: screening every 2 years for women aged 50–75
- Mammography screening → -30% decrease in breast cancer mortality (Swedish Two-County Trial)
3 main challenges in breast cancer screening:
1. False-positive findings → unnecessary biopsies
2. False-negative findings → missed cancers ("interval cancer")
3. Over-diagnosis → over-treatment
Why add MRI to screening?
- MRI has much higher cancer detection rate (CDR/1000: 16.5 with MRI vs. 5–6 with mammography alone)
- But MRI limitations: high cost, long duration, requires contrast agents, limited availability
EUSOBI Recommendations 2024:
- Regular mammography remains the mainstay of breast cancer screening
- High-risk women + extremely dense breast tissue → use MRI
- Women should actively participate in personalized screening decisions
4 DL applications in breast MRI (Kapsner's 4 topics):
1. Quality Assurance — automated artifact detection in MRI-derived MIPs
2. Virtual Contrast Enhancement (vCE) — generate contrast-enhanced appearance from contrast-free MRI
3. Lesion Detection — AI-powered CAD system for breast DWI MRI
4. Additional/Incidental Findings — detect pathologies outside region of interest (e.g., aortic aneurysm)
Maximum Intensity Projection (MIP):
- Step 1: subtract pre-contrast from post-contrast 3D image → only contrast-enriched areas remain
- Step 2: project maximum intensities along one axis → 2D overview image
- 66.9% of MIPs have artifacts → DL achieves ~86-94% AUROC in artifact detection
Virtual Contrast Enhancement (vCE):
- Goal: predict contrast enhancement from contrast-free MRI sequences (T1, T2, DWI)
- Avoids risks of contrast agents: allergic reactions, kidney failure, environmental contamination
- GAN produces more realistic-looking vCE images than U-Net (confirmed by Turing test)
Thoracic Aortic Aneurysm (incidental finding):
- "Silent killer": >95% asymptomatic; rupture → >90% mortality
- AI detected aneurysms at ~3.5× higher rate than routine clinical reporting
- Women have +40% probability to die from thoracic aortic aneurysm vs. men