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CHAPTER 21

CHAPTER 21. Breast MR. MAGNETISM. HYDROGEN. H Atomic #1 1 proton (+) 1 electron (-) Present in 60% of human body. HYDROGEN IN MAGNETIC FIELD. Relaxation; no magnetic influence. Steady state; magnetic field aligns atoms. HYDROGEN. RF pulse “on” Protons absorb energy

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CHAPTER 21

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  1. CHAPTER 21 Breast MR

  2. MAGNETISM

  3. HYDROGEN • H • Atomic #1 • 1 proton (+) • 1 electron (-) • Present in 60% of human body

  4. HYDROGEN IN MAGNETIC FIELD • Relaxation; no magnetic influence • Steady state; magnetic field aligns atoms

  5. HYDROGEN • RF pulse “on” • Protons absorb energy • Protons flip 90°/ 180°

  6. HYDROGEN • RF pulse “off” • Protons lose energy • Return to steady state • Released energy (resonance phase) creates image

  7. HYDROGEN • Image created from different relaxation rates of various tissues in breast: • Adipose tissue • Glandular tissue • Healthy tissue • Diseased tissue

  8. MRI UNIT

  9. MRI UNIT DISSECTED

  10. MAGNET • Flux lines display direction of movement of magnetism: In at south pole, out at north pole • Magnetic field encompasses area in and around the magnet that is influenced by the magnetic force

  11. MAGNET • Requires shielding • Passive • Active

  12. COILS • RF • Gradient • Shim • Surface

  13. USE & BENEFITS OF BREAST MR • Check effectiveness of chemotherapy • Extent of disease • If ductal or lobular cancer identified • Postlumpectomy follow-up • Complaint of lymph adenopathy • Implants • Tumor extension to chest wall

  14. BREAST MR LIMITATIONS • Too sensitive; benign conditions as well as malignant are visualized; false-positive results • Often false-positives are biopsied • Expensive exam

  15. ACS RECOMMENDS SCREENING BREAST MR • First-degree relative with BRCA1 or BRCA2 • 20–25% or higher lifetime risk of developing breast cancer • Received radiation treatments to chest between ages 10 and 30 • First-degree relative with genetic mutation of TP53 or PTEN genes • Diagnosed with breast cancer

  16. MAGNET IS ALWAYS ON • MRI safety sign

  17. MRI SAFETY

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