Cardiac MRI Techniques

Cardiac MRI Techniques - Cardiac Pulse Party

📌 Mnemonic: Cine Perfuses Phases Late, Tissue Mapped!

• Cine Imaging (SSFP): Assesses cardiac function, volumes, wall motion. Gold standard for LV/RV volumes.
• Myocardial Tissue Characterization:
  • T1/T2 Mapping: Quantitative values for diffuse fibrosis (T1), edema (T2).
  • LGE (Late Gadolinium Enhancement): Identifies focal scar/fibrosis (e.g., MI, myocarditis). Nulls normal myocardium.
  • PSIR (Phase-Sensitive Inversion Recovery): More robust LGE, less TI-sensitive.
• Stress Perfusion: Detects ischemia; first-pass gadolinium during stress.
• Phase Contrast (PC-MRI): Quantifies blood flow, velocity (valvular lesions, shunts).

⭐ LGE is typically performed 10-15 minutes after gadolinium administration to allow for optimal contrast between scarred and normal myocardium.

Cardiac MRI Techniques - Heartbeat Snapshots

Provides detailed cardiac anatomy, function, tissue characterization, and flow. Key sequences:

• Cine MRI (SSFP - Steady State Free Precession):
  • Assesses cardiac volumes, ejection fraction, regional wall motion.
  • Gold standard for LV/RV function.
• Late Gadolinium Enhancement (LGE):
  • Identifies myocardial scar, fibrosis (e.g., post-MI, myocarditis).
  • Gadolinium retained in damaged tissue.

  ⭐ LGE is the gold standard for myocardial viability assessment.

• T1 & T2 Mapping:
  • Quantitative tissue characterization.
  • T1: Diffuse fibrosis, infiltrative diseases.
  • T2: Myocardial edema, inflammation.
• Stress Perfusion MRI:
  • Detects inducible ischemia under pharmacological stress (e.g., adenosine).
• Phase Contrast (PC-MRI):
  • Quantifies blood flow velocity & volume (e.g., valvular lesions, shunts).

Cardiac MRI Techniques - Myocardial Secrets

• Cine (SSFP): Foundation for function; reveals wall motion abnormalities.
• T2-Weighted (e.g., STIR): Unveils myocardial edema/inflammation (acute injury).
• Late Gadolinium Enhancement (LGE): Gold standard for scar/fibrosis. Pattern reveals etiology. Uses specific $T_I$.
• T1 Mapping: Quantifies diffuse myocardial fibrosis & infiltrative disease. Detects changes before LGE.
• T2 Mapping: Quantifies myocardial water content (edema). More sensitive than T2W imaging.
• Perfusion (First-Pass): Highlights inducible ischemia under stress.

⭐ LGE is the cornerstone for assessing myocardial viability and scar, typically performed 10-20 minutes post-contrast.

Cardiac MRI Techniques - Cardiac Plumbing Probes

• Phase Contrast MRI (PC-MRI): Quantifies blood flow.
  • Measures velocity & volume.
  • Key: Velocity Encoding (VENC) - set above peak velocity to prevent aliasing.
  • Applications: Shunt (Qp/Qs), valvular stenosis/regurgitation, pulmonary hypertension.
• MR Angiography (MRA): Visualizes vessel anatomy.
  • Contrast-Enhanced (CE-MRA): Gadolinium-based. Excellent for aorta, pulmonary arteries.
    • Precise contrast bolus timing is critical.
  • Non-Contrast MRA:
    • Time-of-Flight (TOF): Bright blood from inflow.
    • Steady-State Free Precession (SSFP): Innately bright blood; good for coronary MRA.

⭐ PC-MRI is pivotal for non-invasively quantifying shunt fractions (Qp/Qs) in congenital heart diseases like ASD or VSD.

High‑Yield Points - ⚡ Biggest Takeaways

• CINE imaging (SSFP): Gold standard for ventricular function, volumes, and mass.
• Late Gadolinium Enhancement (LGE): Key for myocardial viability, scar, fibrosis; pattern is diagnostic.
• T1 mapping: Quantifies diffuse myocardial fibrosis (native T1, ECV) and aids in edema detection.
• T2 mapping: Detects and quantifies myocardial edema (acute MI, myocarditis).
• Stress perfusion MRI: Evaluates myocardial ischemia with pharmacological stress.
• Phase Contrast (PC-MRI): Measures blood flow velocity/volume for valvular issues and shunts.