Quantitative MRI and Emerging Methods
Core concepts
Quantitative MRI aims for reproducible, scanner-independent metrics. Key methods include T₁ mapping (inversion recovery, Look-Locker, MOLLI), T₂ mapping (multi-echo spin echo), T₂ mapping* (multi-echo GRE), and diffusion imaging (DWI, DTI, ADC). ADC reflects water mobility; restricted diffusion is bright on DWI and dark on ADC.
Advanced techniques
MR elastography measures tissue stiffness; MR spectroscopy quantifies metabolites (NAA, choline, lactate); perfusion (DCE, ASL) measures blood flow. These methods demand careful calibration and are sensitive to motion and B₀ inhomogeneity.
Traps
- Confusing DWI (b-value weighting) with ADC (calculated map).
- Assuming T₁ mapping is field-independent; T₁ changes with B₀.
- Forgetting that spectroscopy requires shimming and water suppression.
Rule of thumb
Restricted diffusion: high b-value DWI bright + ADC dark. T2 shine-through: DWI bright + ADC bright. This pair of patterns answers most diffusion questions.