Table 1.
Comparison between ASL-based BBB imaging and DCE-MRI.
| ASL-based BBB imaging | DCE-MRI | |
|---|---|---|
| Main MRI sequence | pCASL | Dynamic GRE |
| Spatial resolution (maximum) | Lower (1.9 mm × 1.9 mm × 4 mm) | Higher (0.55 mm × 0.55 mm × 5 mm) |
| Total scan time (minimum) | Shorter (5.53 min) | Longer (16 min) |
| Tracer (size) | Endogenous labelled proton (≈ 18 Da) | Exogenous gadolinium (550 Da) |
| Measured object | Water exchange rate across BBB | Gadolinium permeability across BBB |
| Mathematical model (recommended model) | Water exchange model (regularized SPA) | Pharmacokinetic model (Patlak model) |
| Output parameter | kw | Ktrans |
| Normal reference value among studies | Constant | Random |
| Intra-patient reproducibility | Good (ICC ≈ 0.75) | Good (ICC ≈ 0.75) |
| Pathological status (Alzheimer’s disease) | Lower kw values | Higher Ktrans values |
ASL, arterial spin labeling; BBB, blood–brain barrier; DCE-MRI, dynamic contrast-enhanced magnetic resonance imaging; GRE, gradient echo; ICC, intra-class correlation coefficient; pCASL, pseudo-continuous arterial spin labeling; SPA, single-pass approximation.