Table 3.

Multimodal imaging assessment of MMA.

Technique Focus	Advantages (A)/Disadvantages (D)
Brain CT Brain parenchyma damage	A: Easily accessible in the acute phase; Short acquisition time D: Poor spatial resolution; No information about vessels
CT Angiography Vessel imaging	A: Non-invasive technique; Good spatial resolution; Short acquisition time; Widely available D: Radioexposition; Contrast administration; Poor temporal resolution (without dynamic acquisition)
CT Perfusion Cerebral perfusion	A: Good temporal and spatial resolution; Short acquisition time; Acetazolamide can also be used to assess the CerebroVascular reactivity D: Whole-brain perfusion technology not widely available; Radioexposition; Potential underestimation of CBF in patients with EC-IC collaterals
Brain MRI Brain parenchyma damage	A: Non-invasive; Very good tissue and spatial resolution D: Magnetic field limitations; Claustrophobia; Long acquisition time
DSC-MRI Cerebral perfusion	A: Non-invasive; No exposure to ionizing radiation D: Requires contrast administration; Not fully standardized; Extensive collaterals can prolong arterial transit delays (causing inaccurate assessment of perfusion)
ASL-MRI Cerebral perfusion	A: Non-invasive; No exposure to ionizing radiation or contrast administration; Easy assessment and performance on children D: Not fully standardized; Extensive collaterals can prolong arterial transit delays (causing inaccurate assessment of perfusion); Drug challenge (acetazolamide) with potential side effects
MR Angiography Vessel imaging	A: Non-invasive; No contrast administration; Good spatial resolution in first and second-degree branches D: Relatively long acquisition time; Motion artifacts
Vessel Wall Imaging Vessel wall inflammation or remodeling	A: Differential diagnosis from other steno-occlusive diseases (vasculitides, atherosclerosis, dissections, etc.) D: Not validated for follow-up
DSA Vessel imaging	A: High spatial resolution; High temporal resolution with hemodynamic evaluation; Gold standard for vessel disease D: Invasive; Contrast administration
Transcranial (Color-Coded) Duplex Ultrasound Hemodynamicscerebrovascular reactivity and reserve	A: Non-invasive; Bedside executable; Repeatable; Low cost D: Dependent on acoustic window quality; Diagnostic and grading criteria are not validated in MMA; Operator-dependent
15O-PET Cerebral hemodynamic statuscerebrovascular reactivity and reserve (15O-water PET)	A: Non-invasive; Quantitative measurement of hemodynamic impairment; Useful for follow-up D: Long acquisition time; Not widely accessible; Highly expensive; Radioexposition

Abbreviations (alphabetical order): ASL: Arterial Spin Labeling; CT: Computer Tomography; DSA: Digital Subtraction Angiography; DSC: Dynamic Susceptibility Contrast; MR/MRI: Magnetic Resonance/MR Imaging; 15O-PET: Positron Emission Tomography.