Table 1.

Imaging recommendations for methods and patient selection for clinical reperfusion trials

Baseline imaging markers that favor treatment response of thrombectomy
Treatment-Related Acute Imaging Target (TRAIT) for thrombectomy
Large artery occlusion Small core Large core-perfusion mismatch (penumbral marker) Good cerebral collaterals
Imaging selection of patients for acute reperfusion trials (not limited to endovascular therapies): Recommendations
Imaging for defining the Treatment Relevant Acute Imaging Target (TRAIT) is highly recommended for patient selection Additional time spent acquiring additional imaging information must be balanced against risk of delay in initiating reperfusion therapies Pre-randomization vascular imaging should be obtained in acute endovascular trials. This would usually be done by CTA or MRA. Catheter angiography is included as a method for patient selection but it is understood that it is not likely the initial method for patient selection in a clinical trial Vascular, core, mismatch and collateral imaging each have added value for identifying TRAIT and enriching sample toward greatest effect size. More than one imaging method and threshold criterion is acceptable for these purposes, but should be standardized within a trial Particularly in phase II trials with small sample sizes, both vascular and advanced tissue imaging may offer insights into patient populations that cannot be obtained from clinical data alone, and are recommended to assist characterization of patient populations and improve understanding of experimental therapies
Proposed imaging methods for patient selection
TRAIT	Proposed imaging methods
Artery occlusion	CTA MRA Catheter angiography
Core	ASPECTS on NCCT Volume of severely decreased CBV or CBF from PCT Volume of acute DWI lesion from MRI
Mismatch	Volume of perfusion lesion (by PCT, Magnetic Resonance Perfusion (MRP) or Arterial Spin Labeling (ASL)) to core volume
Cerebral collaterals	CTA source images Single- or multiphasic CTA Contrast-enhanced MRA Catheter angiography