HIR can be easily assessed on automatically processed perfusion maps and predicts the rate of collateral flow, infarct growth, and clinical outcome 1).

Relative cerebral blood volume (rCBV) and hypoperfusion index ratio (HIR) may serve as markers of collateral circulation in acute ischemic stroke (AIS) patients prior to endovascular therapy 2).

1)
Olivot JM, Mlynash M, Inoue M, Marks MP, Wheeler HM, Kemp S, Straka M, Zaharchuk G, Bammer R, Lansberg MG, Albers GW; DEFUSE 2 Investigators. Hypoperfusion intensity ratio predicts infarct progression and functional outcome in the DEFUSE 2 Cohort. Stroke. 2014 Apr;45(4):1018-23. doi: 10.1161/STROKEAHA.113.003857. Epub 2014 Mar 4. Erratum in: Stroke. 2014 May;45(5):e92. PubMed PMID: 24595591; PubMed Central PMCID: PMC4047639.
2)
Arenillas JF, Cortijo E, García-Bermejo P, Levy EI, Jahan R, Goyal M, Saver JL, Albers GW. Relative cerebral blood volume is associated with collateral status and infarct growth in stroke patients in SWIFT PRIME. J Cereb Blood Flow Metab. 2017 Jan 1:271678×17740293. doi: 10.1177/0271678×17740293. [Epub ahead of print] PubMed PMID: 29135347.