Stroke CT calculator (ASPECTS, CTA-SI-ASPECTS, pc-ASPECTS, CTA collateral scores)

Note: this calculator can be used to calculate multiple different indices used in the CT assessment of acute stroke depending on the clinical scenario and the type of the exam, for further information please read the detailed ‘Notes’ section below.

Notes

ASPECTS (Alberta stroke programme early CT score)

Illustrations of the evaluated cortical and deep areas:

^{Case courtesy of Dr Subash Thapa, Radiopaedia.org, rID: 40018}

• ASPECTS is a 10 point score for the rapid assessment of middle cerebral artery (MCA) territory ischemic stroke
• For each area showing hypodensity one point is deducted.
• Brain/stroke window reconstructions should be used for the assessment.
• The location of cortical areas is somewhat intuitive. As a rule of thumb M1-3 are at the level of basal ganglia, while M4-6 at the level of the ventricles superiorly.
• ASPECTS scores ≤7 predict poor functional outcome and increased risk of hemorrhagic transformation, while ≤8 correlates with a poorer outcome of thrombolysis.
  • ^{Pexman JH, Barber PA, Hill MD, Sevick RJ, Demchuk AM, Hudon ME, Hu WY, Buchan AM. Use of the Alberta Stroke Program Early CT Score (ASPECTS) for assessing CT scans in patients with acute stroke. AJNR Am J Neuroradiol. 2001 Sep;22(8):1534-42. PMID: 11559501; PMCID: PMC7974585.}

CTA-SI-ASPECTS

• CT angiography source image ASPECTS is assessed on brain window reconstructions of the CTA source images, otherwise the scoring system is identical to the original ASPECTS.
• It has been shown that CTA-SI-ASPECTS ≥8 is a better predictor of good clinical outcome and final infarct size than conventional ASPECTS.
  • ^{Park JS, Lee JM, Kwak HS, Chung GH. Predictive value of CT angiography source image ASPECTS in patients with anterior circulation acute ischemic stroke after endovascular treatment: ultimate infarct size and clinical outcome. J Neurointerv Surg. 2019 Apr;11(4):342-346. doi: 10.1136/neurintsurg-2018-014359. Epub 2018 Nov 24. PMID: 30472673.}
• In this Radiopaedia case I have illustrated how CTA-SI-ASPECTS can markedly improve diagnostic confidence compared to the noncontrast ASPECTS score:

pc-ASPECTS

• Assessed on brain/stroke window reconstructions in the same manner as ASPECTS.
• pc-ASPECTS is a 10 point score too, but any pontine or midbrain involvement reduces the score by 2 points regardless of uni/bilateral presentation.

Single phase CTA (sCTA) collateral score

• It is true for all three scoring systems that higher scores predict better clinical outcome. Note that if possible the multiphase CTA score should be preferred.
• Fortunately all of the original publications are open access:
  • ^{Tan IY, Demchuk AM, Hopyan J, Zhang L, Gladstone D, Wong K, Martin M, Symons SP, Fox AJ, Aviv RI. CT angiography clot burden score and collateral score: correlation with clinical and radiologic outcomes in acute middle cerebral artery infarct. AJNR Am J Neuroradiol. 2009 Mar;30(3):525-31. doi: 10.3174/ajnr.A1408. Epub 2009 Jan 15. PMID: 19147716; PMCID: PMC7051470.}
  • ^{Maas MB, Lev MH, Ay H, Singhal AB, Greer DM, Smith WS, Harris GJ, Halpern E, Kemmling A, Koroshetz WJ, Furie KL. Collateral vessels on CT angiography predict outcome in acute ischemic stroke. Stroke. 2009 Sep;40(9):3001-5. doi: 10.1161/STROKEAHA.109.552513. Epub 2009 Jul 9. PMID: 19590055; PMCID: PMC2754152.}
  • ^{Souza LC, Yoo AJ, Chaudhry ZA, Payabvash S, Kemmling A, Schaefer PW, Hirsch JA, Furie KL, González RG, Nogueira RG, Lev MH. Malignant CTA collateral profile is highly specific for large admission DWI infarct core and poor outcome in acute stroke. AJNR Am J Neuroradiol. 2012 Aug;33(7):1331-6. doi: 10.3174/ajnr.A2985. Epub 2012 Mar 1. PMID: 22383238; PMCID: PMC3888794.}

Multiphase CTA (mCTA) collateral score

• The multiphase collateral score improves sensitivity by demonstrating the dynamics of filling delay in the collateral vessels in the affected brain region.
• If multiphase CTA is performed this score should be used.
• Qualitative assessment of mCTAs is fairly dichotomic
  • 4-5: good collateral status
  • ≤3: poor collateral status, predicitive of poor outcome
• This Radiopaedia case of mine illustrates the value of mCTA scoring.
• MIP reconstructions are particularly useful for gross assessment of collateral status.
• It has been shown that patients with poor sCTA but good mCTA score have a high probability of good functional outcome.
  • ^{García-Tornel A, Carvalho V, Boned S, Flores A, Rodríguez-Luna D, Pagola J, Muchada M, Sanjuan E, Coscojuela P, Juega J, Rodriguez-Villatoro N, Menon B, Goyal M, Ribó M, Tomasello A, Molina CA, Rubiera M. Improving the Evaluation of Collateral Circulation by Multiphase Computed Tomography Angiography in Acute Stroke Patients Treated with Endovascular Reperfusion Therapies. Interv Neurol. 2016 Sep;5(3-4):209-217. doi: 10.1159/000448525. Epub 2016 Sep 1. PMID: 27781051; PMCID: PMC5057069.}

Further reading

• Radiopaedia.org articles
  • ASPECTS and pc-ASPECTS
  • CTA-SI-ASPECTS
  • single phase CT angiographic collateral scores
  • mCTAs

Last updated: 2021-11-13