European Radiology

, Volume 24, Issue 2, pp 390–396 | Cite as

Time-resolved assessment of collateral flow using 4D CT angiography in large-vessel occlusion stroke

  • Andreas M. J. FrölichEmail author
  • Sarah Lena Wolff
  • Marios N. Psychogios
  • Ernst Klotz
  • Ramona Schramm
  • Katrin Wasser
  • Michael Knauth
  • Peter Schramm



In acute stroke patients with large vessel occlusion, collateral blood flow affects tissue fate and patient outcome. The visibility of collaterals on computed tomography angiography (CTA) strongly depends on the acquisition phase, but the optimal time point for collateral imaging is unknown.


We analysed collaterals in a time-resolved fashion using four-dimensional (4D) CTA in 82 endovascularly treated stroke patients, aiming to determine which acquisition phase best depicts collaterals and predicts outcome. Early, peak and late phases as well as temporally fused maximum intensity projections (tMIP) were graded using a semiquantitative regional leptomeningeal collateral score, compared with conventional single-phase CTA and correlated with functional outcome.


The total extent of collateral flow was best visualised on tMIP. Collateral scores were significantly lower on early and peak phase as well as on single-phase CTA. Collateral grade was associated with favourable functional outcome and the strength of this relationship increased from earlier to later phases, with collaterals on tMIP showing the strongest correlation with outcome.


Temporally fused tMIP images provide the best depiction of collateral flow. Our findings suggest that the total extent of collateral flow, rather than the velocity of collateral filling, best predicts clinical outcome.

Key Points

• Collateral flow visibility on CTA strongly depends on the acquisition phase

• tMIP offers the best visualisation of the extent of collaterals

• Outcome prediction may be better with tMIP than with earlier phases

• Total extent of collaterals seems more important than their filling speed

• If triggered too early, CTA may underestimate collateral flow


Tomography, X-ray computed Four-dimensional computed tomography Stroke Collateral circulation Brain imaging 



Four-dimensional computed tomographic angiography


Alberta Stroke Program Early CT Score


Cerebral blood flow


Cerebral blood volume


Intraclass correlation coefficient


Maximum intensity projection


Multi-modal Computed Tomography


Modified Rankin Scale score


National Institutes of Health stroke scale


Regional leptomeningeal score


Single-phase computed tomography angiography


Thrombolysis in cerebral infarction


Temporal maximum intensity projection


Time to drain


Volume perfusion computed tomography



The department has a research agreement with Siemens AG, Forchheim, Germany. Andreas Frölich, Michael Knauth and Peter Schramm have received speaker’s honoraria from Siemens AG, Forchheim, Germany. Ernst Klotz is a full-time employee of Siemens AG, Forchheim, Germany.

We would like to inform you that part of the current patient collective (about two-thirds of the population) has been subject to previous analyses. However, the current study reports fundamentally new data on collateral strength assessed in a time-resolved fashion, while previous analyses were focused on the delineation of thrombi [12], the depiction of incomplete vascular occlusions [13] and the predictive value of perfusion parameter maps [18].


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Copyright information

© European Society of Radiology 2013

Authors and Affiliations

  • Andreas M. J. Frölich
    • 1
    Email author
  • Sarah Lena Wolff
    • 1
  • Marios N. Psychogios
    • 1
  • Ernst Klotz
    • 3
  • Ramona Schramm
    • 1
  • Katrin Wasser
    • 2
  • Michael Knauth
    • 1
  • Peter Schramm
    • 1
  1. 1.Department of NeuroradiologyUniversity Medical Centre GöttingenGöttingenGermany
  2. 2.Department of NeurologyUniversity Medical Centre GöttingenGöttingenGermany
  3. 3.Siemens AGComputed Tomography H IM CR R&D PAForchheimGermany

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