Elsevier

World Neurosurgery

Volume 88, April 2016, Pages 119-125
World Neurosurgery

Original Article
Parametric Digital Subtraction Angiography Imaging for the Objective Grading of Collateral Flow in Acute Middle Cerebral Artery Occlusion

https://doi.org/10.1016/j.wneu.2015.12.084Get rights and content

Purpose

To report the feasibility of parametric color-coded digital subtraction angiography (DSA) in complementing the traditional, subjective way of leptomeningeal collateral assessment in acute middle cerebral artery (MCA) occlusions.

Methods

Thirty-three consecutive patients with acute MCA occlusion who received endovascular treatment were recruited for investigation. Eighteen of 33 consecutive patients were included. The target downstream territory (TDT) of MCA and reference point at terminal internal carotid artery of each patient was contoured by 5 raters independently on the basis of anteroposterior 2-dimensional DSA. Two parameters of relative maximum density of TDT (rDensitymax) and peak time interval (ΔPT) between reference and TDT were extracted by the use of parametric DSA analysis software. Interrater reliability was tested with intraclass correlation coefficients. Parameters with sufficient interrater reliability entered validity evaluation. Then, the correlation test with the American Society of Interventional and Therapeutic Neuroradiology collateral grading system and efficacy in predicting favorable clinical outcome was evaluated.

Results

The intraclass correlation coefficient of rDensitymax and ΔPT were 0.983, 95% confidence interval 0.968−0.993 and 0.831, 95% confidence interval 0.705−0.923, respectively. The parameter rDensitymax showed a strong correlation with the American Society of Interventional and Therapeutic Neuroradiology collateral grading system score (r of Spearman correlation test = 0.869, P < 0.001) and mRS at 3 months (partial correlation coefficient = 0.616, P = 0.009), whereas ΔPT_average did not. A cut-off point of 0.224 in rDensitymax predicted a favorable clinical outcome with high sensitivity and specificity.

Conclusions

The relative maximum contrast density of MCA territory on 2-dimensional DSA measured by parametric imaging technique appears to be a simple and reliable metric for the assessment of leptomeningeal collaterals in cases of acute MCA occlusion.

Introduction

Leptomeningeal collateral, also known as pial collateral, is one of the most important collateral filling pathways for patients with acute ischemic stroke. For patients with inadequate antegrade blood flow, pial collaterals are major determinants of tissue fate1 and reported to be correlated with smaller infarction volume compared with the poor ones.2, 3 It also indicates a greater possibility of reperfusion and better clinical outcome in patients with acute middle cerebral artery (MCA) occlusion who received endovascular therapy.4, 5

There has been no direct, quantitative way to assess cerebral collateral. They usually are assessed indirectly by different modalities of images, namely digital subtraction angiography (DSA), computed tomography angiography, dynamic computed tomography angiography, and arterial spin-labeling, to name a few.6 DSA stands out for its high spatial and time resolution and often is taken as the reference in many studies that focus on collateral assessment.7, 8, 9 The most widely used collateral grading system based on DSA is the American Society of Interventional and Therapeutic Neuroradiology collateral grading system (ACG). The ACG evaluates both the extent of perfusion and the speed of retrograde filling and has been recommended by the Cerebral Angiographic Revascularization Grading panels10 for collateral assessment.

In clinical practice, however, the differentiation between partial and complete perfusion of ischemic area (ACG grade 2 or 3) requires extensive experience, especially when MCA territory is overlapped by the branches of the anterior cerebral artery (ACA). Moreover, “partial” or “complete” might not be precise enough to characterize leptomeningeal collaterals because acute MCA occlusion patients with ACG grade 2 often have heterogeneous clinical outcomes.5, 11, 12 In this study, we reported the feasibility of using a parametric color-coded DSA analysis method13, 14 for the quantitative assessment of leptomeningeal collaterals in patients with acute MCA occlusion.

Section snippets

Patients

The study was approved by our institutional ethical committee. Patients with acute ischemic stroke who received endovascular recanalization treatment in our center during September 1, 2013, to April 20, 2015, were reviewed retrospectively for this study. The inclusion criteria were as follows: 1) unilateral MCA/M1 segment occlusion confirmed by DSA; and 2) image data compatible with the quantitative DSA analysis tool (syngo iFlow, Siemens Medical GmbH, Forchheim, Germany). Exclusion criteria

Clinical Characteristics

The age of included patients varied from 34 to 85 years of age; 6 were women. National Institute of Health Stroke Scale scores ranged from 7 to 26. Four of the 18 patients were evaluated to be ACG grade 1, 6 to be grade 2, and 7 to be grade 3; 1 patient had complete and rapid retrograde blood flow (grade 4). Fourteen cases were successfully reperfused after endovascular intervention, 10 had favorable clinical outcome within 3 months (mRS ≤ 2), and 3 were moderately to severely impaired in

Discussion

An optimal angiographic collateral assessment criterion should have high interrater reproducibility, high correlation with clinical outcome, and simplicity and feasibility in implementation while ensuring characterization of relevant angiographic findings.10

The parameter rDensitymax roughly reflects the extent of collateral perfusion within TDT. Because the MCA region is overlapped by itself in the anteroposterior view, we infer that rDensitymax represented the maximum coverage of collateral as

Conclusions

The relative maximum contrast density of MCA territory on 2D DSA measured by parametric imaging technique appears to be a simple and reliable metric for the assessment of leptomeningeal collaterals in acute MCA occlusion cases. Further studies with larger sample sizes are needed.

References (17)

  • S. Jung et al.

    Factors that determine penumbral tissue loss in acute ischaemic stroke

    Brain

    (2013)
  • F.O. Lima et al.

    Prognosis of untreated strokes due to anterior circulation proximal intracranial arterial occlusions detected by use of computed tomography angiography

    JAMA Neurol

    (2014)
  • D.S. Liebeskind

    Collateral circulation

    Stroke

    (2003)
  • O.Y. Bang et al.

    Collateral flow predicts response to endovascular therapy for acute ischemic stroke

    Stroke

    (2011)
  • D.S. Liebeskind et al.

    Collaterals at angiography and outcomes in the Interventional Management of Stroke (IMS) III trial

    Stroke

    (2014)
  • F. McVerry et al.

    Systematic review of methods for assessing leptomeningeal collateral flow

    AJNR Am J Neuroradiol

    (2012)
  • H. Chen et al.

    Using standard first-pass perfusion computed tomographic data to evaluate collateral flow in acute ischemic stroke

    Stroke

    (2015)
  • O.C. Singer et al.

    Collateral vessels in proximal middle cerebral artery occlusion: the ENDOSTROKE study

    Radiology

    (2015)
There are more references available in the full text version of this article.

Cited by (0)

Conflict of interest statement: Supported by Natural Science Foundation of China, grant number 81171092, Shanghai Science and Technology Innovation Plan, grant number 13411950300, and Subjects construction 1255 plan of Changhai hospital, grant number CH125520100, but there is no conflict of interest in association with the work that could have affected the results and there has been no significant financial support for this work that could have influenced its outcome.

Wan-ling Wen and Yi-bin Fang contributed equally to the work.

View full text