Strategies of Collateral Blood Flow Assessment in Ischemic Stroke: Prediction of the Follow-Up Infarct Volume in Conventional and Dynamic CTA

S.E. Beyer; K.M. Thierfelder; L. von Baumgarten; M. Rottenkolber; F.G. Meinel; H. Janssen; B. Ertl-Wagner; M.F. Reiser; W.H. Sommer

doi:10.3174/ajnr.A4131

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Fig 1.
Definition of arterial, arteriovenous, and venous phases. Example of the separation the 3 phases by using the time-to-peak contrast enhancement of the contralateral middle cerebral artery and the superior sagittal sinus in a typical patient.
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Fig 2.
Comparison of conventional and dynamic CTA. A, MIP (10-mm) of conventional CTA source images. Volume of hypoattenuation (1 representative section outlined) is 90.5 mL. B, Temporal MIPs (10 mm) of dynamic CTA source images reconstructed for the arteriovenous phase. Volume of hypoattenuation (1 representative section outlined) is 7.5 mL. The follow-up infarct volume was 6.5 mL.
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Fig 3.
Inclusion and exclusion flow chart.
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Fig 4.
Comparison of collateral grading systems. The coefficient of determination is an indicator of model fit. Higher values indicate a better explanation of the variance of the outcome variable.
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Fig 5.
Examples of the volume of hypoattenuation and collateral vessels. A and B, Examples of 2 typical patients. The top rows show 10-mm MIPs of each phase in dynamic CTA. The areas of hypoattenuation of these MIPs are outlined, and the total lesion volumes of each phase are given beneath the images. The bottom rows show 20-mm MIPs of each phase in dynamic CTA, illustrating the collateral vessels. Collateral grades for each phase are given beneath the images and correspond to (in the order given) the 20-point relative score, the 5-point relative score, and the 4-point absolute score. The area of infarction on follow-up is shown on the right.

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Table 1:

Patient characteristics and univariate linear regression analysis to determine the effect of patient characteristics on follow-up lesion size

	All Patients (N = 136)	β-Coefficient^{^a}	P Value^{^a}
Age (yr)^{^b}	70.4 ± 13.8	β = −0.043	.235
Male sex (No.) (%)	56 (41.2)	β = 1.434	.157
Time from symptom onset to initial imaging^{^c} (min)^{^d}	139 (89–227)	β = −0.001	.897
Time to follow-up imaging (days)^{^d}	3 (1–5)	β = −0.095	.051
Additional ICA occlusion (No.) (%)	65 (47.8)	β = 4.911	<.001
Visible early temporal branch (No.) (%)	28 (20.6)	β = −2.431	.048
IV thrombolysis (No.) (%)	90 (66.2)	β = −3.926	<.001
Mechanical recanalization (No.) (%)	72 (52.9)	β = −3.776	<.001
Follow-up lesion volume^{^e} (mL)^{^d}	79 (19–218)	N/A	N/A

Note:—N/A indicates not available.
↵a Results of univariate linear regression analysis with follow-up lesion volume (square-root-transformed) as a dependent variable. Positive β-values indicate an increase in follow-up lesion volume.
↵b Mean.
↵c Documented for 70 patients.
↵d Median (first-third quartile).
↵e As measured by DWI-MRI (b=1000) or NECT.

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Table 2:

Model fit of multivariate linear regression for follow-up lesion volume^{^a}

	Conventional CTA (R²)	Dynamic CT Angiography (R²)
	Conventional CTA (R²)	Arterial Phase	Arteriovenous Phase	Venous Phase
4-Point absolute	0.392	0.439	0.462	0.374
5-Point relative	0.348	0.349	0.441	0.321
20-Point relative	0.436	0.421	0.483	0.368
Volume of hypoattenuation	0.483	0.567	0.614	0.586

Note:—R² indicates the adjusted coefficient of determination corrected for sex, time to follow-up imaging, additional ICA occlusion, visible early temporal branch, IV thrombolysis, and mechanical recanalization. It is an indicator of model fit; higher values indicate a better explanation of the variance of the outcome variable.
↵a Overall, dynamic CTA allows a better prediction of follow-up lesion volume than conventional CTA. Specifically, model fit was highest for reconstructions of dynamic CTA images within the arteriovenous phase. Models containing the volume of hypoattenuation performed better than models containing any of the collateral vessel grading scores.