[Background] It is expected that thrombus density and perviousness measurements are dependent on CT slice thickness, because density values are blurred in thicker slices. This study quantifies the effect of slice thickness on thrombus density and perviousness measurements. [Methods] Thrombus density and perviousness measurements were performed in 50 patients for varying slice thicknesses, using a manual and semi-automated technique. Linear regression was performed to determine the dependence of density measurements on slice thickness. Paired t-tests were used to test for differences in density and perviousness measures for varying slice thickness. [Results] Thrombus density decreased for increasing slice thickness with approximately 2HU per mm. Perviousness measurements were significantly higher for thick slice compared to thin slice NCCT. [Conclusion] Thick slice NCCT scans result in an underestimation of thrombus density and overestimation of thrombus perviousness.

Background and Purpose-Preclinical studies showed that thrombi can be permeable and may, therefore, allow for residual blood flow in occluded arteries of patients having acute ischemic stroke. This perviousness may increase tissue oxygenation, improve thrombus dissolution, and augment intra-arterial treatment success. We hypothesize that the combination of computed tomographic angiography and noncontrast computed tomography imaging allows measurement of contrast agent penetrating a permeable thrombus, and it is associated with improved outcome. Methods-Thrombus and contralateral artery attenuations in noncontrast computed tomography and computed tomographic angiography images were measured in 184 Multicenter Randomized Clinical trial of Endovascular treatment of acute ischemic stroke in the Netherlands (MR CLEAN) patients with thin-slice images. Two quantitative estimators of the thrombus permeability were introduced: computed tomographic angiography attenuation increase (Δ) and thrombus void fraction (ε). Patients were dichotomized as having a pervious or impervious thrombus and associated with outcome, recanalization, and final infarct volume. Results-Patients with Δ≥10.9 HU (n=81 [44%]) and ε≥6.5% (n=77 [42%]) were classified as having a pervious thrombus. These patients were 3.2 (95% confidence interval, 1.7-6.4) times more likely to have a favorable outcome, and 2.5 (95% confidence interval, 1.3-4.8) times more likely to recanalyze, for Δ based classification, and similarly for ε. These odds ratios were independent from intravenous or intra-arterial treatment. Final infarct volume was negatively correlated with both perviousness estimates (correlation coefficient,-0.39 for Δ and-0.40 for ε). Conclusions-This study shows that simultaneous measurement of thrombus attenuation in noncontrast computed tomography and computed tomographic angiography allows for quantification of thrombus perviousness. Thrombus perviousness is strongly associated with improved functional outcome, smaller final infarct volume, and higher recanalization rate.