Investigation of foam structure formation in the Freeze Foaming process based on in-situ computed tomography

Novel isophorone diisocyanate-based flexible polyurethane foams were prepared by the one-step method in a computerized foam qualification system (FOAMAT). The experimental conditions to obtain this type of foams, in relation to the nature and concentration of catalysts as well as the reaction temperature, were established as no data were available in scientific literature. The chemical reactions occurring during the foam generation process were monitored in situ by attenuated total reflectance-FTIR spectroscopy. The kinetics of the foam generation was fitted to an nth order model and the data showed that the foaming process adjusted to a first-order kinetics. The physical changes as pressure, foam height, and dielectric polarization were monitored by the FOAM software (FOAMAT). According to these parameters, the foaming process was divided into four steps: bubble growth, bubble packing, cell opening, and final curing.

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Heterogeneity between proximal and distal aspects of occlusive thrombi on pretreatment imaging in acute ischemic stroke

The Neuroradiology Journal ◽

10.1177/19714009211049713 ◽

2021 ◽

pp. 197140092110497

Author(s):

Tetsuya Hashimoto ◽

Takenobu Kunieda ◽

Tristan Honda ◽

Fabien Scalzo ◽

Latisha K Sharma ◽

...

Keyword(s):

Computed Tomography ◽

Ischemic Stroke ◽

Region Of Interest ◽

Hounsfield Unit ◽

Distal Segment ◽

Large Vessel Occlusion ◽

Anterior Circulation ◽

Vessel Occlusion ◽

The Difference

Background The potential heterogeneity in occlusive thrombi caused by in situ propagation by secondary thrombosis after embolic occlusion could obscure the characteristics of original thrombi, preventing the clarification of a specific thrombus signature for the etiology of ischemic stroke. We aimed to investigate the heterogeneity of occlusive thrombi by pretreatment imaging. Methods Among consecutive stroke patients with acute embolic anterior circulation large vessel occlusion treated with thrombectomy, we retrospectively reviewed 104 patients with visible occlusive thrombi on pretreatment non-contrast computed tomography admitted from January 2015 to December 2018. A region of interest was set on the whole thrombus on non-contrast computed tomography under the guidance of computed tomography angiography. The region of interest was divided equally into the proximal and distal segments and the difference in Hounsfield unit densities between the two segments was calculated. Results Hounsfield unit density in the proximal segment was higher than that in the distal segment (mean difference 4.45; p < 0.001), regardless of stroke subtypes. On multivariate analysis, thrombus length was positively correlated (β = 0.25; p < 0.001) and time from last-known-well to imaging was inversely correlated (β = −0.0041; p = 0.002) with the difference in Hounsfield unit densities between the proximal and distal segments. Conclusions The difference in density between the proximal and distal segments increased as thrombi became longer and decreased as thrombi became older after embolic occlusion. This time/length-dependent thrombus heterogeneity between the two segments is suggestive of secondary thrombosis initially occurring on the proximal side of the occlusion.

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