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Original research
Clot permeability and histopathology: is a clot’s perviousness on CT imaging correlated with its histologic composition?
  1. John Charles Benson1,
  2. Sean T Fitzgerald2,3,
  3. Ramanathan Kadirvel2,
  4. Collin Johnson2,
  5. Daying Dai2,
  6. Doyle Karen3,
  7. David F Kallmes1,
  8. Waleed Brinjikji1
  1. 1 Department of Neuroradiology, Mayo Clinic, Rochester, Minnesota, USA
  2. 2 Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
  3. 3 CURAM- Centre for Research in Medical Devices, National University of Ireland Galway, Galway, Ireland
  1. Correspondence to Dr John Charles Benson, Neuroradiology, Mayo Clinic, Rochester MN 55905-0002, USA; Benso905{at}


Background Clot perviousness in large vessel occlusion has been shown to be associated with improved recanalization outcomes with mechanical thrombectomy and intravenous thrombolysis.

Objective To evaluate the association between clot perviousness based on thrombus attenuation increase (TAI) on CT, and histologic composition of clots in acute ischemic stroke (AIS).

Methods A retrospective review was completed of patients with AIS secondary to large vessel occlusion, non-contrast CT (NCCT) and CT angiography (CTA) images, and histologic analysis of the retrieved clot. TAI was measured by subtracting clot attenuation on NCCT from the attenuation on CTA. Up to 3 regions of interest (ROIs) were evaluated on each clot; the average attenuation was used for analysis if multiple ROIs were assessed. Pervious clots were defined as TAI ≥10 Hounsfield units (HUs); impervious clots had TAI <10 HU. Histopathologic analyses of clots were assessed for relative compositions of red blood cells (RBCs), white blood cells (WBCs), fibrin, and platelets/other.

Results 57 patients were included. Pervious clots were more likely to be RBC rich (p=0.04); impervious clots were more likely to be fibrin and WBC rich (p=0.01 for both). Pervious clots also had greater RBC density than impervious clots (49.8% and 33.0%, respectively; p=0.006); fibrin density of pervious clots was lower than that of impervious clots (17.8% and 23.2%, respectively; p=0.02).

Conclusion Clot perviousness, assessed on NCCT and CTA imaging, is associated with higher RBC density and lower fibrin density, offering a possible explanation for the higher rates of successful thrombectomy and favorable clinical outcome seen in such patients.

  • stroke
  • thrombectomy

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  • Contributors JCB participated in the data collection and imaging review, and drafted the manuscript. STF, RK, CJ, DD, and DK participated in the review and interpretation of imaging and pathology data. DFK and WB participated in the conceptualization and design of the study, performed the statistical analysis, assisted in the interpretation of data, and revised the manuscript.

  • Funding This study was funded by an NIH grant: 1R01NS105853-01.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Correction notice Since this paper was first published online, the funding statement has been updated.

  • Patient consent for publication Not required.