Background and PurposeIn acute ischemic stroke (AIS) management, CT-based thrombus density has been associ-ated with treatment success. However, currently used thrombus measurements are proneto inter-observer variability and oversimplify the heterogeneous thrombus composition. Ouraim was first to introduce an automated method to assess the entire thrombus density andthen to compare the measured entire thrombus density with respect to current standardmanual measurements.Materials and MethodIn 135 AIS patients, the density distribution of the entire thrombus was determined. Density dis-tributions were described using medians, interquartile ranges (IQR), kurtosis, and skewedness.Differences between the median of entire thrombus measurements and commonly appliedmanual measurements using 3 regions of interest were determined using linear regression.ResultsDensity distributions varied considerably with medians ranging from 20.0 to 62.8 HU andIQRs ranging from 9.3 to 55.8 HU. The average median of the thrombus density distribu-tions (43.5±10.2 HU) was lower than the manual assessment (49.6±8.0 HU) (p<0.05).The difference between manual measurements and median density of entire thrombusdecreased with increasing density (r = 0.64; p<0.05), revealing relatively higher manualmeasurements for low density thrombi such that manual density measurement tend overes-timates the real thrombus density.@en