Can hematoma shape or heterogeneity of hematoma density predict ICH growth?
A 2009 study published in stroke presented a new scale for categorizing ICH based on the shape and homogeneity of the intracerebral hematoma. The study applied this novel 5-point categorical scale to randomly baseline CT images of ICH. Density and shape were defined as either homogeneous/regular (Category 1 to 2) or heterogeneous/irregular (Category 3 to 5). The density and shape was then correlated to the risk of hematoma expansion.
A hematoma arising from a solitary focus will have a more regular shape, and a more homogeneous density of blood. Hemorrhage arising from multiple foci will have an irregular shape. Heterogeneous CT density may reflect either 1.) active hemorrhage, 2.) more variable hemorrhagic time course, 3.) multifocality or multiple bleeding vessels. Density of blood on CT in ICH is related to 1. age of blood, 2. time course, 3. number of foci of hemorrhage and 4. hematocrit.
In relation to time course: liquid blood from active hemorrhage hypoattenuates on CT scans relative to surrounding brain or associated organized hyperattenuating thrombus. As clot retracts, hypoattenuating serum is released. As thrombi progressively liquefy into breakdown products, sites of hemorrhage become less dense on CT. Hypoattenuating edematous changes in perihematoma region evolve (in part) due to RBC hemolysate products such as thrombin and iron with associated BBB disruption.
Categorical Scales for shape (left) and density (right) of ICH
The 2 scales ranged from Category 1 (most regular shape and most homogeneous density) to Category 5 (most irregular shape and most heterogeneous density). Each progressive category added an extra lesion edge irregularity on the shape scale or degree of density variation on the density scale.
In cases of “satellite” bleeds, progressive irregularity and heterogeneity features could be joined or separate from the principal hemorrhage. Hematomas with more numerous lesion edge irregularities or more heterogeneous density than represented on the scale were assigned the maximum rating.
The study concluded that larger ICHs were significantly more irregular in shape, heterogenous in density and had greater growth. Density heterogeneity independently predicted ICH growth. Irregular shape was not identified as an independent ICH growth predictor.
Barras, C. D. et al. “Density And Shape As CT Predictors Of Intracerebral Hemorrhage Growth”. Stroke40.4 (2009): 1325-1331. Web.