Cerebral venous sinus density on noncontrast CT correlates with hematocrit

Abstract

Background and purpose: A positive correlation between HCT and CT attenuation of intravascular blood has long been assumed but has never been established by using substantial patient numbers and modern CT equipment. The purpose of this study was to determine whether apparent increased attenuation on CT in cerebral venous sinuses can be attributed to hemoconcentration alone and to assess whether sinus thrombosis can be differentiated from hemoconcentrated blood based on attenuation values alone.

Materials and methods: We measured HUs in a region of interest within the confluence of dural venous sinuses in 166 unenhanced head CTs and correlated these data with HCT and HGB values in male and female patients aged 2 to 100 years. We then compared these data with similar measurements in 8 patients with recent venous sinus thrombosis. Two-tailed t test and linear regression analyses were performed to evaluate HGB and HCT between groups and with measured CT attenuation of intravascular blood, respectively.

Results: A statistically significant relationship was noted between both HCT and HGB with CT attenuation. Seven of 8 patients with sinus thrombosis had attenuation values >70, but none of the normal subjects had HUs >70.

Conclusions: Hemoconcentration correlates with CT attenuation in cerebral venous sinuses. Our findings suggest that comparing the ratio of HUs to HCT may be useful in gauging concern for sinus thrombosis.

Fig 1.

An example to demonstrate region of interest placement within the inferior aspect of the superior sagittal sinus.

Fig 2.

Scatterplot of sinus attenuation as a function of HCT with an HU >70 discriminating almost all cases with thrombosis from those without.

Fig 3.

Unenhanced CT of subjects A (HU 92, HCT46) and B (HU 86, HCT 36), both with documented superior sagittal sinus thromboses, compared with subjects C (HU 66, HCT 43) and D (HU 64, HCT 43), without thrombosis. Note that hemoconcentration may mimic the appearance of a sinus thrombosis.

Fig 4.

H:H ratio distribution demonstrates very little overlap between values for subjects without and with thrombosis, with no overlap when the value is ≥2.0.