This patient has a history of chronic obstructive pulmonary disease with polycythemia (hemoglobin 19.7 g/dl / hematocrit 60.4%). Normal renal function. No history of previous intravenous contrast media administration. 

Normal blood (hematocrit 45%) measures approximately 40 HU. Increase in the circulating red cell mass (hematocrit over 60%) results in diffuse hyperdensity of cerebral vessel with a density over 55 HU.