抄録
CT-scans made it possible to estimate the age of intracranial hematomas which had been almost impossible in conventional radiological studies. However, attenuation values of hematomas only reflect the concentration of hemoglobin in the hematoma and do not always indicate the age of the hematoma. This report proposes the usefulness of measurement of the methemoglobin to total hemoglobin (oxyhemoglobin and methemoglobin) ratio to determine the hematoma age more accurately.
Both the attenuation of hematomas in CT and the concentrations of total hemoglobin, oxyhemoglobin and methemoglobin in the hematomas of 75 cases of intracerebral hematoma, 34 cases of acute and subacute extracerebral hematoma and 29 cases of chronic subdural hematoma were analysed. Using a phantom, the correlation between the attenuation values and the concentration of hemoglobin was also studied.
The results supported the previous reports that the attenuation values of hematoma depended mainly on the concentration of total hemoglobin. It was shown that, in cases of intracerebral hematoma and acute extracerebral hematoma, chronological decrease of the attenuation values was well correlated with the decrease in concentration of total hemoglobin and with the increase in the ratio of methemoglobin.
On the other hand, in more than half (69%) of chronic subdural hematomas, the attenuation values or the concentration of hemoglobin and the amount of methemoglobin were not well correlated with the elapsed time from the trauma. Their attenuation values were much higher, and the methemoglobin was much lower than those of the standard curves obtained from the cases of intracerebral hematomas. These findings strongly indicated that recurrent or intermittent hemorrhages had occurred during the enlarging process of chronic subdural hematomas. It was also suggested that hematomas with low ratios of methemoglobin might be rather fresh even with hypodense CT findings.
