Fast FLAIR MR Images of Intracranial Hemorrhage

PURPOSE: To evaluate the signal characteristics of intracranial hemorrhage, as seen on fluid attenuatedinversion recovery(FLAIR) MR imaging according to various stages, and to compare FLAIR imaging with spin-echo T1-and T2-weighted MR imaging. MATERIALS AND METHODS: We retrospectively evaluated fast FLAIR images along withspin-echo T1- and T2-weighted MR images of 32 lesions in 26 patients (12 males and 14 females, aged 3-84 yrs) withintracranial hemorrhagic lesions. For imaging, a 1.5T unit was used, and the nature of the lesions was found to beas follows : intracranial hemorrhage(n=15) ; tumor(n=9) ; infarction (n=4) ; arteriovenous malformation (n=3) ;and arachnoid cyst with hemorrhage(n=1). On the basis of spin-echo MR imaging, lesions were classified as acute,early subacute, late subacute, early chronic, or late chronic stage. The signal characteristics of intracranialhemorrhage were analysed in accordance with each staging, as seen on MR FLAIR imaging, and compared to the stagingseen on spin-echo T1- and T2-weighted MR imaging. RESULTS: For the 32 hemorrhagic lesions, staging was found to beas follows : acute(n=4) ; early subacute(n=8) ; late subacute(n=11) ; early chronic(n=5) and late chronic(n=1). Inthe remaining three patients with arteriovenous malformation, the stage of the hemorrhage was found to be mixedsubacute and chronic. The signal intensity of hemorrhage, as seen on FLAIR imaging during the acute andearly-subacute stage, was low, and during the late subacute stage it was high ; for T2WI, the findings weresimilar. FLAIR imaging, however, showed that hemorrhage intensity during the early chronic stage was low, and thatof the late chronic stage was very low ; these findings were similar to those of T1WI. CONCLUSION: The signalintensity of intracranial hemorrhage, as seen on FLAIR imaging, was not characteristic ; it was similar to that ofT2WI during the acute and subacute stages, and similar to that of T1WI during the chronic stage. When usedtogether with spin-echo T1- and T2-weighted MR imaging, however, FLAIR imaging may be useful for theclassification of chronic intracranial hemorrhage as either early or late stage.