Detection of subarachnoid haemorrhage with magnetic resonance imaging

Objectives-To measure the sensitivity and specificity of five MRI sequences to subarachnoid haemorrhage. Methods-Forty one patients presenting with histories suspicious of subarach noid haemorrhage (SAH) were investigated with MRI using T1 weighted, T2 wei ghted, single shot fast spin echo (express), fluid attenuation inversion re covery (FLAIR), and gradient echo T2* sequences, and also by CT. Lumbar pun cture was performed in cases where CT was negative for SAH. Cases were divi ded into acute (scanned within 4 days of the haemorrhage) and subacute (sca nned after 4 days) groups. Results-The gradient echo T2* was the most sensitive sequence, with sensiti vities of 94% in the acute phase and 100% in the subacute phase. Next most sensitive was FLAIR with values of 81% and 87% for the acute and subacute p hases respectively. Other sequences were considerably less sensitive. Conclusions-MRI can be used to detect subacute and acute subarachnoid haemo rrhage and has significant advantages over CT in the detection of subacute subarachnoid haemorrhage. The most sensitive sequence was the gradient echo T2*.