CT angiography with helical CT in the assessment of acute stage of subarachnoid hemorrhage.

Purpose: We evaluated the usefulness of helical CT in the preoperative assessment of ruptured cerebral aneurysms during the acute stage of subarachnoid hemorrhage (SAH).
Methods: Nine patients with 13 aneurysms were included in this study. Helical CT scanning was performed before preoperative angiography. The section thickness and the table-movement speed were 1-2 mm/sec. Helical CT scanning was started 20 sec after the start of injection of 100 ml of contrast agent at a rate of 3 ml/sec.
Results: The average CT value of SAH was 51.9 Hounsfield units (HU) and that of the aneurysm was 191.7 HU. Nine of 13 aneurysms greater than 3.0 mm in diameter were identified by three-dimensional CT angiography (3DCTA). In seven cases, the information provided by 3DCTA images, maximum intensity projection images, and multiplanar images, was very useful in surgical planning, providing information concerning the configuration of the neck and relationships between the aneurysm and brain parenchyma. Four aneurysms in two cases were not depicted by 3DCTA because they were located outside the imaging volume. This problem was overcome by changing the imaging volume according to the extent of origin of SAH.
Conclusion: We conclude that helical CT in patients with SAH is useful for surgical planning, providing valuable information that cannot be obtained by conventional angiography.