Diagnosing a large slowly enhanced cerebral aneurysm using four-dimensional multiphase dynamic contrast-enhanced computed tomography angiography.

Our patient was diagnosed with acute subarachnoid hemorrhage on plain head computed tomography (CT). Multiphase dynamic contrast-enhanced CT angiography on a 64-row multidetector scanner revealed a large aneurysm in the left middle cerebral artery that was not detected on conventional helical CT angiography. We believed that increased intracranial pressure and rough thrombus within the aneurysm delayed its peak enhancement. Our case demonstrates the diagnostic utility of four-dimensional CT with multiphase volume data in cases of lesions with delayed enhancement.