Graphic Profiles of Cerebral Perfusion in Dynamic CT Imaging of Hyperacute Ischaemic Stroke

Abstract

Ischaemic stroke accounts for 80% of cerebrovascular disease. It is the third commonest cause of death, the second cause of dementia and the primary cause of disability. The widespread availability of CT scanning, the speed of examination and its low cost make CT the gold standard for early diagnosis of stroke before the mechanisms of cell swelling are triggered heralding irreversible neuronal damage. CT scanning allows morphological assessment of brain parenchyma demonstrating or excluding any bleeding and direct or indirect signs of ischaemia. It also allows perfusion imaging to display the cerebral territory at risk. Our study aimed to devise a dynamic CT perfusion imaging technique for use on an ordinary spiral CT system to be combined with morphological study and head and neck CT angiography to disclose the cause of the stroke correlated to clinical findings. Eighty patients with transient and permanent clinical forms of acute ischaemic stroke were referred to our institution within 0.5 to eight hours after clinical onset of symptoms. All patients underwent standard CT scan followed by CT perfusion imaging, intracranial CT angiography, neck CT angiography and brain CT scan after contrast administration. Each patient received a 40 ml bolus of iodate contrast agent for each examination for a total of 120 ml at a concentration of 300 mg/ml. CT perfusion imaging yielded a graph obtained over a ROI centred on the lentiform nuclei showing the peak time (PT) equal to the mean transit time (MTT) and dependent on cerebral blood flow (CBF). The graphic profiles of perfusion correlated to clinical findings and intra and extracranial CT angiography MIP reconstructions demonstrated the etiopathogenesis of stroke, the vascular territory affected and the prognosis. Combined with morphological study of brain parenchyma, CT angiography and clinical findings, CT perfusion graphs offer an immediate diagnosis of hyperacute ischaemic stroke allowing prompt therapeutic decisions to improve the prognosis.