Purpose: Thrombolytic therapy has emerged as a new treatment option in the hyperacute stage of ischemic stroke. Although a 15% increase in meaningful rccovery has been observed at three months, it can also trigger devastating hemorrhagic transformations. Therefore, it is important to select suitable patients to undergo this treatment. The purpose of the present study was to evaluate the feasibility of cerebral blood flow (CBF) measurement by xenon-enhanced CT (Xe-CT) in patients with acute ischemic stroke as well as its potential in identifying the occluded artery and the stroke subtype. In effect, this study examines the potential for Xe-CT to select the appropriate candidates for thrombolytic therapy.
Methods : In 36 sequential patients (average age: 64.1 ± 13.1) with sudden-onset of ischemic stroke (except for lacunar stroke) who had presented to our hospital within two hours after the onset, we performed Xe-CT and MRI diffusion-weighted imaging (DWI). A selective cerebral angiography was also done if further evaluation was warranted. We examined the sensitivity of Xe-CT in demonstrating the ischemic area compared with that of DWI, its potential to identify the stroke subtype, its ability to determine infarction and hemorrhage based on CBF thresholds, and its contribution to selection of thrombolysis candidates.
Results: Xe-CT was completed safely in 31 out of 34 patients (91%). Within three hours after symptom onset, Xe-CT detected the ischemic area in most of the patients (94%), whereas DWI failed to do so in 24%. Of 14 patients who underwent both Xe-CT and angiography, the diagnosis of the stroke subtype determined by Xe-CT was confirmed to be correct by angiography in 11 patients (79%). The CBF threshold of nonhemorrhagic infarction in the gray matter became constant (19ml/100g/min) at 3-5 hours after the onset. In hemorrhagic infarction, however, the threshold was initially found to be lower (9ml/100g/min) at 3-5 hours and reaching comparable levels with non-hemorrhagic subtypes (17ml/100g/min) at 5-6 hours. Fourteen patients (39%) were excluded from participation in angiography or subsequent thrombolysis because of their Xe-CT findings.
Conclusion: This study found that Xe-CT was feasible in patients with hyperacute ischemic stroke and more sensitive than DWI in detecting the ischemic area. Moreover, Xe-CT provided crucial information including the stroke subtype and residual CBF in the ischemic territory. Therefore, CBF measurement by Xe-CT may be useful in the patient selection criteria for thrombolytic therapy in the hyperacute phase.
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