Accuracy of dynamic perfusion CT with deconvolution in detecting acute hemispheric stroke

Abstract

Background and purpose: Dynamic perfusion CT (PCT) with deconvolution produces maps of time-to-peak (TTP), mean transit time (MTT), regional cerebral blood flow (rCBF), and regional cerebral blood volume (rCBV), with a computerized automated map of the infarct and penumbra. We determined the accuracy of these maps in patients with suspected acute hemispheric stroke.

Methods: Forty-six patients underwent nonenhanced CT and dynamic PCT, with follow-up CT or MR imaging. Two observers reviewed the nonenhanced studies for signs of stroke and read the PCT maps for TTP, MTT, rCBF, and rCBV abnormalities. Sensitivity, specificity, accuracy, and interobserver agreement were compared (Wilcoxon tests). Nonenhanced CT and PCT data were reviewed for stroke extent according to previously reported methods. Sensitivity, specificity, and accuracy of the computerized maps in detecting ischemia and its extent were determined.

Results: Compared with nonenhanced CT, PCT maps were significantly more accurate in detecting stroke (75.7-86.0% vs. 66.2%; P <.01), MTT maps were significantly more sensitive (77.6% vs. 69.2%; P <.01), and rCBF and rCBV maps were significantly more specific (90.9% and 92.7%, respectively, vs. 65.0%; P <.01). Regarding stroke extent, PCT maps were significantly more sensitive than nonenhanced CT (up to 94.4% vs. 42.9%; P <.01) and had higher interobserver agreement (up to 0.763). For the computerized map, sensitivity, specificity, and accuracy, respectively, were 68.2%, 92.3%, and 88.1% in detecting ischemia and 72.2%, 91.8%, and 87.9% in showing the extent.

Conclusion: Dynamic PCT maps are more accurate than nonenhanced CT in detecting hemispheric strokes. Despite limited spatial coverage, PCT is highly reliable to assess the stroke extent.

Fig 1.

55-year-old man with right homonymous hemianopsia and right-body hemisensory loss. Admission nonenhanced CT 6 hours after symptom onset was unremarkable (both reviewers), except for an attenuated left PCA (arrowheads, one reviewer). PCT shows prolonged MTT and reduced rCBF in the left PCA territory. rCBVs are reduced only in a small part of the left thalamus but are increased in the rest of the PCA territory. The areas correspond to infarct and penumbra on the computerized automated map. Figure and legend continues.

Fig 1.

Continued.—Admission CTA shows an occluded left P1 segment, which had recanalized but remained focally stenotic on follow-up MR angiography 3 days later. Follow-up DW image shows completed stroke in the predicted left thalamic infarct core. The penumbra did not infarct, most likely because of early recanalization; the MTT and rCBF abnormalities were however, categorized as false-positive since delayed MR imaging was selected as the criterion standard.

Fig 2.

77-year-old woman with acute-onset left hemiparesis. Admission nonenhanced CT 2 hours after onset is normal. TTP and MTT are prolonged in the right superficial MCA territory (arrows). rCBFs are normal, but rCBVs are higher than contralateral values. TTP and MTT changes are not explained by any vascular abnormality; right carotid bifurcation (arrowhead) and intracranial arteries are normal. Final diagnosis was TIA. Follow-up CT 14 days later was normal. TTP and MTT changes were regarded as false-positive and most likely related to luxury perfusion due to TIA.