Purpose The region defined as ‘at risk’ penumbra by current CT perfusion (CTP) maps is largely overestimated. We aimed to quantitate the portion of true ‘at risk’ tissue within CTP penumbra and to determine the parameter and threshold that would optimally distinguish it from false ‘at risk’ tissue, that is, benign oligaemia.
Methods Among acute stroke patients evaluated by multimodal CT (NCCT/CTA/CTP) we identified those that had not undergone endovascular/thrombolytic treatment and had follow-up NCCT. Maps of absolute and relative CBF, CBV, MTT, TTP and Tmax as well as summary maps depicting infarcted and penumbral regions were generated using the Intellispace Portal (Philips Healthcare, Best, Netherlands). Follow-up CT was automatically co-registered to the CTP scan and the final infarct region was manually outlined. Perfusion parameters were systematically analysed – the parameter that resulted in the highest true-negative-rate (ie, proportion of benign oligaemia correctly identified) at a fixed, clinically relevant false-negative-rate (ie, proportion of ‘missed’ infarct) of 15%, was chosen as optimal. It was then re-applied to the CTP data to produce corrected perfusion maps.
Results Forty seven acute stroke patients met selection criteria. Average portion of infarcted tissue within CTP penumbra was 15%±2.2%. Relative CBF at a threshold of 0.65 yielded the highest average true-negative-rate (48%), enabling reduction of the false ‘at risk’ penumbral region by ~half.
Conclusions Applying a relative CBF threshold on relative MTT-based CTP maps can significantly reduce false ‘at risk’ penumbra. This step may help to avoid unnecessary endovascular interventions.
- ct perfusion
- blood flow
- ct angiography
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Contributors SP and DO made a substantial contributions to the conception and design of the work together with data interpretation and analysis. DL, YM, YK, SY and EL made a signinificant contribution to the radiological data acquisition, analysis and interpretation. ZIH contributed to the work design and submission process. SK did the final revision of the statistical analysis of the data. SP, DG and DT were in charge of drafting the work and revising it critically for important intellectual content. All the authors gave their final approval for this version to be published.
Competing interests YK and SY are employees of Philips Healthcare.
Patient consent Obtained.
Ethics approval Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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