Penumbra Pattern Assessment in Acute Stroke Patients: Comparison of Quantitative and Non-Quantitative Methods in Whole Brain CT Perfusion

Background And Purpose

While penumbra assessment has become an important part of the clinical decision making for acute stroke patients, there is a lack of studies measuring the reliability and reproducibility of defined assessment techniques in the clinical setting. Our aim was to determine reliability and reproducibility of different types of three-dimensional penumbra assessment methods in stroke patients who underwent whole brain CT perfusion imaging (WB-CTP).

Materials And Methods

We included 29 patients with a confirmed MCA infarction who underwent initial WB-CTP with a scan coverage of 100 mm in the z-axis. Two blinded and experienced readers assessed the flow-volume-mismatch twice and in two quantitative ways: Performing a volumetric mismatch analysis using OsiriX imaging software (MM_VOL) and visual estimation of mismatch (MM_EST). Complementarily, the semiquantitative Alberta Stroke Programme Early CT Score for CT perfusion was used to define mismatch (MM_ASPECTS). A favorable penumbral pattern was defined by a mismatch of ≥30% in combination with a cerebral blood flow deficit of ≤90 ml and an MM_ASPECTS score of ≥1, respectively. Inter- and intrareader agreement was determined by Kappa-values and ICCs.

Results

Overall, MM_VOL showed considerably higher inter-/intrareader agreement (ICCs: 0.751/0.843) compared to MM_EST (0.292/0.749). In the subgroup of large (≥50 mL) perfusion deficits, inter- and intrareader agreement of MM_VOL was excellent (ICCs: 0.961/0.942), while MM_EST interreader agreement was poor (0.415) and intrareader agreement was good (0.919). With respect to penumbra classification, MM_VOL showed the highest agreement (interreader agreement: 25 agreements/4 non-agreements/κ: 0.595; intrareader agreement 27/2/0.833), followed by MM_EST (22/7/0.471; 23/6/0.577), and MM_ASPECTS (18/11/0.133; 21/8/0.340).

Conclusion

The evaluated approach of volumetric mismatch assessment is superior to pure visual and ASPECTS penumbra pattern assessment in WB-CTP and helps to precisely judge the extent of 3-dimensional mismatch in acute stroke patients.