Introduction/Purpose Computed tomography perfusion (CTP) is a common imaging modality utilized to assess acute ischemic stroke (AIS) patient eligibility for mechanical thrombectomy. This assessment is done using an ischemic tissue ratio (penumbra to infarct) which is required to be greater than 1 for patients to be eligible for thrombectomy. Since various CTP software utilize different perfusion parameters and thresholds, there are known to be discrepancies in the amount of ischemic tissue quantified for each and therefore conflicting decisions regarding thrombectomy eligibility across software. This study aimed to assess the volumetric agreement of infarct between CTP and 24-hour follow-up fluid-attenuation inversion recovery (FLAIR) magnetic resonance imaging (MRI) along with the number of patients who would be misdiagnosed as ineligible for thrombectomy based on penumbra to infarct ratios by each CTP software.
Materials and Methods Eighty-one emergent large vessel occlusion AIS patients who underwent successful reperfusion (thrombolysis in cerebral infarction 2b/2c/3) were included in this study. Predicted infarct and penumbra volumes were quantified within RAPID, Sphere, and Vitrea CTP software and compared with infarct measurements from FLAIR MRI. The following CTP parameters and thresholds were used to quantify ischemic tissue through comparison with contralateral hemispheres: RAPID: infarct=30% reduction of cerebral blood flow (CBF), penumbra=6 second increase in time to reach maximal residue function; Sphere: infarct=25% reduction of CBF (and 5 second increase of time-to-peak (TTP)), penumbra=5 second increase in TTP; Vitrea: infarct=38% reduction in cerebral blood volume (and 5.3 second increase in TTP or 55% reduction in mean-transit-time), penumbra=5.3 second increase in TTP or 5.8 second increase in delay time or 58% reduction in CBF. Penumbra to infarct ratios were calculated utilizing each software.
Results Mean infarct differences, represented as 95% confidence intervals, between each software and FLAIR MRI are as follows: RAPID=6.96±4.93 mL, Sphere=-0.07±6.11 mL, Vitrea=4.13±4.73 mL. Mean absolute errors for each CTP software compared with FLAIR MRI are: RAPID=14.48 mL, Sphere=15.43 mL, Vitrea=11.44 mL. Mean penumbra to infarct ratios for each CTP software are: RAPID=70.93; Sphere=32.72; Vitrea=12.33. Total number of patients misdiagnosed as ineligible for thrombectomy (penumbra to infarct ratio less than 1 but successful reperfusion was conducted) for each software: RAPID=1.23% (1/81), Sphere=6.17% (5/81), Vitrea=25.93% (21/81).
Conclusions Sphere provided the most accurate results regarding the closest predicted CTP infarct volume to the true FLAIR MRI infarct volume, although with slightly higher error in its measurements compared to RAPID and Vitrea. Penumbra to infarct ratio analysis indicated RAPID and Sphere to provide the most accurate assessment regarding patient eligibility for thrombectomy. However, it appears sacrificing ischemic tissue measurement precision is required for more accurate inclusion of patients as thrombectomy eligible. This is seen by the significantly high mean penumbra to infarct ratio for RAPID which may suggest a caution overestimation of penumbra to label as many patients as possible as thrombectomy eligible for the purpose of regaining lost neurological function.
Disclosures R. Rava: None. M. Mokin: 1; C; NIH grant support R21NS109575. 2; C; Canon Medical Systems Corporation, Cerebrotech, Imperative care. M. Waqas: None. J. Davies: 1; C; National Center for Advancing Translational Sciences of the National Institutes of Health under award number KL2TR001413. 3; C; Penumbra. 4; C; RIST Neurovascular. E. Levy: 2; C; Claret Medical, GLG Consulting, Guidepoint Global, Imperative Care, Medtronic, Rebound, StimMed. 4; C; NeXtGen Biologics, RAPID Medical, Claret Medical, Cognition Medical, Imperative Care (formerly the Stroke Project), Rebound Therapeutics, StimMed, Three Rivers Medical. Y. Hoi: 5; C; Canon Medical Systems Inc. A. Siddiqui: 2; C; Amnis Therapeutics, Boston Scientific, Canon Medical Systems USA Inc, Cerebrotech Medical Systems Inc, Cerenovus, Corindus Inc, Endostream Medical Ltd, Guidepoint Global Consulting, Imperative Care, Integra LifeSciences Corp, Medtronic, MicroVention, Northwest University–DSMB Chair for HEAT Trial, Penumbra, Q’Apel Medical Inc, Rapid Medical, Rebound Therapeutics Corp, Serenity Medical Inc, Silk Road Medical, StimMed, Stryker, Three Rivers Medical, Inc., VasSol, W.L. Gore & Associates. 4; C; Amnis Therapeutics, Apama Medical, Blink TBI Inc, Buffalo Technology Partners Inc, Cardinal Consultants, Cerebrotech Medical Systems, Inc, Cognition Medical, Endostream Medical Ltd, Imperative Care, International Medical Distribution Partners, Neurovascular Diagnostics Inc, Q’Apel Medical Inc, Rebound Therapeutics Corp, Rist Neurovascular Inc, Serenity Medical Inc, Silk Road Medical, StimMed, Synchron, Three Rivers Medical Inc, Viseon Spine Inc. C. Ionita: 1; C; Equipment grant from Canon Medical Systems, Cummings Foundation support. K. Snyder: 2; C; Canon Medical Systems Corporation, Penumbra Inc, Medtronic, Jacobs Institute.
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