Introduction
: Endovascular thrombectomy is the gold standard treatment for acute ischemic strokes with large vessel occlusions (LVO). Manual image analysis is often time consuming and requires clinicians to be skilled in reading perfusion scans, as well as vessel images. RapidAI software has an automated processor to detect LVO of the middle cerebral artery and is analyzed in this study. A novel metric, number‐needed‐to‐review (NNR), is introduced to assess the clinical efficiency of this software.
Methods
: This is a retrospective review of patients with a suspected ischemic stroke and an image processed by RapidAI software from 11/1/2020 to 4/30/2021 at a regional hospital system. Only M1 LVOs were included. Sensitivities, specificities, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the following: Rapid LVO detection, gaze deviation (GD), hyperdense sign (HDS), Tmax >6 seconds, and NIHSS at presentation. The NNR was calculated for an M1 occlusion.
Results
: 559 patients were included in this study. M1 occlusion was detected in 42 (7.5%) cases. Rapid LVO detection software was found to have a sensitivity of 71%, specificity of 94%, PPV of 49%, and NPV of 92% for a M1 occlusion. When both GD and HDS were combined with Rapid LVO, the specificity and PPV increased to 100% for a M1 occlusion. A negative LVO software combined with either a low (<15 mL on Tmax >6s) or high (<50 mL on Tmax >6s) Tmax threshold were found to have a specificity and PPV of 100% for no M1 occlusion. The combination of GD, HDS, Rapid LVO+ (for M1 occlusion) and Rapid LVO‐ with a low Tmax threshold (for no M1 occlusion) yielded 24 images NNR per 100 cases. When the combination of GD, HDS, Rapid LVO+ was combined with Rapid LVO‐ and a high Tmax threshold, the NNR per 100 cases was 16. With the addition of NIHSS<7 for the remaining cases in the high Tmax group, the NNR per 100 cases decreased to 9.
Conclusions
: The addition of GD and HDS to the Rapid LVO increases the specificity and PPV for a M1 occlusion. When combined with a negative Rapid LVO detection and either a low or high Tmax >6s threshold, the NNR is significantly decreased. As few as 9 images per 100 would be needed to be manually reviewed by a clinician during stroke triage.