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Methinks CTA Stroke is a radiological computer aided triage and notification software, parallel workflow tool for use by hospital networks and trained clinicians to identify and communicate images of specific patients to a specialist, independent of standard of care workflow.

Methinks CTA Stroke uses an artificial intelligence algorithm to analyze images for findings suggestive of a pre-specified clinical condition and to notify an appropriate medical specialist of these findings in parallel to standard of care image interpretation.

Identification of suspected findings is not for diagnostic use beyond notification.

Specifically, the device analyzes CT angiogram images of the brain acquired in the acute setting and sends to PACS and/or notifications to a neurovascular specialist that a suspected large vessel occlusion has been identified and recommends review of those images. Images can be previewed through an image viewer. Methinks CTA Stroke is intended to analyze terminal ICA, MCA-M1 and MCA-M2 vessels for LVOs.

Images that are previewed are for informational purposes only and not intended for diagnostic use beyond notification. Notified clinicians are responsible for viewing non-compressed images on a diagnostic viewer and engaging in appropriate patient evaluation and relevant discussion with a treating physician before making care-related decisions or requests. Methinks CTA Stroke is limited to analysis of imaging data and should not be used in-lieu of full patient evaluation or relied upon to make or confirm diagnosis.

Methinks CTA Stroke is a software-only device which is intended to be used by trained physicians involved in the management of Acute Stroke (AS) patients at emergency settings or other departments across the stroke care pyramid model. They include trained physicians such as emergency physicians, neurologists, general radiologists, neurovascular interventionists, neuroradiologists and any trained stroke professionals.

The target patients (intended patient population) are male and female in the adult population (above 21 years old) with suspected Acute Stroke.

The Methinks CTA Stroke device analyzes Computed Tomography Angiography (CTA) images from the intended patient population to identify suspected Large Vessel Occlusions (LVO). This information is to be used in conjunction with other patient information by a professional to assist with triage/prioritization of medical images.

The input of the software is Computed Tomography Angiography (CTA) in DICOM format from patients suspected of Acute Stroke. The outputs of the software are notifications sent to the trained physicians intended to be used in conjunction with other patient information for professional judgment to assist with triage/prioritization.

Here is a comprehensive breakdown of the acceptance criteria and the study proving the Methinks CTA Stroke device meets those criteria, based on the provided FDA 510(k) clearance letter:

Acceptance Criteria and Study Details for Methinks CTA Stroke

Context: The Methinks CTA Stroke device is a radiological computer-aided triage and notification software that uses an AI algorithm to analyze CT angiogram images for findings suggestive of a Large Vessel Occlusion (LVO) and notifies a neurovascular specialist.

1. Table of Acceptance Criteria and Reported Device Performance

The direct acceptance criteria (pre-specified performance goals) are explicitly stated in the document for Sensitivity and Specificity. The time to notification is also presented as a performance metric.

Note: While the document states "Sensitivity and specificity exceed the pre-specified performance goals for LVO," the specific numerical thresholds for these goals are not provided in the extract.

2. Sample Size Used for the Test Set and Data Provenance

• Test Set Sample Size: 336 cases
  • LVO Positive: 110 cases
  • LVO Negative: 226 cases
• Data Provenance: Retrospective, blinded, multicenter, multinational study. Institutions included in the validation study were different from institutions included in training, ensuring separation and representativity. This was verified by checking countries, states, and ZIP codes. The specific countries are not mentioned beyond "multinational."

3. Number of Experts Used to Establish Ground Truth and Qualifications

• Number of Experts: Two primary readers, with a third expert for adjudication. (Total of 3 experts involved in establishing ground truth for any given case of disagreement)
• Qualifications of Experts: US board-certified neuroradiologists. (No years of experience are specified).

4. Adjudication Method for the Test Set

• Method: Majority vote (2+1 adjudication). Ground truth was established by two US board-certified neuroradiologists. If they disagreed regarding LVO findings, a third ground truther established the final ground truth based on the majority vote.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

• The provided document does not indicate that an MRMC comparative effectiveness study was done looking at how human readers improve with AI vs. without AI assistance. The study focuses solely on the standalone performance of the AI algorithm.

6. Standalone Performance (Algorithm Only)

• Yes, a standalone performance study was done. The reported Sensitivity and Specificity values (98.2% and 91.6% respectively) represent the performance of the AI algorithm itself in identifying LVOs, without human-in-the-loop assistance for the core performance metrics.

7. Type of Ground Truth Used

• Ground Truth Type: Expert consensus. Specifically, it was established by two US board-certified neuroradiologists, with a third neuroradiologist for adjudication in case of disagreement.

8. Sample Size for the Training Set

• The document does not explicitly state the sample size used for the training set. It only mentions that "Institutions included in the validation study were different from institutions included in training," but the training dataset size is not provided.

9. How Ground Truth for the Training Set Was Established

• The document does not explicitly describe how ground truth for the training set was established. It only details the ground truth establishment process for the test set. It is implied that similar expert review would have been used, but no specific methodology or number of readers are provided for the training data.

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