Computerized tomography (CT) is the mainstay imaging modality for assessing changes in ventricular volume in patients with a ventricular shunt (1-2) or external ventricular drain (EVD) (3). Rapid and accurate assessment of ventricular volume is critical for determining stability or change and can be complicated by significant differences in head position between scans. We evaluated the performance of a novel fully automated CT registration and subtraction method, CoPilot, to improve reader accuracy and certainty compared with current standard-of-care CT.
In a retrospective evaluation of 49 ventricular shunt or EVD patients who underwent sequential head CT scans with CoPilot, reader performance (of one neurosurgery and two radiology residents) was assessed relative to a goldstandard read based on a board-certified neuroradiologist's interpretation. Reader ratings were assessed on ability to discern change versus stability in ventricular volume between scans using standard axial CT reformats versus CT CoPilot reformats and subtraction images.
Of the 49 cases, ventricular volume was increased in 13, decreased in 17, and unchanged in 19. CT CoPilot showed significant improvement in detecting interval ventricular volume change (increase or decrease) (p = 0.045), but not unchanged volume. Furthermore, CT CoPilot improved reader certainty in determining increased (90 vs. 67%) or decreased ventricular volume (92 vs. 78%) (p = 0.001). Inter-rater reliability (IRR) for interpretation of standard axial CT and CT CoPilot images were 86 and 93%, respectively.
CT CoPilot significantly improves the reader's ability to detect changes in ventricular volume between sequential scans in patients with ventricular shunts or EVD (i.e. improves agreement with the expert read), as well as the reader's degree of certainty. CoPilot may serve as an additional tool for rapid assessment of change in ventricular volume in the setting where determining subtle change is of critical clinical importance.