Purpose: Segmentation of cerebral white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF) in head CT is important for subsequent quantitative analysis and automated detection of cerebral pathology. We introduce VCAST, a new volumetric annotation tool aimed at delineating soft tissue in non-contrast CT (NCCT) and CT perfusion (CTP).
Methods and Materials: VCAST supports traditional 2D visualizations and annotations, and provides functionalities to facilitate 3D segmentations based on pre-calculated grids of volumetric clusters where the clusters are spatially coherently grouped based on HUs. Clicking a cluster in a 2D-plane allows for inclusion of the 3D-cluster in the output segmentation.
Ten patients with suspicion of ischemic stroke were included in this retrospective study, five NCCTs and five whole brain CTPs (320-row detector scanner). Temporal average CTA was reconstructed from CTP and in one slice in arbitrary direction, WM, GM and CSF were annotated two times by one observer using VCAST. In NCCT, a subvolume of approximately 22 mm^3 was randomly selected in which CSF was annotated by one observer, using VCAST either with 2D (slice-based) or 2D and 3D (cluster-based) annotation support. Dice coefficients and annotation times were reported.
Results: Dice coefficients were 0.86A+-0.04, 0.91A+-0.02, 0.87A+-0.02 for CSF, GM and WM respectively. CSF annotation times reduced from 16A+-9 to 8A+-5 minutes with 3D cluster support (p=0.02). CSF Dice similarity was 0.81A+-0.03.
Conclusion: VCAST is a volumetric annotation tool which reduces the time to obtain 3D segmentations in head CT while maintaining good overlap with a slice-based approach.