Clinical utility of temporal subtraction imaging in head CT: a pictorial review

Temporal subtraction (TS) imaging highlights interval changes by computing a voxel-wise difference between spatially registered serial CT examinations, converting side-by-side comparison into a single map of change. Although TS head CT has been validated for acute cerebral infarction detection, its application across the broader spectrum of intracranial pathologies has not been systematically described. We present a pictorial review of twelve clinical cases covering hemorrhagic, ischemic, vascular, neoplastic, and degenerative pathologies. TS imaging was particularly effective for lesions near the visual detection threshold, multi-focal interval findings, and bilateral symmetric changes. It also supported exclusion of new lesions in structurally complex backgrounds. Characteristic artifacts from source-image degradation, scanner protocol differences, and retained contrast are also illustrated. TS head CT is a broadly applicable reading aid with potential to improve diagnostic conspicuity across a wide range of intracranial pathologies. Awareness of characteristic artifacts is essential for accurate interpretation.