Subtraction multiphase CT angiography: A new technique for faster detection of intracranial arterial occlusions.

Objective: To describe and evaluate a novel technical development to improve detection of intracranial vessel occlusions using multiphase CT angiography (MPCTA).

Materials And Methods: The institutional ethics committee approved the study. Fifty patients (30 consecutive distal (M2 or smaller) anterior circulation occlusions, ten M1 occlusions, ten cases without occlusion) presenting with suspected AIS who underwent MPCTA were included. Post-processing of MPCTA studies created "subtraction" and "delayed enhancement" (DE) datasets. Initially, non-contrast CT and MPCTA studies for each patient were evaluated. Readers' confidence, speed and sensitivity of detection of intracranial vessel occlusions were recorded. After an interval of at least 4 weeks, readers were provided with post-processed images and studies were re-evaluated.

Results: While the sensitivity of detection of intracranial vessel occlusions was equal for both conventional MPCTA and subMPCTA, the mean time taken to identify a vessel occlusion decreased by 64 % using subMPCTA (16 s vs. 45 s with conventional MPCTA) (p<0.001). In addition, confidence in interpretation improved (from 4.4 to 4.9) using subMPCTA (p<0.001).

Conclusion: SubMPCTA is a novel technique that aids in identifying small intracranial vessel occlusions in the suspected AIS patient. SubMPCTA increases confidence in interpretation and reduces the time taken to detect intracranial vessel occlusions.

Key Points: • SubMPCTA processes MPCTA data to better demonstrate intracranial arterial occlusions. • SubMPCTA increases confidence and speed of interpretation of MPCTA studies. • SubMPCTA may aid in rapidly differentiating acute ischaemic stroke from stroke mimics.