Contrast bolus timing in CT-angiography and CT-perfusion: insights from a large clinical dataset

Introduction: CT-Perfusion (CTP) is an essential part of stroke imaging. Incomplete coverage of the contrast bolus in CTP can lead to errors in post-processing that might hamper the identification of the infarct core or tissue at risk. However, the arrival of the contrast bolus depends on various technical and patient individual factors. This study investigated whether timing information from CT-angiography (CTA) can be used to optimize bolus coverage in CTP.

Methods: We retrospectively reviewed cases with a multimodal stroke protocol for suspected ischemic stroke. Information on the contrast injection timing of CTA and CTP was extracted from the DICOM headers. Bolus arrival information were obtained from the CTP scan including peak time, height, and width and correlated with patient age and ejection fraction (the latter available in n = 868). The contrast timing information of the CTA was used to simulate optimized CTP timing.

Results: A total of 1,843 cases were included. CTP bolus peak position was associated with peak width (Pearsons's r = 0.89, p < 0.001), age (Pearsons's r = 0.40, p < 0.001), ejection fraction (Pearsons's r=-0.25, p < 0.001), and time to scan initiation based on triggering in CTA (Pearsons's r = 0.83, p < 0.001). Using information of the CTA timing to adjust the CTP timing, the variance of the AIF peak could significantly be reduced (p < 0.001).

Conclusion: Our data indicate that patient individual characteristics lead to substantial variances in the contrast bolus arrival which could hamper CTP analysis. To ensure optimized coverage of the contrast bolus. CTP timing can significantly and safely be improved using timing information of preceding CTA.