Using a contemporary sample of patients, we have demonstrated that multimodal imaging can be acquired and processed in a timely manner. The acute stroke imaging process must be efficient to maximize the benefit of reperfusion paradigms based on CTP. In the endovascular thrombectomy era, upfront CTA is critical for patient selection. This report provides real world acute stroke CT time metrics for the purpose of benchmarking – cerebral CTA should be available within 6 to 7 minutes of a NCCT and CTP an extra 5 to 8 minutes. Our data reflect the inherent differences in work processes (timing of IV cannulation) and imaging processes (cerebral CTA from CTP data compared to arch to vertex CTA) at the study hospitals, this makes our data more generalizable.
We have focused on the imaging turnaround time alone to address the concern that additional perfusion imaging adds significant time delays in hyperacute stroke workflow. Indeed, if multimodal CT is not routinely performed upfront for all hyper-acute stroke, the addition of CTA alone may significantly delay the treatment workflow for patients with emergent large vessel occlusion presented to primary stroke centers.7 As recent as 2013, the median upload time for CTP alone was 23 minutes in health systems comparable to ours.8 With advances in hardware, network bandwidth and automated CTP processing, our overall median turnaround time is similar to the median of ~ 12 minutes from NCCT to completion of CTP processing reported in the multicenter Australasian EXTEND trial program which uses CTP exclusively for patient selection.4 Our definition of turnaround time, which starts from the planning scan, means routine median time recorded at Christchurch is even slightly faster than attended in EXTEND.
Extra information carries a cost, but the delay is minimal for most patients as shown by our data over a three-month period. We acknowledge the limitations; we did not record potential reasons for delay in patients with longer turnaround time, which most likely are due to patient factors such as agitation or difficult cannulation. Secondly, we only analyzed 3 months of data at each center but given the medians were consistent, additional cases are unlikely to change results. Thirdly, both our centers utilize automated perfusion processing, which may not be generally available and is likely to be faster than semi-automated processing using proprietary software.