Several randomized trials have shown the superiority of endovascular stroke treatment compared to standard medical therapy.1-2 However, after this fundamental change in acute stroke patients’ care, several factors influencing the clinical outcome after stroke treatment came into focus.3 Continuous evolution of endovascular techniques resulting in higher revascularization rates and shorter intervention times are just one element in the vibrant development of endovascular stroke treatment.4-5

Probably even more important are the intrahospital time delays. A recently published meta-analysis focusing on intrahospital timings found every 4-minute delay in intrahospital time to result in 1/100 patients with a worse outcome on the modified Rankin Scale.6 The workflow analysis of the ESCAPE trial showed that the increase of every 30 minutes from CT imaging to reperfusion reduced the probability of achieving an independent functional outcome by 8.3%.7 Therefore, we and others focused on reducing intrahospital time delays and made substantial progress over the last years.8 Even after standardizing intrahospital procedures, door to groin times of around 60-70 min have been reported for direct admission patients.8, 9 From our perspective, stroke management has to rely on absolute necessary aspects of acute stroke care and abandon all unnecessary time delays occurring from admission to reperfusion. Hence, we developed and implemented a one stop management of stroke patients, in which the usual multidetector CT (MDCT) and MDCT-angiography/perfusion evaluation is bypassed. Patients presenting with a National Institutes of Health Stroke Scale (NIHSS) ≥ 7 (as of January 2017) are now directly transferred to the angio suite. They are then examined by flat detector CT (FDCT) and FDCT-angiography and treated by endovascular means in case of a large vessel occlusion (LVO) subsequently.

We first started our one stop management back in January 2016 with transfer patients. As the majority of those patients is treated with thrombolysis during transport to our comprehensive stroke center, repeated imaging is justified to exclude an intracranial hemorrhage. We recently published a paper showing high sensitivity and specificity of FDCT in the detection of intracranial hemorrhages.10 Based on this study, we also implemented this one stop management in direct admission or “mothership” patients in June 2016. Download Publication
We only included patients with an NIHSS ≥ 10 in this first step. After treating 30 patients with this protocol we analyzed our findings and have submitted a manuscript, which is currently under review. The initial experience shows that we were able to significantly reduce our door to CT and door to groin times, while successfully differentiating ischemic from hemorrhagic stroke. In January 2017, we lowered the one stop management threshold to an NIHSS ≥ 7 based on a study indicating that an NIHSS ≥ 7 in the best threshold for predicting LVO.11

Imaging Protocol

Patients presenting with neurological symptoms consistent with severe acute stroke (according to a score of 7 and above on National Institutes of Health Stroke Scale) are directly transferred to our angiography suite (Artis Q; Siemens Healthcare GmbH, Forchheim, Germany). Our one stop approach consists of a non-enhanced FDCT scan and a multi-phase FDCT angiography (FDCTA). The following parameters are applied for FDCT and FDCTA respectively:

FDCT – 20 s rotation; 200° total angle with approx. 500 projections; 109 kV; 1.8 μGy/frame;
effective dose ∼2.5 mSv

FDCTA – intravenous injection of 60 ml contrast agent (Imeron 400; Bracco Imaging GmbH, Konstanz, Germany) at an injection rate of 5 ml/s followed by 60 ml saline chaser at the same injection rate of 5 ml/s; a power injector is used for injection; 2 x 10 s rotation; 200° total angle (0.8° per frame); 70 kV; 1.2 μGy/frame; effective dose ∼2.8 mSv;

The first rotation of the FDCTA is timed after a bolus-tracking digital subtraction angiography to capture the peak arterial phase, while the second phase is acquired automatically after 5 seconds correlating to the venous phase. We collimate the FDCT for depiction of the cerebrum only, thus reducing radiation dose, but plan the FDCTA without any collimation in order to delineate the carotid bifurcation with the caudal section of the scan.

FDCT and FDCTA projections are reconstructed on a commercially available postprocessing workstation (Syngo X Workplace; Siemens Healthcare GmbH). For FDCT, a “HU smooth” kernel and “DynaCT Clear” algorithm are applied to obtain images with a 512 × 512 matrix. These are reconstructed with 5 mm slice thickness and 3 mm interslice distance. FDCT images are used for the detection of intracranial hemorrhage and larger ischemic lesions. Images acquired according to our protocol proved to be a reliable and accurate tool for the detection of intracranial hemorrhage. Gray–white differentiation is feasible in the supratentorial region.10

For FDCTA, a “HU normal” kernel is utilized. Images are reconstructed as maximum intensity projections (MIPs) with a slice thickness of 24 mm and an interslice distance of 3 mm. We separately reconstruct and save the arterial and venous phase with thick MIPs. Additionally, a fused image of both FDCTA datasets is reconstructed as a thick intracranial MIPs series and we also reconstruct a thin MIP series (2mm slice thickness, 1mm interslice distance) for evaluation of the carotid bifurcation and the proximal internal carotid artery. FDCTA images allow for a reliable detection of occluded vessels and for the evaluation of collateral status. We chose to omit perfusion imaging from our protocol due to the susceptibility of current protocols to patient motion, the time-intensive character of dynamic perfusion acquisitions/reconstructions and the inability of dynamic perfusion imaging to reliably predict treatment effect of endovascular therapy on a recent analysis of the MR CLEAN trial.12 Additionally, the only perfusion product available on FDCT at the moment is PBV-imaging. A prospective study has already shown that PBV-maps can overestimate CBV-lesions derived from “real” dynamic MDCT Perfusion images.13 A delayed acquisition of PBV-images could solve this problem, but has the disadvantage of limited detectability of arterial occlusions due to the venous contrast phase. In contrast, imaging of collaterals is a good predictor of both patient outcome and treatment effect, even when performed on single phase CTA.14 The use of a biphasic FDCTA in our protocol with a late, venous phase allows for the additional detection of late cerebral collaterals and eliminates the danger of misjudging collateral status. Also, the proposed FDCTA protocol is a commercially available product, which can be used in any modern Siemens angio suite as soon as the bolus tracking DSA sequence is configured by an application assistant. The effective dose of our protocol (overall effective dose of ~5 mSv) is comparable to published MDCT stroke protocols with multiphase MDCTA and lower than MDCT protocols comprising perfusion imaging. Although the coverage of our FDCTA protocol cannot be compared to cervical MDCTA scans depicting the aortic arch, the coverage is long enough to evaluate the carotid bifurcation.


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