Should a one-stop CT for stroke do CTA or CTP first?

A "one-stop" CT examination of the head in stroke is also known as multimodal CT imaging of the skull, including CT scan (NCCT), CT angiography (CTA), and CT perfusion imaging (CTP
).

In accordance with the latest AHA/ASA guidelines, perfusion tests are not recommended for patients with ischemic stroke within 6 h to select patients suitable for mechanical thrombectomy, and it is recommended to evaluate patients with ACS including CT perfusion, MRI DWI, or MRI perfusion imaging, and to screen for intravascular mechanical thromboplasty therapy
in patients with anterior circulation aortic occlusion 6 to 24 h from the last normal time.

Hemorrhagic stroke and ischemic stroke

According to the latest Chinese guidelines, patients with suspected acute ischemic cerebrovascular disease are usually clinically evaluated for neurological deficits to determine whether the patient is a mild stroke or a stroke due to suspected large vascular occlusion
.

When large blood vessel occlusion is suspected, "time is the brain", and the imaging method is the shorter the examination process in the case of meeting the following conditions: the examination equipment can be put into use immediately; Short inspection time; The patient has no contraindications to examination and is easy to monitor during the examination; It can provide the necessary cerebrovascular morphology and blood flow perfusion information of brain tissue.

Imaging examination mode of acute ischemic cerebrovascular disease is mainly divided into three types: CT mode, MR mode and CT/MR mixed mode
.

The time window is defined as the anterior circulation intra-arterial treatment window of 6 hours (femoral artery puncture initiation time), and perfusion imaging
is not recommended for patients who intend to undergo intra-arterial therapy within 6 hours of onset, after CTA or MRA examination has confirmed the presence of large vascular occlusion.

For patients with acute ischemic cerebrovascular disease with anterior circulation artery occlusion, if the overtime window (6 to 24 hours) or the time of onset is unknown, perfusion imaging is highly recommended to evaluate the core infarction area and ischemic semi-dark band to help screen patients
suitable for intraarterial therapy.

There is a problem here, if you do CTA first and find out the criminal blood vessels, you need to wait for the contrast agent to be excreted after the CTA is completed, and then perform CTP examination
.

Considering that most of the responsible blood vessels of acute ischemic cerebrovascular disease are in the base section of the ICA skull and intracranial blood vessels, in order to save examination time, reduce the amount of radiation and contrast agent used in patients, CTP data is recommended to reconstruct cranial CTA when the equipment allows, and the image quality can meet the diagnostic needs
of the emergency department for acute ischemic cerebrovascular disease 。 When post-CTP management shows clear hypoperfusion changes in brain tissue, but CTP reconstructed cranial CTA does not show intracranial macrovascular abnormalities, suggesting that the responsible vessel may be an extracranial segment ICA, it is recommended to perform head and neck CTA after CTP, or direct DSA in
combination with clinical conditions.

The results of the Interventional Stroke III Study (IMS III) suggest that one-stop CT does not delay recombinant tissue plasminogen activator (rt⁃PA) thrombolytic therapy or intravascular therapy
for ischemic stroke.

summary

For acute ischemic stroke with a definite onset of less than 6 hours, CTP examination may not be required, and for patients with onset of 6-24 hours or patients with unknown onset time, one-stop CT examination should be performed, in order to save examination time, CTP examination should be performed first, and CTP data should be used for head CTA reconstruction and lateral branch circulation assessment, and if necessary, head and neck CTA should
be performed.