Follow-up of intracranial aneurysms treated with the Surpass flow diverter: comparison of subtraction CTA and DSA. Part I: a prospective case cohort study

Using flow diverters (stent-like implants that divert the flow from the
aneurysm sac) to treat unruptured intracranial aneurysms is increasingly
accepted as the treatment of choice. Nowadays, the gold standard for
radiological follow*up (FU) to evaluate the degree of occlusion of aneurysms is
digital subtraction angiography (DSA). Some non-invasive diagnostic methods
have also been described, but there is a lack of evidence about their
reliability.
Subtraction CT angiography (sCTA) is a promising non-invasive technique with an
accurate spatial resolution that could theoretically provide the same
information as DSA.
We will perform a sCTA and a DSA, the latter of which is the standard
radiological FU, and will then compare the accuracy of the two methods in terms
of the visualisation of the degree of occlusion of an aneurysm. The first
radiological FU will be scheduled for 1 month after treatment with the Surpass
flow diverter device (Surpass).

Primary objective:
- To determine the accuracy of sCTA compared to DSA in the visualisation of the
degree of occlusion in the FU of intracranial aneurysms treated with Surpass.

Secondary objectives:
-To determine the accuracy of sCTA compared to DSA in the visualisation of the
patency of the parent vessels, and the correct deployment, position and
apposition of the Surpass.
-To assess the complications related to the two diagnostic methods.

Single centre, prospective case cohort study.

In addition to the standard FU DSA, patients will undergo a sCTA 1 month after
the implantation of the Surpass. This will not lead to a longer admission, as
we will schedule both studies on the same day. This may mean that a patient has
to stay in the hospital for a slightly longer time (approximately 1 hour). As
sCTA is a non-invasive technique, with side-effects that only very rarely arise
as a result of the administration of the contrast agent, any additional risks
are estimated to be nearly zero.
As it is still unclear when aneurysms precisely occlude after implantation of
the Surpass, we will schedule the first radiological FU 1 month thereafter. If
we obtain evidence about actual occlusion times, we may be able to discharge
patients from further FU earlier. This would have important financial and
patient-related emotional consequences.
An extra 50cc of contrast agent will be administered in addition to the
standard care DSA. Patients at risk of contrast-induced nephropathy will be
excluded from participation. Adverse reactions related to the use of the
contrast agent (Xenetix) are generally mild to moderate, and transient. The
adverse reactions most commonly reported are feeling of warmth, pain and oedema
at the injection site. The hypersensitivity reactions are usually immediate
(during the injection or over the hour following the start of the injection) or
sometimes delayed (one hour to several days after the injection).
The total amount of extra radiation that patients will receive at each sCTA is
2.6 mSv.