Assessment of coronary stent patency by photon counting CT

Computed tomography (CT) is routinely used to non-invasively visualize and
assess coronary arteries for presence of atherosclerosis. Coronary stenoses are
often treated by percutaneous coronary intervention (PCI) including placement
of a stent in the affected coronary artery. If after coronary stenting, the
patient has recurrent angina, this may be due to in-stent restenosis.

Although assessment of coronary stent patency is possible to a certain degree
with current CT scanners it is still hampered by technical limitations of the
scanner, the lack of sufficient spatial resolution to visualize the small stent
diameter as well as blooming artefacts generated by the stent metal. In the
clinical setting, in-stent restenosis (ISR) is one of the main long-term
complications after coronary stent placement. This results in the routine use
of invasive coronary angiography (ICA) to determine stent patency.

The use of ICA comes along with complications of the invasive procedure. To
determine stent patency by CT identifying the vessel lumen within a fraction of
a millimeter, and thus a much higher spatial resolution is required. Photon
Counting CT (PCCT) is a completely new technique that offers specific
advantages over the currently available city systems.

PCCT uses photon-counting detectors, which can overcome some of the technical
shortcomings associated with CCTA. PCCT offers an improvement in spatial
resolution up to a factor of three and furthermore eliminates electronic noise
which greatly improves image quality.

At Erasmus MC, one of the world's first commercially available photon counting
CT scanners has been installed that is cleared for clinical use.

Given the improvements in spatial resolution with photon counting CT we expect
that noninvasive determination of coronary stent patency with PCCT will be
possible with a higher sensitivity and specificity than before.

To assess the diagnostic performance of PCCT to identify the luminal patency
compared with ICA as the reference standard, in patients with a history of PCI
with stent placement and to assess image quality by applying different image
reconstruction techniques.

This study is a prospective, single-centre study.

Participants in this study gain no direct individual benefit from
participation. The knowledge gained will be incorporated in the optimization of
PCCT scan. This will be of benefit for other patients that will have to undergo
CT scanning in the future.

Potentially patients participating in the current study may have to undergo
repeat imaging to determine stent patency. If this is the case, they might
benefit from the knowledge gained in the current study.

There is a risk associated with the performance of the photon counting CT scan
due to administration of additional radiation dose and contrast material.

The benefit of this research project, which is an increase in knowledge leading
to health benefit, justifies the additional radiation risk of the order of one
in a hundred thousand, corresponding to an effective dose of 6 mSv for a normal
average adult. In clinical routine iodinated contrast material is considered to
be safe to administer up to 2 millilitres per kilogram of body weight.

Participants in this study will not be exposed to a total iodinated intravenous
contrast dose of more than this threshold. Additionally, there is the risk of
an allergic reaction to iodinated contrast material. Therefore, patients that
have a known contrast allergy cannot participate. Since intravenous iodinated
contrast material administration may decrease renal function, we will not
include patients with an eGFR of less than 30 ml/min/1.73m2. Therefore, we feel
the additional risk of iodinated contrast material administration with regard
to a decrease in renal function to be very low.