Virtual Monoenergetic Imaging of the Lower Extremities Using Dual-Energy CT Angiography in Patients with Diabetes Mellitus: A Randomized Controlled Trial

Type 2 diabetes mellitus (DM) is the most common metabolic disorder in the
world and a major risk factor for cardiovascular disease, given its high
prevalence. Peripheral arterial disease (PAD) in the lower legs represents a
major complication of type 2 diabetes, often causing ischemic ulceration,
gangrene and amputation.
While digital subtraction angiography (DSA) remains the gold standard for
diagnosis of PAD, its invasive and time-consuming character makes it unsuitable
to use in a large group of patients. Therefore, computed tomography angiography
(CTA) is currently the method of choice for diagnosing PAD in the lower legs.
Dual-energy CTA (DECTA) has several advantages over conventional CTA, due to
different applications such as virtual mono-energetic imaging (VMI) and bone
removal software. DECTA uses raw data from high and low energy radiation (high-
and low-keV) beams to create low-keV images to improve image contrast and
iodine signal. In recent years, several studies have shown that VMI
reconstructions provide the best image contrast with the least possible noise
in low-keV reconstructions.
Often, patients suffering from PAD show reduced iodine levels in the lower legs
due to significant stenosis or occlusion upstream. Additionally, evaluation of
the lower leg arteries in patients with PAD is often challenged by medial
arterial calcifications causing blooming artefacts. Therefore, imaging of the
lower legs in this particular group of patients can benefit from DECTA.

Several observational studies have been published evaluating DECTA for imaging
of the lower legs, comparing this technique with conventional CTA.
However, to the best of our knowledge, no randomised controlled trial has been
conducted comparing both conventional CTA and DECTA in patients with DM
suffering from PAD.
Thus, the purpose of our randomised controlled trial is to evaluate the
diagnostic accuracy and clinical utility of dual energy CTA using VMI with
conventional CTA in assessing PAD of the lower extremities in patients with
Rutherford stage 4 or higher. Additionally, it will explore the potential
benefits of DECTA in terms of image quality, radiation dose reduction, and
visualization of small vessels.

We aim to conduct a double blind randomized controlled trail conducted at
Haaglanden Medisch Centrum (HMC), The Hague (The Netherlands). Patients with
diabetes mellitus who are scheduled to undergo a CTA of their lower legs for
suspected arterial disease with Rutherford stage 4 or higher will be recruited
at the outpatient clinic for vascular surgery or the 'Eerste Diabetische
Voethulp' outpatient clinic.
Participants will be randomly assigned to one of two study groups: one group
will undergo a dual-energy CTA with VMI reconstructions (DECTA group) and the
other group will undergo the conventional mono-energetic CTA (CCTA group).
Imaging parameters and details concerning contrast media administation can be
found in chapter 3 of our researchprotocol.
Two blinded, experienced interventional radiologist will score the DECTA and
conventional CTA using a five point scale to asses image quality, image noise
and vessel contrast (Table 1 in our research protocol).

Participants are refered to the department of radiology for a CT scan of the
abdomen and lower extrimities as part of the standard care. Participants will
undergo either a dual energy CTA or a conventional CTA; both have a similar
radiation dose and similar of iodine dosage. There will be no extra risk
associated with participation. As the study consists of only one CTA-scan, no
additional hospital visits are necessary.