Non-invasive imaging of arteries, with computed tomography (CT) or magnetic resonance imaging (MRI), has become the reference for the assessment of most anatomic regions, from the intracranial to the plantar arteries. Besides some location-specific peculiarities, in particular the coronary arteries that require electrocardiogram synchronization, some common limitations are systematically encountered. First, small vessels are difficult or impossible to accurately assess as they are at (or below) the limit of spatial resolution of clinical systems. Second, calcifications, bones and dense artificial materials are limitations for CT examinations [1,2]. Indeed, not only they hamper the correct assessment of stenosis due to blooming artifacts but, especially in very small vessels, they are often indistinguishable from enhanced lumen making even the basic judgment of vascular patency unachievable. Third, regardless of the imaging modality employed, administration of contrast material is generally required and elicits well-known concerns [3].

MRI can overcome some of these limitations thanks to angiographic sequences with background suppression and sequences capable of revealing arterial lumen without the need for using contrast material. However, MRI examinations are sparsely available, expensive, and time-consuming. In addition, the above-mentioned sequences are prone to several pitfalls and of limited use for regions other than intracranial vessels [4].

On the contrary, spectral photon counting CT (SPCCT) has the potential to overcome these limitations by combining all the advantages of CT with its new features. With these revolutionary scanners, spatial resolution is greatly improved, and blooming artifacts are reduced, for instance in coronary arteries [5,6]. Furthermore, as photons are directly counted and classified in specific energy bins, SPCCT allows for the so-called “K-edge imaging.” This technique relies on the specific depiction of certain elements [7]. The prerequisite is that the K-edge of the element of interest needs to fall in the range of energy values that can be explored with SPCCT. Therefore, the list of depictable materials includes gadolinium but not iodine that has its K-edge at 33 keV, too low to be imaged with SPCCT. Therefore, following injection of gadolinium in the circulation system of a living creature, K-edge imaging enables visualization (and quantification) of this sole element, hence only the enhanced vascular lumina, in a purely angiographic image.

The purpose of this study was to investigate the feasibility of K-edge angiography after different gadolinium-based contrast agents (GBCA) injection in atherosclerotic rabbits with a SPCCT prototype.