Ultra Low Iodine Loaded Spectral CT Angiography (CTA)

CT angiography (CTA) of the aorta and the lower limb is one of the most important tools for diagnostic, evaluation of the severity of the peripheral arterial disease, decision making, treatment planning and follow-up; but usually requires the use of iodine contrast medium. Due to the high prevalence of renal impairment (eGFR \< 90 ml/min/1.73m) in the elderly hospitalized population (more than 90% among inpatients aged over 60 years) contrast-medium-induced nephropathy is a major concern in this population. The recently introduced spectral CT technique utilizes x-rays covering a spectrum of energy-levels as opposed to conventional CT in which x-rays are set to one specific energy level. This technology offers many possibilities, such as "boosting" the x-ray contrast effect of iodine. This improves the vascular enhancement of the contrast medium using low-energy, virtual monoenergetic imaging (VNI). The objectives of this study are: Evaluation of ultra-low iodine load CTA protocols of the aorta and lower extremities. To investigate whether dual-layer in combination with with virtual monoenergetic imaging (VMI) allows for reduction of contrast medium (CM) in CTA of the aorta and lower limbs i with sustained objective and subjective image quality parameters.