Personalized low-iodine dual-layer spectral CT protocol for post-endovascular aortic repair imaging: a BMI/eGFR-adapted strategy preserving renal function, quality and diagnostic confidence.

BACKGROUND: To evaluate image quality improvements of a low-iodine contrast medium (CM) protocol optimized with dual-layer spectral CT (DLCT) in patients undergoing post-endovascular aortic repair (EVAR) follow-up. METHODS: This single-center retrospective study included 83 consecutive patients (mean age: 75 ± 7.3 years) undergoing post-EVAR CTA with a low-iodine protocol optimized for DLCT (IQon, Philips Healthcare). The CM injection protocol, adapted to eGFR and BMI, comprised eight dose-flow categories. Pre-, post-scan eGFR and radiation dose were recorded. Dose-length product (DLP) was compared between true non-contrast (TNC) and virtual non-contrast (VNC) reconstructions. Objective image quality was assessed in standardized ROIs (aorta, iliac arteries, endoleak) by measuring mean attenuation (MA), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) on control CTA (iDose), and virtual monoenergetic images (VMI) at 55 keV and 40 keV. Subjective image quality was rated using a 5-point Likert scale. RESULTS: No change in eGFR was observed post-CTA (p=0.5617). Substituting TNC with VNC reduced DLP by 546.2 ± 176.3 mGy·cm (-34.3 ± 1.4%, p<0.0001). Across all ROIs, MA, SNR, and CNR were highest with VMI 40 keV, followed by VMI 55 keV and control (all p<0.0001). Vascular enhancement scores were superior with VMI 40 keV versus VMI 55 keV (p=0.0014) and control (p<0.0001), while metal artifact ratings did not differ (p>0.9999). One false-positive type IIa endoleak occurred with VNC, but diagnostic confidence was unchanged (p=0.8150). CONCLUSIONS: This low-iodine protocol optimized for DLCT significantly reduced radiation dose and improved objective and subjective vascular enhancement without impairing renal function or diagnostic confidence in endoleak detection.