Use of ultra-low contrast dose CT aortography for the management of aortic aneurysmal disease.

Purpose: Computed tomography aortography (CTA) is used in the assessment of aortic pathologies and planning of surgical intervention. However, its dependence on iodinated contrast can result in development of contrast-induced acute kidney injury (CI-AKI). The potential concern of CI-AKI has spurred research into the potential of administration of low contrast volumes in CTA investigations while maintaining overall diagnostic appeal. Several studies have shown that CTA using contrast volumes as low as 30 mL (equivalent to 10.5 g of iodine) can still yield scans of diagnostic quality. We present a retrospective pilot study to evaluate the feasibility of utilising an ultra-low volume of iodinated intravenous contrast in a population of patients with severe renal insufficiency with referral from our vascular surgery unit for CTA evaluation of the thoracic and abdominal aorta.

Methods: This retrospective pilot study examined 12 CTA scans performed with 20 mLs of iodinated contrast and assessed image quality with both quantitative and qualitative markers. All scans were performed on a Siemens SOMATOM Force dual-source CT scanner. Quantitative assessment values were measured via attenuation values at eight aortoiliac locations and used to calculate a signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) at each location. Qualitative analysis of image quality and viability for surgical intervention was obtained from subjective clinical assessment by an interventional radiologist and vascular surgeon.

Results: Obtained quantitative assessment values included mean attenuation 189.9 HU, mean SNR 9.6 and mean CNR 8.0. All 12 scans demonstrated individual mean SNR values above predetermined quality thresholds while only five scans produced individual mean CNR values above threshold. Eleven of 12 scans were determined to be of sufficient quality for diagnosis and planning of surgical intervention.

Conclusions: Our results suggest that CTA utilising an ultra-low contrast dose of 20 mLs (6 g iodine) yields scans of diagnostic quality for therapeutic decision-making in vascular surgical intervention.