Spectral computed tomography angiography using a gadolinium-based contrast agent for imaging of pathologies of the aorta

Abstract

Objectives: Especially patients with aortic aneurysms and multiple computed tomography angiographies (CTA) might show medical conditions which oppose the use of iodine-based contrast agents. CTA using monoenergetic reconstructions from dual layer CT and gadolinium (Gd-)based contrast agents might be a feasible alternative in these patients. Therefore, the purpose of this study was to evaluate the feasibility of clinical spectral CTA with a Gd-based contrast agent in patients with aortic aneurysms.

Methods: Twenty-one consecutive scans in 15 patients with and without endovascular aneurysm repair showing contraindications for iodine-based contrast agents were examined using clinical routine doses (0.2 mmol/kg) of Gd-based contrast agent with spectral CT. Monoenergetic reconstructions of the spectral data set were computed.

Results: There was a significant increase in the intravascular attenuation of the aorta between pre- and post-contrast images for the MonoE40 images in the thoracic and the abdominal aorta (p < 0.001 for both). Additionally, the ratio between pre- and post-contrast images was significantly higher in the MonoE40 images as compared to the conventional images with a factor of 6.5 ± 4.5 vs. 2.4 ± 0.5 in the thoracic aorta (p = 0.003) and 4.1 ± 1.8 vs. 1.9 ± 0.5 in the abdominal aorta (p < 0.001).

Conclusions: To conclude, our study showed that Gd-CTA is a valid and reliable alternative for diagnostic imaging of the aorta for clinical applications. Monoenergetic reconstructions of computed tomography angiographies using gadolinium based contrast agents may be a useful alternative in patients with aortic aneurysms and contraindications for iodine based contrast agents.

Keywords: Aortic aneurysm; Dual energy; Gadolinium; Monoenergetic reconstruction; Spectral computed tomography angiography.

Fig. 1

Conventional (A) and MonoE40 (B) axial reconstruction of a Gd-enhanced CT angiography of the abdominal aorta

Fig. 2

Values of MonoE40 (A, B) and conventional reconstruction (C, D) of the thoracic (A, C) and abdominal Aorta (B, D) on unenhanced images and images after contrast agent administration in the arterial phase. ***: p < 0.001. HU = Hounsfield units

Fig. 3

Ratio (A, B) and difference (C, D) in attenuation of the conventional and the MonoE40 reconstructions in the thoracic (A, C) and abdominal Aorta (B, D). **: p < 0.01; ***: p < 0.001. HU = Hounsfield units

Fig. 4

A shows a conventional reconstruction of a Gd-enhanced CTA (arterial phase); mean attenuation of the aorta is 73 HU. In B MonoE40 reconstruction of Gd-enhanced CTA demonstrates the aorta in arterial phase, mean attenuation of the aorta is 191 HU. C illustrates an iodine-enhanced CTA (arterial phase) of the same patient; mean attenuation of the aorta is 153HU.

Fig. 5

In this figure for image A-C windowing was identical (centre: 100 HU; widths: 600 HU). A shows a conventional reconstruction of a Gd-enhanced CTA (arterial phase); mean attenuation of the aorta is 95 HU. In B MonoE40 reconstruction of the aorta is demonstrated in a venous phase; mean attenuation of the aorta is 80 HU. C illustrates MonoE40 reconstruction of a Gd-enhanced CTA (arterial phase); mean attenuation of the aorta is 220 HU; the white arrow marks the early endoleak. In D a fusion of an arterial MonoE40 with a contrast dye map is shown; the white arrow marks the early endoleak [Note: The contrast dye map is an algorithm developed to highlight iodine. However, Gd can be isolated to a certain extent, too]