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Observational Study
. 2017 May;27(5):1787-1794.
doi: 10.1007/s00330-016-4559-0. Epub 2016 Aug 23.

Non-contrast 3D black blood MRI for abdominal aortic aneurysm surveillance: comparison with CT angiography

Chengcheng Zhu #  1 , Bing Tian #  2 , Joseph R Leach  1 , Qi Liu  2 , Jianping Lu  2 , Luguang Chen  2 , David Saloner  1   3 , Michael D Hope  1
Affiliations
Observational Study

Non-contrast 3D black blood MRI for abdominal aortic aneurysm surveillance: comparison with CT angiography

Chengcheng Zhu et al. Eur Radiol. 2017 May.

Abstract

Objectives: Management of abdominal aortic aneurysms (AAAs) is based on diameter. CT angiography (CTA) is commonly used, but requires radiation and iodinated contrast. Non-contrast MRI is an appealing alternative that may allow better characterization of intraluminal thrombus (ILT). This study aims to 1) validate non-contrast MRI for measuring AAA diameter, and 2) to assess ILT with CTA and MRI.

Method: 28 patients with AAAs (diameter 50.7 ± 12.3 mm) underwent CTA and non-contrast MRI. MRI was acquired at 3 T using 1) a conventional 3D gradient echo (GRE) sequence and 2) a 3D T1-weighted black blood fast-spin-echo sequence. Two radiologists independently measured the AAA diameter. The ratio of signal of ILT and adjacent psoas muscle (ILTr = signalILT/signalMuscle) was quantified.

Results: Strong agreement between CTA and non-contrast MRI was shown for AAA diameter (intra-class coefficient > 0.99). Both approaches had excellent inter-observer reproducibility (ICC > 0.99). ILT appeared homogenous on CTA, whereas MRI revealed compositional variations. Patients with AAAs ≥5.5 cm and <5.5 cm had a variety of distributions of old/fresh ILT types.

Conclusions: Non-contrast 3D black blood MRI provides accurate and reproducible AAA diameter measurements as validated by CTA. It also provides unique information about ILT composition, which may be linked with elevated risk for disease progression.

Key points: • Non-contrast MRI is an appealing alternative to CTA for AAA management. • Non-contrast MRI can accurately measure AAA diameters compared to CTA. • MRI affords unique characterization of intraluminal thrombus composition.

Keywords: Abdominal aortic aneurysm surveillance; CT angiography; Diameter measurement; Intraluminal thrombus composition; Non-contrast MRI.

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Figures

Fig. 1
Fig. 1
Measurement of ILT and psoas muscle signal intensities (on GRE images). a A patient with old ILT (ILTr < 1.2) and b) with fresh ILT (ILTr > 1.2)
Fig. 2
Fig. 2
a Comparison between MRI and CTA for the diameter measurements of AAA. b Interobserver agreement of diameter measurements using MRI and CTA
Fig. 3
Fig. 3
A patient with type 1 intra-luminal thrombus (predominately fresh ILT). Hyperintense signal (compared with muscle) of the ILT is shown on black blood and GRE images, while CTA shows homogenous attenuation. Red arrows show the ILT. Red asterisks show the aorta lumen
Fig. 4
Fig. 4
A patient with type 2 intra-luminal thrombus (mixture of fresh and old ILT). Hyperintense and hypointense signals of the ILT are exhibited with black blood MRI; only a bright signal is evident by GRE; homogenous attenuation is seen with CTA. Red arrows show the ILT. Red asterisks show the aorta lumen
Fig. 5
Fig. 5
A patient with type 3 intra-luminal thrombus (only old ILT). An iso-intense signal of the ILT is shown by MRI, and homogenous attenuation is shown by CTA. Red arrows show the ILT. Red asterisks show the aorta lumen
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