Abstract 13480: High Resolution MRI for Characterization of Inflammation within Abdominal Aortic Aneurysm
Background: Abdominal aortic aneurysms (AAAs) with focal inflammation have been reported to grow 3 times faster than those without. Ultrasmall superparamagnetic iron oxide (USPIO) particles can identify inflammation (macrophages) in vivo using MRI. USPIOs induce both T1 and T2* shortening. Previous studies used 2D T2* mapping methods, which had limited slice resolution (5mm). We aim to evaluate 3D higher resolution techniques for inflammation imaging.
Hypothesis: 3D MRI can identify AAA inflammation with high resolution.
Methods: Four MRI sequences were evaluated at 3T: traditional 2D T2* mapping (5mm slice); black blood fast-spin-echo (FSE) and ultra-short-TE (UTE) sequences with 1.3mm isotropic resolution, scan time 7 and 4 minutes; gradient echo (GRE) with 1.3x1.3x2.6mm3 resolution in a breathhold (17s). Sequences were firstly tested in saline phantoms with USPIO concentrations 0.94mg Fe/L to 600mg Fe/L. 27 patients (all male, age 69±4.7, diameter 4.3±1.0cm) underwent MRI before and 2-3 days after USPIO injection. All patients had T2* and FSE scans. GRE and UTE were preliminary tested in 8 and 5 patients.
Results: Phantom Study: UTE signal continually rises with increasing USPIO concentrations, whereas T2* values drop. Both FSE and GRE show signal increase-and-drop curves, however with different peaks (7.5 versus 60mg Fe/L). Patient study: In 27 patients, 10 patients were inflammation positive (T2* value decrease >60%, Figure 1), and all showed FSE signal change: 3 drop, 3 increases, 4 both). GRE and UTE showed signal enhance (Figure 1b). 6 of them (60%) underwent intervention. Of the 17 negative patients, only 1 had intervention (p=0.004).
Conclusion: 3D high resolution MRI can be used to identify USPIO uptake within AAA, with good agreement with traditional 2D T2* mapping method. AAA inflammation is related to progressive disease. These methods may help risk stratify patients with AAA disease by characterizing and quantifying inflammation.
Author Disclosures: C. Zhu: None. T.A. Hope: None. H. Haraldsson: None. F. Faraji: None. D. Saloner: None. M. Hope: None.
- © 2016 by American Heart Association, Inc.