E1919. Dynamic Enhancement Pattern and Renal Angiography of Second Generation Iron-Based MR T1 Contrast Agent in Rabbit Model
  1. Whal Lee; Seoul National University Hospital
This study aimed to evaluate the in vivo enhancement pattern of a second-generation 3 nm-sized MR contrast agent named Extremely Small Iron Oxide Nanoparticles (ESIONs) and compare with that of gadolinium-based contrast agent in a rabbit model.

Materials and Methods:
From February 2019 to September 2019, 12 rabbits underwent inversion recovery contrast-enhanced 3.0T MRI using second generation 3nm-sized ESIONs. Four other rabbits underwent the same MRI with a gadolinium-based contrast agent(Gd-DOTA, Guerbet) as control group. The images were obtained precontrast and every 20 seconds until 160s, 5 min, 10 min, 20 min, and 30 min after contrast injection. The contrast agent was injected at a rate of 1 cc/sec with dosage of 0.1 µmol/kg of ESIONs and 0.2mmol/kg of Gd-DOTA, respectively. The mean signal intensity (SI) was measured manually at seven representative sites: the right hepatic lobe, inferior vena cava, left ventricle (LV), abdominal aorta, renal cortex, renal medulla, and the bladder. The Mann Whitney test was performed for 40s and 10 min postcontrast scan. Additionally, high resolution and very high resolution MR angiography were performed in one rabbit at 60s scan.

In LV and aorta, Gd-DOTA showed steep SI rise at 20s and rapid decrease, ESIONs showed slightly slower SI rise and then persistent enhancement exhibiting plateau. No signal change was detected in the bladder using ESIONs until 30 min, explaining its longer duration in intravascular pools. At 40s scan, ESIONs showed comparable intravascular enhancement in LV and abdominal aorta to Gd-DOTA(p > 0.05). In IVC, the highest SI for each contrast agent were not significantly different(p = 0.262), although SI of ESIONs reached the peak slowly. In the liver and kidney parenchyma, ESIONs showed significantly lower SI in both 40s and 10 min scan. Because contrast between vasculature and renal parenchyma was maximized, renal segmental vasculature was distinguishable only using ESIONs. In contrast, as renal parenchyma began to strongly enhance shortly after contrast injection, distinction of renal vasculature was not possible using Gd-DOTA.

ESIONs offered comparable first-pass MR angiography to that of Gd-DOTA and was better in the delayed scan by longer duration in intravascular pools. Also its lower SI in the renal parenchyma make smaller vascular structure easier to identify.