Abstract
Ferumoxytol is an ultrasmall super paramagnetic particles of iron oxide (USPIO) agent recently used for magnetic resonance (MR) vascular imaging. Other USPIOs have been previously used for assessing inflammation within atheroma. We aim to assess feasibility of ferumoxytol in imaging carotid atheroma (with histological assessment); and the optimum MR imaging time to detect maximum quantitative signal change post-ferumoxytol infusion. Ten patients with carotid artery disease underwent high-resolution MR imaging of their carotid arteries on a 1.5 T MR system. MR imaging was performed before and at 24, 48, 72 and 96 hrs post ferumoxytol infusion. Optimal ferumoxytol uptake time was evaluated by quantitative relaxometry maps indicating the difference in T2* (ΔT2*) and T2 (ΔT2) between baseline and post-Ferumoxytol MR imaging using 3D DANTE MEFGRE qT2*w and iMSDE black-blood qT2w sequences respectively. 20 patients in total (10 symptomatic and 10 with asymptomatic carotid artery disease) had ferumoxytol-enhanced MR imaging at the optimal imaging window. 69 carotid MR imaging studies were completed. Ferumoxytol uptake (determined by a decrease in ΔT2* and ΔT2) was identified in all carotid plaques (symptomatic and asymptomatic). Maximum quantitative decrease in ΔT2* (10.4 [3.5–16.2] ms, p < 0.001) and ΔT2 (13.4 [6.2–18.9] ms; p = 0.001) was found on carotid MR imaging at 48 hrs following the ferumoxytol infusion. Ferumoxytol uptake by carotid plaques was assessed by histopathological analysis of excised atheroma. Ferumoxytol-enhanced MR imaging using quantitative 3D MR pulse sequences allows assessment of inflammation within carotid atheroma in symptomatic and asymptomatic patients. The optimum MR imaging time for carotid atheroma is 48 hrs after its administration.
Highlights
Ferumoxytol is an ultrasmall super paramagnetic particles of iron oxide (USPIO) agent recently used for magnetic resonance (MR) vascular imaging
This study reports the simultaneous acquisition of quantitative T2 (qT2) and qT2* 3D pulse sequences and qT2 and qT2* values in assessing the temporal dependency of ferumoxytol-enhanced MR imaging of carotid atheroma
In this study we measured both T2 and T2* relativities and found them to be significantly correlated (r = 0.492) post-USPIO infusion at 48 hrs. This fundamental information about the temporal dependence of ferumoxytol may potentially form the basis of use of this pharmaceutical agent in future studies aimed at assessing pathophysiology of atherosclerosis and atherosclerosis-related inflammation; and in determining efficacy of established and novel anti-atherosclerotic drugs using MR imaging studies
Summary
Ferumoxytol is an ultrasmall super paramagnetic particles of iron oxide (USPIO) agent recently used for magnetic resonance (MR) vascular imaging. Ferumoxytol-enhanced MR imaging using quantitative 3D MR pulse sequences allows assessment of inflammation within carotid atheroma in symptomatic and asymptomatic patients. Several MR imaging studies have demonstrated the optimal time window for detection of macrophages following the infusion of ferumoxtran-10 in patients with carotid atherosclerotic disease[9,10]. The plasma half -life of Ferumoxytol is (10–14 hrs) compared to (≈ 24 hrs) of Ferumoxtran-10 and it has different relaxivity (r1 = 15 mM−1s−1, r2 = 89 mM−1s−1) and r1 = 9.9 mM−1s−1, r2 = 65 mM−1s−1 respectively)[11] Based on these differences, it can be hypothesised that ferumoxytol has a different optimal post-infusion imaging window
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