Ferumoxytol-enhanced Magnetic Resonance Research Articles

High-resolution three\u2011dimensional contrast\u2011enhanced magnetic resonance venography in children: comparison of gadofosveset trisodium with ferumoxytol

BackgroundGadofosveset is a gadolinium-based blood pool contrast agent that was approved by the United States Food and Drug Administration in 2008. Its unanticipated withdrawal from production in 2016 created a void in the blood pool agent inventory and highlighted the need for an alternative agent with comparable imaging properties.ObjectiveThe purpose of our study is to compare the diagnostic image quality, vascular contrast-to-noise ratio (CNR) and temporal signal characteristics of gadofosveset trisodium and ferumoxytol at similar molar doses for high-resolution, three-dimensional (3-D) magnetic resonance (MR) venography in children.Materials and methodsThe medical records and imaging data sets of patients who underwent high-resolution 3-D gadofosveset-enhanced MR venography (GE-MRV) or ferumoxytol-enhanced MR venography (FE-MRV) were retrospectively reviewed. Two groups of 20 pediatric patients (age- and weight-matched with one patient common to both groups; age range: 2 days–15 years) who underwent high-resolution 3-D GE-MRV or FE-MRV at similar molar doses were identified and analyzed. Qualitative analysis of image quality and vessel definition was performed by two blinded pediatric radiologists. Interobserver agreement was assessed with the AC1 (first-order agreement coefficient) statistic. Signal-to-noise ratio (SNR) and CNR of the inferior vena cava and aorta were measured in the steady-state venous phase. Medical records were retrospectively reviewed for any adverse reactions associated with either contrast agent.ResultsMeasured SNR and CNR of the inferior vena cava were higher for FE-MRV than GE-MRV (P = 0.034 and P < 0.001, respectively). The overall image quality score and individual vessel scores of FE-MRV were equal to or greater than GE-MRV (P = 0.084), with good interobserver agreement (AC1 = 0.657). The venous signal on FE-MRV was stable over the longest interval measured (1 h, 13 min and 46 s), whereas venous signal on GE-MRV showed more variability and earlier loss of signal. No adverse reactions were noted in any patient with either contrast agent.ConclusionFerumoxytol produces more uniform and stable enhancement throughout the entire venous circulation in children than gadofosveset, offering a wider time window for optimal image acquisition. FE-MRV offers a near-ideal approach to high-resolution venography in children at all levels of anatomical complexity.

Ferumoxytol-enhanced three-dimensional magnetic resonance imaging of carotid atheroma- a feasibility and temporal dependence study

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.

Ferumoxytol-enhanced cardiovascular magnetic resonance detection of early stage acute myocarditis

BackgroundThe diagnostic utility of cardiovascular magnetic resonance (CMR) is limited during the early stages of myocarditis. This study examined whether ferumoxytol-enhanced CMR (FE-CMR) could detect an earlier stage of acute myocarditis compared to gadolinium-enhanced CMR.MethodsLewis rats were induced to develop autoimmune myocarditis. CMR (3 T, GE Signa) was performed at the early- (day 14, n = 7) and the peak-phase (day 21, n = 8) of myocardial inflammation. FE-CMR was evaluated as % myocardial dephasing signal loss on gradient echo images at 6 and 24 h (6 h- & 24 h-FE-CMR) following the administration of ferumoxytol (300μmolFe/kg). Pre- and post-contrast T2* mapping was also performed. Early (EGE) and late (LGE) gadolinium enhancement was obtained after the administration of gadolinium-DTPA (0.5 mmol/kg) on day 14 and 21. Healthy rats were used as control (n = 6).ResultsLeft ventricular ejection fraction (LVEF) was preserved at day 14 with inflammatory cells but no fibrosis seen on histology. EGE and LGE at day 14 both showed limited myocardial enhancement (EGE: 11.7 ± 15.5%; LGE: 8.7 ± 8.7%; both p = ns vs. controls). In contrast, 6 h-FE-CMR detected extensive myocardial signal loss (33.2 ± 15.0%, p = 0.02 vs. EGE and p < 0.01 vs. LGE). At day 21, LVEF became significantly decreased (47.4 ± 16.4% vs control: 66.2 ± 6.1%, p < 0.01) with now extensive myocardial involvement detected on EGE, LGE, and 6 h-FE-CMR (41.6 ± 18.2% of LV). T2* mapping also detected myocardial uptake of ferumoxytol both at day 14 (6 h R2* = 299 ± 112 s− 1vs control: 125 ± 26 s− 1, p < 0.01) and day 21 (564 ± 562 s− 1, p < 0.01 vs control). Notably, the myocardium at peak-phase myocarditis also showed significantly higher pre-contrast T2* (27 ± 5 ms vs control: 16 ± 1 ms, p < 0.001), and the extent of myocardial necrosis had a strong positive correlation with T2* (r = 0.86, p < 0.001).ConclusionsFE-CMR acquired at 6 h enhance detection of early stages of myocarditis before development of necrosis or fibrosis, which could potentially enable appropriate therapeutic intervention.

Ferumoxytol-enhanced MR Angiography for Vascular Access Mapping before Transcatheter Aortic Valve Replacement in Patients with Renal Impairment: A Step Toward Patient-specific Care.

Purpose To assess the technical feasibility of the use of ferumoxytol-enhanced (FE) magnetic resonance (MR) angiography for vascular mapping before transcatheter aortic valve replacement in patients with renal impairment. Materials and Methods This was an institutional review board-approved and HIPAA-compliant study. FE MR angiography was performed at 3.0 T or 1.5 T. Unenhanced computed tomographic (CT) images were used to overlay vascular calcification on FE MR angiographic images as composite fused three-dimensional data. Image quality of the subclavian and aortoiliofemoral arterial tree and confidence in the assessment of calcification were evaluated by using a four-point scale (4 = excellent vascular definition or strong confidence). Signal intensity nonuniformity as reflected by the heterogeneity index (ratio between the mean standard deviation of luminal signal intensity and the mean luminal signal intensity), signal-to-noise ratio, and consistency of luminal diameter measurements were quantified. Findings at FE MR angiography were compared with pelvic angiograms. Results Twenty-six patients underwent FE MR angiography without adverse events. A total of 286 named vascular segments were scored. The image quality score was 4 for 99% (283 of 286) of the segments (κ = 0.9). There was moderate to strong confidence in the ability to assess vascular calcific morphology in all studies with complementary unenhanced CT. The steady-state luminal heterogeneity index was low, and signal-to-noise ratio was high. Interobserver luminal measurements were reliable (intraclass correlation coefficient, 0.98; 95% confidence interval: 0.98, 0.99). FE MR angiographic findings were consistent with correlative pelvic angiograms in all 16 patients for whom the latter were available. Conclusion In patients with renal impairment undergoing transcatheter aortic valve replacement, FE MR angiography is technically feasible and offers reliable vascular mapping without exposure to iodine- or gadolinium-based contrast agents. Thus, the total cumulative dose of iodine-based contrast material is minimized and the risk of acute nephropathy is reduced. © RSNA, 2017 Online supplemental material is available for this article.

USPIO-enhanced MR Angiography of Arteriovenous Fistulas in Patients with Renal Failure

To determine the feasibility of using ferumoxytol-enhanced magnetic resonance (MR) angiography to depict the vasculature of hemodialysis fistulas and improve image quality compared with nonenhanced time-of-flight (TOF) MR angiography. The study was institutional review board approved and was in compliance with HIPAA regulations. All participants provided written informed consent. TOF and first-pass ferumoxytol-enhanced MR angiography were performed in 10 patients with upper extremity autogenous fistulas. Ferumoxytol was administered as a bolus solution containing 430 μmol of elemental iron. A qualitative comparison was performed on maximum intensity projection images. Lumen depiction was evaluated by using a five-point scale. The uniformity of intraluminal signal intensity was measured as the ratio between the mean signal intensity of the entirety of the imaged fistula and its standard deviation. The contrast-to-noise ratio (CNR) between intraluminal signal and adjacent tissue was evaluated as a function of image acquisition time. Lumen depiction scores, luminal signal heterogeneity, and CNR efficiency were compared between TOF and ferumoxytol-enhanced MR angiography by using a Wilcoxon-Mann-Whitney test. Flow artifacts were greatly reduced by the use of ferumoxytol-enhanced MR angiography. Ferumoxytol-enhanced MR angiography had significantly better performance than TOF MR angiography as measured with the following: lumen depiction scores in all segments (mean, 4.7±0.1 [standard error of the mean]; vs 3.0±0.3 for arterial inflow, 4.1±0.3 vs 1.9±0.3 for arterial outflow, 3.7±0.3 vs 1.8±0.2 for anastomosis, and 4.5±0.2 vs 2.1±0.2 for venous outflow; P<.001), intraluminal signal homogeneity (0.3±0.02 vs 0.4±0.06, P=.005), and CNR efficiency in the venous outflow (5.1±0.6 vs 2.5±0.4, P=.01). This study demonstrates the feasibility of using ferumoxytol-enhanced MR angiography in imaging hemodialysis fistulas with consistently superior image quality compared with nonenhanced TOF MR angiography.

Lower Extremity Deep Venous Thrombosis: Evaluation with Ferumoxytol-enhanced MR Imaging and Dual-Contrast Mechanism—Preliminary Experience

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study, whose purpose was to prospectively evaluate the use of a dual-contrast mechanism in conjunction with an iron oxide blood pool contrast agent, ferumoxytol, to depict deep venous thrombosis (DVT). Nine patients with lower extremity DVT detected with duplex ultrasonography (US) were imaged with magnetic resonance (MR) imaging and ferumoxytol. Three techniques, including precontrast two-dimensional time-of-flight (TOF) imaging, ferumoxytol-enhanced bright-blood imaging, and ferumoxytol-enhanced dark-blood imaging, were applied. Image quality for precontrast and ferumoxytol-enhanced images was analyzed by using a four-point scale. Thrombus was depicted as a filling defect within the blood pool on bright-blood images and as bright tissue that appeared highly contrasted against a dark background on dark-blood images. Image quality of ferumoxytol-enhanced images was uniformly superior to that of precontrast TOF images (P = .007). Compared with precontrast TOF images, ferumoxytol-enhanced bright-blood images had higher contrast-to-noise ratios (CNRs) between thrombus and blood (P = .051), whereas ferumoxytol-enhanced dark-blood images showed significantly higher CNRs between thrombus and surrounding muscle (P = .008). Ferumoxytol-enhanced MR imaging can depict DVT with a dual-contrast mechanism and show the extent of thrombus.

Ultrasmall Superparamagnetic Iron-Oxide–enhanced MR Imaging of Normal Bone Marrow in Rodents: Original Research: Original Research 1

The objective is to compare three different ultrasmall superparamagnetic iron oxides (USPIOs) for magnetic resonance (MR) imaging of normal bone marrow in rodents. Femoral bone marrow in 18 Sprague-Dawley rats was examined by using MR imaging before and up to 2 and 24 hours postinjection (PI) of 200 mumol of Fe/kg of SHU555C (n = 6), ferumoxtran-10 (n = 6), or ferumoxytol (n = 6), using T1-weighted (50 ms/1.7 ms/60 degrees = repetition time [TR]/echo time [TE]/flip angle) and T2*-weighted (100 ms/15 ms/38 degrees = TR/TE/flip angle) three-dimensional spoiled gradient recalled echo sequences. USPIO-induced bone marrow was evaluated qualitatively and quantified as signal-to-noise ratio (SNR) and change in signal intensity (DeltaSI) values. A mixed-effect model was fitted to the SNR and DeltaSI values, and differences among USPIOs were tested for significance by using F tests. At 2 hours PI, all three USPIOs showed marked positive signal enhancement on T1-weighted images and a corresponding marked signal loss on T2*-weighted images. At 24 hours PI, the T1 effect of all three USPIOs disappeared, whereas T2*-weighted images showed persistent signal loss on SHU555C and ferumoxytol-enhanced MR images, but not ferumoxtran-10-enhanced MR images. Corresponding SNR and DeltaSI values on T2*-weighted MR images at 24 hours PI were significantly different from baseline for SHU555C and ferumoxytol, but not ferumoxtran-10. All three USPIO contrast agents, ferumoxtran-10, ferumoxytol, and SHU555C, can be applied for MR imaging of bone marrow. Ferumoxtran-10 apparently reveals a different kinetic behavior in bone marrow than ferumoxytol and SHU555C.