Abstract
ObjectivesFerumoxytol is an alternative to gadolinium-based compounds as a vascular contrast agent for magnetic resonance angiography (MRA), particularly for patients with chronic kidney disease (CKD). However, dose-related efficacy data are lacking. We aimed to determine the optimal (minimum effective) dose of ferumoxytol for MRA in patients with CKD.MethodsFerumoxytol-enhanced MRA (FeMRA) was performed at 3.0 T in patients with CKD after dose increments up to a total of 4 mg/kg. Image quality was assessed by contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) in the abdominal aorta and inferior vena cava. Quadratic regression analyses were performed to estimate the effects of dose increments on CNR and SNR.ResultsTwenty-three patients underwent FeMRA (mean age 60 [SD 13] years, 87% men, 48% had diabetic nephropathy) with cumulative doses of 0, 1, 2, 3 and 4 mg/kg of ferumoxytol. On regression analyses, a parabolic relationship was observed between ferumoxytol dose and signal with progressive signal loss using doses exceeding 4 mg/kg. A dose of 3 mg/kg achieved ≥ 75% of predicted peak CNR and SNR and images were deemed of excellent diagnostic quality.ConclusionsIn patients with CKD undergoing FeMRA, a dose of 3 mg/kg provides excellent arterial and venous enhancement. The benefits of increasing the dose to a theoretically optimal value of 4 mg/kg appear to be negligible and likely of minimal, if any, diagnostic value.Key Points• Ferumoxytol is used off-label as an MRI contrast agent but dose-related data are lacking.• In patients with CKD requiring MR angiography, a dose of 3 mg/kg provides excellent vascular enhancement.
Highlights
Ferumoxytol, an iron oxide nanoparticle compound with superparamagnetic properties, was originally designed as an intravascular contrast agent for magnetic resonance imaging (MRI) [1], it was commercialised as an intravenous iron therapy for anaemia
Optimal dose was selected on the basis of the minimum effective dose (MED) to achieve diagnostic imaging rather than maximum signal intensity criteria to the ‘As Low As Reasonably Achievable (ALARA) principle’ employed to minimise radiation exposure
Two patients were excluded from analysis due to failure to acquire all repeated fast lowangle shot (FLASH) sequences because of claustrophobia necessitating abandonment of the scan
Summary
Ferumoxytol, an iron oxide nanoparticle compound with superparamagnetic properties, was originally designed as an intravascular contrast agent for magnetic resonance imaging (MRI) [1], it was commercialised as an intravenous iron therapy for anaemia. Ferumoxytol has high relaxivity at 1.5 T and 3.0 T [2] with theoretical advantages as a contrast agent for MRA. It is not filtered by the glomerulus but is removed from the circulation via macrophage phagocytosis with the remaining iron oxide particles taken up by the reticuloendothelial system of the liver, spleen and bone marrow being incorporated into body iron stores for red blood cell synthesis. Given its long intravascular half-life, it can potentially be used without the need for bolus timing with imaging in a ‘steady state’ when the arterial and venous vasculatures are enhanced
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