Table 1.

List of iron oxide (IO)-based contrast agents that have been clinically approved or entered clinical trials for magnetic resonance (MR) imaging (adapted from [6,8,9,10]). Relaxivities were measured at 1.5 T.

Commercial Name	NP Size, Coating and Relaxivities (mM−1 s−1)	Intended Use, Status on the Marked
Endorem in EU/Feridex® IV in USA	150 nm, dextran-coated IO NPs r1 = 10.1 and r2 = 120	Primarily designed for liver imaging, approved, and withdrawn from the market due to a lack of users.
Resovist®	60 nm, carbodextran-coated IO NPs r1 = 9.7 and r2 = 189	Primarily designed for liver imaging, approved, currently available only in Japan.
Gastromark® in EU/Lumirem in USA	>300 nm, siloxane-coated IO NPs Relaxivity n.a.	Approved as an oral contrast agent, withdrawn from the market due to a lack of users.
Rienso in EU/Faraheme® in USA	30 nm, carboxyhydrate-coated IO NPs, r1 = 15 and r2 = 89	Approved for iron-deficiency treatment, withdrawn from EU market, available in US to treat iron-deficiency anaemia in adults with chronic kidney disease, off-label use as MRI contrast agent.
Sinerem® in EU/Combidex® in USA	30 nm, dextran-coated IO NPs r1 = 9.9 and r2 = 65	Intended for diagnostic use in the characterisation of lymph nodes visualised by MRI, Phase III completed, application was withdrawn in 2007 before approval, failed to demonstrate a statistically significant benefit for sensitivity and specificity.
VSOP C184	Citrate coated 4-8 nm IO NPs, r1 = 14 and r2 = 33.4	Clinical trials for MR angiography, not approved.
Abdoscan®	3.5 µm Relaxivity n.a.	Oral gastrointestinal imaging, approved in EU but taken off the market in 2000.
Siena Plus®	59 nm IO NPs Relaxivity n.a.	Injected subcutaneously to detect lymph nodes with Sentimag® device, approved in EU. In USA, it is limited to investigational use only.