Table 2.

Ferumoxtran-10 (Combidex), Ferumoxytol, and Gd-DTPA (Magnevist)^a

Feature	Ferumoxtran-10 (Combidex)	Ferumoxytol	Gd-DTPA (Magnevist)
Basic element	Iron9	Iron oxide	Gadolinium(III)
Molecular composition	Iron oxide coated with dextran9	Iron oxide coated with semisynthetic carbohydrate	Gadolinium chelated with diethylenetriamine pentaacetic acid
r1 (mmol/s) at 0.47 T, 39 °C	239	3810	3.4
r2 (mmol/s) at 0.47 T, 39 °C	539	8310	4
Elimination plasma half-life	24−30 h9	14 h11	1.6 h
Relative size of the particle	Around 30 nm9	Around 30 nm11	0.357 nm
Permeability to intact BBB	Minimal	Minimal	Minimal
Clinical significance of the enhancing area	Imaging sites of BBB abnormality mainly in the presence of inflammatory cells	Imaging sites of BBB abnormality mainly in the presence of inflammatory cells	Detects abnormality in BBB and abnormal vascularity
Typical times to peak enhancement in brain tumors	24−72 h1	24 h3	3.5−25 min
Signal change on T1-weighted sequence	High signal at low concentrations, low signal at higher concentrations12	High signal at low concentrations, low signal at higher concentrations	High signal
Signal change on T2-weighted sequence	Low signal	Low signal	Slightly low signal
Distribution	Initially a blood pool agent and then intracellular in macrophages and reactive astrocytes	Initially a blood pool agent and then intracellular in macrophages and reactive astrocytes	Extracellular
Imaging dose	2.6 mg of Fe/kg diluted in 100 ml (infusion)	1−4 mg/kg	0.2−0.6 ml/kg (0.1−0.3 mmol/kg)
Rate of administration	Infused over 30 min	Bolus	10 ml/min or as bolus at 10 ml/15 s
Excretion	Stored with the body's iron reserve and used in hemopoesis	Stored with the body's iron reserve and used in hemopoesis	Renal

BBB, blood-brain barrier.

^aThe table shows the relevant features of the two contrast agents used in this study (modified from Murillo et al.¹³). There are differences in size, half-lives, clinical significance of the enhanced areas, distribution (plasma half-life), and side effects. GBCAs have excellent safety profiles in individuals with normal renal function and can be given in multiple doses. Ferumoxtran-10 is given slowly to avoid pseudoallergic reactions. Ferumoxytol can be administered as a bolus. A particle offerumoxtran-10 or ferumoxytol is almost 100 × larger than a GBCA.