Elsevier

Academic Radiology

Volume 12, Issue 9, September 2005, Pages 1190-1197
Academic Radiology

Original investigation
Ultrasmall Superparamagnetic Iron-Oxide–enhanced MR Imaging of Normal Bone Marrow in Rodents: Original Research: Original Research1

https://doi.org/10.1016/j.acra.2005.05.014Get rights and content

Rationale and Objectives

The objective is to compare three different ultrasmall superparamagnetic iron oxides (USPIOs) for magnetic resonance (MR) imaging of normal bone marrow in rodents.

Materials and Methods

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 μmol of Fe/kg of SHU555C (n = 6), ferumoxtran-10 (n = 6), or ferumoxytol (n = 6), using T1-weighted (50 ms/1.7 ms/60° = repetition time [TR]/echo time [TE]/flip angle) and T2*-weighted (100 ms/15 ms/38° = 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 (ΔSI) values. A mixed-effect model was fitted to the SNR and ΔSI values, and differences among USPIOs were tested for significance by using F tests.

Results

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 ΔSI values on T2*-weighted MR images at 24 hours PI were significantly different from baseline for SHU555C and ferumoxytol, but not ferumoxtran-10.

Conclusion

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.

Section snippets

Animals and Animal Procedures

The study was approved by the committee on animal research of our institution. Twenty 4-week-old female Sprague-Dawley rats (Charles River Laboratories Inc. Wilmington, MA) with a body weight of 150 g initially were included in the study. Of these, two rats were excluded from evaluation because they died during the MR imaging examination. The remaining 18 rats were randomly assigned to one of three groups: six rats each were administered an intravenous injection of either ferumoxtran-10,

Qualitative Results

On early T1-weighted SPGR images, up to 2 hours PI, all three contrast agents showed intense signal enhancement (+2) of the femoral bone marrow (Figure 1). At 24 hours PI, no remaining T1 signal enhancement (0) was observed for all rats after SHU555C administration and all rats after ferumoxytol administration, as well as 50% (3/3) of evaluated rats after ferumoxtran-10 administration. Bone marrow in three other rats showed slight persistent ferumoxtran-10 T1 enhancement (+1).

On early

Discussion

Data from this study show that the three USPIO contrast agents, ferumoxtran-10, ferumoxytol, and SHU555C, can be applied equally for T1- and T2-weighted MR imaging of bone marrow. USPIO-enhanced early postcontrast T1-weighted MR images provide marked positive bone marrow enhancement because of a perfusion effect, whereas delayed postcontrast T2-weighted images provide marked negative bone marrow enhancement because of iron oxide uptake in bone marrow macrophages. In rodents, this negative bone

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