Sensitivity of USPIO-enhanced R2 imaging to dynamic blood volume changes in the rat kidney

✍ Scribed by Pippa Storey; Lin Ji; Lu-Ping Li; Pottumarthi V. Prasad

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 698 KB
• Volume: 33
• Category: Article
• ISSN: 1053-1807
• DOI: 10.1002/jmri.22526

✦ Synopsis

Abstract

Purpose:

To determine whether MRI in combination with an intravascular contrast agent is sensitive to pharmacologically induced vasodilation and vasoconstriction in the rat kidney.

Materials and Methods:

R~2~ imaging was performed in 25 Sprague Dawley rats at 3 Tesla in the presence of ferumoxytol, an ultrasmall superparamagnetic iron oxide (USPIO) agent with a long plasma half‐life. R~2~ changes were measured following manipulation of blood volume by intravenous administration of adenosine, a short‐acting vasodilator, or N^G^‐nitro‐L‐arginine methyl ester (L‐NAME), a long‐acting nitric oxide synthase inhibitor with known vasoconstrictive effects. As a control, R~2~ responses to adenosine and L‐NAME were also examined in the absence of ferumoxytol.

Results:

In the presence of ferumoxytol, adenosine induced a significant increase in R~2~, while L‐NAME produced a reduction, although the latter was not statistically significant. Control experiments revealed small R~2~ changes in the absence of ferumoxytol. An incidental finding was that the cross‐sectional area of the kidney also varied dynamically with adenosine and L‐NAME.

Conclusion:

Our results suggest that ferumoxytol‐enhanced R~2~ imaging is sensitive to adenosine‐induced vasodilation. The responses to L‐NAME, however, were not statistically significant. The variations in kidney size and the R~2~ changes in the absence of ferumoxytol may reflect alterations in the volume of the renal tubules. J. Magn. Reson. Imaging 2011;33:1091–1099. © 2011 Wiley‐Liss, Inc.