Quantitative evaluation of the relaxivity effects of iodine on GD-DTPA enhanced MR arthrography.
OBJECTIVE
To quantify the effect of iodine on the gadolinium (Gd) contrast-enhanced signal in MR arthrography.


METHODS
Saline solutions of Gd contrast agent (0-1 mmol/liter) were mixed with iodinated contrast agent (0-185 mmol/liter). The T1 and T2 relaxation constants of these solutions were measured at 1.5T. Different types of commonly used iodinated contrast agents as well as sodium iodide (NaI) solutions were also analyzed.


RESULTS
Iodine caused significant T2 shortening and some T1 shortening in Gd contrast solutions. Both contrast agents independently obeyed the standard relaxation relation, and their mixture obeyed a modified version of this relation. The side chains in various iodine molecules and their viscosities affected the relaxation properties differently. For various spin-echo (SE) sequences, the signal from synovial fluid containing different concentrations of the two contrast agents was calculated. The T2-weighted signal appeared to be most affected by the increase in iodine concentrations. In the absence of Gd contrast, all SE sequences showed an initial increase in signal from iodine contrast.


CONCLUSIONS
A generalized relation for the relaxivities of Gd contrast in the presence of iodine was established. The side chains of iodine contrast were found to alter the relaxivities of Gd contrast. Imaging with proton density (PD)-weighted SE with only iodine contrast agent was found to be feasible.
Ganguly
Arundhuti
A
Lucas MRS Center, Department of Radiology, Stanford University, 1201 Welch Road, Stanford, CA 94305, USA. aganguly@stanford.edu
Gold
Garry E
GE
Butts Pauly
Kim
K
Mayer
Dirk
D
Moseley
Michael M
MM
Pelc
Norbert J
NJ
Fahrig
Rebecca
R
D003287:Contrast Media / Q000737:chemistry*; D003973:Diatrizoate / Q000737:chemistry*; D019786:Gadolinium DTPA / Q000737:chemistry*; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging; D012815:Signal Processing, Computer-Assisted; D014783:Viscosity
D003287:Contrast Media; D003973:Diatrizoate; D019786:Gadolinium DTPA