Effect of ovariectomy on contrast agent diffusion into lumbar intervertebral disc: a dynamic contrast-enhanced MRI study in female rats

Purpose: The purpose was to study the effect of estrogen deficiency on contrast agent diffusion into intervertebral disc in a rat model. Materials and Methods: Seven-month-old female Sprague Dawley rats were used. Fourteen rats had ovariectomy, and nine rats had sham surgery. Magnetic resonance imaging (MRI) of sagittal midsection of lumbar spine was performed with a 1.5-T magnet. Dynamic MRI was performed after a bolus injection of Gd-DOTA (0.3 mmol/kg) through tail vein. Eight hundred images were acquired at 0.6 s per acquisition. Regions of interests were drawn over three discs per rat. Maximum enhancement (E-max) and enhancement slope (E-slope) were evaluated. MRI was carried out at baseline and 8 weeks postsurgery. Result: All disc enhancements demonstrated an initial fast wash-in phase followed by a second slower wash-in phase. For initial wash-in phase, E-max(1) and E-slope(1) of all rats remained unchanged at the two time points. For second wash-in phase, E-max(2) and E-slope(2) of control rats remained unchanged, while with ovariectomized rats, E-max(2) showed reduction at 8 weeks (4.5%+/-5.6%) compared to baseline (10.3%+/-6.3%, P=.037), and E-slope(2) was lower at 8 weeks (0.015+/-0.017) than the baseline (0.029+/-0.022), although it was not statistically significant (P=.101). Conclusion: Ovariectomy induced detectable decrease in second wash-in phase of contrast agent into lumbar disc. (C) 2012 Elsevier Inc. All rights reserved.