Dynamic Contrast-enhanced MRI in Paget's Disease of Bone--correlation of Regional Microcirculation and Bone Turnover

The purpose of this study was to evaluate regional microcirculation in Paget's disease of bone (PD) with dynamic contrast-enhanced MR imaging (DCE-MRI). Additionally, we correlated regional bone perfusion with alkaline phosphatase as serum marker of bone turnover. We examined 71 patients with PD (27 men, 44 women, 67+/-10 years) localized at the axial and appendicular skeleton. Contrast uptake was analyzed using a two-compartment model with the output variables amplitude A and exchange rate constant k(ep). Color-coded parametric images were generated to visualize microcirculation. Serum levels of alkaline phosphatase (AP) were compared with DCE-MRI parameters. Amplitude A and exchange rate constant k(ep) were significantly increased in PD compared to unaffected bone (A(PD) 0.81+/-0.24 vs. A(control) 0.34+/-0.1 and k(ep PD) 4.0+/-2.86 vs. k(ep control) 1.73+/-0.88, p<0.001). There was a significant correlation (r(s)=0.5-0.7) of DCE-MRI parameters and AP at the axial (pelvis, spine) and appendicular skeleton (femur, tibia). The long bones showed increased circulation of the advancing peripheral zones and no vascularization of the central part, which had been replaced by fatty tissue. Regional microcirculation in PD is inhomogeneous with focal areas of excessive hypervascularity, especially in the advancing peripheral zone. There is a significant correlation of bone circulation and bone turnover in PD. DCE-MRI might therefore be a diagnostic tool for monitoring therapeutic effects of bisphosphonates in Paget's disease of bone.