Pharmacokinetic Modeling Study on Bone Perfusion of Osteoporosis

Introduction: Clinical, epidemiological and histological studies have indicated a link between vascular disease and osteoporosis (1). Dynamic contrast-enhanced MRI (DCE-MRI) provides a more direct measure of bone perfusion. DCE-MRI studies have consistently shown how semi-quantitative perfusion parameters are consistently reduced in osteopenic and osteoporotic bone compared to normal bone mineral density (BMD) subjects (2). However, semi-quantitative parameters provide limited information on the physiological processes affected. The purpose of this study, was to apply a modified Brix pharmacokinetic model to the investigation of bone perfusion in subjects of varying BMD with a view to increasing our knowledge of the bone perfusion anomalies occurring in osteoporosis. Methods: The cohort comprised 165 subjects (65 males, 100 females, age>65 yrs). Both DCE-MRI and H MR spectroscopy was performed on each subject. H MR spectroscopy yielded the percentage marrow fat content of bone. DCE-MRI data were acquired in the mid-lumbar sagittal plane for male subjects and in the transverse plane through the mid-L3 vertebral body region for female subjects (Fig.1). A bolus of gadoteric acid at a concentration of 0.15 mmol per kilogram body weight was injected, followed by a dynamic scanning with a short T1-weighted gradient-echo sequence (2.7/0/95; prepulse inversion time, 400 ms; flip angle, 15°). A region of interest (ROI) was drawn manually encompassing the trabecular bone (Fig. 1), from which a time-signal intensity curve was generated. A pharmacokinetic model (3,4) (Eq.1) was employed to analyze DCE-MRI data. ( ) ( )