High-resolution magnetic resonance imaging to assess trabecular bone structure in patients after transplantation: a...

After organ transplantation patients have a higher incidence of osteoporotic fractures. Bone mineral density (BMD) measurements to assess fracture risk are of limited value in these patients. On the other hand, structure-based techniques have shown promise. In this review, the use of high-resolution magnetic resonance imaging in the analysis of the trabecular bone structure in patients before and after renal and cardiac transplantation cross-sectionally is presented. The analyses of calcaneal trabecular structure were compared with BMD with regard to the prediction of therapy-induced bone loss and osteoporotic fracture status. Sagittal and axial T1-weighted spin-echo sequences with a voxel size of 0.2 x 0.2 x 1 mm were performed at 1.5 T and structure measures analogous to bone histomorphometry were calculated. In addition, fracture status of the spine and of the peripheral skeleton was assessed. Structure measures showed significant differences between healthy controls and patients before and after renal and cardiac transplantation (p < 0.01). Osteoporotic fractures were found in approximately 35% of the transplant patients; the percentage was higher in the cardiac transplants. Structure measures and BMD were lower in patients with fractures; differences were more significant in the cardiac transplant patients. Using receiver operating characteristic analyses the diagnostic performance in differentiating patients with and without fractures was highest when BMD and structure measures were combined. Structure measures performed better than BMD in the cardiac transplant patients, whereas results were comparable in the renal transplant patients. In conclusion, structure measures determined in high-resolution magnetic resonance images may be useful in assessing changes of trabecular bone after organ transplantation and may improve the prediction of fracture risk.