QUANTITAVE MR IMAGING FOR THE IN VIVO ASSESSMENT OF TRABECULAR BONE QUALITY

摘要

A major concern for space flight crews during long duration space mission is the effect of weightlessness on the skeletal system. In particular, bone loss has been noted in astronauts and cosmonauts exposed to microgravity from a few weeks to six months. Bone loss, which appears to increase in general proportion to mission length, may seriously enhance the risk of fracture during and after extended space flight. In past MIR and ISS missions, X-rays based techniques were used to assess pre- and post-flight cortical and trabecular bone mineral density (BMD). It has been shown, however, that BMD can explain only about 60% of the bone mechanical competence. Other methods are, therefore, required for the evaluation of bone quality. To this end, magnetic resonance imaging (MRI) has proved to be a promising technique, being able to provide information pertaining both to trabecular bone density and structure. The main purpose of this study was to assess the use of quantitative MRI of the calcaneus for the prediction of vertebral fractures. The results show that the effective transverse relaxation time (T2) is sensitive to alterations in bone quality not capture by density. The potential application of MRI for the study of skeletal alterations in crewmembers after prolonged space mission is proposed.