Endocrine Abstracts

Introduction: Dual energy X-ray absorptiometry (DXA) scans are regarded as the gold standard for assessing bone health. However, an inability to distinguish between cortical and trabecular bone as well as the use of inapproapriate size corrections mean that this technique is of limited clinical use in conditions affecting either bone microarchitecture or patient size. We have trialled the use of high resolution MRI (micro MRI) in the measurement of bone microarchitecture in patients with different metabolic disorders.

Methods: A TrueFISP pulse sequence was optimised for high resolution imaging using a 3T Siemens Verio scanner. Images were acquired form the proximal tibia of: seven adults with osteogenesis imperfecta (OI) (ages 21–45) and seven age and sex matched controls (ages 20–45); five teenagers with childhood onset GH deficiency (GHD) (ages 16–19) and five sex matched controls (ages 21–22). Micro MRI images were analysed using in house software developed in IDL.

Results: Patients with OI were found to have a 42% reduction in apparent bone volume (appBV) (P<0.01), a 37% reduction in apparent number of trabeculae (appTbN) (P<0.01) and a 47% increase in apparent spacing between trabeculae (appTbSp) (P<0.01). GHD patients had a 14% increase in appTbSp (P=0.038) and 7.4% reduction in appBV (P=0.024). Coefficient of variation was low for both intra (appBV 0.55%, appTbTh (apparent trabecular thickness) 0.95%, appTbN 1.02%, appTbSp 1.32%) and inter (appBV 2.09%, appTbTh 2.00%, appTbN 0.87%, appTbSp 1.17%) operator reproducibility.

Conclusion: With the use of routinely available scanning equipment, we have shown there to be differences in the bone microarchitecture between volunteers with OI, where the bones are grossly affected, and controls. We have also shown that this technique is sufficiently sensitive for detecting more subtle changes in bone microarchitecture that may be found in young adults with GHD.