Endocrine Abstracts

Background: High-resolution magnetic resonance imaging (hrMRI) can assess trabecular bone microarchitecture but the number of image slices required for reliable assessment is unclear.

Methods: MRI was performed just below the growth plate of the proximal tibia from 20 healthy controls (all females; median age 21 years (range 18.35) and ten cases (3M:7F; median age 19.5 years (range 16.48) with known bone abnormalities including osteogenesis imperfecta and other endocrinopathies using a 3T-MRI with an isotropic resolution of 0.3 mm. Images were analysed using Matlab to generate the trabecular bone microarchitecture parameters, including apparent trabecular volume to total volume (appBV/TV), trabecular thickness (appTbTh), trabecular number (appTbN), and trabecular separation (appTbSp). The mean values obtained from 20 of the most central images (20IM) were compared to that for ten images (10IM), five images (5IM), and one image (1IM) from the centre of the total image set using linear regression analysis. ANOVA was used to compare the means between groups and Levene’s tests used to assess the significance of the co-efficient of variations (CV) within subjects.

Results: The mean trabecular bone microarchitecture estimates from 10IM, 5IM, and 1IM were strongly and positively related to the estimates from 20IM for appBV/TV (r=1.00, r=0.99, and r=0.97, all P<0.001), appTbTh (r=1.00, r=0.99, and r=0.97, all P<0.001), appTbN (r=1.00, r=1.00, and r=0.98, all P<0.001), and appTbSp (r=1.00, r=0.99, and r=0.98, all P<0.001). The mean intra-subject CV (S.D.) for appBV/TV in healthy controls was 2.6% (1.1%) for 20IM, 3.0% (1.5%) for 10IM, and 3.1% (1.5%) for 5IM. Cases have higher mean appBV/TV CV (S.D.) at 3.7% (2.1%) for 20IM, 4.7% (3.0%) for 10IM, and 4.3% (3.1%) for 5IM; all P>0.05 when compared to that of controls. Furthermore, sub-analysis of the four cases with osteogenesis imperfecta, a more severe osteopathy, demonstrated even higher mean CV (S.D.) at 4.6% (2.7%) for 20IM, 7.1% (3.1%) for 10IM, and 5.9% (3.6%) for 5IM (P=0.037, P=0.028, and P=0.017 respectively).

Conclusions: These findings indicate that partial MRI sets can reliably represent a larger complete set of images when assessing trabecular bone microarchitecture parameters. However, in cases with severe abnormalities of bone health, a larger set of images may need to be analysed to improve precision.