Quantification of bone involvement in Gaucher disease: MR imaging bone marrow burden score as an alternative to Dixon quantitative chemical shift MR imaging--initial experience

PURPOSE: To develop a semiquantitative magnetic resonance (MR) imaging bone marrow burden (BMB) score with inclusion of both axial and peripheral bone marrow in Gaucher disease as an alternative to MR imaging with the Dixon quantitative chemical shift imaging (QCSI) technique.

MATERIALS AND METHODS: Two experienced musculoskeletal radiologists with no experience in evaluating Gaucher disease blindly analyzed MR images of lumbar spines and femora. Interobserver and intraobserver variability were tested. In addition, the BMB score was determined as a parameter to evaluate bone marrow response to enzyme supplementation therapy. Finally, the BMB score was compared with fat fraction measurements obtained with Dixon QCSI. Differences between groups were analyzed by using the nonparametric Mann-Whitney test. A P value of less than.05 was considered to represent significance. Correlation was calculated by using two-tailed nonparametric rank correlation (Spearman rho).

RESULTS: In 30 patients (mean age, 39.3 years; age range, 12-71 years) the mean fat fraction was 0.20 (range, 0.08-0.40). The BMB score range was 3-13 points. A significant correlation was found between the two observers when using BMB (rho = 0.91, P <.001). The intraobserver variation showed a significant correlation (rho = 0.99, P <.001). There was a significant correlation between BMB and QCSI (rho = -0.78, P <.001). Although BMB was less sensitive than Dixon QCSI, it showed enough sensitivity to allow detection of bone marrow response to enzyme supplementation therapy.

CONCLUSION: BMB is a reproducible semiquantitative scoring system that is easy to use. It combines MR imaging of both axial and peripheral bone marrow and shows a significant correlation with QCSI.