Quantification of skeletal involvement in adults with type I Gaucher's disease: Fat fraction measured by Dixon quantitative chemical shift imaging as a valid parameter

OBJECTIVE. The objective of our study was to determine the merit of the fat fraction of axial bone marrow measured by Dixon quantitative chemical shift imaging (Dixon QCSI) as a clinical parameter to quantitatively assess the extent of skeletal involvement in type I Gaucher's disease. MATERIALS AND METHODS. Dixon QCSI was performed in 30 adult patients (age range, 18-69 years; mean, 39 years) with type I Gaucher's disease who were untreated. The relationship between the mean value of the fat fraction in vertebrae L3, L4, and L5 and the presence, absence, and severity of clinical bone complications (chronic bone pain, bone crisis, fracture, avascular necrosis, and joint replacement) as well as the conventional MR imaging of bone marrow involvement were studied. Also the relationship of fat fraction to sex, age, and other disease parameters (history of splenectomy, liver and spleen volume, plasma chitotriosidase, hemoglobin level, and platelet count) was evaluated. Our results were compared with the fat fraction of healthy volunteers. RESULTS. The fat fraction measured in patients with Gaucher's disease ranged from 0.08 to 0.40 (mean, 0.20). Bone complications occurred primarily in patients with a fat fraction of less than 0.23. Univariate logistic regression analysis indicated that for every decrease of 0.1 of the fat fraction, the risk of bone complications increased 85% (p < 0.05). The fat fraction was correlated with liver size, but no correlation with other disease parameters was found. In the patient population, the fat fraction was significantly lower than in the healthy population (range, 0.27-0.55; mean, 0.37; p < 0.001). CONCLUSION. The fat fraction of the lumbar spine when measured with Dixon QCSI is associated with the occurrence of bone complications. It may, therefore, be a clinically useful parameter.