A study conducted in adolescents and young adults with CF utilized pQCT to evaluate bone geometry of the radius. Although BMD was normal for these subjects, pQCT data indicated that the subjects had a reduced cortical thickness. Reduced cortical thickness has been shown in cadaveric studies to be predictive of mechanical strength. Currently, patients with CF are evaluated annually for bone disease with DXA, and screening usually starts at approximately age. However, the above study suggests that this approach may not be sufficient to detect early bone changes that may impact fracture risk. Furthermore, bone disease in children may manifest earlier than adolescence, which would suggest that screening should start at an earlier age in these vulnerable patients. The following study is therefore proposed as a translational pilot study to examine the potential role of pQCT as a screening approach for bone disease in children with CF. The investigators expect to find bone deficits by pQCT but not DXA, and better correlation of inflammation and bone turnover markers with pQCT measurements than with DXA measurements.