Medical Director Norton Leatherman Spine Center Louisville, Kentucky, United States
Introduction: Hounsfield Units (HU) within a Region of interest (ROI) on CT scans as a proxy for bone mineral density is widely used in adult patients. However, the utility of CT, and its correlation with DEXA measurements, has not been evaluated in children and adolescents.
Methods: Patients less than 18 years old with both a lumbar spine CT scan and a DEXA scan within 6 months were identified. Indications for imaging included malignances, congenital syndromes, menstrual issues, trauma, auto-immune disease and eating disorders. An ROI was used to measure the HU for each lumbar vertebral body using the bone window on axial cuts. Patient charts were reviewed for DEXA reports, medical comorbidities, and demographics. Patients were then stratified by Z score [≥ -1.0, between -1.0 and -2.0, and ≤-2.0] and matched by age and BMI to a cohort of healthy children.
Results: A total of 79 patients between the age of 4 and 17 years were included. A moderate correlation between mean DEXA Z-score and mean HU on CT was found (r2=0.42, p< 0.001). When stratified by Z score [≥ -1.0, between -1.0 and -2.0, and ≤-2.0], patients with a Z score of ≤ -2.0 had a lower mean HU on CT compared to age matched controls, which was statistically significant. Age matched controls: 231.69 HU, Z-score >= (-1.0): 244.59 HU, Z-score Between -1.0 and 2.0: 216.50 HU and Z-score <= (-2.0): 176.54 HU (p=0.007).
Conclusion : A lower HU was identified on lumbar CT in children and adolescents with DEXA Z-scores less than -2.0, when compared to healthy age and BMI matched controls. This is the first study to compare BMD on DEXA and CT in pediatric patients. This study suggests that HU on opportunistic CT scans of the spine may be used as a good proxy for bone mineral density in the pediatric population.
How to Improve Patient Care: HU on opportunistic CT scans of the spine may be used as a good proxy for bone mineral density in the pediatric population.
