Hounsfield unit for the diagnosis of bone mineral density disease: A proof of concept study

• We examined the correlation between HU from CT scan and bone mineral density from DXA sacan.
• A HU of 91 can safely exclude normal bone density, whilst a HU of 203 can exclude osteoporosis.
• HU correlate moderately with patient's age and bone mineral density as measured by DXA scan.
• HU is available on CT scan at no extra patients cost or radiation.

ObjectivesOur aim is to correlate Hounsfield units (HU) from lumbar Computed Tomography scans (CT) with Bone Mineral Density (BMD) values from Dual-energy X-ray Absorptiometry scans (DXA) for the diagnosis of bone mineral density disease.MethodsWe enrolled 114 women, conducted both CT and DXA scans on them to assess the correlations between the mean lowest HU at lumbar vertebrae and the BMD values from DXA scan. Statistical analysis was used to assess the correlations between HU and the patients' BMD and age.ResultsWe noted moderate correlations between the lowest HU at L1–L4 and the BMD from DXA scan which is significant (correlation coefficient, 0.563). DXA scans showed a normal BMD in 33.3% of patients, osteopenia in 43.9%, and osteoporosis in 22.8% respectively. We also determined that a HU of 203 would exclude osteoporosis (90% sensitivity for normal BMD) and a threshold of <91 would exclude normal bone mineral density (86% sensitivity for osteopenia, 60% sensitivity for osteoporosis). Mean HU values consistently decreased with increasing decade of life, from 182.8 ± 42 in the fourth decade to 82.13 ± 32 in the eighth (correlation coefficient, 0.527).ConclusionsHU values are moderately correlated with the patients' age and BMD values from DXA scan, with 203, safely excluding osteoporosis and <91 excluding normal BMD. Prospective studies with a larger number of patients are needed, where multiple thresholds could be applied and more distinguished values for normal bone density, osteopenia, and osteoporosis can be obtained.