Which vertebral levels provide practical HU-based assessment for osteoporosis screening? A comparative analysis from T1 to S2.

Abstract

To identify practical vertebral HU measurement strategies for opportunistic bone mineral density (BMD) screening using routine CT. Seven anatomical segmental combinations were defined: upper thoracic (T1-T4, UT), mid-thoracic (T5-T8, MT), lower thoracic (T9-T12, LT), thoracolumbar (T11-L2, TL), upper lumbar (L1-L2, UL), lower lumbar (L3-L5, LL), and sacral (S1-S2, SA). Correlations between HU and DEXA-derived T-score were analyzed for both single vertebrae and multi-segment combinations, using the full-segment average (T1-S2, TS) as reference. Stepwise linear regression across 19 vertebrae generated an exploratory combination (EC) model. ROC analysis and age-sex subgroup analyses were performed. A total of 300 patients were enrolled (150 males, 150 females; mean age 54.94 ± 14.39 years). Both single- and multi-segment measurements correlated positively with T-score. TS showed the strongest correlation (r = 0.799) and highest predictive performance (AUC = 0.914). Among single vertebrae, T5 showed the strongest correlation (r = 0.785). Among anatomical combinations, TL showed one of the strongest correlations (r = 0.787) and favorable predictive performance (AUC = 0.912). Subgroup analyses showed stable TL performance across sex groups, whereas the strongest correlation and predictive performance were observed in the 51-60-year age subgroup. Both single- and multi-segment HU measurements were effective for BMD assessment. The TL segment represents a practical HU-based assessment approach for opportunistic osteoporosis screening on routine CT, with stable predictive performance and practical clinical value.