Distribution and Variability of Trabecular Attenuation in the Thoracic Spine on Routine Chest CT

Background: Heterogeneity in vertebral trabecular bone attenuation may influence fracture risk. Chest computed tomography (CT) offers an opportunity to assess attenuation variability without additional radiation exposure. This study aimed to evaluate the distribution and variability of trabecular attenuation in the thoracic (T) vertebrae (T5–T12) on chest CT and to investigate the association between attenuation variability and chest wall composition.Methods: This retrospective study included 101 adults aged 18–65 years who underwent chest CT. Trabecular attenuation was measured from T5 to T12, and attenuation variability was quantified using the coefficient of variation (CV%). Chest wall composition, including pectoralis major (PM) area and attenuation and subcutaneous fat area, was assessed at the T4 level. Associations were analyzed using Spearman correlation and multivariable linear regression.Results: There was significant regional variation in thoracic vertebral trabecular characteristics. Mean trabecular attenuation progressively decreased from T5–T6 to T12 (p < 0.001), with relatively stable values across T7–T11. Attenuation variability was lowest at T5–T6, increased at T8–T9 (p < 0.001), and decreased again at T11–T12, with no significant difference between the two lowest segments (p = 0.708). On multivariable analysis, age was independently associated with increased attenuation variability (B = 0.198, p < 0.001). In contrast, PM muscle area (p = 0.588), PM muscle attenuation (p = 0.080), and subcutaneous fat area (p = 0.263) were not significantly associated with attenuation variability. Conclusion: Thoracic vertebral trabecular attenuation and its variability show level-dependent variation. Age was significantly associated with increased attenuation variability, whereas sex and body composition parameters were not independent predictors.