Figure 4:

Variations in mean L1 trabecular attenuation values according to sex, presence of intravenous (IV) contrast agent, and method of measurement (manual vs automated [auto]). Mean L1 trabecular attenuation is higher for women until postmenopausal age, when values for men and women are strikingly similar (top). The effect of intravenous contrast agent is most notable for patients younger than 40 years. For older adults, the effect of intravenous contrast agent may not be clinically relevant for opportunistic bone mineral density screening (middle). The fully automated technique for L1 trabecular attenuation yields higher values compared with manual region-of-interest placement (average, ∼20 HU) (bottom). Age groups are on the x-axis and error bars indicate standard deviations. * P < .01; ** P < .005.