Figure 2. The effect of tube voltage on (a) effective dose, (b) optical density (OD) difference of the L5 transverse process and (c) signal-to-noise ratio (SNR) of a trabecular structure on the L1 vertebra for the anteroposterior projection. The effect of tube voltage on (d) effective dose, (e) OD difference of the L3 spinous process and (f) SNR of a trabecular structure on the front of the L1 vertebra for the lateral projection.