Figure 3. The effect of two grids with strip density N=40 cm^-1 with aluminium and carbon fibre covers and interspaces and a third grid with a strip density N=70 cm^-1, strip width d=20 µm with carbon fibre covers and interspaces on (a) effective dose, (b) optical density (OD) difference of the L3 transverse process and (c) signal-to-noise ratio (SNR) of the trabecular structure on the L3 vertebra for the anteroposterior projection. The effect of the same grids on (d) effective dose, (e) OD difference of the L3 spinous process and (f) SNR of the trabecular structure at an anterior position on the L5 vertebra for the lateral projection.