Figure 7.

Steps to estimate slice thickness based on direct visual measurement with QUART Phantom. (a) Determination of HU_min and HU_mean to calculate the window/level for direct visual measurement. The minimum HU is determined from region of interest (ROI) over the air gap projection region and the mean HU is determined from background region. (b) Drawing of max ROI covers the all dark region and min ROI covers only inside of the dark region. [Color figure can be viewed at wileyonlinelibrary.com]