[Subject Thickness Measurement and Entrance Surface Dose Estimation Using an RGB-D Camera in Chest Radiography]

This study aimed to quantify the effect of measurement duration on subject thickness accuracy using an RGB-D camera at a source-to-image distance (SID) of 200 cm for chest radiography and to evaluate the accuracy of entrance surface dose (ESD) estimation based on 1-s measurements.

A chest radiography phantom was evaluated at subject thicknesses of 20, 25, 30, and 35 cm. Subject thickness was measured five times at measurement durations of 1, 5, and 10 s and compared with caliper measurements. ESD estimated from the mean subject thickness obtained over 1 s was compared with the reference ESD calculated from the caliper-based thickness.

The maximum subject thickness error was 0.48 cm, the maximum relative error was +1.4%, and the maximum standard deviation was 0.12 cm. No significant differences among measurement durations were found at 20, 25, or 30 cm. At 35 cm, an overall difference was found, but no pairwise difference was significant after adjustment for multiple comparisons. The maximum relative error in ESD estimation was +0.6% at 35 cm.

Under static phantom conditions at an SID of 200 cm, subject thickness measurements obtained over 1 s and the resulting ESD estimates were close to the reference values. These findings support further evaluation of short-duration RGB-D measurements for chest radiography.