Optimal exposure factors for lumbar spine AP in computed radiography examinations

In diagnostic radiography, selection of kVp and mAs to produce acceptable image quality with a minimum dose has been a challenge even for experience radiographers. The aim of this study was to determine optimal exposure factors for lumbar spine AP examinations in computed radiograph using dose-image quality analysis.

A female anthropomorphic phantom was used for dose-image quality analysis to determine the optimal exposure factors (mAs and kVp) for lumbar spine AP. Indirect method was used to estimate the entrance skin dose (ESD) to the anthropomorphic phantom. kVp values of 70, 80, 90 and100 were selected while mAs values of 16, 18, 20,22,25, 28,32, 36, 40, 45 and 50 were also selected for the acquisition of all the images. Three (3) senior radiographers evaluated the image quality using image quality criteria set up by European Commission.

The result indicated that the image quality score increased as ESD (mGy) increased. However, there was no significant change in image quality score between ESD of 1.941 and 4.882 mGy. 70 kVp and 22 mAs were accepted as optimal exposure factors for standard body size lumbar spine AP examinations in diagnostic radiography of computed radiography (CR).

Optimization of exposure factors (kVp and mAs) is necessary in radiographic examinations to ensure safe use of radiation in medicine. It ensures effective patient dose management because radiograph with high quality can be obtained for effective diagnostic information.