Are the target exposure index and deviation index used efficiently?

INTRODUCTION

Exposure index (EI) is important to evaluate correct exposure in radiography and thus important for image quality. The purpose of this study was to evaluate whether the target exposure index (EI) and deviation index (DI) were used efficiently.

METHODS

Radiography departments in Iceland, using <10 years old equipment, were invited to participate. For each x-ray unit, admin users were asked about the use of EI and data was gathered on EI for five body parts (BP); lumbar spine, chest, hip, knee and hand. For each of the five BP, 100 examinations from the past year were selected randomly (or all, if < 100). The EI from one predefined view was recorded and the corresponding DI calculated.

RESULTS

A total of ten x-ray units, from four manufacturers and located at eight departments, were included in the study. The departments involved are comprised of a university hospital, smaller hospitals, and miscellaneous private departments. Two departments (25%) had not set EI, five (62.5%) used default values and only one had revised EI values. In four departments (50%) radiographers favored "acceptable EI range" over DI. The mean EI was significantly different (p < 0.05) from the EI in the majority of the five BP, in four out of the six departments that had defined EI. In total 30% of images from all departments combined had DI outside the range of -3.0 < DI < +3.0. The standard deviation of DI was from 1.4 to 2.7.

CONCLUSION

The study shows that the EI and DI are not used efficiently, regardless of equipment vendor or department characteristics.

IMPLICATIONS FOR PRACTICE

Current recommendations on targeting the mean DI of 0 need to be reinforced. Theoretical knowledge and training need to be improved.