Optimising beam quality for chest X-ray imaging: Insights from over two decades of peer reviewed publication

Optimisation of beam quality for chest radiography has been extensively investigated and reported on, but there are few comparisons of the reported study methods, outcomes and recommendations. This work aims to compile the available data on this subject with the objective of identifying and categorising the methods used to optimise chest x-ray (CXR) imaging, and to determine if a particular beam quality can be distinguished as optimal.

A literature review was carried out on papers investigating optimisation of beam quality for CXR exposures. The identified studies (n = 29, spanning 2001-2020) were grouped into descriptive categorical variables. Statistical analysis (Fisher's exact testing) was used to investigate the relationships between the materials, methods and results drawn from literature concerning the CXR optimisation process.

The primary decisions in each CXR optimisation study concern the type of source image used and the image assessment approach adopted. Across the literature, 240 potential combinations of methodological variables were found. The findings are highly variable, and no standardised optimisation approach emerges. The literature provides no definitive evidence for an optimal beam quality in chest radiography. While the most frequently recommended tube voltages were in the 90-110 kV range, this accounted for only 43% of studies. Only one-third of the analysed studies accounted for the influence of filtration.

These findings pose a challenge for medical physicists engaging in optimisation activities in clinical departments and support the case for standardising both the approaches for optimisation of the technical parameters in general radiography, and the reporting of same.