Optimisation of radiation dose and image quality for AP pelvis radiographic examination

Background and rationale:Optimising radiation dose and image quality in medical imaging is essential in minimising radiation risk and ensuring images are fit for purpose. This thesis uses novel methods for image quality assessment and radiation dose/image quality optimisation. The antero-posterior (AP) pelvis projection was used as a focus for optimisation.Methods:In the first part of this thesis a visual grading image quality assessment scale is developed and validated in order to assess radiographic image quality. The scale validation is conducted in two phases; the initial phase uses phantom images and is further tested in phase two with cadaveric images. The scale development and validation is guided by psychometric theory and in particular Bandura’s guidelines. In the second part of this thesis a framework is developed to systematically optimise the radiation dose and image quality for AP pelvis radiographic examinations. The methodology development for this section is guided by the factorial based experimental design. The optimisation includes manual and automatic exposure control modes. The image quality is visually assessed using the previously developed (novel) image quality scale and physically using a signal to noise ratio. The optimisation work is conducted with the aim of achieving two objectives: 1) identifying the optimum practice that would produce images with suitable quality and low radiation dose; 2) conducting a systematic investigation into the main effect of the primary acquisition factors on the response variables (e.g. image quality (IQ) and effective dose (E)).Results:A scale of 24 items was produced. These scale items had good inter-item correlation (≥0.2) and high factor loadings (≥0.32). Cronbach's alpha (reliability) revealed that the scale has acceptable levels of internal reliability for both phantom and cadaver (α= 0.8 and 0.9, respectively). The factor analysis suggested that the scale is multidimensional (assessing multiple quality themes). Accordingly, it is likely that this scale will be applicable in both clinical and research practices. The optimum practice was identified, resulting in suitable quality images with a lower dose (i.e. 88 to 94 % less than the UK average adult AP pelvis dose of 0.7 mSv) for both manual and AEC modes. Furthermore, it was identified that kVp had the biggest effect on radiation dose, image quality and figure of merit (P˂0.05) when compared with mAs and SID. The factorial design proved to be an efficient approach in optimising the radiation dose and image quality, and also for exploring the main effect of acquisition factors on radiation dose and image quality.Conclusion:This novel method for developing and validating image quality assessment scale shows promise. As such it is a recommended model for developing scales for other radiographic projections. The factorial design should be considered for use in future work due to its efficiency in optimising the radiation dose and image quality systematically. Finally, the AP pelvis scale, in its current form, could be used in future assessments of AP pelvis image quality