Balancing image quality and dose in diagnostic radiology

The formation of images in diagnostic radiology involves a complex interplay of many factors and the ideal balance is to obtain an image, which is adequate for the clinical purpose with the minimum radiation dose. Some factors are classified as physical parameters and can be measured objectively in physical test phantoms, but the diagnostic images must still be interpreted by human observers which does not always mean an ideal observer. This subjective nature of image interpretation makes the objective approach to a full assessment difficult. The ideal method for evaluation of imaging techniques is through clinical trials. Scoring of image quality criteria relating to features observed in a normal clinical radiograph gives a simple method through which image quality can be assessed and related to the radiation dose used. But if optimal performance is to be achieved, it is necessary to understand both the influence of the physical factors in the image formation on dose and image quality and to apply the correct methodology in these analyses of optimisation of the imaging process.