X-ray medical imaging. Dose and X-ray sources

Radiography and radioscopy (or fluoroscopy) are the two oldest and most widespread medical imaging modalities. Their unrivalled ability to combine resolution and penetration of biological tissues means that they will remain, for decades to come, among the most important in terms of both number of radiology procedures and cost to healthcare systems. Understanding how X-ray imaging equipment works is therefore a necessity for users, and also for engineers thinking about improvements – especially as, like all imaging technologies, it is impacted by the emergence of digital technology, which offers prospects many of which have yet to be explored or exploited.

The first in a series of seven articles devoted to X-ray imaging, this article sets out some of the basic physics involved in understanding X-ray imaging, and looks at the various definitions given to the concept of dose, specifying a few orders of magnitude specific to medical imaging. Depending on the context, this common term designates X-ray fluence (incident or exposure dose), energy absorbed by tissues or by a detector (absorbed dose), or measures health impact (equivalent and effective doses). The third section describes how X-ray sources and their associated high-voltage generators work. We conclude with a few technological perspectives for this family of components.