Chest x-rays are widely considered the most useful imaging modality in the assessment of infants with respiratory distress. They may be used to assess aeration, infiltration, edema, or congenital lung malformations. Additionally, they may be used to check the position of cathethers or tubes used in the NICU or to monitor pulmonary inflation when high frequency oscillation is used.
Mechanism of Action
X-rays are a form of electromagnetic radiation whose penetration of human tissue varies with tissue density. As they pass through the body, X-rays are differentially absorbed, and the penetrating rays traditionally captured to form an image on photographic film. More recently, medical X-ray equipment has moved to computerized radiology (CR ), using a reusable phosphor receptor plate. This plate, although more costly than film, requires lower radiation exposure, and can be re-used several thousand times to create digital images. Many high-end hospitals have now moved to digital radiology (DR ) which replaces the X-ray receptor plate with a matrix of sensors capture the image much like a digital camera. The X-ray source is typically a vacuum tube which accelerates electrons to the point that they collide with a metallic target, creating an X-ray. Image interpretation may or may not be performed by the same person who administers the X-ray, with the roles often separated.
Current use in High-Resource Settings
Most high-resource hospitals have a dedicated radiology department and use digital or computerized radiology to complete tests rapidly and share images with multiple departments at once. X-ray may be supplemented with other imaging modalities to aid in particular diagnoses. Hospitals may also have a mobile x-ray system for patients who may not be easily moved to the x-ray room.
Application in Low-Resource Settings
Access to x-ray is relatively rare outside urban hospitals. Where x-ray equipment is available, it may be second hand or donated. In response to the scarcity of x-ray, the WHO has approved a design specification known as the World Health Imaging System for Radiology (WHIS-RAD). Since establishing the specification, two companies have sold and installed approximately 1,500 WHO-approved WHIS-RAD systems. Today, less than half of all WHIS-RAD systems remain operational, highlighting maintenance issues. Mobile units pose a somewhat less expensive alternative, although they tend to sacrifice some image resolution, and most are not designed for the harsh usage environments of some low -resource settings.