Why can X-rays pass through human soft tissue?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram of the electromagnetic spectrum showing different types of waves arranged by wavelength and frequency, from gamma rays and X-rays to ultraviolet, visible light, infrared, microwave, TV/FM radio, shortwave radio, AM radio, and longwave radio. — X-ray The relationship of X-rays to other electromagnetic radiation within the electromagnetic spectrum.

X-rays are able to pass through human soft tissue primarily due to the differential absorption of radiation by materials of varying density, composition, and homogeneity.1

Because soft tissues are less dense than structures like bone, they allow a greater proportion of X-ray photons to pass through them rather than being absorbed. This property is fundamental to diagnostic imaging, as it enables the creation of images that differentiate between internal structures based on how much radiation they block. When higher contrast is required to visualize specific soft tissue areas, medical professionals may use a contrast medium, which is a substance that is comparatively opaque to X-rays.1