Find out more about the Wellcome Image Awards as well as Wellcome Images, the image library behind the Awards.

X-ray computed tomography

X-ray computed tomography (CT) is a minimally invasive medical imaging technique that uses 2D X-rays to create 3D images of the internal structures of the body. X-rays are absorbed by different body parts in varying degrees; in an image, soft tissue body parts that allow X-rays to pass through show up grey, and hard body parts like bone that block X-rays show up white.

In CT, a series of X-rays are taken by numerous rotating X-ray beams, so that the body is imaged from all angles. Many image 'slices' are taken, which are then built up into 3D images using digital geometry processing. Because of the inherent high-contrast resolution of CT, tissues that differ in density by just 1 per cent can be distinguished in the resulting images.

Micro-computed tomography (micro-CT) uses X-rays to virtually slice an object to produce 3D images. It works in a similar way to conventional medical CT, but on a smaller scale and usually at higher resolution. Micro-CT is commonly used in biomedical research: for example, to create a digital 3D model which can be virtually cut and rotated without damaging the precious original.


2014 Wellcome Image Award winner, Mechanical heart pump 
Credit: Anders Persson  

Combing CT with other medical scans

Positron emission tomography (PET) is used to show how well parts of the body are working by putting radioactive markers into the body and then detecting them as they collect in different areas. Combining CT and PET scans together provides information about what a particular part of the body looks like and also how well it is working.


2016 Wellcome Image Award winner: Detecting stroke
Credit: Nicholas Evans, University of Cambridge

Contrast media

Soft tissue structures are often difficult to see clearly in medical scans. Contrast agents are substances that block X-rays, and are administered orally, intravenously or rectally to improve the contrast of soft tissue, allowing structures such as blood vessels and the gastrointestinal tract to show up more clearly.


2017 Wellcome Image Award Winner: Pigeon thermoregulation

Credit: Scott Echols, Scarlet Imaging and the Grey Parrot Anatomy Project