In early 2000, a young radiologist was posed this question over a beer: What does the word ‘futuristic’ mean to you?

For Anthony Butler – the radiologist in question – the word conjured up out-of-this world concepts, like space and travel to the potentially-habitable but challenging planet of Mars. So, when Anthony needed a name for the futuristic medical scanner he had invented with his physicist father, Professor Phil Butler, the pub conversation sprang to mind.

In this article, I’ll tell you how the MARS collaboration came about, how its colour x-ray technology works, and where the collaboration is heading (spoiler: not to planet Mars but into clinics around the world).


“Semiconductors change nuclear and particle physics, and the world at large” – Dr Erik Heijne.


Figure: A dead fly, imaged by the first particle or photon counting detector in the mid-1990s. Image courtesy of Heijne, E.H., History and future of radiation imaging with single quantum processing detectors (2020).

In the 1970s, physicist Dr Erik Heijne of the European Organization for Nuclear Research (CERN) proposed using semiconductors and silicon electronic integrated circuits for the charged particle experiments at CERN. As its name implies, semiconductor material conducts current, but this current can be modified, especially by a quantum of light or other radiation. Together with Dr Michael Campbell, they designed microscopically pixelated quantum sensors for use in particle physics experiments. During that development, x-ray sources were used to test the quality of the detectors and the benefit of this semiconductor detector technology to detect x-ray photons became evident. This led Campbell and others to propose the development of the ‘Medipix’ family of imaging devices in the 1990s.

One of the earliest images captured by Medipix1, the first photon-counting detector intended for medical use, was a dead fly – pictured to the left. Several years later, CERN engineers, working with the support of the institutes comprising the Medipix3 Collaboration, produced the Medipix3RX chip. Corrections and upgrades made this newest detector ‘photon processing’ instead of simple ‘photon counting’. How does Medipix technology relate to medical imaging?

X-ray photons behave differently depending on what material they pass through. With photon processing, each x-ray photon is detected, its energy or behaviour determined, and then sorted into corresponding energies.  This allows the technology to colour-code different parts of the body, and its components, with identification of atomic or molecular composition (1). For example, x-rays passing through bone will display different energies to x-rays passing through soft tissue, and each can be assigned a different colour.

Figure: Early New Zealand MARS researcher – Late 2005, Nick Cook’s pinkie was the first 2D image of a living human captured by Medipix-incorporated MARS technology.

In addition, the very small pixels of Medipix3RX, combined with a clever scheme to correctly measure the energy and position of each x-ray photon, provide much higher resolution compared to standard detector technology used in current x-ray imaging systems. This can be likened to your TV: the more pixels in your 55-inch screen, the greater the resolution.

Professors Phil and Anthony Butler had been collaborating with CERN since the early 2000s and recognised the potential of Medipix for clinicians, researchers, and – ultimately – patients.

Following successful preliminary studies with Medipix, they established the MARS Collaboration in 2006 to realise this potential by developing and commercialising the technology. They built a team of researchers, clinicians, mathematicians, physicists, and engineers. They first developed and sold ‘small-bore’ scanners for research purposes. Then, in 2018, CEO Phil Butler made history as the first living human scanned with the Medipix-derived MARS scanner (if you don’t count Nick Cook’s 2D pinkie image). The following year, the team developed a specialist wrist scanner for use in acute care clinics.



Future point-of-care MARS scanners aim to improve equity of access to advanced diagnostics.


Figure: The first 3D image of a living human image captured by Medipix-incorporated MARS technology in 2018. Of course, the cuts are not real, but just virtual, by the computer.

What is the MARS team up to now? The team is focused on ‘point-of-care’ scanners – scanners that are designed small enough to fit inside your general practitioner’s office or after-hours clinic. The goal is to improve access to advanced – or futuristic – diagnostics and better healthcare.

The team has started clinical trials of their specialised wrist scanner, beginning in New Zealand and Swiss clinics, and expanding throughout 2021 to more in Europe and Asia. In the future, the technology will be used for other conditions, such as cancer diagnosis and management, cardiovascular imaging, brain imaging, and other bone and joint conditions.

While we are not the only player in the game, MARS scanners incorporating the Medipix detector and associated readout systems are unique and can have significant impact in a growing number of medical applications. With 300 million CT scans performed globally each year, improving each just a little will have a massive health impact and benefit a lot of people. That is why colour x-ray is the future and discussions over a beer (or two) can be quite fruitful.




Written by Dr Chiara Lowe, Communications Officer for MARS Bioimaging Ltd.

Professor Anthony Butler, President Medical at MARS Bioimaging Ltd is a consultant radiologist at Christchurch Hospital, Professor at the Universities of Canterbury and Otago in Christchurch, New Zealand, and member of The Medipix and CMS Collaborations at CERN.

Professor Phil Butler, Chief Executive Officer at MARS Bioimaging Ltd is a Professor of Physics at the University of Canterbury and long-standing member of The Medipix Collaboration at CERN.

The MARS Team

One Thought to “Colour x-ray is the future: an introduction to MARS”

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