Comment: Three ways to move mammography into the 21st century

More than a million women in England missed out on vital breast cancer screening in 2021-22, according to the Breast Cancer Now charity. The prospect of undergoing a painful – or at least uncomfortable – mammogram can often be one of the reasons for women avoiding the vital screening. But the latest generation of technology has the potential to move mammography into the 21st century.

Flexible X-ray detectors

The human body is made up of all sorts of shapes and sizes of bones, ligaments, muscles, organs and tissue, almost none of which are flat. Why, therefore, are most scanners – including mammography equipment – flat and rigid?

The primary reason for using flat radiographs is historical. Black-and-white analogue photography (and X-ray radiography from which it derives) relies on the photosensitive nature of film. The structure of this film, when exposed to light, is invisibly modified as photoelectrons are liberated from the silver halide crystal and proceed to form a metallic silver speck which grows with extended exposure.

Once exposed, the film can be fixed and developed onto photosensitive paper in a dark room. The inherent consequence of this exposure process is that both the film and the photographic paper must be held flat and parallel to each other to avoid distorting the image. Consequently, although the film itself is flexible, the process that is used to produce photos or radiographs from the exposed film means it can only practically be used flat.

Since the early 2000s, newer flat-panel X-ray detectors have replaced a large segment of the radiography film market, as they offer the ability to see X-rays on screen immediately, without the time-consuming post-processing step required for radiographic film. However, these have introduced a further limitation, as they are fabricated using the same basic technology as displays, such as TVs and computer monitors, which are typically designed using amorphous silicon thin film transistors printed on glass backplanes.

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With the advent of newer technologies for curved screens and flexible electronics, it should be feasible to move away from flat detectors for mammograms towards ones that can be shaped to fit around the breast – and possibly even customised to some degree using printed electronics on a custom-made mould. The discomfort reported by many women could then be eliminated as the breast would no longer have to be compressed to fit onto a flat-panel X-ray detector.

Lower-dose mammograms

The NHS routinely offers breast screening every three years to all women aged 50-70. The age range has been chosen because the risk of developing breast cancer increases with age, while the mammogram itself (an X-ray) also has a risk of causing cancer associated with it due to the radiation exposure. In short, the benefits of detecting cancer outweigh the risks of causing cancer from radiation exposure from age 50 and above.

The logical conclusion, therefore, is that if the radiation dose could be reduced for mammograms (while maintaining the same quality of image), the breast screening programme could be offered at an earlier age – thereby increasing the chances of detecting cancer in women below the age of 50. Several oncologists already advocate the concept of personalised breast cancer screening, according to a patient’s own unique health history and risk factors. A lower-dose mammography service would strengthen that approach.

The latest X-ray detector materials hold the promise of higher sensitivity to X-rays, which inherently means better images for the same dose – or the same image quality for a lower dose, which is exactly what is needed in the case of mammograms.

AI and 3D X-ray imaging

The use of artificial intelligence (AI) within X-ray imaging is already starting to show some significant and proven benefits. In many cases it has proved to be as accurate as two consultants working together when it comes to detecting cancer in patients, according to research, with fewer false positives. This offers the prospect of faster results for patients, improved productivity for consultants and lower costs for the health service.

In addition, digital breast tomosynthesis is a new form of mammography, which takes multiple low-dose exposures of each breast from a series of angles. The resulting set of X-rays is then reconstructed using complex mathematics to create a 3D image of the breast. This 3D image can then be digitally mapped into 2D radiographs on screen to see clear sectional ‘slices’ through the breast at different depths. This technique has been reported to provide higher sensitivity (although with slightly lower specificity) than mammography for detecting breast cancer.

In conclusion, to move mammography into the 21st century, medical equipment manufacturers should be seeking out newer detector technologies which provide enhanced 3D images at lower doses, feeding the images into AI algorithms with improved detection capabilities and ideally using pain-free curved detectors to encourage screening for as wide a group of patients as possible.

Dan Cathie, CEO of Silveray