Using high-energy X-rays emitted by a special type of particle accelerator, scientists have intricately captured the damage caused by COVID-19 to the lungs' smallest blood vessels.

Scientists from University College London (London, UK) and the European Synchrotron Research Facility (ESRF; Grenoble, France) used a new revolutionary imaging technology called Hierarchical Phase-Contrast Tomography (HiP-CT), to scan donated human organs, including lungs from a COVID-19 donor. HiP-CT enables 3D mapping across a range of scales, allowing clinicians to view the whole organ as never before by imaging it as a whole and then zooming down to cellular level.

The technique uses X-rays supplied by the European Synchrotron (a particle accelerator) in Grenoble, France, which following its recent Extremely Brilliant Source upgrade (ESRF-EBS), now provides the brightest source of X-rays in the world at 100 billion times brighter than a hospital X-ray. Due to this intense brilliance, researchers can view blood vessels five microns in diameter (a tenth of the diameter of a hair) in an intact human lung. A clinical CT scan only resolves blood vessels that are about 100 times larger, around 1mm in diameter. Using HiP-CT, the research team has seen how severe COVID-19 infection 'shunts' blood between the two separate systems - the capillaries which oxygenate the blood and those which feed the lung tissue itself. Such cross-linking stops the patient's blood from being properly oxygenated, which was previously hypothesized but not proven.

The team is using HiP-CT to produce a Human Organ Atlas which will display six donated control organs: brain, lung, heart, two kidneys and a spleen, and the lung of a patient who died of COVID-19. There will also be a control lung biopsy and a COVID-19 lung biopsy. The Atlas will be available online for surgeons, clinicians and the interested public. The researchers are confident that the scale-bridging imaging from whole organ down to cellular level could provide additional insights into many diseases such as cancer or Alzheimer's Disease. The team hopes the Human Organ Atlas will eventually contain a library of diseases that affect organs on a range of scales, from 1 to 100s of microns to entire organs, helping clinicians as they diagnose and treat a wide range of diseases. The team also hope to use machine learning and artificial intelligence to calibrate clinical CT and MRI scans, enhancing the understanding of clinical imaging and enabling faster and more accurate diagnosis.

"By combining our molecular methods with the HiP-CT multiscale imaging in lungs affected by COVID-19 pneumonia, we gained a new understanding how shunting between blood vessels in a lung's two vascular systems occurs in COVID-19 injured lungs, and the impact it has on oxygen levels in our circulatory system," said Danny Jonigk, Professor of Thoracic Pathology, Hannover Medical School, Germany.

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