‘Google Earth for the Human Heart’ Accelerates Advances in Cardiovascular Medicine

Researchers from University College London (UCL) and the European Synchrotron Radiation Facility (ESRF) have now imaged both healthy and diseased hearts in greater detail than ever before, providing a valuable resource for improving our understanding of cardiovascular disease.

This study Radiologyis an atlas of the human heart that captures the anatomy of the entire organ down to 20 micrometers (half the width of a human hair), with certain areas imaged down to the cellular level.

The atlas will facilitate studies of both healthy and diseased hearts that were not possible before, revealing the anatomy and connections within the organ, with potential applications ranging from improving treatments for arrhythmias to creating more lifelike models for surgical training.

Cardiovascular disease is the leading cause of death worldwide. Ischemic heart disease, which weakens the heart due to reduced blood flow, accounted for 8.9 million deaths, or 16% of all deaths, worldwide in 2019, a figure that has increased by more than 2 million since 2000.

Clinicians commonly use imaging techniques such as ultrasound, computed tomography and magnetic resonance imaging to diagnose cardiovascular disease, but these techniques don’t provide detailed structural information about what’s going on inside organs. To get a more detailed image, organs must be sliced ​​into thin slices and scanned, severely limiting the field of view.

In recent years, a type of particle accelerator called a synchrotron has been used to develop new imaging techniques that overcome these limitations. Synchrotron studies of whole fetuses and small animal hearts have been published, but these have always been at a scale much smaller than the major organs in adults.

In the study, scientists from UCL and ESRF used an X-ray technique called hierarchical phase-contrast tomography (HiP-CT) to image two entire adult hearts at a scale of 20 micrometres, providing a comprehensive, detailed 3D picture of the entire organ.

One heart came from a 63-year-old Caucasian male donor (control group) with no history of heart disease, and the other came from an 87-year-old Caucasian female donor with a history of ischemic heart disease, hypertension, and atrial fibrillation. It is not possible to image a living human heart with this method because the radiation dose is too high.

Professor Peter Lee, lead author of the study from University of London’s School of Mechanical Engineering, said: “The atlas we have created is like a Google Earth for the human heart. It allows us to look at the whole organ at a global scale, and then zoom in to ground level to see cardiovascular features in unprecedented detail.”

“One of the big advantages of this technology is that it gives us a complete 3D view of the organ, about 25 times better than a clinical CT scanner. What’s more, we can zoom in on selected areas down to the cellular level, allowing us to see the same detail as we see under a microscope, but with 250 times more precision, without having to cut into the sample.”

“Being able to image an entire organ in this way reveals details and connections that weren’t visible before.”

Detailed imaging of the cardiac conduction system, which generates and transmits the electrical signals that make the heart muscle pump, is one example of how this research will impact cardiovascular medicine.

Professor Andrew Cook, an author of the study and a cardiac anatomist at the Institute of Cardiovascular Sciences, University of London, said: “With today’s technology, it is extremely difficult to accurately interpret the anatomical structures underlying disease conditions such as arrhythmias, so the use of the imaging techniques we have demonstrated here has great potential to lead to new treatments.”

“We believe our findings can help researchers understand the development of abnormal heart rhythms and the effectiveness of ablation strategies to treat them. For example, we now have a way to determine differences in the thickness of the tissue and fat layer between the outer surface of the heart and the protective sac that surrounds it, which could have implications for treating arrhythmias.”

The two hearts were imaged at the European Synchrotron Radiation Facility in Grenoble, France, which has the world’s most bright X-ray source.

Lead author of the study, Dr Joseph Brunet, Visiting Scientist at UCL’s Department of Mechanical Engineering and ESRF, said: “When we first saw the heart with HiP-CT, we were absolutely amazed as we could clearly see the soft tissues that are normally invisible in conventional X-ray images. This was only possible because of the way phase-contrast X-rays interact with these tissues, and the high energy that the ESRF can produce to penetrate the entire organ.”

But this solution is not without challenges: Imaging a single heart would generate 10 terabytes of data, a million times more than a standard CT scan.

Paul Tafforeau, one of the study authors from ESRF, who invented the HiP-CT technique, said: “ESRF’s beamline facilities are currently the only place in the world where it is possible to image entire adult human organs with such high levels of contrast, and we are still far from the limits of the technology. The main limiting factor is the processing of the very large data generated by HiP-CT.”

This work contributes to the “Human Organ Atlas” project, which aims to build an open science image database of all human organs in health and disease. The atlas is available online.