In the photon mode: scientists will increase the accuracy of tomographs at the quantum level

Russian scientists have obtained new data on the scattering behavior of photons. The position of these light particles is recorded during positron emission tomography to determine the exact position of cancerous tumors. The result of the experiments will make it possible to avoid errors in noise suppression on tomographic images and create more advanced imaging methods for patients' internal organs. According to experts, the fight against distortion on CT has become one of the main directions of development of this technology today. The data obtained opens the way to the creation of a new generation positron emission tomograph.

Photons for the diagnosis of cancerous tumors

Scientists at the Moscow Institute of Physics and Technology (MIPT), together with colleagues from the Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS), have obtained unexpected experimental results on the behavior of photons during so—called Compton scattering, one of the main forms of photon interaction. Light particles are detected during positron emission tomography (PET) to accurately determine the location of cancerous tumors, so the new fundamental data will help avoid errors during diagnosis, as well as help create a new generation of PET devices.

The Compton effect is called the scattering of a photon by a charged particle, most often an electron. Previously, it was believed that this loses quantum entanglement, that is, the ability of particles to be in several states at the same time. However, research on a special installation has shown that it is almost completely preserved.

— According to the results that we obtained at the INR RAS facility, quantum entanglement is preserved almost completely even at significant scattering angles. This discovery calls into question existing ideas about the interaction of photons and opens up new opportunities for creating a new generation PET device," said Sultan Musin, one of the authors of the study, an assistant at the Department of General Physics at MIPT.

A new generation tomograph

In modern PET devices, photon pairs generated during the annihilation process are recorded. This data is used to accurately determine the location of the tumor. However, photon scattering, when interacting with surrounding tissues, distorts information, creating noise and reducing image clarity. The study calls into question the current methods of filtering these noises and opens up the possibility of creating new, more accurate approaches.

— Our results have shown that the entangled states of annihilation photons do not collapse to separable ones, as previously thought. This discovery not only changes the understanding of quantum entanglement, but also represents a challenge for the further development of quantum technologies in the field of medical imaging," added Sultan Musin.

According to experts in the field of visual diagnostic methods, any research that provides scientists with new knowledge related to noise reduction during CT scans plays an important role in obtaining more accurate images and, consequently, in correctly understanding the location of tumors in the patient's body.

— In all methods of medical diagnostics, both radiation and non-radiation, noise abatement is one of the main vectors of technology development. The new data may improve the accuracy of tomography, which is now considered the gold standard. Getting rid of noise is very important when images are analyzed by a specialist rather than a neural network, since with low quality, the diagnostician may miss something. The human body is a highly light—scattering environment, so reducing noise will increase the information content of the images," said Ivan Pyanov, associate professor at the Institute of Biomedical Systems at the National Research University MIET.

The phenomenon of quantum entanglement is one of the fundamental resources of quantum technologies, Professor Sergey Kulik, scientific director of the Center for Quantum Technologies at the Lomonosov Moscow State University Faculty of Physics, explained to Izvestia.

— This property is used in many practical applications of quantum technologies — in the construction of quantum communication systems, in quantum computing devices and in highly sensitive quantum sensors. The effect discussed in this paper may be directly related to the creation of a new generation of PET, but it requires further study in terms of diagnostic applications in medicine, biology and in the restoration of images of objects in a diffusing environment," said Sergey Kulik.

According to Stanislav Stragnov, head of the Laboratory for the analysis of public health indicators and digitalization of healthcare at MIPT, it is necessary to technically work out the methodology for creating devices that can apply the discovered effect. Until a new generation of CT scanners is created, it makes no sense to talk about any applied achievements. At the same time, it is worthwhile to establish mass production and implementation of such devices, the expert emphasized.