Science Translational Medicine: scientists have developed low radiation PET scanners that can detect early cancers 2017-06-05
Source: Nanfang Daily, 2017-05-15, 13:45

The University of California at Davis research team has developed a new PET scanner, the explorer". The study confirmed that the Explorer could reduce the radiation dose by 40 times compared with the current PET scan and still acquire the same image signals as the existing scanners. It is reported that this research is expected to show itself in the early field of cancer testing, while in other areas of medical research, such as drug research and development, the same potential great.
PET (Positron Emission Computed Tomography), meaning "positron emission tomography", its working principle is to inject the body of radioactive material, and then use the signs of radioactive particle tracking and neurodegenerative diseases such as tumor. It is reported that PET scanning has unique advantages in the diagnosis of early diseases, especially in the discovery of early cancer. In recent years, this technology has been gradually adopted by international and domestic medical institutions. However, the existing PET scan is no dispute: the scanning range is relatively small, and the speed is slow, so the scan is subject to a larger radiation dose, and even increase the risk of cancer. New research is expected to solve the problem.
The results were published in the latest issue of the journal Science, translational medicine, and published in the Journal science.
Existing technical arguments
Non deterministic detection results are known for radiation risk
The history of PET is not short. As early as the 70s of the last century, PET scanners were introduced into the clinic. In recent years, the popularity of PET is often associated with CT, that is, the so-called "PET - CT" detection". CT is no stranger to us, its official name is "X ray computed tomography, X - Ray computed tomography", as the name implies, namely X ray transmission body, detection of X rays through the body after the rest of the ray, after computer processing the image can be quite detailed picture of human anatomy, of great help the doctor make a diagnosis.
But for early cancers such as cancer, the tumors are too small or have no apparent structural changes and cannot be judged by CT or magnetic resonance imaging. But in theory, PET is able to distinguish between the no obvious structural changes in lesions: PET was detected before the injection of 18F FDG (to 2-fluoro-2-deoxy-D-glucose), the drug will be 18 markers in glucose positron radionuclide fluoride. The drug into the body, involved in human metabolism, and malignant tumor theory for the glucose consumption than normal cells, which will accumulate a lot of positron nuclide, formed a "bright spot", which is the PET capture equipment "".

18F FDG has been hailed as a "century molecule" because it is able to meet the imaging of most cancers". In addition, 18F - FDG does not apply to all cancers, and other drugs can be used for prostate cancer, brain cancer, and so on. But it is worth noting that, for some gastric cancer, prostate cancer, bladder cancer, kidney cancer and so on, PET detection effect is not satisfactory.
In addition, the drugs injected into the human body are radioactive, and the radiation produced may cause potential harm to the human body. In 2009, a publication published in the journal radiology of the North American Radiological Society warned that the whole body PET - CT scan was accompanied by a large dose of radiation and cancer risk.
The medical community has not reached a full consensus on how much this harms, or even how likely it is to assess the possible benefits of disease treatment.
Because of the test results and potential radioactive query, many doctors have said that not recommended for healthy people to use PET - CT equipment. But in 2011 the Ministry of Health issued the "2015 national 2011 - positron emission tomography configuration plan" also stressed that "strict standards to strengthen the allocation of medical institutions, access management, regulating the use, protection of the legitimate rights and interests of patients. The positive rate of PET - CT examination was not less than 70%." In other words, in the face of possible risks, doctors can use the device only when it is possible to diagnose a possible (70%) suspected cancer.
"Explorer" is more than just detecting early cancers
The research team at the University of California at Davis confirmed that the Explorer could reduce the radiation dose by 40 times compared with the current PET scan and still acquire the same image signals as the existing PET scanners. "So our scanner can do what takes 20 minutes to complete at 30 seconds, or you can dramatically reduce radiation doses and scan with very little radiation dose." Professor Ramsey Badawi, one of the project's leaders, said.
The benefits of reducing radiation are not just to make healthy people less risk for early cancer screening, but more importantly, they have important potential in medical research.
"We can reduce the radiation dose to repeatedly scan the same subjects in a long time, so that we can better determine the chronic diseases such as arthritis, diabetes and obesity pathogenesis, causes and treatment methods." Ramsey Badawi expresses.
In fact, many medical professionals told reporters that many human diseases, especially chronic diseases, can be described as "know it, but I do not know why," for its causes, the course of disease is unknown". And the explorer, after greatly reducing the radiation measurement, can do a large sample of healthy people, trying to "crack" the cause of the disease.
Another advantage of the explorer, said, is that it has a wider range of images and a higher resolution than traditional PET scanners. "This allows us to collect images faster, thus significantly reducing the blurring caused by the motion of the scanner during scanning."."
Another possible development of explorer is drug development, and researchers can use PET to monitor how drugs affect the organism. "Perhaps, in the future, pharmaceutical companies will be able to know the dose of a drug in the liver, in addition to knowing whether the drug has reached the tumor site.". So it can help us filter out better candidate drugs, thereby reducing the failure rate of clinical trials. Tangent representation.
"We can also do similar monitoring for medical treatments such as cell therapy. Specifically, it is the labeling of immune cells or stem cells, recording their activity in the body through PET scans, thereby monitoring the efficacy and prognosis." Cut said.
The future is expected to be in clinical practice within 3 years
Badawi also noted that "explorers" another application direction is toxicology. For example, he says, many nanoparticles enter the body through lipstick, sunscreen, etc., but we don't know how they affect the body. "Now, we can try to mark some nanoparticles with persistent tracers, and explorers will be able to track them under the premise of increased sensitivity, and the length of time is up to 1 months."
At the same time, because of the almost no risk of low doses of radiation, "explorers" can also be involved in basic studies of pregnant women and children, such as fetal brain development, child development disorders and so on.
Personally, it also hopes that this technique will be applied to the study of multisystem diseases. "The application of the Explorer will be very extensive," says Mr Li. "I believe that future doctors and researchers will use this technique in ways we have never even thought of, and that will be very exciting."." The research team is expected in the second half of 2018, the "Explorer" will be the first human experiments and clinical trials in FDA (U.S. Food and Drug Administration) approval, hoping to enter the clinical team in 3 years.
The distance from the laboratory to the application is not short. One of the big problems facing the research team is that the Explorer will cost 5 - 6 times as much as an existing scanner. Another challenge is that, based on the high precision of explorer, in order to process large amounts of data, they still need to improve and develop new programs to achieve all of their functions.