Positron emission computed tomography (PET/CT)
PET (positron emission tomography) is an emerging diagnostic method of nuclear medicine based on the ability to use a PET scanner to track the distribution of biologically active compounds labeled with positrons in the body. Pozitrons occur during the positron beta decay of radionuclide, which is part of the radiopharmaceutical, which is introduced into the body before the study. To date, PET is a key technology in the diagnosis of cancer, since it allows you to identify the disease even before the manifestation of clinical symptoms. The PET study is usually combined with computed tomography (CT) scans to overlay the results on the patient's "body map."
Method
Positron emission computed tomography (PET/CT) is a radionuclide tomographic method for the study of internal human organs. The method is based on the registration of a pair of gamma quanta that occur during annihilation of positrons with electrons. Pozitrons occur during the beta decay of radionuclide, which is part of the radiopharmaceutical, which is intravenously injected into the body before the study and selectively accumulated in tumor tissues.
This method is based on the ability, using special detection equipment (PET scanner), to track the distribution in the body of biologically active compounds labeled with positron-emitting radioisotopes. To date, PET mainly uses positron-emitting isotopes of elements of the second period of the periodic system, most often fluorine-18, which has optimal characteristics for use in PET: a short half-life and the least radiation energy.
Most often, for positron emission tomography, a biological analogue of glucose is used - fluorodeoxyglucose (FDG), the molecule of which contains radioactive (positron-emitting) nuclide fluorine-18 (18-FDG). FDG is administered to the patient, after which it is distributed throughout the body. Tumor cells consume glucose much more intensively than others, this allows you to register areas of drug accumulation (FDG) using a PET scanner - clusters of tumor cells.
The use of a radiopharmaceutical requires the organization of a full-fledged production - a cyclotron complex in the immediate vicinity of a medical institution. To obtain fluorine-18, a cyclic accelerator such as a medical cyclotron, less often a linear accelerator, is used. The target is usually pure or oxygen-enriched-18 water that is proton bombarded. Oxygen-18, in turn, is obtained by the method of low-temperature rectification.
There are already similar PET centers in Russia, for example, in Moscow, St. Petersburg, Khabarovsk, Khanty-Mansiysk, Kazan. At the beginning of 2019, there are about thirty such operating centers with their own production in Russia.
How does a PET scanner differ from a gamma camera?
PET scanners and gamma cameras (scintigraphy machines) are nuclear diagnostic installations that are considered the most accurate in oncology, cardiology and neurosurgery. How are they different? The principle of operation is approximately the same: the patient is injected with a radiopharmaceutical (RMP), which accumulates in a certain organ or tissue and emits weak energy quanta, and the diagnostic installation captures this radiation and forms images. Thanks to the short half-life, the FPM is quickly removed from the body (from several hours to two days) and does not harm the patient, so you should not be afraid of radiation. The dose of radiation received during one examination is ten times less than the dose received after the image on the X-ray apparatus.
The difference between PET and gamma camera is the number of images. PET forms a 3D volumetric image of the area under study, and the gamma camera forms only given projections. I.e. PET (which is usually combined with CT) gives a more accurate picture. But the equipment of the gamma camera is cheaper and easier to install/launch. Therefore, gamma cameras are more common. However, according to 2009 data, 80% of those 200 gamma cameras installed in Russia are already morally and physically outdated. For comparison, in the United States at that time, more than 12 thousand gamma cameras functioned and annually more than 15 million patients undergo scintigraphy on them.
Chronicle of the development of technology
2023
PET/full-body CT scanner presented, which is inexpensive and displays images without noise
On June 24, 2023, American researchers at Washington University in St. Louis (WUSTL) reported the development of a new system that combines positron emission (PET) and computer (CT) tomography capabilities. The solution is designed to scan the whole body to detect malignancies. Read more here.
A new word in the treatment of depression and Alzheimer's. The resolution of PET scanners was first increased to a level that allows counting the nuclei of the brain stem
On June 24, 2023, Canadian researchers at the Sherbrooke Center for Molecular Imaging announced the development of an ultra-high resolution positron emission tomograph (PET). This scanner is expected to help treat all sorts of ailments, including Alzheimer's disease.
PET is an actively developing diagnostic and research method of nuclear medicine. It is based on the registration of a pair of gamma quanta arising from the annihilation of positrons with electrons. The method makes it possible to study various processes, such as metabolism, transport of substances, ligand-receptor interactions, gene expression, etc.
The new PET scanner provides high spatial resolution - 1.25 mm, which is twice as much as a high-resolution research tomograph (HRRT). In this way, the nuclei of the brain stem can be visualized and quantified. This makes it possible to detect early changes associated with many diseases.
 | Positron emission tomography is useful in the study of neurological phenomena and for diagnostic purposes, but until now its potential has been somewhat limited by poor spatial resolution. The ultra-high resolution scanner is a qualitative leap in PET technology. It opens up new possibilities for early diagnosis of various conditions, "said Vincent Doyon, a master's student in radiation sciences and biomedical research. |  |
The developed system allows characterizing previously indistinguishable areas of the brain that can be associated, in particular, with Alzheimer's disease, depressive disorders, visual perception disorders, tinnitus and other conditions. In addition, the new scanner can be used for research purposes.[1]
New PET scan method developed to detect inflammation
At the end of January 2023, a tool called a LW223 for a positron emission tomograph for scanning to detect inflammation was presented. Researchers received just under $2.5 million to test it. Read more here.
2022
GE Healthcare has released its first all-digital PET/CT scanner
In mid-October 2022, GE Healthcare introduced the first fully digital PET/CT system in its range for the diagnosis of cancer. Positron emission tomography combined with X-ray computed tomography, which is a hybrid radionuclide diagnostic technique widely used in oncology worldwide. Read more here.
A portable PET device for scanning certain organs is presented
In early July 2022, Radialis Medical introduced the Radialis PET Imager portable positron emission tomography imaging machine. The system entered the market with the ability to adapt to the patient, and not vice versa, the manufacturer claims. Read more here.
2021
PET/full-body CT scanner announced for $8.9 million
At the end of July 2021, Quibim, which develops AI solutions for analyzing medical images, joined a Spanish project worth $8.9 million to create a PET/CT scanner for simultaneous imaging of the entire body. Read more here.
PET is the most effective tool for detecting recurrent brain metastases
In early May 2021, a study was published in The Journal of Nuclear Medicine, the results of which say that positron emission tomography (PET) is the most effective tool for detecting metastases brain and evaluating the effectiveness of modern treatments. When the results MRI of -monitoring are unclear, the addition of PET with 18F-FET helps physicians accurately diagnose recurrent brain metastases and reliably assess the patient's response to therapy.
New treatment options for patients with brain metastases, such as immune checkpoint inhibitors and targeted therapy, are quite effective but can cause many side effects. In this regard, the results of MRI imaging with contrast enhancement can vary greatly, and it becomes difficult to assess the response to treatment.
| | In fact, these new treatments require brain imaging that cannot be performed with conventional MRI, "explained Norbert Galldiks, professor of neurology, neurologist and neuro-oncologist at the University Hospital of Cologne and Research Center in Jülich. - In our study, we tried to determine whether adding PET 18F-FET could help overcome some of these problems. | |
The retrospective study included patients with melanoma and lung cancer with brain metastases who received treatment with immune checkpoint inhibitors or targeted therapy alone or in combination with radiation therapy. Researchers have shown that PET results with 18F-FET can help doctors assess the response when routine MRI data is insufficient. Thanks to PET, doctors were able to correctly identify recurrence of brain metastases and identify patients who responded to treatment.[2]
2020: New PET/CT method for prostate cancer diagnosis emerges
At the end of October 2020, the researchers presented evidence that the PET/CT technique with PSMA (prostate specific membrane antigen) allows us to effectively differentiate localized and metastatic cases of high-risk prostate cancer (PC).
The stage of PCa is usually determined by computed tomography, in particular the abdominal cavity and pelvis, as well as osteoscintigraphy. However, in such cases, the volume of disease often remains underestimated due to the low sensitivity of these methods. The researchers conducted a posterior analysis and believe that a higher sensitivity of PET/CT with PSMA allows us to detect PCa metastases in time, and conception can favorably affect the results of PCa treatment at high risk.
The study evaluated 249 high-risk/very high-risk PCa patients who underwent PET with PSMA between December 2016 and January 2020. The new technique made it possible to accurately assess the status of the disease, and also revealed the local spread of cancer beyond the prostate gland, invasion of the seminal vesicles or into the surrounding structures in 8.1% of patients assigned to stage T2 in previous MRI. Overall, PET with PSMA revealed 19.7% of patients with regional lymph node involvement and 9.4% of patients with metastatic involvement. Although these areas have not always been confirmed by biopsy, it can be argued from previous studies that 85-98% of the lesions detected are PC metastases.
The researchers believe that earlier detection of metastases will allow personalization of treatments and significantly improve the results of therapy in patients during the early stages of metastasis. Despite the high sensitivity of the method, the use of PET/CT with PSMA is still limited.[3]
2017: Siemens Healthcare fixes vulnerabilities in PET scanners
On August 7, 2017, Siemens Healthineers announced a software update for positron emission tomography scanners. The company fixes vulnerabilities that hackers could theoretically exploit to break into this medical equipment. Read more here.
Notes
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