The physical principle of PET imaging is the use of cyclotron, accelerating charged particles to attack the target nucleus, through the nuclear reaction to produce positron radionuclides, and synthesize the corresponding imaging agent, introduced into the body is located in the target organ, these nuclides in the process of decay emission of positrons, this positron interactions, the annihilation of radiation occurs, emitting the direction of the opposite direction, the energy is equal to that of the two photons of PET imaging. PET imaging uses a series of paired detectors arranged 180° to each other and connected to the line to detect the annihilation of no radiation photons, thus obtaining the tomographic distribution of the body's positronic nuclides, showing the location, morphology, size and metabolic function of the lesion, and diagnosing the disease.
18F-FDG, an analog of glucose, is the most commonly used clinical imaging agent. After intravenous injection of 18F-FDG, it enters the cell through the cell membrane with the help of glucose transporter protein, and the phosphorylation of intracellular 18F-FDG under the action of has glucokinase generates 6-PO4-18F -FDG, which cannot be further metabolized due to the structural differences between 6-PO4-18F-FDG and glucose.
The vast majority of malignant tumor cells are characterized by high metabolism, especially the division and proliferation of the cells of malignant tumor cells are faster than normal cells, and the energy consumption is increased accordingly, glucose is one of the main sources of energy for tissue cells, and the abnormal proliferation of malignant tumor cells is one of the as long as sources of energy for tissues, and the abnormal proliferation of malignant tumor cells requires the over-utilization of glucose by increasing the glucose membrane transport capacity and the activity of major regulatory enzymes in the glucose metabolic pathway.
Tumor cells can accumulate a large amount of 18F-FDG, and PET imaging can show the location, morphology, size, quantity, and distribution of radioactivity within the tumor. At the same time, the primary foci and metastatic foci of tumor cells have similar metabolic properties, and a single injection of 18F-FDG can conveniently carry out whole-body imaging. 18F-FDG PET whole-body imaging has a unique value for understanding the whole-body extent of tumor involvement. Clinically for tumors, 18F-FDG is only used for the diagnosis of malignant tumors and the differential diagnosis of benign and malignant, clinical staging, evaluation of therapeutic efficacy and monitoring of recurrence. According to the characteristics of glucose metabolism in the brain, 18F-FDG is mainly used for epilepsy focal localization, progeria dementia, cerebrovascular disease, depression diagnosis and research; it is also used to study the relationship between local physiological functions of the brain and glucose metabolism, such as visual and auditory stimuli, emotional activities, memory activities, etc. caused by glucose metabolism changes in the corresponding cerebral cortical regions. The main use of PET is to estimate myocardial survival.
PET in brain tumors, intracranial tumors are divided into two categories: primary and secondary tumors. Primary intracranial tumors occur in the haunted tissues, meninges, cerebral nerves, pituitary gland, blood vessels and residual embryonic tissues. Secondary tumors refer to malignant tumors in other parts of the body that have metastasized or invaded into the skull.PET imaging is mainly used for characterization of intracranial tumors, understanding of biological characteristics, identification of recurrence and fibrous scar formation after treatment, and evaluation of therapeutic efficacy, etc.
The PET imaging system is designed for the treatment of intracranial tumors.
PET/CT is clinically used for early diagnosis of tumors and positioning of biological targets for radiation therapy of tumors, diagnosis of coronary blood supply, cardiac function and myocardial blood flow metabolic diseases and neurological diseases. It can simultaneously obtain 8 layers of CT scan data and images, and can get the same machine the same anatomical position of the functional metabolism of PET images, after the same machine image fusion technology can simultaneously show the organ cell metabolism and anatomical structure of the changes and abnormal metabolism in the anatomical structure of the actual position.
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In recent years, through the research and development of a number of medical institutions and companies such as GE***, the essence of the two imaging technologies have been combined into one, resulting in the development of PET-CT, a combination of X-CT and PET, which represents a breakthrough in diagnostic imaging technology and the diagnosis of tumors and cardiovascular diseases. This breakthrough in technology marks a new era in diagnostic imaging technology and diagnosis of tumors and cardiovascular diseases.
The current PET/CT scanning system is not a brand new diagnostic imaging system, it is actually an organic combination of PET and X-CT equipment, including a PET scanner, an X-CT scanner, and a computer software platform that connects the two scanning images and **** the same processing, which makes it a single composite imaging system.
With a single scanner, it is possible to use the X-ray scanner as a single image system.
Compared with simple X-CT or PET, the advantage of PET/CT imaging is that it can not only provide accurate anatomical images of the whole body (including three-dimensional imaging and tomographic images) through a single rapid scanning image, but also draw specific biometabolic distribution maps of different tissues and organs based on different positronic imaging drugs, so that a variety of foci of various tissues and organs can be accurately localized and characterized or quantified. The results can be used to accurately localize and characterize various lesions in various tissues and organs, or to perform quantitative or semi-quantitative analysis.
Before PET/CT was introduced, X-CT technology was already very popular, and PET technology has been widely used in the diagnosis and research of various oncological diseases and a variety of neurological diseases, cardiovascular system diseases, and many other diseases. As a new generation, PET/CT technology is more superior than X-CT or PET imaging alone, and its clinical applications and medical research should be more extensive.
The application of PET/CT in tumor diseases is mainly an extension or expansion of PET tumor imaging, which can be summarized in the following aspects in general:
1. benign and malignant differential diagnosis of tumors, and provide accurate sites for puncture or tissue biopsy for difficult foci;
2. staging and grading of malignant tumors;
3. ( Using a variety of PET imaging agents) to determine the diversified metabolic properties of tumor foci;
4. Providing accurate localization for radiotherapy (especially precision radiotherapy) of malignant tumors;
5. Evaluating the efficacy of various treatments for tumors;
6. Identifying tumor recurrence at an early stage;
7. Searching for primary foci of metastatic tumors of unknown origin
8, Prognostic judgment of malignant tumors.
Compared with PET tumor imaging alone, PET/CT tumor imaging has significant advantages: on the one hand, lesions with positive PET images are easy to locate accurately, and about 10-25% of lesions that are not easy to locate on PET images can be easily identified on PET/CT images; it is easier to implement targeted lesion puncture or biopsy through the accurate localization of PET/CT images, as well as to implement accurate radiotherapy plans. and precise radiotherapy planning. On the other hand, PET/CT tumor imaging is more sensitive and accurate than PET tumor imaging alone, and in many cases, tumor staging is clearer or early recurrence of the tumor can be more easily identified, and therefore a significant percentage of cases will be treated with more appropriate surgical plans (e.g., the efficiency of secondary surgery will be improved, etc.) or other effective treatments.
As the imaging speed of PET/CT has been greatly improved, many units have begun to apply 11C-tumor imaging agent for PET/CT imaging, in order to improve the accuracy of tumor diagnosis and provide clinical diagnostic information on the diversity of tumor biological characteristics, and to provide a more specific and objective diagnostic basis for guiding the treatment of tumors and evaluating the efficacy of treatment.
It is believed that with the use of PET/CT equipped with high-grade CT, not only can various PET imaging be completed, but also through the accurate anatomical localization of CT images, comprehensive judgment can be made on the cardiovascular system and neurological diseases in terms of morphology, blood flow, and metabolism, which greatly improves the accuracy of diagnosis. It is believed that the application of PET/CT in the cardiovascular system and the nervous system will continue to increase in the near future.
PET can accurately determine myocardial viability and measure the absolute value of coronary blood flow, so it plays an important role in the diagnosis of coronary artery disease, and PET/CT will improve the diagnosis of coronary artery disease to a new level by combining the advantages of CT and PET.
The combination of CT and PET cardiac technologies enables a more comprehensive study of the heart's functional status. PET/CT successfully combines CT and PET functions organically, and opens up a whole new world of coronary artery disease diagnosis, realizing a "one-stop" examination (i.e., a single examination that provides comprehensive cardiac information), thus providing clinicians with a more comprehensive diagnostic tool. It is a one-stop examination (i.e., a single examination can get comprehensive information about the heart), which provides favorable help for clinicians to accurately diagnose and correctly treat heart diseases.
Radiotherapy, together with surgery and chemotherapy, is one of the three major therapeutic tools for tumor treatment. About 60-70% of tumor patients need radiation therapy alone or in combination with chemotherapy and surgery. In order to improve the effect of radiation therapy for tumors, it is necessary to maximize the concentration of rays into the lesion area to kill tumor cells and minimize the damage to normal tissues. Generally, multiple irradiation fields are used to ensure that the abnormally growing tumor cells are irradiated by the dose of the treatment machine, while the impact on the surrounding normal tissues is minimized.
PET/CT combines PET functional molecular imaging technology and CT anatomical imaging function organically, not only can the PET, CT and PET/CT functions of the device be used separately in the clinic, but also the simulation positioning function of the radiation plan can be accomplished more accurately and conveniently using PET/CT. Because PET/CT is used in PET/CT fusion images to outline the scope of the tumor, so it can accurately distinguish between normal tissue and tumor tissue, display tumor growth and metabolism, timely detection of the effect of tumor treatment, as well as timely modification of the treatment plan.
The development and utilization of PET/CT and other functional imaging devices and new imaging agents have led to important changes in the definition of radiotherapy target area, resulting in the concept of biological target area (BTV).
The simulated localization of tumor radiation therapy using PET/CT is currently the best simulated localization method, which will significantly improve the effect of tumor treatment.
At present, different imaging technologies have been combined together in the clinic through image fusion methods to achieve the purpose of localization, periodicity, quantification, and characterization for disease diagnosis.
The so-called PET/CT is an integrated device that combines the PET function of positronic radiotracer imaging and the CT function of X-ray imaging, and uses the same examining bed and the same image-processing workstation to conduct a whole-body examination.
As a result, PET/CT is not only the most advanced imaging device available today, but also represents the future of imaging.
The combination of the new PET/CT and 13NH3, which simultaneously provides subtle coronary artery anatomy and myocardial function, makes this new examination method truly safe, non-invasive, highly sensitive, highly specific, clearly positioned, clearly characterized, precisely quantified, and regularly accurate. With the increasing installation of medical cyclotron and PET/CT in China and people's deeper understanding of molecular imaging, it is believed that the application and research of functional imaging in blood perfusion will be taken to another level, creating a good platform for the continuous development of molecular medicine in China.
In the past two years, PET/CT in the clinical diagnosis of coronary artery disease has shown that PET/CT has an irreplaceable role in myocardial perfusion status, myocardial viability, and ventricular wall motion function. We believe that PET/CT will play an increasingly important role in the diagnosis of coronary artery disease.
PET/CT is a new functional molecular diagnostic imaging device that organically combines the functions of state-of-the-art PET and CT. PET can express the metabolic information of tumor foci through the use of metabolic imaging agents, anaerobic imaging agents, and other medications, through which the boundaries between tumor tissues and normal tissues as well as non-tumor tissues around the foci can easily be determined, and tumor cells within the tumor foci can be identified. The PET/CT fusion image can provide both precise anatomical structure image and biological target area material.
The use of PET/CT for radiotherapy planning is an entirely new area of clinical practice. As PET/CT belongs to the functional molecular imaging, it provides the distribution of tumor tissues in the lesion, so it can provide a reliable basis for the ray distribution of three-dimensional conformal intensity-modulated radiotherapy, which can truly achieve non-uniform dose output, improve the treatment effect, reduce the recurrence, and reduce the degree of occurrence of radiotherapy reaction, which has a broad application prospect.
The use of PET/CT integrated machine, the perfect fusion of PET image and CT image, can better display the tumor site, can accurately distinguish the edge of the tumor, size, morphology, and the relationship between the surrounding than adjacent. It is very helpful for the selection of clinical treatment plan. It is of great value to the accurate positioning of radiation therapy, and can assist in determining the optimization of radiotherapy plan in the oncology department to minimize the irradiation of non-tumor sites. Therefore, the use of the most advanced PET/CT integrated machine is of great significance for the diagnosis and staging of small lung nodules, assisting surgeons in selecting surgical indications and guiding the comprehensive treatment of lung cancer.