The basic principle of ECT imaging is that radioactive drugs are introduced into the body and metabolized to form differences in radioactive concentrations between internal and external organs or lesions and normal tissues, and these differences are detected and re-imaged through computer processing. ECT is flexible in its imaging modalities, allowing for planar and tomographic, static and dynamic, local and whole-body imaging. In addition, it can also provide various functional parameters of organs, such as time-radiation curves, providing multifaceted information for tumor diagnosis and treatment. It is mainly used for the examination of thyroid cancer, bone and other parts of tumor, especially commonly used for the detection of bone metastatic tumor, which can detect the lesion 3-6 months earlier than the ordinary X-ray film. Therefore, it is useful for some cancers that are more prone to bone metastasis. Such as breast cancer, lung cancer, prostate cancer, esophageal cancer, etc., even if there is no bone pain, they can be examined before or after surgery in order to detect metastases at an early stage. However, it must be noted that bone inflammation, blood flow changes, fracture repair, joint degeneration, bone deformity lesions and metabolic bone lesions may also show positive results, which should be differentiated. ECT structure and working process: It has a probe specialized in detecting nuclear rays (γ-rays), a holder that fixes the probe and can rotate in all directions, and a central console equipped with a system program (a high-performance electronic computer that can run at high speed and perform a lot of data processing and storage, 16-64 bits). Under the control of the acquisition program, the probe collects the γ-rays emitted from the target organ and directs the cathode of the photomultiplier tube (P.M.T) (matrix arranged on the photoconductive surface of the crystal surface, often with 50 to 107 branches) through the crystal light amplification (into visible light) and turns into an electrical pulse signal, which is delivered to the computer at the designated position by the position decoder, and the computer converts the signal into digital by analog/digital (A/D). stored. Under the control of the processing program, the computer will carry out the digital/analog (D/A) conversion, according to the signal source pawns on the direction of the pixel (pixel) point on the screen projected into an image. This image is a single planar image (two-dimensional), with overlapping information and large blurring, and is only suitable for small organ imaging or dynamic imaging, and is difficult to observe deep structures. If the probe is rotated in the center of the target organ and acquired in multiple planes, a three-dimensional image, the so-called ECT image, can be obtained. This image is cut by a certain thickness, and the image of the distribution of the developer in different directions and depth planes can be observed. ECT classification: 1, SPECT , that is, single photon emission computed tomography. The basic structure of SPECT is divided into 3 parts, i.e. rotating probe device, electronic circuit, computer system for data processing and image reconstruction, etc. In addition to tumor lesions, SPECT can also show changes in local organ functions, such as left heart function and kidney function after chemotherapy. The system can also show local organ function changes, such as left heart function and kidney function changes after chemotherapy. 3.PET, i.e. Positron Emission Computed Tomography. As the name implies, it is the use of positron-emitting nuclide drugs for examination. PET is mainly used for the study of glucose metabolism, protein substitution and oxygen metabolism in focal tissues, and is most widely used in the field of oncology. The most current application is the early diagnosis of tumors and the identification of residual masses after treatment. It is often difficult to distinguish brain tumors from residual masses after radiotherapy or chemotherapy for nasopharyngeal carcinoma and lung and mediastinal masses, but it is easy to distinguish their nature by PET imaging using 18F, flurodeoxyglucose (18F, FDG). If 18F-FDG is taken up in the lesion, it indicates that there are surviving cancer cells in the lesion, suggesting recurrence; if 18F-FDG is negative, it is fibrosis. Examination methods and scope of application According to the clinical requirements, there are static and dynamic imaging; planar and tomographic imaging; local and systemic imaging; motion and resting imaging. Now we introduce the methods and scope of application of each method: static imaging, refers to the acquisition of a certain observation surface in a certain period of time, the total distribution of radioactivity images. It is mostly used for small organ imaging and rough observation of the morphology, location, size and radiological distribution of an organ, and analysis of occupying lesions. For example, thyroid imaging, rib gland imaging, static plane imaging of brain, lung, heart, liver, pelvis, spleen and kidney, localization of gastrointestinal bleeding, Meckel’s diverticulum, lymph nodes, transplanted organs, pancreas, adrenal glands, testes, prostate and other organs, etc. Because of its simple method, it is widely applicable. Dynamic imaging refers to the acquisition of a certain observation surface of an organ in successive times to obtain dynamic planar images at different times, which can provide information on the region of interest (ROI) at different times, and can also show the target organ activity on film. Due to the introduction of the “time-radioactivity curve”, the concept is very suitable for organ function judgments. For example, functional indicators of the thyroid, brain, heart, liver, kidney, gastric emptying, bone uptake, liver and gallbladder, etc. Cardiac blood pool gating circuit-controlled R-wave triggered (gated) imaging is also a kind of dynamic imaging, that is, R-wave triggered acquisition of radioactive information at different points in a cardiac cycle, and the heart volume curve is fitted with the payload function. From this curve, a series of indicators of cardiac systolic and diastolic function can be obtained separately. Recently, this method has been reported to be used for lung imaging to obtain pulmonary function maps of the respiratory motion cycle. Planar imaging, i.e., two-dimensional imaging, is the opposite of tomographic (three-dimensional) imaging, where only one plane can be observed at a time. It should include static plane, dynamic plane, local plane, motion plane and resting plane imaging, because it is not yet possible to perform a one-time whole-body tomography, so whole-body imaging is called “whole-body XX”, such as “whole-body bone imaging”, do not call “whole-body bone planar imaging”. Tomography, is a 360 degree (or 180 degree) rotation of the target organ to collect multi-planar information, the computer image processing (reconstruction, layer cutting, magnification, projection) to get a certain thickness of different viewing surface and depth of the cross-sectional image. This image computer can combine them into a stereogram (rotated in different directions and at different speeds for observation). It is most suitable for the visualization of large organs, such as: brain, heart, lungs, liver, etc., to analyze occupying lesions, blood supply, organ volume measurements, etc. Cerebral perfusion tomography has unique advantages in diagnosing cerebral ischemic diseases and epilepsy; myocardial perfusion tomography diagnoses “coronary heart disease”, myocardial infarction and prognosis, etc. It is a non-invasive examination method that is closest to the effect of catheterization. Local imaging, as opposed to whole-body imaging, includes a wide range of local planar imaging, and all kinds of examination methods for each organ separately are called local imaging. Whole-body imaging refers to the whole-body collection of radioactive distribution information and acquisition of whole-body distribution images after the imaging agent enters the body. For example: whole body bone imaging, whole body blood pool imaging, whole body lymphatic imaging, whole body soft tissue imaging, whole body tumor marker imaging and whole body distribution imaging of drugs in animal experiments, etc. Whole-body bone imaging can detect metastases at an early stage in cases of nasopharyngeal carcinoma, lung cancer, breast cancer, intestinal cancer, anterior cleft adenocarcinoma and other cases that are most prone to bone metastases. It also plays an important role in helping to make decisions about surgical treatment (e.g. amputation). Exercise (stress) imaging, or stress imaging, is a method of capturing information about the distribution of nuclear imaging agents in target organs (mainly the heart) under stress, just like the “exercise test” of the electrocardiogram. In the case of the heart, there are gated circuit control imaging and myocardial gated imaging; myocardial and blood pool tomography; and myocardial and blood pool gated control layer imaging. The latter is difficult to be widely used because of the large amount of information, tedious processing and large data storage, some of which are not worth the cost. Currently, the most commonly used images are “gated planar images of the cardiac blood pool” and “tomographic images of myocardial perfusion”. These two sets of data plus exercise and resting controls are comprehensive enough, and some use drug controls to provide more effective parameters, such as the determination of recoverable myocardial cells (surviving myocardium) in myocardial infarction is of great clinical value. Resting imaging, which shows the uptake and distribution of nuclear imaging agents in the heart while the patient is at rest. It is often used in conjunction with exercise imaging. What should be noted when receiving ECT: 1. Cerebral blood flow tomography: 1 or 2 days before the examination, patients should stop taking cerebrovascular dilation drugs to increase the sensitivity of the examination. Oral potassium perchlorate should be taken 30~60 minutes before the injection of imaging agent to close the choroid plexus and thyroid gland to reduce interference. 5~10 minutes before and after the injection, the patient should rest as much as possible to reduce the sound and light stimulation, rest in bed to keep calm and put on the eye mask and earplug until about 10 minutes after the injection of the imaging agent. The head should not be moved during the examination to ensure the authenticity of the image. 2, myocardial perfusion imaging: the day before the examination should stop using drugs such as nitroglycerin, echocardium, and Dioscorea. If the exercise stress test is performed, it is best to stop using the drugs such as insulin, cardioplegia, betalactam, isobodine and methoxyphenidate two days before. For myocardial drug loading test, drugs such as pansentin, dobutamine and aminophylline should be discontinued 24 hours before the test. Breathing should be kept steady during the test to minimize interference of septal motion with myocardial imaging. Those who have a cardiac pacemaker should inform the doctor for the reference of image analysis. 3. Systemic bone imaging: Drink more than 500ml of water within 2 hours after the injection of imaging agent. Empty urine before examination. If there is urine A stained clothes and skin, scrub the skin and change clothes and pants before examination. If you have a metal prosthesis or breast implant, you should inform the doctor of the implant site. Barium meal and barium enema should not be done two days before the examination. In order to avoid the retention of barium in the intestine to affect the image observation. 4.Glomerular filtration rate measurement: stop using diuretics, such as dihydrocoumarol, tachyphylaxis, etc., three days before the examination. Drink about 300ml of water 30 minutes before the examination, and empty the urine during the examination. 5.Esophageal motor function imaging and gastric emptying measurement: Patients should fast for 6-12 hours before the examination and stop taking atropine, cardiac painkillers, desbuterol, dextran, cimetidine, famotidine and gastrodynamic drugs such as morpholine, Prebux, etc. as prescribed by the doctor. 6. Thyroid imaging: Stop using iodine-containing drugs and iodine-rich foods such as kelp, nori, sea fish and shrimp, etc., and stop using thyroid tablets as prescribed by the doctor. Iodine contrast agents should be used for at least three weeks before the test. In case of children or patients who cannot cooperate during the examination, sedation can be used before the examination. If the patient cannot cooperate with the examination due to pain, analgesics can be used beforehand. Metal objects such as jewelry, metal buttons, belts, keys, coins, etc. should be removed from the examined area before the examination. Most of the drugs used for ECT are excreted in the urine, so drinking more water after the test can speed up the excretion of drugs.