Positron emission computed tomography, or PET CT, is a study of the internal organs of a person using the radioisotope diagnostic method. A PET scan is also called two-photon emission tomography, due to the fact that this method is based on the detection of a pair of gamma rays.
PET is a modern way of early diagnosis of cancer, cardiology and neurological diseases. In oncology, PET is used to diagnose malignant neoplasms, search for distant metastases and monitor treatment.
Positron emission tomography is distinguished by high accuracy of the study, minimal radiation load on the body, the ability to examine all organs in one visit. The study itself is completely painless.
PET, unlike any other research methods, does not study the anatomical features of organs and tissues, but the chemical processes that occur in them. With oncological diseases, chemical processes change, this can be seen as a change in the color gamut and intensity of the processes, which is different from the norm.
Thus, thanks to PET, the oncological process that has begun can be seen long before the tumor forms. Ultrasound, CT, MRI can detect the problem only when the tumor has already appeared and reached a certain size (for the modern MRI device, at least 1-2 mm).
PET will also help determine whether this tumor is malignant or benign, which is especially important when there is no way to obtain biopsy material.
PET detects blood flow in tissues and tissue consumption of glucose and oxygen. A certain amount of a radioactive drug (radioactive glucose) is injected into the patient's body. Radiation from radioactive glucose is recorded by a special scanner, which transfers all the information received to the computer. The computer processes and visualizes it.
Metabolic cells consume more glucose. This is what distinguishes cancer cells from ordinary ones. The more radioactive drug is captured by the tissues, the brighter they look in the resulting image. Such sites are called "hot." Conversely, the less drug is captured - the dimmer the image is obtained, such areas are called “cold”.
Metabolism in malignant neoplasms is significantly higher than in healthy tissues. Therefore, malignant tumors give a brighter, “hot” picture.
Radioactive glucose itself breaks down in less than a day and is completely excreted by the body.
Due to the fact that the PET study covers the entire body, you can draw up the most complete operational plan. This will remove all affected tissue, if possible in each case. Which in turn will significantly reduce the risk of further relapse.
Using PET, you can accurately determine the stage of cancer, see if the lymph nodes are affected even before they begin to grow. This allows you to apply anti-cancer therapy significantly more effectively.
At the end of chemo- and radiation therapy, PET allows you to determine the effectiveness of the treatment.
A PET scan will detect metastases when other diagnostic methods are not yet able to do this.
Say, an X-ray examination of the lungs can only cause suspicion of metastases in case of shading. Confirm their presence can be either traumatic tissue puncture or PET, but a PET study will determine the size of metastasis and recognize the spread of cancer cells in the early stages of the disease.
Unlike scintigraphy, which also uses radioisotopes, the PET image is three-dimensional, which makes it possible to more accurately assess the picture of the disease.
The study itself is as follows: the patient lays on the couch, which slides into the apparatus. The device itself is like a short pipe. The procedure lasts from half an hour to an hour. Before this, the patient receives a specially prepared radioactive preparation by inhalation or intravenously.
There are few contraindications for positron emission tomography. A PET test is contraindicated for pregnant and lactating women, as well as for those patients who are not able to calmly, without any movements, lay out the time required for the study.
Positron emission tomography - a study quite expensive. It costs from 50,000 rubles. In Russia, devices for such a study are available only in large cities.
Of course, it makes no sense to conduct a PET study as a preventive examination of a healthy person. To do this, it will be enough to regularly do an analysis on tumor markers.
If by nature the tumor slowly metastasizes, in this case it is also possible to limit oneself to tumor markers or other tests and regular medical examination by an oncologist.
If the tumor was removed at a later stage and prone to rapid metastasis, then it makes sense to conduct a PET study. With the apparent high cost of this study, the patient receives as a result the whole picture of the changes taking place in his body. Based on this, the doctor can choose a more gentle and, accordingly, less costly method of treatment.
At current drug prices, a PET study, in many cases, pays for itself and allows you to save on drugs much more than the study itself cost. In addition, tumor processes, thanks to a PET study, will be detected and suppressed long before they can be diagnosed with other standard methods. Therefore, they will do much less harm to the patient’s body.
And in the case of all kinds of lymphomas, the PET study, by its reliability, simply has nothing to replace. Other research methods here will be significantly inferior to PET diagnostics, both in accuracy and completeness, and in the rate of detection of metastases.