Already, many people, arguing about PET / CT, know that this is a new, very accurate method for the early diagnosis of oncology, neurological diseases and cardiovascular pathologies. He, unlike CT or MRI, does not show a picture of the anatomical features of the patient’s body, but fixes the functioning of certain organs and tissues. How PET scanning is carried out and how to prepare for it, we will describe in this article.
What diseases are diagnosed with PET / CT?
Positron emission tomography is a complex study, with the help of which it is possible to diagnose tumors that do not give clinical manifestations, and cancer metastases in the initial stage. In addition, it allows you to control the course of the disease, the results and effectiveness of therapy.
In cardiology, PET / CT diagnostics are used in cases of coronary heart disease and before coronary artery bypass grafting. In neurology, it is used to diagnose multiple sclerosis, and in psychiatry, Alzheimer's disease at an early stage, when external manifestations of the onset of pathology have not yet been observed. By the way, this examination makes it possible to distinguish Alzheimer's disease from other pathologies leading to senile dementia (Parkinson's or Huntington 's disease ).
Using PET, brain function is assessed after a stroke and seizures are diagnosed for epilepsy.
PET / CT: reviews on the benefits of this diagnostic method
PET has many advantages over other modern diagnostic methods . First of all, this method is the most accurate of all existing, and besides, it can replace several traditional surveys. In addition, PET does not cause pain, does not have harmful side effects on the human body and allows you to detect a pathological process in the early stages.
Reviews available among doctors about PET / CT make it possible to talk about this method as a way to obtain reliable information at a stage in which structural changes visible to the eye do not yet exist. And this, as you know, allows you to start treatment at the very early stages of the development of the disease, which significantly increases the effectiveness of therapy.
The principle of PET examination
It is worth noting, telling about the features of PET / CT, that this examination allows you to register blood flow in organs and tissues, as well as the last glucose consumption.
A small, harmless to humans, amount of a radioactive substance that is carried by blood through the tissues is injected into the body of the subject. The faint radiation coming from it is captured by PET and transmitted to a computer. There is information processing and image creation. Moreover, the more radioactive substance is in the tissues, the brighter they look in the picture - these are the so-called “hot” areas, and the places where there are few substances look dull - these are “cold” areas.
Developing cancer cells are especially in need of glucose, they have an active metabolism, which gives them a bright (“hot”) image after PET / CT. Thus, with PET diagnostics, it is possible to detect only cancer cells that have begun their pathological growth and even refine the prognosis of their growth.
PET / CT procedures
Depending on what the tasks of the examination are, the doctor may need certain methods of conducting the described diagnostics with different radiopharmaceuticals:
- PET with 11C-choline;
- PET with 18F-fluorodeoxyglucose;
- PET with 11C-methionine;
- PET with 13N-ammonium.
So, for example, for the diagnosis of malignant gliomas (brain tumors), the results of PET / CT with methionine are required, which allow an assessment of the degree of its malignancy.
To ensure that the results are as reliable as possible, the day before the study, the patient is recommended to exclude from the diet all protein-containing foods: meat, fish, milk and soy. You can only eat vegetables and fruits. You should come to the clinic on an empty stomach, and you are allowed to drink water in unlimited quantities (but not carbonated or sweet).
When is choline diagnosed?
To assess the condition of the body in prostate cancer, as well as in tumors of the liver and brain, PET / CT with choline is most often performed.
This substance is involved in the construction of cell walls, therefore, when a radionuclide is introduced into it, it is possible to visualize the presence of even small metastases, which are visible in the form of luminous points in the pictures.
These studies are carried out in 2 stages - immediately after the administration of the radiopharmaceutical and after 40 minutes. Scanning is done on an empty stomach and without the use of fluid (it is completely excluded in the morning).
1-2 weeks before the examination, the patient is recommended to exclude from the diet:
- eggs
- peas;
- soy, lentils and beans;
- liver (and other offal);
- spinach;
- cabbage;
- peanut;
- oatmeal;
- orange juice and any vitamins (especially group B).
How is the survey
In the room where the PET / CT examination is carried out, the patient is asked to turn off the mobile devices and offer to go to the waiting room, where the patient should relax and calm down for 20 minutes. This is necessary to improve the quality of pictures.
After this, the subject is administered an intravenous radiopharmaceutical and wait another half hour until the substance is distributed in the tissues of the body. By the way, if at this time there is a need to go to the toilet, you can not ignore it. Next, the patient is asked to go to a PET scanner that looks like an X-ray machine. The examination process itself lasts about 45 minutes (brain scanning, however, may take 1.5 hours).
If necessary, during the procedure, someone from the medical staff may approach the patient. In the case of a study of the heart, the patient can be given a dosed physical load, which will demonstrate the features of blood supply and the functioning of this organ.
It may take from several hours to 2 business days to process the material. It all depends on the type and complexity of the examination.
How is the whole body examined
The whole body PET / CT procedure is usually performed to the bottom of the pelvis. The question of whether to capture the skull in this case remains controversial. Many centers do not. If it is necessary to examine anatomically difficult places, a targeted scan is performed with the introduction of a contrast medium (iodine preparations).
Scanning begins, as a rule, from the pelvic region to exclude the change in image that appears as a result of the gradual filling of the bladder. Each position is scanned for at least 4 minutes (emission scan) plus another 2 minutes (transmission scan).
A full body PET scan allows you to complete a complete surgery plan to remove all affected tissue if possible.
Contraindications for PET / CT
It should be noted, speaking about PET / CT, that this examination is contraindicated in some cases, since the data may be distorted. For example, this happens in the early postoperative period after an open biopsy (in these cases, a minimum of 4 weeks after surgery is expected). PET is also contraindicated after recent chemo- or radiation therapy. In the latter case, a three-month break is recommended.
Inflammatory processes in the body: abscesses, infections and sarcidosis - can give false positive results when scanned. In such situations, care must be taken in what PET / CT shows.
In some other cases (for example, with claustrophobia or if the patient has difficulty lying down), the scan protocol changes depending on the patient's condition.
What to remember when preparing for PET / CT
In order for PET / CT diagnostics not to give you unpleasant sensations, and its results to be of the highest quality, you need to follow a few general rules for any type of procedure:
- For PET / CT, dress warmly and comfortably.
- Clothing and body should not have metal objects and jewelry.
- You can take 1 liter of drinking unsweetened and still water with you.
- Women are obliged to inform the doctor about the existing or possible pregnancy, as well as about breastfeeding, as in these situations, scanning is strictly prohibited.
- Be sure to mention the presence of allergic reactions.
- And for patients with diabetes, special preparation for PET / CT is required.
- In situations where the examination is performed in the pelvic area, the introduction of a catheter into the bladder may be necessary.
- Throughout the examination, the patient should be motionless, you can not change the position.
- If no other recommendations are given, then immediately after the scan, the examinee can return to his normal lifestyle, and in order to accelerate the removal of radiopharmaceuticals, he should drink as much liquid as possible.
How to interpret the results of PET / CT: what does this conclusion mean?
After the scan is performed, the results are given to the patient’s hands. Immediately, it is worthwhile to warn everyone who is prescribed this examination from trying to independently interpret them - this is only the responsibility of the attending physician (health workers conducting PET also do not give any recommendations).
Lack of expertise may lead to misinterpretation of the results. They may seem more severe than it actually is or, conversely, not requiring medical intervention. The results of PET / CT can only be correctly interpreted by the doctor who sent you for this examination. And if you decide on it yourself, then, regardless of what the conclusion will be from your point of view, it is best to demonstrate it to a specialist for accurate diagnosis and prescribing the necessary treatment.