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PET scan or tomography; Everything you need to know about this diagnostic tool

Study guide

PET scan is a type of imaging that allows a doctor to examine certain internal diseases. How does this type of imaging work? What are the side effects? What diseases are used to examine? ‌ In the following, we will answer all these questions and provide you with more information about PET scans. Stay with us until the end of the article.

What is a PET Scan?

For dosing or “positron emission tomography” or PET for short, a special dye containing a radioactive tracer is used. Depending on the area of ​​the body being examined, the detectors may be oral, inhaled, or injected to be absorbed by the organ or tissue. PET scans are usually performed on an outpatient basis and the person can perform daily tasks after the test.

Identifying the tracer with a PET scan helps the doctor check the function of the tissue or organ. PET scans can also measure blood flow, oxygen consumption and the amount of sugar consumed by the body.

The tracer accumulates in areas with more chemical activity, and this is useful because some body tissues and certain diseases have more chemical activity. These areas of the patient’s body show bright spots on the PET scan.

Reason for doing a pet scan

Your doctor may order a PET scan to check blood flow, oxygen consumption, or metabolism. Tomography shows problems at the cellular level and gives the doctor a good view of complex systemic diseases.

PET scans are mostly done in the following cases:

  • Cancer;
  • Heart problems;
  • Brain disorders include problems with the central nervous system.


Cancer cells make more fuel than normal cells. Due to this high chemical activity, the cancer cells show bright spots on the PET scan. That’s why PET scans are useful for both cancer diagnosis and the following:

  • Investigating the spread of cancer;
  • Evaluation of the effect of cancer treatment;
  • Check for cancer recurrence.

Of course, this scan is carefully examined by a doctor, because non-cancerous diseases may also look like cancer in the scan. Solid tumors and some cancers may also not be detected on tomography.

Heart problems

PET scans show areas of reduced blood flow to the heart. A healthy heart receives more traces of unhealthy tissue or tissue that has little blood flow.

Different colors and levels of brightness at different levels indicate tissue function, and your doctor can determine the next steps in treatment.

Brain disorders

Glucose is the main fuel of the brain. During tomography, the tracer binds to compounds such as glucose. PET scans determine the parts of the brain with the highest glucose intake by determining radioactive glucose. Therefore, the doctor uses a scan to check the function of the brain and abnormal areas.

PET scans are also used to diagnose central nervous system disorders, such as:

  • Alzheimer’s disease;
  • Depression;
  • Epilepsy;
  • Head injury;
  • Parkinson’s disease.

Comparison of PET scans with other experiments

PET scans show metabolic changes at the cellular level of an organ or tissue. This is important because diseases usually start at the cellular level. CT scan and MRI (MRI) can not show problems at the cellular level.

PET scan detects any initial changes at the cellular level. CT scans and MRIs can only detect subsequent changes in the structure of an organ or tissue.

Diagnosis of the disease at the cellular level allows the physician to have a better view of a complex systemic disease, such as:

  • Coronary artery disease or blockage of the heart;
  • Brain tumors;
  • Memory disorders;
  • Convulsive disorders.

In many cases, a CT scan or a MRI scan can be used. CT scans use special X-ray equipment only for in-body imaging. MRI scans use magnetic fields and continuous radio pulses to create images of internal structures such as organs, soft tissues, and bones.

When each of these scans is accompanied by a PET scan, the resulting images are called “image mergers”. A computer combines the images of these scans to create a three-dimensional image that provides more accurate detection by providing more information. Some solid tumors are diagnosed this way, including:

  • Lung;
  • the brain;
  • Throat;
  • Chest;
  • Neck;
  • Colorectal;
  • Head and neck;
  • Lymphatic system;
  • Pancreas;
  • prostate;
  • Skin;
  • Thyroid.

Gallium scan is similar to PET scan in which gallium citrate is injected as a radioactive tracer. Gallium scans are usually done 1 to 3 days after the injection. So it is a multi-day process.

These scans are not commonly used to diagnose cancer, although some types of gallium scans are combined with newer tests, such as tomography.

Disadvantages of PET Scanning

PET scans have a radioactive detector, but the amount of radioactivity in the detector is small and poses little risk to the body. Of course, it is better to talk to your doctor about the possible dangers.

The harms of a PET scan are small compared to its value in diagnosing serious diseases.

The tracer is essentially glucose attached to a radioactive component. Even if you have a history of kidney disease or diabetes, your body can easily excrete the tracer. Of course, some people need to do this test more carefully, as described below.

People with allergies or other illnesses

Some people may be allergic to the tracker. People who are allergic to iodine, aspartame or saccharin should tell their doctor.

People who cannot use an iodine detector usually receive a dilute and sweetened barium detector with saccharin. These people usually have one of the following:

  • Asthma;
  • allergy;
  • water shortage;
  • Heart disease;
  • kidney disease;
  • History of allergic reaction to PET scan;
  • Blood Cell Disorders, Polycythemia, Multiple Myeloma;
  • Medication regimen includes beta blockers, nonsteroidal anti-inflammatory drugs, or interleukin-2.

Pregnant women

Radioactive waves are not safe for the developing fetus. If you are pregnant or think you may be pregnant, you should not have a CT scan.

People who use PET CT scans

The person using this method needs an additional tracker. Therefore, this method may be harmful for kidney patients or people whose creatinine levels have risen due to medication.

Other risks

If you are afraid of the dark or afraid of the needle, this test may be a little uncomfortable for you. The injection can also cause symptoms such as bleeding, bruising or swelling.

Prepare for a pet scan

Prepare for a pet scan

Your doctor will explain to you how to prepare for a PET scan, just talk to your doctor about all prescription medications, over-the-counter medications and supplements.

A few days before the pet scan

You may be asked to limit strenuous physical activity, such as exercise, 24 to 48 hours before the test.

The day before the pet scan

You may be asked to take a low-sugar, low-carb diet up to 24 hours before your test appointment. You should also avoid the following foods and drinks:

  • Bread;
  • Rice;
  • Pasta;
  • Alcohol;
  • Cereals;
  • Yogurt and milk;
  • Fruit and juice;
  • Candy, including chewing gum and peppermint tablets.

Foods you can use:

  • توفو;
  • Nuts;
  • Meat;
  • Non-starchy vegetables.

Hours before the pet scan

  • If you faint for a pet scan, do not eat anything on the morning of the test. If you have to take medicine, just drink some water.
  • If you do not faint, do not eat anything for 6 hours before the test. Remember not to use chewing gum, candy, cold candy or mint pills. Of course, you can drink water or take the recommended medications.
  • You may be asked to wear hospital gowns. Metal can disrupt laboratory equipment, so you need to remove your jewelry.
  • If you are using PET, medical equipment such as a pacemaker or prosthesis will not interfere with your test results, but you will not be able to use PET MRI.

Other considerations

You should inform your doctor about other conditions, for example:

  • Are you pregnant or do you think you are pregnant?
  • You are breastfeeding: You need to express your milk 24 hours before the test. Also, you should not breastfeed your baby for 24 hours after the test.
  • You have diabetes: Fasting can affect blood sugar levels, so you need to use a special protocol to get tested. You will probably be told to take your regular dose of insulin and eat a light meal 4 hours before the scan.

How to do a pet scan

Before the test, you will receive the tracer by injection, drink solution or inhaled gas. The body needs time to absorb the tracker, so you will have to wait an hour before performing the scan. Of course, the time required for full absorption of the tracer in the body depends on the target area.

Limit your movement while waiting, be calm and keep yourself warm. If you have a brain scan, it is best to avoid TV, music and reading. The scan may take 30 to 45 minutes. At this time, you were lying on a narrow table that ended up in a pet machine (a machine like the letter O). The table slides gently into the machine and the scan is performed. This test is painless.

You should lie down during the scan. The technician will explain this to you. You may be asked to hold your breath for a few seconds. You will hear buzzing and clicking during the test. When all the images have been considered, you get out of the car and the test is complete.

After the pet scan

After the test, you can do your daily chores unless your doctor tells you otherwise.

Of course, the radioactive material stays in your body for 12 hours, so it is better to limit contact with pregnant women and babies during this time. After the test, drink plenty of water to get the tracker out of your body. In general, the whole tracker is removed from your body after a day. During this time, a specialist will interpret your tomography images and provide them to your doctor, who will talk to you about the test results in a few days.

PET scan centers in Iran

According to a conversation between Tasnim News Agency and Sajjad Razavi, Director General of the Inspection Office of the Ministry of Health, it is possible to use a PET scan diagnostic device in comprehensive cancer centers. Operation and use of this device must be done with complete safety and necessary accuracy, and the private sector can use this device if it has the capacity.

Also, in an interview with Ibrahim IRNA, Ibrahim Reision, a former economic adviser to the Minister of Health, it was decided to establish 14 centers and comprehensive cancer centers in the country and to deploy advanced PET scan centers in all 14 centers. This highly advanced device is used in rapid diagnosis and treatment of cancer with the help of radioactive technology. Among the centers that have PET scanners:

  • Masih Daneshvari Hospital;
  • Shariati Hospital;
  • Farabi Hospital;
  • Provincial Nuclear Medical Centers.

How much does a pet scan cost?

According to Massoud Vafamanesh, in Iran, three tariffs have been approved for the use of this device, which is 2 million and 900 thousand Tomans for the public sector, about 4 million and 500 thousand Tomans for the semi-government sector such as Masih Daneshvari Hospital and 6 million and 500 thousand Tomans for the private sector.

You say

How familiar are you with the PET scan test? ‌ Have you ever done the PET scan test? ‌ If you wish, you can share your experience and opinion with us in the comments section and send this article to your friends through social networks. do.

Warning! This article is for educational purposes only and you should consult your doctor or specialist to use it. more information






PET scan or tomography; Everything you need to know about this diagnostic tool

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