PET-CT

USG, CT scan or MRI are anatomical imaging modalities. They give information about size, location, relations of internal organs and contrast enhancement pattern. However, they do not give much information about metabolism or functional status of the organs in general. PET scan gives metabolic information not available on CT scan or MRI. This is very useful for diagnosis and treatment monitoring. As metabolic changes happen before anatomical changes, possibility of early detection of disease or detection of changes after therapy is greater with PET scan.

Further usually USG, CT scan or MRI is done for particular region of the body. While PET CT scan is generally whole body scan when done in cancer patients. It helps in detection of disease spread in the entire body in single examination.

FDG is F-18 fluorodeoxyglucose. It is a molecule similar to glucose tagged with Fluorine-18 – a radioactive positron emitting isotope. Most of the cancer cells are metabolically more active than normal cells and need more glucose for metabolism. This increased glucose consumption can be visualized on PET scans. This allows your doctor to detect disease before it may be seen on other imaging tests.

Following are some of the reasons PET CT scan is advised by your doctor:

• Detection of cancer
• Determine whether a cancer has spread in the body.
• To assess the effectiveness of treatment.
• To determine if a cancer has come back after treatment.
• To assess tissue metabolism and viability.
• To determine the effects of a heart attack (Myocardial infarction) on areas of the heart (in combination with myocardial perfusion scan).
• To evaluate brain abnormalities, such as tumors, memory disorders, seizures and other central nervous system disorders.
• To locate the site of infection or inflammation in case of undiagnosed fever of long duration (Pyrexia of Unknown origin)

• Please take appointment for the PET CT scan (Contact: 8308233334).
• Do not consume any calories in the form of food, drinks (No tea, coffee, coconut water, etc.) or intravenous glucose (DNS or RL) for at least 4 hours before your scan.
• More than 12 hrs fasting is better (especially in diabetic patients).
• You may have desired amount of plain water.
• Continue to take any medication prescribed by your physician till the night before scan.
• Bring your morning medications with you. You may be allowed to consume them after consultation with nuclear medicine physician.
• If you have diabetes, discuss this with your physician. The fasting blood sugar should be <150mg/dl.
• If you are, or think you may be pregnant discuss this with your physician.  PET is not performed on pregnant women.
• If you are breast feeding, then discuss with the physician. You may have to discontinue breast feeding and avoid close contact with baby for a day or so after the scan.
• Please remove all metallic objects (Jewellary, coins, key chain, etc.) before coming for scan.
• Please bring warm clothes without chain or decorative buttons (Shawl, plain woolen sweater) if you cannot tolerate cold / A.C.
• Please carry all files, medical reports, scan reports, films and CDs related to your illness.
• Please inform if you have any special requirements like wheelchair, trolley, lift or oxygen while taking the appointment.

PET CT scanner is a large machine with a round, donut-shaped hole in the middle. You will lie on a narrow table that slides in and out of this hole. PET CT machine looks like a CT or MRI unit. The computer workstation that processes the imaging information is in a separate control room. This is where the technologist operates the scanner and monitors your exam in direct visual contact. The technologist will be able to hear and talk to you using a speaker and microphone.

Although actual PET CT scan is for 10-15 min and total procedure is of 1.5 to 2 hours, you may need to spend 5-6 hours at the centre.

PET CT scan is non-invasive. Except for intravenous injections, it is usually painless.

• You will be asked to change into the hospital gown or you can bring your own gown.
• Your blood sugar is checked with glucometer and an intravenous (IV) cannula is usually inserted into the vein in hand. This maybe little painful like a pin-prick.
• You may have to wait for your turn for a while. You may have plain water during waiting period and may pass urine if desired. There is no need to hold urine before or during PET CT scan procedure.
• Doctor or nurse will see you before or after the preparation for the scan and may ask relevant questions regarding your illness. He may ask for your medical records and guide you about the procedure overall.
• Once you are called for the scan, technologist will inject the radioactive dye (FDG) through IV cannula and would ask you to wait in specially designed waiting room for minimum 45 to 90 mins.
• While in the post-injection waiting room, you are supposed to relax and not do much physical activity. You may sleep if you desire. Preferably avoid excessive talking, carrying mobile phone or books with you.
• After waiting period is over, you would be asked to empty your bladder and enter PET CT scan room.
• You have to lie on the PET CT machine couch for 10-15 min in comfortable position. You would be given blanket as room would have low temperature for smooth functioning of the machine.
• You are not supposed to move during the scan. Normal breathing movements are ok.
• You may be injected IV contrast if required for your study through IV cannula.
• Immediately after the scan, you would be asked to wait in separate area before you leave.
• If there is any additional scan needs to be done, like delayed scan, contrast scan or repeat scan due to movement observed during scan, you would be informed so.
• Before leaving, IV cannula is removed and you would be asked to change into your own clothes. Please check your belongings before you leave.

Except for intravenous injections, most procedure is painless. Reports of significant discomfort or side effects are rare.

You will feel a slight pin prick when the technologist inserts the needle into your vein for the intravenous line. You may feel a cold sensation moving up your arm during the radiotracer injection. Generally, there are no other side effects.

It is important to remain still during the exam. Having to remain still or in one position for long periods may cause discomfort.

If you have a fear of closed spaces, you may feel anxious during the exam.

• Your activity will not be restricted. You may drive if you wish, resume your normal diet, exercise and take all prescribed medications.
• It is advisable to avoid close contact with children < 5 years or age and pregnant ladies for next 24 hrs.
• Avoid breast feeding and close contact with your baby for next 24 hrs (Where applicable).

Reception would inform you about the report availability time.

You may collect the report from reception at given time.

• Because nuclear medicine exams use only a small dose of radiotracer, they have a relatively low radiation exposure. This is acceptable for diagnostic exams. Thus, the potential benefits of an exam outweigh the very low radiation risk.
• Doctors have been using diagnostic procedures with radioactive medicine for more than six decades. There are no known long-term adverse effects from such low-dose exposure.
• Your doctor always weighs the benefits of PET CT scan against any risks. Your doctor will discuss the significant risks prior to treatment and give you an opportunity to ask questions.
• Allergic reactions to radiotracers are extremely rare and usually mild. Always tell the nuclear medicine personnel about any allergies you may have. Describe any problems you may have had during previous exams.
• The radiotracer injection may cause slight pain and redness. This should rapidly resolve.
• If your examination needs administration of oral or intravenous contrast agent, there are additional side effects involved. These can be reviewed in detail at: https://www.radiologyinfo.org/en/info/safety-contrast