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PET
CT

Positron emission tomography with computed tomography (or PET-CT as it is commonly known as) is an advanced imaging technique used to study various diseases. PET scan is a 3D image obtained from studying functions of human body at the cellular levels. This image is then fused to structural information obtained by a CT scan, giving us the best of both worlds, a fused functional-anatomic image..

The PET-CT scanner is named ‘Biograph Horizon’. Breach candy hospital is the first site in Mumbai and only the 2nd site in the country to have procured this latest model of PET-CT developed by Siemens healthcare, Germany.

The scanner has new redesigned detectors comprising of LSO crystals that have a compact rearrangement, because of which there are twice as much the number of crystal elements. The smaller the crystal elements and denser the arrangement, the sharper are the images. This translates into increased resolution and sharpness of the images.

It utilises an advanced ‘Time-of-flight’ technology with high speed electronics, to enable scans that are faster and with a lower radiation dose, and at the same time, having a better image quality. There is upto 200% improvement in singal-to-noise ratio and image contrast with this technology. This essentially means you get superior quality of scan at lower radiation dosage.

Basics of PET-CT hat is a PET-CT scan ?

It is an abbreviation of ‘Positron emission tomography with computed tomography’. It is the imaging of the function and activity of tissues in the body based on an injection of a radioactive medicine. The tracer, most of the times, a radioactive form of glucose, is usually injected intravenously. This tracer goes to most of the cells in the body as a normal distribution, but accumulates more in cells with higher activity, which usually corresponds to the site of disease. On the PET scan these are seen as bright areas.

What are the common indications?

Cancers:

Cancer cells light up bright on the PET scan because they have higher metabolic activity as compared to normal cells, thus enabling to pick disease with higher sensitivity. PET scans are of immense value in

  • etecting cancer
  • Assessing if the cancer has spread
  • In an on-going therapy, checking if the treatment is effective
  • To assess response to therapy after completion of the therapy
  • Surveillance to see if the disease has recurred

PET scans however must be read with caution since many non-cancerous but active disease cells also can show activity on the scan.

Brain disorders

PET scans can be used in the evaluation of certain brain disorders like

  • Dementias like Alzheimer’s disease
  • Epilepsy and seizure disorders
  • Brain tumours

Heart disease:

In specific subset of patients who have suffered a heart attack, it is vital to know if the damaged portion of heart is still viable. Only if it shows a live tissue in that area would a cardiac surgery or a stenting will have positive outcomes. Cardiac PET scan is the most sensitive method to demonstrate myocardial viability in a post infarct setting.

Investigation of undiagnosed fever:

In fevers that stay undiagnosed despite 2-3 weeks of investigation, PET scan has a significant role to play. Because it is so sensitive, it helps to identify the site of abnormality and acts as a guide for further management plan.

What are the risks involved ?

For the PET-CT scan, a radioactive medicine will be injected in the body. This does not have any side effects since it is a radioactive form of the glucose. Additionally, the amount of radiation you are exposed to is very minuscule to cause any side effects. However it is not advisable to get the scan done if you are pregnant or in on-going breast feeding. Speak to your doctor if either of these conditions exist.

The CT portion of the PET-CT involves administration of intravenous iodinated contrast, which is the same medicine that is used in a conventional CT scan. There would be no major effects in majority of the cases with the exception of some burning sensation at the site of injection or some nausea. Additional uncommon but documented side effects are vomiting, Rare allergic reactions are also known, may manifest in the form of rashes and chills, in some instances with transient breathing difficulty. These are usually manageable with simple solutions and drugs.

PREPARATION & SCAN

Speak to your doctor:
  • If you ever had an allergic reaction to prior imaging procedures
  • If you are a diabetic
  • If you're pregnant or think you might be pregnant
  • If you're breast-feeding
  • If you're afraid of enclosed spaces (claustrophobic)

You are expected to come with a minimum of 6 hours fasting. Only plain water without any additives is allowed during this period.

Please withhold all your medications during the period of fasting

If you are a diabetic:

It is advisable to stay fasting longer, usually overnight with an early dinner. On the day of your scheduled test, please do not take any medications for diabetes since you already would be fasting. Once you are in the department, your baseline blood sugars would be assessed and further course of action will be communicated to you then.

What can you expect once in the department ?

The overall procedure including the waiting time post injection would take close to 2 hours, although the scan duration itself is usually 10 min. Occasionally, there may be a need to take an additional set of images as well.

Once in the department, you will have a brief consultation with the nuclear medicine specialist who would then decide the protocol and supervise your scan.

Thereafter an intravenous injection of the radioactive medicine would be administered. Please notify the nursing staff if you have thin veins or have had difficult IV lines in previous procedure, in which case we may have a standby anaesthetist to secure your IV line.

The usual waiting time, also known as uptake time, post injection is about 60-90 minutes. This is the time required for the tracer to be distributed in the body. During this period, you may be asked to drink 1 later of colourless and tasteless liquid depending on your scan protocol.

You would be seated in a separate area designated as ‘radioactive zone’. Please note that patient relatives are advised not to frequent these areas since it is a radiation zone. The scan duration usually is about 10 minutes. The scanner is like a large double ring donut, very similar looking to a conventional CT scanner.

During the scan:

You will be lying on a padded table that moves in the scanner ring as the scan starts. An iodinated contrast maybe injected while on table depending on the scan protocol tailored to you indication. This usually causes a warm flush as it passes in your veins. There maybe occasional nausea. Apart from this, the procedure is painless. 

You are expected to lay as still as possible without appreciable movements. A motion-free scan acquisition highly improves the quality of scan.

After the PET scan:

You can continue with your regular activities once the scan is done. You will not feel drowsy or sedated.

It is advisable to stay away from pregnant women and very young kids (usually under ages of 5 years) for the next 4-6 hours. Good hydration ensures washout of the radioactive material through the urine.

Results

These are complex set of images that need reconstruction and interpretation. In addition, the films and images need to be carefully printed. Please allow a day for the results to be ready.

Providing any prior scans will enable to add a comparison note, which greatly enhances the report value and has a significant impact in further management. Please do not forget to get your prior scans (CT, PET-CT or MRI) for comparisons at the outset.

We work Monday to Saturday. The scans are performed in the morning to noon hours.

You can call us on these numbers within office hours

022-2366 7730/31

We’d never like to miss your call. Hence for outside office hours, we have a hotline number: 7506478015. Call us on this number and we shall help you for the needful.

You can drop us an email at petct@breachcandyhospital.org. We shall get back to you the earliest.

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Breach Candy Hospital Trust, 60 A - Bhulabhai Desai Road Mumbai : 400026

   +91 - 22 - 23667788

   info@breachcandyhospital.org