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Positron Emission Tomography–Computed Tomography (PET-CT)

Positron Emission Tomography-Computed Tomography, also known as Positron Emission Tomography or PET-CT scan, can display the metabolic state of cells in various parts of the body and check important body functions such as blood flow, oxygen use, and glucose metabolism of organs. Through the use of 3D colour images and radioactive material, PET-CT can pinpoint abnormal metabolic activity in organs and tissues and evaluate how well they are functioning.

Positron emission tomography (PET) is particularly useful in the diagnosis of malignant tumors because most malignant tumors exhibit high metabolic rates and rapid cell division. Its clinical significance includes:

  • Detect cancer at an early stage
  • Determine whether a tumor is malignant
  • Determine whether a cancer has spread in the body
  • Identify the source of cancer
  • Plan a treatment
  • Evaluate the effectiveness of treatment

Below is information on the side effects of Positron Emission Tomography (PET), the latest technologies, and our services.

Who is suitable for receiving positron emission tomography (PET-CT)?

Positron emission tomography (PET-CT) scans for cancer, assesses whether cancer cells have spread in the body, evaluates the effectiveness of the treatment, and detects whether cancer has returned after treatment. It can also be used to locate infection sites in heart or brain diseases. It is often used to investigate epilepsy, Alzheimer’s disease, cancer, and heart disease. One special type of PET scan is PSMA, which stands for Prostate Specific Membrane Antigen. It can identify lesions suspicious for prostate cancer when the level of prostate specific antigen is very low. With PSAM PET scan, therapy can be targeted more directly as it can assess the area of the prostate, as well as lymph glands and bones.

Before receiving PET-CT, patients will be injected with a small amount of radioactive substances, including the most commonly used (2-[Fluorine-18]fluoro-2-deoxy-D-glucose, FDG). It will be accumulated in the lesion tissue, providing three-dimensional colour images to accurately detect the location of the lesion, together with combined images from PET-CT and computer scanning. This technique is often used to complement X-rays or MRI to provide more insights into the disease and evaluate prognosis of the tumor in the early and late stages of cancer treatment.

What are the side effects of PET-CT?

Radioactive substances and isotopes used in PET-CT can be discharged from the human body within a short period. The amount of radiation produced by PET-CT is minimal, and the scanning process causes no pain. It is safe and rarely associated with significant side effects. After receiving the examination, it is recommended that patients drink plenty of water to flush the radioactive substances out of their bodies.

However, the side effects of PET-CT on children and pregnant women have not yet been confirmed. Therefore, close contact with children under 5 years old and pregnant women should be avoided within 24 hours after the examination. If you are pregnant or breastfeeding at the time, you are not advised to take the PET-CT to avoid potential risks to the fetus or infant.


The process of PET-CT scans takes about 1 to 2 hours. The procedure is as follows:

  1. You will be changed into inspection suits.
  2. Your height, weight, blood pressure, and blood sugar levels will be measured.
  3. You will explain your family history and personal medical history.
  4. You will receive isotope intravenous injection (e.g. F18-FDG glucose*, C11 acetate**).
  5. You need to rest for about 60 minutes.
  6. You need to drain the urine as much as possible before the scan.
  7. You will be scanned for about 15 to 20 minutes. You should relax, lie down, and breathe normally.
  8. If necessary, you may also be given a developer injection.
  9. You can rest in the lounge after inspection.

*18-F FDG is a type of glucose and is the most common radiopharmaceutical used in PET scan. An FDG PET scan can be used to assess the presence, location and severity of cancers. Glucose is a common substance that every cell in your body needs in order to function and therefore will be taken up by cells. Diabetic patients do not need to worry; it would take 4,000 doses of FDG to equal the glucose in 1 teaspoon of sugar. FDG has a half-life of approximately 110 minutes, so it is quickly expelled from your body.

** C-11 Acetate is another radiopharmaceutical that use in PET scan. It is particularly useful in imaging liver cancer, low grade lymphoma, and prostate cancer. If dual-tracer (C-11 Acetate + 18-F FDG) scan is necessary, the patient will further receive another dose of 18-F FDG after the C-11 Acetate scan is completed, and the procedure will proceed as for the 18-F FDG scan.

Latest Technology - Positron emission tomography - GE Discovery PET/CT 710

The Hong Kong Integrated Imaging Diagnostic Centre is equipped with the Discovery PET/CT710, the latest PET/CT scanner launched in 2015 from GE. The system’s unique design guarantees that in every step of the treatment, the parameters are in line with the PERCIST1.0 international standard. It can also automatically match the results of two scans and accurately measure quantitative parameters such as SUV. The precise comparison enables accurate clinical diagnosis. Unlike traditional positron emission tomography, GE’s revolutionary precision quantitative PET platform, Q.Clear, has resolved some century-long issues that previous PET images cannot achieve and offered the following advantages:

  • Generates images that are two times clearer and ensures the quantitative accuracy of SUV
  • Achieve high-definition images and accurate quantification at the same time
  • Features built-in ASiR low-radiation technology that can reduce radiation doses generated during the scan by up to 50%.

Are there any other diagnostic alternatives to PET-CT?

Positron emission tomography (PET-CT) is not the only diagnostic service. Features of various medical screening , imaging/diagnostic and interventional services differ. Patients should consult their doctors and choose the most suitable check-up plan according to their needs. Understand more



Advantages:X-ray can present a specific outline of the organs in the body clearly.

Application on Cancer Treatment:Breast cancer screening and diagnosis, including computer-reconstructed 3D mammography

Radiation:Minimal radiation exposure



Advantages:Ultrasound can observe the immediate changes in organs. However, the penetration of bones and other tissues is lower, as well as the image resolution.

Application on Cancer Treatment:Cancer screening, such as prostate ultrasound and bladder ultrasound。

Radiation:No ionizing radiation

Computed Tomography (CT)


Advantages:CT is capable of scanning the entire body by producing hundreds of cross-sectional images to form two-dimensional and three-dimensional images.

Application on Cancer Treatment:Multiple cancer diagnoses

Radiation:Radiation is stronger than X-ray, but in recent years, low-dose Computed Tomography (CT) technology has been developed.

Learn More

Positron Emission Tomography–Computed Tomography (PET-CT)


Advantages:PET-CT uses 3D colour images to improve the accuracy of anatomical images and data by computer scanning.

Application on Cancer Treatment:Early-staged tumor diagnosis, Malignant tumour differentiation, Determine cancer staging and primary location and Monitor the effectiveness of treatment

Radiation:The latest ASIR low-radiation technology can reduce radiation dose by 50% compared with traditional PET-CT scanning.

Learn More

Magnetic Resonance Imaging (MRI)


Advantages:MRI shows morphology of the soft tissues and nerve veins with extremely high image contrast.

Application on Cancer Treatment:Diagnose the location of the tumors and the development of the tumors

Radiation:No ionizing radiation

Our centre’s services

  • 3D Mammogram Services
  • Computed Tomography (CT)
  • Positron Emission Tomography–Computed Tomography (PET-CT)
  • 3 in 1 – PET and CT and MRI
  • Ultrasound Check-up

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