What is (PET)?

(PET) is an advanced medical imaging technique that produces high-resolution three-dimensional images by detecting the distribution of radiopharmaceuticals in the body. This principle is based on a positron annihilation reaction in which a radiopharmaceutical (fluoride deoxyglucose, FDG, etc.) is injected into the body and releases positrons, which collide with surrounding electrons to generate gamma rays, which are then captured by a PET scanner and converted into an image. This technique can show the metabolic activity of cells, especially cancer cells, where active metabolism significantly increases FDG uptake.

Compared to other imaging tests, PET scans offer unique advantages in functional imaging. For example, computed tomography (CT) and magnetic resonance imaging (MRI) primarily provide anatomical details, while PET can reveal the metabolic state of tissues. The combination of PET and CT (PET-CT) or MRI (PET-MRI) hybrid technology allows for the acquisition of both structural and functional information, further improving diagnostic accuracy. In recent years, public hospitals and private healthcare institutions in Hong Kong have widely adopted PET-CT equipment to provide more accurate diagnostic services for patients with cancer and neurological diseases.

Main Applications of PET Scanning

Tumor diagnosis and staging

The use of PET scans in oncology is particularly pronounced. FDG-PET can detect the high metabolic properties of cancer cells, which can help doctors identify primary tumors and metastases. For instance, according to the data from the Hong Kong Health Bureau, PET scans have an accuracy of more than 90% in staging lung cancer, which is much higher than traditional imaging methods. Additionally, PET scans can also assess treatment efficacy and monitor whether tumors have recurred, providing an important basis for clinical decision-making.

Brain disease diagnosis

In neurological diseases, PET scans can help diagnose Alzheimer's and Parkinson's diseases by analyzing glucose metabolism and the distribution of certain proteins, such as β-amyloid. A study by the Chinese University of Hong Kong noted that PET scans are 85% more sensitive in diagnosing early Alzheimer's disease. For patients with epilepsy, PET can identify abnormally discharged brain regions and provide guidance for surgical treatment.

Diagnosis of heart disease

PET scans can assess the blood supply and metabolic status of the heart muscle and distinguish between surviving heart muscle and scar tissue. This is very important for patients with coronary heart disease to undergo recirculation. The guidelines of the Hong Kong Society of Cardiology recommend PET as one of the gold standards for myocardial activity assessment.

Preparation before PET scan

Patients must strictly follow the preparatory procedures to ensure accurate scan results.

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• Dietary restrictions: Fasting is required for 6 hours before the scan, but clean water can be drunk. Avoid high-sugar diets so as not to affect FDG intake.
• Precautions when taking medication: Continue taking your regular medications unless directed by your doctor. Diabetics need to adjust their insulin dosage.
• Notification of special circumstances: People who are pregnant, breastfeeding, or suffering from claustrophobia should inform their healthcare team in advance. The Hong Kong Association of Radiologists recommends that pregnant women avoid PET scans unless absolutely necessary.

The process of PET scanning

The scan usually takes 2-3 hours, and the main steps are as follows:

1. Injection of radiopharmaceuticals: After the FDG intravenous injection, lie still for 45 to 60 minutes and wait for the drug to be dispensed.
2. Scanning Process: The patient will lie flat on the scanning table and the device should surround the body for imaging and remain still for about 20-30 minutes.
3. Be careful after scanning: Drink plenty of water to speed up the excretion of drugs and avoid close contact with pregnant women and children for more than 6 hours.

Risks and side effects of PET scans

The risks of PET scanning mainly include:

• Radiation exposureThe radiation dose ET scan for is about 7 to 10 millisieverts, which corresponds to 3 to 5 years of natural background radiation. The Hong Kong Atomic Energy Board emphasizes that frequent testing should be avoided while the dose is within a safe range.
• anaphylaxis: A very small number of people can be allergic to radiopharmaceuticals, and symptoms are usually mild, such as rash and itching.
• Other risks: There is temporary discomfort at the injection site, and abnormal blood sugar levels may affect the image quality.

Interpreting PET Scan Results

PET reports are typically analyzed by nuclear medicine experts and focus on:

• Standardized Intake Values (SUV): Quantifying FDG intake, higher SUVs are associated with a higher likelihood of malignancy.
• Distribution of lesions: Multiple hypermetabolic lesions may suggest metastasis.

Patients should discuss the results in detail with their doctor and develop a follow-up treatment plan. For instance, the Hong Kong General Oncology Centre adjusts radiation therapy or chemotherapy regimens for cancer patients based on PET results.

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