Positron Emission Tomography (PET Scan) is an advanced medical imaging technique primarily used for disease diagnosis, treatment assessment, and disease progression monitoring. Its principle involves using radioactive tracers and specialized cameras to capture real-time images of metabolic activity in the human body, excelling in detecting cancers, cardiovascular diseases, and neurological abnormalities. This technology combines nuclear medicine with computed tomography (CT) or magnetic resonance imaging (MRI) for hybrid scans, providing three-dimensional images to assist physicians in making accurate diagnoses.
The key feature of PET Scan is its "functional imaging" capability, which reveals cellular metabolic states and complements traditional anatomical imaging techniques such as X-ray or ultrasound. In cancer treatment, it is often used for staging, evaluating treatment response, and early detection of recurrence. Additionally, in neurology, it can assess brain metabolic abnormalities in conditions like Alzheimer’s disease or Parkinson’s disease, serving as an important non-invasive diagnostic tool.
The core technology of PET Scan involves the application of "radioactive tracers." Patients are injected with a small amount of radioactive isotopes (e.g., Fluorine-18 sodium fluoride), which circulate through the bloodstream and accumulate in metabolically active tissues such as tumor cells. The scanner detects gamma photons emitted during tracer decay, and computer algorithms reconstruct these signals into three-dimensional images showing the distribution and intensity of metabolic activity.
Unlike traditional imaging techniques, PET emphasizes "biological function" rather than "anatomical structure." For example, even if a tumor has not yet caused noticeable tissue deformation in early stages, its metabolic activity may already be abnormal, allowing PET to detect lesions earlier. Modern combined scans like "PET-CT" or "PET-MRI" integrate structural and functional information, providing a more comprehensive diagnostic basis.
Main indications include:
Additionally, it is used for immune system diseases (e.g., inflammatory bowel disease) activity assessment or pre-organ transplant tissue rejection risk evaluation. Physicians may combine PET Scan with other imaging techniques based on individual case needs to improve diagnostic accuracy.
The examination process generally involves four steps:
Regarding dosage, the radiation exposure from a single scan is approximately equivalent to three years of natural background radiation, with doses adhering to international safety standards. The tracer dose is adjusted based on body weight and the scanned area, but the total volume is only a few milliliters. Due to its short half-life (about 110 minutes), most of the tracer is excreted via the kidneys within 24 hours.
Main advantages include:
For example, in cancer patients post-chemotherapy, PET Scan can quickly evaluate whether tumor metabolic activity has decreased, avoiding unnecessary prolongation of treatment. In neurological diseases, it can differentiate types of dementia, helping physicians adjust treatment strategies.
The vast majority of patients experience only mild discomfort, with potential risks including:
Important Precautions: Fasting instructions should be followed before the exam (usually 4-6 hours fasting), as high blood sugar levels can affect tracer metabolism. Diabetic patients should adjust insulin or oral hypoglycemic medications to ensure accurate imaging.
Contraindications include:
Patients should inform their healthcare provider if pregnant, breastfeeding, or allergic. Diabetic patients need to adjust blood sugar control plans and fast for 8 hours before the exam to ensure accurate imaging.
PET Scan does not directly interact with medications, but attention should be paid to:
If the patient is undergoing chemotherapy or targeted therapy, inform the physician about medication timing and dosage to evaluate the appropriateness of the scan timing. Tracers do not chemically interact with common drugs but may be affected by medications influencing metabolism.
Clinical studies show that PET Scan has a sensitivity of over 90% in cancer diagnosis, with lymph node staging accuracy surpassing traditional methods by 30%. In cardiology, its ability to assess myocardial viability has been confirmed by multiple studies, effectively predicting post-surgical cardiac function recovery.
The U.S. Food and Drug Administration (FDA) has approved its use for staging in 12 cancers including lung and breast cancers, and European guidelines list it as a standard pre-treatment procedure for certain tumors. In neurology, its diagnostic accuracy for Alzheimer’s disease reaches 95%, making it a gold standard biomarker.
Alternative techniques include:
Choice of alternative depends on the lesion type and diagnostic goal. For example, MRI is preferred for brain structural abnormalities, while PET-CT is the first choice for cancer metastasis assessment. Physicians select the most appropriate imaging combination based on patient condition and medical needs.
What preparations are needed before a PET scan?
Follow medical instructions, usually including fasting for 4-6 hours before the scan and avoiding vigorous exercise. Diabetic patients should inform staff in advance to adjust blood sugar control plans. Wear comfortable clothing and avoid metal jewelry to ensure smooth scanning.
Will the PET scan cause discomfort or pain?
The procedure is generally painless, but some patients may experience a needle prick during tracer injection. The scan lasts about 30 minutes to 2 hours, requiring the patient to lie still. If anxiety occurs, inform staff in advance for possible sedation or support measures.
Can I resume normal activities after the scan?
Normal diet and activities can be resumed immediately after the scan, but drinking plenty of water is recommended to accelerate tracer metabolism. It is advised to wait 24 hours for the radioactive substances to be excreted, avoiding close contact with pregnant women or infants, though it does not significantly restrict daily life.
How are PET scan results combined with other imaging results?
Physicians often fuse PET with CT or MRI images to observe both metabolic activity and anatomical structure simultaneously, improving lesion localization and diagnostic accuracy. For example, in cancer treatment, combined imaging helps assess tumor activity changes and response to therapy.
When can I get the report after the scan? Do abnormal results require immediate treatment?
Reports usually take 2 to 5 working days, interpreted jointly by a nuclear medicine specialist and the treating physician. If abnormalities are found, the doctor will develop a follow-up plan based on lesion characteristics and patient condition. Some cases may require immediate treatment, but decisions are made after comprehensive evaluation.
%201.svg)
Copyright © 2025 MedFrontiers. All Rights Reserved.
