Positron Emission Tomography-Computed Tomography (PET-CT Scan)

A PET scan is an advanced imaging examination that offers detailed information on a particular body organ or specific function of the body. It is commonly used to evaluate and diagnose cancer, neurological disorders of the brain, and cardiovascular disease.

During the PET scan, a radiologist will inject a radioactive tracer into the patient’s body and images of the patient’s body are recorded with a PET scanner. A specialised camera can detect the radiation emitted by the radioactive tracer, and a multidimensional image of the examined area will be generated by the computer.

PET Scan 掃描是「Positron Emission Tomography」（「正電子斷層掃描」），是屬於核子醫學的技術，和 CT Scan 和 MRI Scan 兩種最大的不同是，正電子掃描屬於功能性的檢查（CT 和 MRI 是結構性檢查）。病人需要注射帶有放射性的藥物（一般來說是葡萄糖），如身體有癌細胞、炎症、感染等等，其活躍性會被顯示出來。如果以攝影來做比喻的話，PET Scan 就像一個紅外線相機，而 CT 就是一部高清數碼相機。現在很多癌症病人進行的 PET-CT scan 就是結合了 PET 的功能性及 CT 的結構性檢查，所以正電子斷層掃描非常全面。建議每個病人應該和專家討論，並結合臨床病徵，以便確定最佳的診斷方法。

A PET scan is primarily used to detect and monitor conditions including cancer, neurological disorders, and cardiovascular diseases. It can identify cancer at an earlier stage compared to other imaging technologies (such as CT and MRI scans) and determine whether—and to where—the cancer has spread within the body.

Furthermore, a PET scan can reveal which part of the brain is triggering epileptic seizures, assisting us in formulating appropriate management plans for epilepsy. This examination is also utilized to evaluate Alzheimer's disease and Parkinson's disease, as the resulting images can precisely pinpoint areas of the brain that are not functioning normally. Early detection of these neurological disorders enables us to provide patients with more effective relief and clinical care.

1. Patients should not have undergone any barium x-ray examination 10 days prior to the PET-CT scan.
2. A 6-hour fasting is required prior to the scan. Consumption of alcohol and beverages is prohibited (except water). Avoid medication with high sugar content (e.g. cough syrup, glucose). Avoid chewing gum or candy.
3. A bland and easy-to-digest diet is recommended 1 day prior to the scan.
4. Patients are advised to drink enough water, at least 6 to 8 cups of water 1 day prior to the scan.
5. Avoid intense muscular activities such as strenuous exercise and heavy lifting.
6. Pregnant and lactating women, people with unstable emotions, people with acutely persistent muscle cramps, and diabetic patients with poor blood sugar control should not be screened.

The radiopharmaceutical (also known as a tracer) is injected into the patient's body prior to the scan. The radiotracers usually accumulate in diseased tissues more than in healthy tissues. The images of the body are then acquired by a gamma camera in the PET scanner. The camera detects the positrons emitted from the tracers in the body, and a multi-dimensional image of the examined body part will eventually be generated by the computer. The patient has to lie still after the injection for about 1 hour to wait for the drug to be absorbed, followed by a full body scan (about 30 minutes). The patient will take another 1-1.5 hours of rest as the radiotracer becomes less radioactive over time. The risk of having side effects is low.

PET scans are rarely recommended for pregnant and breastfeeding women.

Children are more susceptible to radiation than adults and are not suitable for PET scanning.