FAQs in CT and PET-CT

How long does a CT scan or PET-CT scan take?
The scan time of a CT exam may vary from 5 (without contrast) to 30 minutes (with contrast). For a PET-CT scan, as it takes time for patient’s body to absorb the radiotracer, it may take 2 to 3 hours for the entire procedure.

Can I take my daily medication?
For patients who have diabetes, please refrain from taking Metformin one day before and two days after the scan if you are having a contrast PET-CT or CT exam/study. For patients who have any allergic history, you may ask to take anti-allergic drug so to reduce the reaction with contrast agent. Please always consult your referring doctor if you have any question about this.

How is CT scan different from an MRI scan?
Firstly, an MRI scan does not pose any radiation risk. Secondly, an MRI scan can be used to view soft tissue more superiorly than that of a CT scan. Thirdly, the spatial resolution and definition for an MRI scan are also better than that of a CT scan. However, the MRI scan time takes longer time and there is noise generated from the scanner during the scan.

Is it safe to have a CT scan?
Radiologist and X-ray technologist (radiographer) are well trained to restrict the use of radiation to obtain diagnostic images. Benefits of a CT scan outweigh the risks of the radiation exposure. Your referring doctor will weigh up the benefits and potential risks and make judgement accordingly.

What is a PET-CT scan?
PET stands for Positron Emission Tomography, and PET-CT is the combination of two imaging techniques in one exam, that is, a PET scan and a CT scan. A PET scan demonstrates how organs and tissues are functioning at the very early stage in a disease, before structural changes take place while the CT scan offers excellent anatomical information. Overall, the PET-CT scan helps physicians diagnose disease and better understand the exact location and extent of disease. The information enable physicians to develop the best treatment plan for the patient.

What are the benefits of a PET-CT scan over others and why is it recommended?
A PET-CT scan focuses on how organs are functioning while an MRI scan or CT scan focuses mainly on the anatomical details, the size and shape of an organ. PET-CT scan is most often used to help the physician to detect the change/function of body tissue and therefore monitoring the treatment response or other therapy strategy.

Is a PET-CT scan painless?
The only pain involved is the needle prick when a small intravenous catheter is set up for you to receive the radiopharmaceutical injection (and contrast agent, if applicable). Just relaxed lying on the scanning table and we will take images of your body.

What is (are) the substance(s) injected inside my body for a PET-CT scan? And is it safe?
For the PET part, the substance being injected is a kind of radiopharmaceutical (RP). The most commonly used radiopharmaceutical is FDG which is a radioactive form of glucose. Other RP such as C11Acetate is particularly useful in imaging liver cancer and prostate cancer.
For the CT part, contrast agent will be injected if it is clinically indicated. Otherwise, a plain PET-CT scan will be proceeded.
The risks associated with a PET-CT scan are minimal. The quantity of radiation is low (10-25mSv) and the RP (FDG and C11-Acetate) degrades so quick that the radioactivity will be very low after 8-10 hours. Please drink plenty of water as FDG is eliminated from the body through urination. Please try to keep away from infants, children and pregnant women, if possible, 8-10 hours after the injection of the RP.

What should I prepare for a PET-CT scan?
Please arrive 15 minutes earlier than the appointment time allocated to you. The appointment time and the address of the imaging center are clearly indicated on the appointment sheet.
Bring your own recent medical records which can be used as references for our radiologist’s reporting.
Do not eat or drink anything for 6 hours before the procedure, with the exception of water. Do not take any sweets, sugary drinks, mints, coffee with cream or milk etc. Avoid taking medications that contain sugar like cough syrup. Always consult your physician regard medication.
Avoid strenuous exercise on the day before and the day of the exam.
An early morning appointment will be arranged for you if you are diabetic because it will take time to correct the glucose level before the scan.
If you have any allergies/allergic reactions to anything, please alert your physician and our staff when you’re referred for the scan. This is particularly for patients who are going to have contrast studies.

Allow 2-3 hours for the entire procedure.
Please read carefully the preparation on the appointment sheet and relax. Our staff will provide explanations and instructions to you about the procedure.