FDG PET-CT
FDG PET-CT in Jaipur
See where disease is active — and understand where it is located.
FDG PET-CT is an advanced molecular imaging examination that combines information about tissue metabolism with detailed anatomical images from CT. It can help physicians evaluate the presence, distribution and activity of disease, particularly in many types of cancer.
At Arovida PET-CT Centre, Jaipur, FDG PET-CT is performed with careful patient preparation and interpreted in the context of the patient's clinical history, previous imaging, pathology and treatment history whenever available.
What is an FDG PET-CT?
FDG PET-CT is a combined Positron Emission Tomography (PET) and Computed Tomography (CT) examination.
During the PET component, a small amount of a radioactive glucose analogue called 18F-FDG (fluorodeoxyglucose) is administered. Many tissues in the body use glucose for energy. Areas with increased glucose metabolism may accumulate more FDG than surrounding tissues.
The PET scan detects this distribution of FDG, while the CT scan provides detailed anatomical information.
By combining the two, PET-CT can show both:
CT shows
Where a lesion is located
PET shows
How much metabolic activity it demonstrates
How does FDG PET-CT work?
The examination generally involves the following steps:
- 1
Patient preparation
Appropriate preparation is important because blood glucose levels, recent physical activity and food intake can influence FDG distribution.
- 2
FDG administration
A small amount of 18F-FDG is administered, usually through an intravenous injection.
- 3
Uptake period
The patient rests quietly for a period of time to allow the tracer to distribute through the body.
- 4
PET-CT imaging
The patient lies comfortably on the scanner while PET and CT images are acquired.
- 5
Image interpretation
The PET and CT information is evaluated together. Relevant findings are interpreted in conjunction with the clinical history and available previous investigations.
Why is FDG PET-CT performed?
The usefulness of FDG PET-CT depends on the disease and the clinical question being asked.
It is commonly used in selected patients for:
Initial staging
To evaluate the extent of known malignancy and identify disease involvement at other sites when appropriate.
Restaging
To reassess disease after initial treatment or when there is concern about persistent or recurrent disease.
Treatment response assessment
To evaluate changes in metabolic activity following treatment in diseases where FDG PET-CT is appropriate.
Suspected recurrence
To investigate suspected recurrent disease when clinical findings, laboratory results or other imaging raise concern.
Evaluation of selected indeterminate lesions
FDG PET-CT may help characterize certain lesions when conventional imaging does not provide sufficient information, although PET findings may not always distinguish malignancy from inflammation or infection.
Unknown primary
In selected patients with metastatic disease where the primary site has not been identified, FDG PET-CT may help search for a possible primary tumour and evaluate the overall extent of disease.
Selected non-oncological conditions
FDG PET-CT can also have applications outside oncology, including selected inflammatory, infectious and other disorders. The appropriate use depends on the clinical situation.
What can FDG PET-CT help your doctor understand?
Depending on the disease and clinical situation, FDG PET-CT may help answer questions such as:
FDG PET-CT in Cancer Care
FDG PET-CT has an important role in the evaluation of several malignancies.
Its clinical utility varies according to the type of cancer, stage, treatment status and the specific question being asked.
It may be used in the evaluation of conditions such as:
The decision to perform FDG PET-CT should be based on the clinical indication and the treating physician's assessment.
FDG PET-CT for Staging
For selected cancers, FDG PET-CT can provide whole-body information that may help determine the extent of disease.
It may demonstrate:
This information can contribute to clinical staging and treatment planning.
FDG PET-CT for Treatment Response
Changes in tumour metabolism can sometimes occur before obvious changes in lesion size.
For appropriate cancers, FDG PET-CT may therefore be useful in assessing metabolic response to treatment.
Depending on the disease and treatment setting, the examination may help identify:
- Reduction in metabolic activity
- Persistent metabolically active disease
- New sites of disease
- Metabolic progression
- Treatment-related changes
Response assessment should be performed using appropriate disease-specific criteria and interpreted in clinical context.
FDG Uptake Does Not Always Mean Cancer
One of the most important things for patients to understand is:
FDG uptake is not synonymous with malignancy.
FDG accumulates in tissues with increased glucose metabolism. This can occur with:
- Malignancy
- Infection
- Inflammation
- Healing or post-treatment changes
- Certain normal physiological processes
Similarly, some cancers may demonstrate relatively low FDG uptake.
Therefore, a PET-CT finding should not be interpreted in isolation.
What does SUV mean?
SUV stands for Standardized Uptake Value.
It is a semi-quantitative measurement used to describe FDG uptake within a region of interest.
SUV can be useful for:
- Comparing uptake between lesions
- Comparing a lesion with background tissues
- Monitoring changes between examinations in appropriate circumstances
- Supporting metabolic response assessment
SUV can be affected by several technical and biological factors, including blood glucose, uptake time, body habitus, scanner characteristics, reconstruction methods and lesion size.
Therefore, SUV should always be interpreted together with the imaging findings and clinical context.
FDG PET-CT Preparation
Good preparation helps ensure reliable imaging.
Fasting
For a typical FDG PET-CT examination, patients are generally asked to avoid food for the specified period before the scan.
Follow the preparation instructions provided by Arovida for your appointment.
Plain water is generally permitted unless you have been given different instructions.
Avoid strenuous exercise
Strenuous physical activity before an FDG PET-CT can increase FDG uptake in muscles and may affect image interpretation.
Follow the centre's instructions regarding exercise restriction before the examination.
Blood glucose
Blood glucose is checked before FDG administration because elevated blood glucose can affect FDG distribution and image quality.
Patients with diabetes require individualized preparation instructions.
If you have diabetes:
- Please inform the centre while scheduling your appointment.
- Do not independently stop or change your diabetes medicines or insulin.
- Our team will provide appropriate instructions based on your appointment time and treatment regimen.
Hydration
Adequate hydration is generally encouraged according to the centre's preparation instructions.
Hydration can help promote urinary clearance of the tracer.
Keep warm and relaxed
Maintaining a comfortable body temperature and resting quietly before imaging can help reduce unwanted muscle activity and improve image quality.
What should I bring for my FDG PET-CT?
Please bring:
What happens on the day of the scan?
Your visit generally follows these steps:
- 1
Registration & clinical information
Your referral, clinical history and previous reports are reviewed.
- 2
Blood glucose assessment
Blood glucose is checked when required before FDG administration.
- 3
FDG injection
The tracer is administered through an intravenous line.
- 4
Resting / uptake period
You will rest quietly while the FDG distributes through your body. Avoid unnecessary movement, talking and physical activity during this period as instructed by the technologist.
- 5
PET-CT scan
You will lie on the imaging table while the scan is performed. The examination itself is generally painless.
- 6
Image processing and interpretation
The acquired PET and CT images are processed and reviewed by the nuclear medicine physician.
How long does an FDG PET-CT take?
The total visit commonly takes several hours, although the exact duration can vary.
The overall time includes:
Please plan your visit accordingly and avoid scheduling another important appointment immediately afterward.
Is FDG PET-CT painful?
The PET-CT scan itself is generally painless.
The only part that may cause brief discomfort is the intravenous injection or placement of the IV line.
You need to remain still during imaging so that clear images can be obtained.
Is FDG PET-CT safe?
FDG PET-CT involves exposure to ionizing radiation from both the radiopharmaceutical and CT component.
The examination is performed when the expected clinical benefit of the information obtained is considered appropriate.
The amount of radiopharmaceutical used is carefully selected according to the examination and patient factors.
The radioactive tracer naturally decays and is eliminated from the body, predominantly through urine.
If you are pregnant, may be pregnant, or are breastfeeding, inform the centre before the examination. Specific instructions may be required depending on the circumstances.
After the FDG PET-CT
After the examination, patients are generally encouraged to:
- Drink adequate fluids as advised
- Empty the bladder regularly
- Follow any specific instructions provided by the centre
Most patients can return to their usual activities unless they have been given other instructions.
Because radiation exposure to others depends on the radiopharmaceutical, dose and individual circumstances, follow the specific radiation-safety instructions provided by the centre.
Important Limitations of FDG PET-CT
FDG PET-CT is a powerful imaging tool, but it has limitations.
FDG uptake is not cancer-specific
Inflammation and infection can also show increased uptake.
Some cancers may show low FDG uptake
Not every tumour has high glucose metabolism.
Very small lesions may be difficult to characterize
Spatial resolution and partial-volume effects can limit PET sensitivity for very small lesions.
Anatomical correlation remains important
PET findings need to be interpreted alongside CT and other available imaging.
Recent treatment can affect findings
Surgery, radiotherapy, chemotherapy and inflammation can influence FDG uptake.
Certain physiological structures normally show FDG uptake
Knowledge of normal physiological distribution is essential when interpreting a scan.
For these reasons, PET-CT findings should always be interpreted in the context of the patient's clinical history and other investigations.
FDG PET-CT & Previous Imaging
If you have undergone previous PET-CT, CT or MRI examinations, please bring the reports and, where possible, the actual images.
Comparison with previous imaging can be particularly useful when assessing:
- Disease progression
- Treatment response
- Recurrence
- New lesions
- Changes in metabolic activity
A meaningful comparison requires appropriate technical and clinical context.
For Referring Physicians
Every PET-CT begins with a clinical question.
The quality and clinical usefulness of an FDG PET-CT interpretation depend not only on the images, but also on the information available to the interpreting physician.
Where relevant, please provide:
- Primary diagnosis
- Clinical indication
- Histopathology
- Current stage
- Previous imaging
- Date of previous PET-CT
- Surgery
- Chemotherapy
- Radiotherapy
- Immunotherapy or targeted therapy
- Relevant laboratory/tumour-marker information
- Specific clinical question
What we aim to provide
The report should communicate clinically relevant information regarding:
- Distribution of disease
- Primary lesion
- Nodal disease
- Distant disease
- Relevant incidental findings
- Treatment-related changes where identifiable
- Comparison with previous imaging where available
- Staging information where appropriate
- Metabolic treatment response where applicable
- A clear overall impression
Clinical communication
For clinically significant or unexpected findings, communication with the referring physician may be appropriate.
If you would like to discuss a case or the appropriate molecular imaging study, please contact our Nuclear Medicine team.
FDG PET-CT FAQs
Your PET-CT Journey Starts Before the Scan
A well-prepared patient and a well-informed interpreting physician can make the imaging process more meaningful.
If you have been advised an FDG PET-CT, our team can guide you regarding appointment scheduling, preparation and the documents you should bring.