PET-CT Scan: Purpose and Procedure

A PET-CT scan is an advanced imaging test that integrates two types of imaging, positron emission tomography (PET) and computed tomography (CT) into one exam. It offers data on the function of tissues and organs and detailed images showing the structure of tissues and organs. PET-CT is frequently used to help determine if cancer has spread, to help plan treatment, to determine the response to treatment, and to look for signs of cancer returning. Additionally, it can be used for certain heart and neurological diseases.

PET-CT scans are done at Molecular Diagnostics and Therapy to facilitate the investigation and management of various health problems as indicated by a physician. This blog describes the PET-CT scan procedure, the preparation for PET-CT, the duration of PET-CT, and other important pet ct test information.

What Is a PET-CT Scan?

PET-CT is an integrated imaging study that combines the information of two types of imaging tests. The PET component involves a radioactive material: a radiotracer. A tracer that is commonly used is fluorodeoxyglucose (FDG), a molecule that is structurally similar to glucose and is used in the body. Regions where the metabolism is more intense may absorb more FDG and may become more prominent on PET images.

The CT component takes X-rays of the body to make detailed pictures of the body. Together with the PET picture, the doctor can also see where a part of the body is abnormal, along with how active that area is. This combination can give you information that might be unable to be acquired with either alone.

Why Is a PET-CT Scan Done?

Doctors may recommend a PET-CT scan for several reasons, particularly during cancer evaluation and treatment. Common uses include:

• Detecting or evaluating certain cancers
• Determining whether cancer has spread to other parts of the body
• Assessing response to cancer treatment
• Checking for possible recurrence after treatment
• Helping with treatment planning
• Evaluating selected neurological conditions
• Assessing certain heart-related conditions

The exact reason for a PET-CT depends on the patient's symptoms, diagnosis, previous test results, and treatment history.

PET-CT Scan Preparation

Because of the effects that food consumption and blood glucose levels have on the distribution of FDG, proper PET-CT scan preparation is important. In several FDG PET-CT studies, patients are asked to avoid food for a few hours before the study. To help maintain hydration, which usually includes drinking plain water is usually allowed and encouraged, though drinks high in sugar or calories should be avoided unless directed otherwise by the medical team.

Individuals with diabetes may be given special instructions for preparation as blood glucose levels can affect the acquisition of good images during an FDG PET-CT examination. Before the scan, tell the medical team if you:

• Have diabetes
• Are pregnant or think you may be pregnant
• Are breastfeeding
• Take regular medicines
• Have any allergies
• Have recently had an infection, surgery, or other significant medical condition

You should follow the preparation instructions provided by the imaging centre because requirements can vary depending on the type of PET-CT being performed.

What Happens During the PET-CT Scan Procedure?

The PET-CT scanning process normally starts with a technologist verifying your information and preparing you for the test. A tiny IV is typically inserted into an arm vein. The prescribed radiotracer is then injected through the IV. Following the injection, it is important to be very still as the radiotracer moves around your body. 

This is usually about 30-60 minutes for FDG PET-CT. At this time, you might be asked to keep still and not move about or talk. After uptake is done, you are positioned on the scanning table. Slow motion: The table is slowly moved into the PET-CT scanner to get the image. The purpose of the scan is to obtain clear images, and this requires the subject to remain still during the scan.

PET-CT Scan Duration

A PET-CT scan lasts for two parts: (1) preparation and tracer injection (2) the scan. Typically, it takes 30 to 60 minutes for the radiotracer to get distributed around the body. The actual scanning time is typically based on the area of the body being scanned and can vary from 30 minutes for the most common type of scan for most patients. So, as a general rule, patients can expect to be at the centre well beyond the time it takes to be scanned. Examination may be longer because of additional imaging, certain imaging procedures, or contrast or special protocols.

What Does a PET-CT Scan Feel Like?

Typically, PET-CT is painless except for the slight discomfort associated with inserting its IV line. The IV might cause a little stinging when it is inserted. In some people, there may be a brief cold sensation in the area of the injection, or the needle may feel a bit cool. When taking a scan, you must remain still on the examination table. It may cause slight discomfort for those who must not move in one position for too long. The opening in the scanner is large and in the shape of a doughnut. People don't spend a long time inside a long, narrow tube as they do with an MRI scanner.

PET-CT Scan Test Details

The exact PET-CT scan test details depend on the reason for the examination and the radiotracer being used. A typical FDG PET-CT may involve:

1. Patient registration and preparation:
Your medical history, medicines, diabetes status, and other relevant information may be reviewed.

2. Blood glucose assessment:
For FDG PET-CT, blood glucose may be checked before the tracer is administered because abnormal glucose levels can affect the examination.

3. Radiotracer injection:
A small amount of the prescribed radiotracer is injected through an IV.

4. Uptake period:
You rest quietly while the tracer distributes through the body.

5. CT scan:
The CT component provides detailed anatomical information.

6. PET scan:
The PET component records the distribution of the radiotracer and provides information about metabolic activity.

7. Image interpretation:
The resulting images are reviewed by appropriately trained imaging specialists, and a report is prepared for the referring doctor.

What Should You Do After a PET-CT Scan?

After the examination, most people can return to their normal activities unless their doctor or imaging team provides different instructions. Drinking plenty of water is generally encouraged after many PET examinations because the radiotracer is gradually eliminated from the body, including through urine. If you are breastfeeding, pregnant, or have another condition requiring special precautions, follow the specific instructions provided by your healthcare team.

Is PET-CT Safe?

PET-CT involves exposure to radiation from both the radioactive tracer used for PET and the CT component. The amount is carefully considered according to the clinical need for the examination. The radiotracer used for PET has a short physical half-life, and its radioactivity decreases naturally over time. Much of the tracer is also eliminated from the body through urine or stool. Before the examination, inform your doctor or imaging team if you are pregnant or breastfeeding so that the benefits and appropriate precautions can be considered.

What Can a PET-CT Scan Show?

A PET-CT scan can provide information about both the structure and metabolic activity of tissues. In cancer care, areas showing increased tracer uptake may indicate increased metabolic activity. However, increased uptake does not always mean cancer because inflammation and infection can also cause increased uptake.

Therefore, PET-CT findings are interpreted together with symptoms, medical history, physical examination, laboratory tests, biopsy results, and other imaging findings when required. A PET-CT scan is an important diagnostic and monitoring tool, but its findings should always be interpreted in the appropriate clinical context.

PET-CT at Molecular Diagnostics and Therapy

At Molecular Diagnostics and Therapy, PET-CT services are available for patients who require advanced nuclear medicine imaging based on their doctor's recommendation. The examination can provide combined metabolic and anatomical information that may help doctors evaluate disease, assess its extent, monitor treatment response, or look for recurrence when clinically appropriate. Patients should follow the centre's specific preparation instructions before arriving for their appointment to help ensure that the examination can be performed properly.

Conclusion

In a PET–CT scan, the patient is given a combination of PET scan and CT scan, which gives information about both the metabolic activity and the anatomical structure of tissues and organs. PET-CT is used in the evaluation, staging, treatment assessment, and surveillance of selected cancers. The correct preparation procedures, especially in the case of PET-CT imaging with a PET radiotracer, are crucial. Patients must also withhold food for a few hours, refrain from sugary beverages, and drink plenty of plain water. Medication instructions may vary, particularly for patients with diabetes. 

In general, the PET-CT scanning process is carried out through the injection of a radio-tracer into the bloodstream via intravenous drip, a brief rest time for uptake, followed by PET and CT imaging. The examination itself takes about 30 minutes to give the PET scan; the actual scanning phase is usually about 30 minutes, though the length of time after tracer uptake varies depending on the examination. For Molecular Diagnostics and Therapy, PET-CT imaging is used to aid in the assessment and management of various illnesses, as indicated by clinical conditions. Best results are achieved when patients follow all the preparation instructions given before examination.