PET/CT Scan

(Took from PETNET Solutions)

PET/CT @Bangkok Hospital

PET/CT Scan BASICS

Positron Emission Tomography (PET) and Computerised Tomography (CT), both are standard imaging tools that allow physicians to pinpoint the location of cancer within the body before making treatment recommendations.

The Highly sensitive PET scan detects the metabolic signal of actively growing cancer cells in the body and the CT scan provides a detailed image  of internal anatomy that reveals the location, size and shape of abnormal cancerous growths.

Each imaging test has particular benefits and limitations but when the results of PET and CT scans are "Fused" together, the combined image provides complete information on cancer location and metabolism.

The bottom line is that you can have both scans - PET and CT - done at the same time.

What is PET/CT?

In one continuous full-body scan (about 30 minutes), PET captures images of miniscule changes in the body's metabolism caused by the growth of abnormal cells, while CT images simultaneously allow physicians to pinpoint the exact location, size and shape of the diseased tissue or tumour.

Essentially, small lesions or tumours are detected with PET and then precisely located with CT

How PET/CT works?

While a CT scan provides anatomical detail (size and location of the tumour, mass, etc.), a PET scan provides metabolic detailed (cellular activity of the tumour, mass, etc.). Combined PET/CT is more accurate than PET and CT alone!

Anatomical: CT scanners send x-rays through the body, which are then measured by detectors in the CT scanner. A computer algorithm then processes those measurements to produce pictures of the body's internal structures.

Metabolic: PET images begin with an injection of FDG, an analogue of glucose that is tagged to the radionuclide F18. Metabolically active organs or tumours consume sugar at high rates, and as the tagged sugar starts to decay, it emits positrons. These positrons then collide with electrons, giving off gamma rays, and a computer converts the gamma rays into images. These images indicate metabolic "hot spots", often indicating rapidly growing tumours (because cancerous cells generally consume more sugar/energy than other organs or tumours).

The entire examination usually take less than 30 minutes, providing comprehensive diagnostic information to your health care team very quickly. The PET/CT system provides exceptional image quality and accuracy of diagnostic information.

What PET/CE sees?

PET/CT scanning integrates PET and CT technologies into a single device, making it possible to obtain both anatomical and biological data during a single exam. This integrated approach permits accurate tumour detection and localisation for a variety of cancers, including:

• Breast
• Esophageal
• Melanoma
• Lymphoma
• Lung
• Colorectal
• Head and Neck
• Ovarian

PET/CT applications:

• Determines extent of disease
• Determines location of disease for biopsy, surgery or treatment planning
• Assesses response to and effectiveness of treatments
• Detects residual or recurrent disease
• May assist in avoiding invasive diagnostic procedure

Benefits of PET/CT

There are tremendous benefits of having a combined PET/CT scan:

• Earlier diagnosis
• Accurate staging and localisation
• Precise treatment and monitoring

With the high-tech images that the PET/CT scanner provides, patients are given a better chance at a good outcome and avoid unnecessary procedures. A PET/CT image also provides early detection of the recurrence of cancer, revealing tumours that might otherwise be obscured by scar tissue that results from surgery and radiation therapy, particularly in the head and neck.

In the past, difficulties arose from trying to interpret the results of a CT scan done at a different time and location than a PET scan, due to the fact that the patient's body position had changed. The combination of PET/CT provides physicians a more complete picture of what is occurring in the body - both anatomically and metabolically - at the same time.

PET/CT Scan Preparation

Patient Preparation

Instructions

• Comfort - PET scans are completely painless, with no side effects.
• Clothing - Dress comfortably and warmly, as some scanner rooms may be cool.
• Food and Drink - Please call the PET Centre for specific instructions. Generally, you should limit the amount of sugar and caffeine on the day before the scan and should not consume anything except water for approximately 6 hours prior to the scan.
• Medications - You may take your regularly scheduled medications prior to arriving for your scan, if they can be tolerated on an empty stomach.
• Diabetic - Please speak with the PET centre nurse or doctor for specific instructions regarding insulin. Generally, you should test your blood sugar level before the scan; it should be approximately 100-200 mh/dL.
• Procedure - Upon arriving at the PET centre, you will receive an injection of radioactive glucose (FDG), which will take approximately 45 minutes to distribute throughout your body. You will be asked to empty your bladder and then lie down on the scanner bed. The scan takes approximately 15 - 60 minutes, depending upon the type of scan you are having and the type of scanner being used. It is important that you lie still during this process. If you need pain medication please bring it with you. You should plan on being at the PET centre for approximately 2 hours.
• After your scan - Once the PET scan is complete, you will be able to leave the PET centre. Make sure you drink plenty of water of other fluids throughout the day to flush the FDG from your body.
• Your PET scan results - The PET scan is interpreted by a trained nuclear medicine physician or radiologist, and results are usually sent to the referring physician within 24-48 hours. You should contact your doctor to discuss the results.

Please note: At Bangkok Hospital, all process completed within 3 hours including reports process.

The Story of PET/CT

Doctors, especially cancer surgeons, were often frustrated in trying to match PET images with CT images to determine the precise location of a tumour in relation to an organ or the spinal column. They had little choice other than to "eyeball" the two separate images and make an educated guess as to the tumour's exact location - until 1992, when engineer Ron Nutt and physicist David Townsend came up with the idea of combining a PET and CT into one machine.

After working on their combined PET and CT concept for three years, Nutt and Townsend received a grant from the National Cancer Institute. This enabled the completion of a prototype machine, which as installed at the University of Pittsburgh medical centre in 1998.

The pair designed the machine to be more patient-friendly by making the diameter of the PET/CT tunnel 28 inches, far more spacious than the typical MRI tunnels.

Time Magazine honoured PET/CT as the "Medical Science Invention of the Year" in 2000, noting that the PET/CT scanner has "provided medicine with a powerful new diagnostic tool".