PET can help physicians effectively pinpoint the source of cancer. This is possible because many cancer cells are highly metabolic and therefore synthesize the radioactive glucose (sugar) that is injected in the patient prior to the exam. The areas of high glucose uptake are dramatically displayed in the scan imagery, as opposed to the anatomical imagery of CT or MRI, which cannot detect active, viable tumors.

If cancer is found early, it can often be cured. A PET scan can be used in early diagnosis, assisting physicians in determining the best method for treatment. A whole body PET scan may detect whether cancer is isolated to one specific area or has spread to other organs before a treatment path is determined.

In one continuous full-body scan (usually 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 tumor.

Essentially, small lesions or tumors 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 tumor, mass, etc.), a PET scan provides metabolic detail (cellular activity of the tumor, 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 analog of glucose that is tagged to the radionuclide F18. Metabolically active organs or tumors 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 tumors (because cancerous cells generally consume more sugar/energy than other organs or tumors).

The entire examination usually takes 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.

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 tumor detection and localization for a variety of cancers, including:

  • Breast
  • Esophageal
  • Cervical
  • 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 localization
  • 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 tumors 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 PET/CT provides physicians a more complete picture of what is occurring in the body – both anatomically and metabolically – at the same time.

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