Positron emission tomography (PET) precisely measures the radiation produced by radioactive tracers that are injected into the bloodstream to produce three-dimensional images of body functions. The machine is used with radioactive medicines (called radiotracers) that are tagged to a naturally occurring chemical in the body, such as glucose. Because the brain uses compounds like glucose, the technique actually produces an image of metabolism, or the rate at which a particular area in the brain uses a specific chemical. As most cancers use glucose and other substances at a rapid rate, more of the tracer is taken up by cancer cells enabling the imaging technique to detect them. PET scanning is a highly sensitive way to detect cancer throughout the body, and often a total body PET scan can be made as a screening tool.
A radiotracer is injected into the patient, where it will travel to the areas that use the natural substance it has been tagged with. For example, cancers use glucose, so it will attract a glucose-tagged radiotracer. As the radiotracer is broken down in the body, it emits energy that the PET scan detects. Often, a CT scan is used at the same time. This produces a three-dimensional image of the brain on a computer monitor, showing different areas of lightness and darkness, which a radiologist interprets.
Fluorodopa, or f-DOPA, is a radiotracer used in brain imaging that shows how dopamine is used and distributed in the brain. Certain brain tumors will absorb more dopamine, making them more visible on the resulting image. f-DOPA PET scans can help detect and stage brain tumors, and search for recurring gliomas.
f-DOPA PET scans can help neurosurgeons plan the best course of treatment, and evaluate the effectiveness of radiation or chemotherapy treatments already underway. It can often show brain tumor activity when other techniques fail to do so.
At the Houston Methodist Peak Center, f-DOPA imaging is one of several new techniques that help us optimize treatment of patients with brain tumors with precision never previously thought to be possible.
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