Positron Emission Tomography (PET)

Positron emission tomography (PET) is an imaging technology that measures the functional activity of biochemical processes in the body. It is most commonly used to identify areas of potentially aberrant metabolic activity, such as the increased glucose consumption typically displayed by malignant tumors. PET is most often deployed in relation to malignant mesothelioma to identify areas of distant metastases.

How PET Works

PET scans create a three-dimensional map of a variety of functional processes in the body. The scan is created using a combination of a scanning machine, a radioactive tracer and a biologically-active substance that the tracer is attached to. The tracer element itself is not dangerous.  Specific substances and tracers can be used to map specific functional processes.

The procedure begins when a patient is injected with the tracer and substance. Following this injection, a waiting period ensues that allows the substance to become concentrated in the tissues under investigation. It is also during this period that the tracer begins to decay, which emits a particle that the scanner can read. At the end of the waiting period, the scan begins. The scanner is tuned to the particle emitted from the tracer and creates a map of the areas in the body in which the particle is detected, which will correspond to the regions in which the biologically-active substance is now concentrated.

The most common substance used in a PET scan is a glucose-analogue called fluorodeoxyglucose (FDG). Cancerous tumors consume glucose at a higher rate than normal tissues consume it, so the presence and relative location of the tumor should be visualized on the scan as a site of increased FDG consumption. While FDG is the most common use of PET, other substances can be used to scan for different types of metabolic and biochemical activity.

PET and Diagnosis

In relation to pleural mesothelioma or peritoneal mesothelioma, PET is typically used for staging purposes and treatment planning, not for diagnostic purposes. After a diagnosis has been definitively determined, the physician must develop a treatment strategy, which is an area where PET can be helpful. The staging guidelines for mesothelioma, as they do for other cancers, state that the discovery of metastatic tumors immediately “upstage” the patient to a Stage IV case—which means the patient will not be eligible for radical surgery, but will be treated with palliative therapies instead. PET is useful in determining the absence or absence of distant metastases, so it has an important role to play in this aspect of mesothelioma treatment.

Risks

PET scans are considered low-risk procedures. The amount of actual radiation is quite low and it degrades very quickly. Side effects have not been reported in patients who’ve undergone the procedure.