Positron Emission Tomography
Diagnosing Malignant Mesothelioma
Continued from: Mesothelioma Diagnosis
Positron emission tomography (PET) produces highly detailed images of the biological functions of the body. Also referred to as a PET scan or PET imaging, positron emission tomography is being used more frequently in the diagnosing of various malignant diseases.
PET scans revolve around the emission of positrons (tiny particles that are emitted from radioactive substances) for the purpose of radiation detection.
Patients undergoing positron emission tomography will be advised by their physician to complete a series of preparatory steps that include:
- Avoid eating food for at least four hours prior to the exam.
- Drink plenty of water.
- Inform the physician of any medications being taken.
- Inform the physician if diabetic.
- Bring any previous imaging scans (CT, MRI, etc.) relevant to the malignancy in question.
- Wear comfortable clothing (Procedure can take from two to four hours).
Anywhere from 30 to 90 minutes prior to undergoing a PET scan, patients receive an intravenous injection of a radioactive substance (e.g. radioactive fluorine) that has been produced in a machine designed to accelerate clusters of charged particles (cyclotron). This radioactive substance is attached to certain types of natural body compounds; glucose is the most commonly used compound, though water or ammonia can also serve the same purpose. After injection, the radioactive substance travels throughout the body, soaking into the tissue being evaluated.
The PET scan itself can take anywhere from 30 to 45 minutes, during which patients lay motionless inside a large, doughnut shaped machine housing a series of detectors. The machine is designed to record the emissions produced by the radioactive substance that has been injected into the body.
There is no pain associated with the radioactive substance that is injected into the patient's body and no pain associated with the scanning portion of the procedure. Following completion, patients are advised to drink plenty of water to help flush the radioactive substance from the body (most radiation is eliminated from the body within 18 hours following the PET scan).
The results of the PET scan are interpreted by a radiologist. It can take anywhere from one to three days for the results to be reported to the patient's attending physician.
A PET scan differs from other types of imaging technology (MRI, CT scan, and x-ray) in that it displays the chemical function of a particular organ or section of tissue. PET scans are able to detect biochemical and metabolic changes suggesting disease before they are detected by standard imaging devices. Another benefit associated with PET scanning is that the radiation dosage is relatively low, equivalent to about half that of a CT scan.
One of the problems associated with positron emission tomography is the diagnostic tool's sensitivity. If a patient's chemical balances are not normal (diabetic patients or those who ate something prior to the test) then PET scans can produce false results.
Medical professionals believe that PET scans hold a great deal of promise in regards to the diagnosing and staging of malignant mesothelioma. Various studies have shown PET scans to be more successful in diagnosing the presence of malignant mesothelioma when compared to standard mesothelioma diagnostic procedures (e.g. thoracoscopy or surgical biopsy). Such studies suggest that although standard imaging tests like CT scans and MRIs should continue to play a role, PET scans are becoming increasingly important in the diagnosis of mesothelioma.
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[Page updated August 2006]