A non invasive nuclear medical imaging technique which detects pair of gamma rays emitted by a positron-emitting radionuclide (tracer), which is introduced into the body ( in blood circulation ) on a biologically active molecule.The concentrations of the tracer imaged will indicate tissue metabolic activity and may indicate cancer metastasis.
The molecule most commonly used is FDG ( fluorodeoxyglucose) , an analogue of glucose. which is concentrated in the tissues of interest in an hour and at that time person is placed in the imaging scanner. The radioisotope undergoes positron emission decay ( also known as beta decay), it emits a positron, an antiparticle of electron with opposite charge. It travels for a short distance and interacts with an electron which leads to annihilation and production of a pair of gamma ( photons ) which is detected by scintillator in the scanning device.
PET scans are read alongside CT or MRI scans giving both anatomic and metabolic information. Modern PET scanners are integrated with CT scanner so called PET-CT and because two scans are performed in immediate sequence during same session , with the patient not changing position, the sets of images are precisely registered.
PET scanner is costly because of the high costs of cyclotrons needed to produce the short-lived radionuclides for the PET scanning.
The PET scan is used for both research and clinical purpose. The clinical use in neurosurgical practice is to detect metastasis and to detect recurrence of the tumor after radiotherapy and chemotherapy. For example, a patient was operated for high grade glioma about one year ago and had already received chemotherapy and radiotherapy comes to the neurosurgeon for the complaints like headache or vomiting or seizure which creates the doubt of tumor recurrence. Then the physician should advise MRI brain with contrast with MR spectroscopy and compare the pre and post operative follow up scans. Sometimes, due to redionecrosis the distinction better tumor recurrence and radionecrosis is not very clear and in this situation a PET scan can be advised.
The molecule most commonly used is FDG ( fluorodeoxyglucose) , an analogue of glucose. which is concentrated in the tissues of interest in an hour and at that time person is placed in the imaging scanner. The radioisotope undergoes positron emission decay ( also known as beta decay), it emits a positron, an antiparticle of electron with opposite charge. It travels for a short distance and interacts with an electron which leads to annihilation and production of a pair of gamma ( photons ) which is detected by scintillator in the scanning device.
PET scans are read alongside CT or MRI scans giving both anatomic and metabolic information. Modern PET scanners are integrated with CT scanner so called PET-CT and because two scans are performed in immediate sequence during same session , with the patient not changing position, the sets of images are precisely registered.
PET scanner is costly because of the high costs of cyclotrons needed to produce the short-lived radionuclides for the PET scanning.
The PET scan is used for both research and clinical purpose. The clinical use in neurosurgical practice is to detect metastasis and to detect recurrence of the tumor after radiotherapy and chemotherapy. For example, a patient was operated for high grade glioma about one year ago and had already received chemotherapy and radiotherapy comes to the neurosurgeon for the complaints like headache or vomiting or seizure which creates the doubt of tumor recurrence. Then the physician should advise MRI brain with contrast with MR spectroscopy and compare the pre and post operative follow up scans. Sometimes, due to redionecrosis the distinction better tumor recurrence and radionecrosis is not very clear and in this situation a PET scan can be advised.
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