PET Imaging

Visualising Metabolic Changes: The Role of PET-CT in Disease Diagnosis and Treatment

PET (Positron Emission Tomography) is a nuclear medicine imaging modality used to visualise the structures within the human body. In most cases, a PET scan is performed in conjunction with computed tomography (CT) scan, known as hybrid imaging.

Consequently, these non-invasive imaging procedures are rapid and sensitive to anatomical and biological changes in the body and provide essential information about how a particular disease behaves in patients: for example, in the staging, restaging and assessing cancer treatment response.

During the PET imaging procedure, the patient is injected with a low dose of the radiopharmaceutical (radiotracer)  such as 18FDG, Na18F, 68Ga-PSMA and 68Ga-DOTATATE. However, conventional CT and MRI (magnetic resonance imaging) use X-rays to obtain 3D anatomical images. An injected radiation dose into the human body distributes to specific areas of high glucose metabolism when using 18FDG to identify abnormal activity in the body.

Also, PET imaging enables the determination of a tumour’s metabolism rate to see if it is still active. A further hybrid uses PET and MRI to facilitate improvement in the visualisation of specific structures: for example, in the brain and pelvic organs.

In another situation regarding lung cancer diagnosis, it is paramount for the oncologist to determine if the patient requires curative surgery and chemotherapy or only palliative chemotherapy. Therefore, to enable this decision, using 18FDG radiotracer in a PET-CT scan will allow the oncologist to verify if the lung cancer has spread to a particular lymph node.

The essence of PET imaging is to evaluate metabolic changes that precede anatomical changes, which MRI observes. Consequently, positron emission tomography imaging is used to detect tumours early and assess dementia and seizures. This is in addition to observing the functions of the heart and in the evaluation of inflammatory diseases.

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