Positron Emission Tomography (PET) scans can utilize a radioactive tracer, in this case 2-deoxy2-[fluorine-18] fluoro-D-glucose (18F-FDG), to visualize malignant tumors in cancer patients. The uptake was compared to glucose to understand the difference in thermal properties, which contribute to the ability to image the cancerous cells. The uptake of 18F-FDG by cancer cells and the imaging process of positron emission tomography were reviewed from a thermodynamic perspective. Gastrointestinal and neurological imaging techniques were reviewed to understand the role of PET imaging in different areas of the human body