Positron emission tomography (PET) is an imaging technique that provides both structural and functional information, in contrast to other imaging modalities which provide mostly structural information such as computed tomography (CT) and magnetic resonance imaging (MRI).

Currently, the most common radiotracer used clinically for PET images is the glucose analog 2‐deoxy‐2‐[¹⁸F]fluoro‐d‐glucose (¹⁸F‐fluorodeoxyglucose or ¹⁸F‐FDG), which has become an important tool for the evaluation of various malignancies and has also been used in the assessment of inflammatory and infectious disease.

The radiotracer has a half‐life of approximately 110 min, enabling its production at regional facilities which then manage distribution to clinical sites.

Patient preparation is critical to the quality of ¹⁸F‐FDG PET. Patients should avoid strenuous exercise for 24 h before the ¹⁸F‐FDG PET study to minimize uptake of the radiotracer in muscles. Patients should, as much as possible, be on a low‐carbohydrate diet for 24 h before the study. Fasting is required for at least 4–6 h (based on Society of Nuclear Medicine and Molecular Imaging procedure standard for tumor imaging with ¹⁸F‐FDG PET/CT) prior to the study. A longer period of fasting (of approximately 12 h) and low‐carbohydrate diet for 24 h may decrease ¹⁸F‐FDG accumulation by the myocardium and improve detection of mediastinal metastases. A high‐fat, low‐carbohydrate, protein‐preferred meal the day before the scan more effectively suppresses cardiac activity by increasing free fatty acid (FFA) availability, which promotes FFA oxidation and inhibits glucose use. Fasting is also important in order to minimize competitive inhibition of FDG uptake by glucose in tumors (most institutions reschedule the patient if the blood glucose level is greater than 150–200 mg/dL).

While fasting, patients should consume at least 2–3 355 mL (12 oz) glasses of water to ensure adequate hydration. Insulin should not be used to adjust the blood glucose at the time of the imaging procedure; recent insulin administration changes the accuracy of standardized uptake value (SUV) determination by altering the biodistribution of ¹⁸F‐FDG, especially in insulin‐sensitive tissue such as muscle, myocardium, and fat. Recent insulin administration also causes low hepatic ¹⁸F‐FDG uptake.

Because ¹⁸F‐FDG is mainly eliminated by urinary excretion, additional preparation can be performed for specific imaging of the pelvic region. This includes IV hydration, Lasix® administration during the study, Foley catheter in the bladder, and retrograde filling of the bladder with sterile saline solution.

A collection of ¹⁸F‐FDG PET images in malignant and inflammatory/infectious diseases is presented in this chapter (Figures 91.1–91.25). Three examples of other more specific PET radiotracers recently approved by the Food and Drug Administration (FDA)for clinical use are also included in this chapter (3,4‐dihydroxy‐6‐⁸F‐fluoro‐l‐phenylalanine [¹⁸F‐FDOPA], an amino acid that resembles natural l‐DOPA, the precursor of the neurotransmitter dopamine (Figure 91.26), ⁶⁸Ga‐DOTA‐d‐Phe(1)‐Tyr(3)‐octreotide [⁶⁸Ga‐DOTA‐TOC], and ⁶⁸Ga‐DOTA‐Tyr3‐Octreotate [⁶⁸Ga‐DOTA‐TATE], which are somatostatin receptor analogs labeled at the positron emitter ⁶⁸Ga (Figures 91.27–91.29)).