Table 1:
Mechanism of action, use, and biodistribution of radiopharmaceuticals commonly used in clinical and research settings.
| Radiotracers | Property | Mechanism of Action | Use | GI Biodistribution |
|---|---|---|---|---|
| 18F-Fluoro-Deoxy-Glucose (FDG) | Glucose analog | Glucose analog | Majority of the oncological imaging | Variable, mild or intense, diffuse or segmental, throughout the GI tract |
| 68Ga-Prostate specific membrane antigen (PSMA) | Similar to glutamate carboxypeptidase II and folate hydrolase I | PSMA expressed on cell membrane, internalized on ligand binding | Prostate cancer | Intense uptake within duodenum and jejunum, variable low-grade uptake within the remainder of the bowel loops |
| Somatostatin receptor Scintigraphy (SRS) | Somatostatin receptor analog | Binds to somatostatin receptor (SSTR) subtypes | Neuroendocrine tumor | More intense within the proximal bowel loops compared to the distal bowel |
| 18F-Sodium Fluoride (NaF) | Analog for hydroxyl group in in the bone matrix | Localization in the hydroxyapatite crystal | Osseous metastases | Not common, if present, it is variable, predominantly with the small bowel |
| 11C-Acetate | Substrate for synthesis of acetyl Co-A | Biomarker for cell membrane lipid synthesis | Myocardial perfusion and oxygen consumption various malignancies, such as hepatocellular carcinoma, prostate cancer, renal and bladder cancers | May have prominent esophageal uptake, low-grade within the small and large bowel |
| 11C/18F-Choline | Precursor of phosphatidylcholine | Biomarker for lipogenesis and biosynthesis of cell membrane | Prostate cancer, hepatocellular carcinoma and brain tumors | Variable but generally colonic uptake is less than the small bowel uptake |
| 11C-methyl-L-methionine | Essential amino acid | Protein synthesis | CNS tumor imaging, prostate and bladder cancers | Variable and intense, stomach uptake higher than in large bowel loops |
| FACBC; commercial name: Axumin | Non-natural synthetic Lleucine analog | Amino acid transporter | Prostate cancer, breast cancer and brain tumors | Variable mild to moderate uptake within the GI tract, more prominent with in the esophagus |
| 18F -Fluoro-Ldihydroxyphenylalanine (FDOPA) | L-DOPA analog | Precursor for catecholamines | Brain tumors and neuroendocrine tumors | Mild uptake within the esophagus. Minimal or no uptake within the bowel loops |
| 18F-Fluoro-ethyl-L-Tyrosine (FET ) | Neutral amino acid analog | Amino acid transporter | Brain tumor | Minimal or no uptake |
| 18F-Fluorothymidine (FLT) | Pyrimidine analog | Biomarker for cell proliferation and thymidine kinase −1 activity | Several cancers for prediction and monitoring of therapy response | Variable, usually low-grade |
| Human Epidermal Growth Factor-2 (HER2) targeted imaging | Humanized mAb against HER2 Receptor | Binds to HER2 receptor | Breast and esophagogastric cancer | Seen one to two days after administration and moves distally over time |
| Iodine-124 (124I) | Positron Emitting Iodine | Functions as Iodide | Thyroid | Seen one to three days after ingestion and decreases over the time |