Inflammation and infection: imaging properties of 18F-FDG-labeled white blood cells versus 18F-FDG.

UNLABELLED: (18)F-FDG and (18)F-FDG-labeled white blood cells ((18)F-FDG-WBCs) are valuable radiopharmaceuticals for imaging focal sites of inflammation and infection. In the present study, the imaging properties of both radiotracers were compared in sterile and septic inflammation models. METHODS: Groups of adult male Sprague-Dawley rats (100-120 g) were injected in the left posterior thigh muscle with saline solution (group 1: controls, n = 15), 0.100 mL of turpentine oil (group 2: sterile inflammation, n = 26), 10(9) viable Escherichia coli bacteria (group 3: E. coli septic inflammation, n = 29), or 10(8) viable Pseudomonas aeruginosa bacteria (group 4: P. aeruginosa septic inflammation, n = 25). Twenty-four hours later, the animals were divided into 2 groups: One received (18)F-FDG intravenously and the other received human white blood cells (WBCs) labeled in vitro with (18)F-FDG injected intravenously. Biodistribution and microPET studies were performed 1 h after radiotracer injection. One hour after injection with cell-associated or free (18)F-FDG, phosphorimaging of abscess and contralateral muscle was performed in specimens collected from animals in groups 1, 2, and 3. The region of interest was selected within the abscess wall and values were converted to kBq/g using a (14)C calibration standard curve. Thin-layer radiochromatography (TLRC) was performed to study the chemical forms of (18)F within the WBCs. RESULTS: Whole-body biodistribution demonstrated a significantly higher uptake ratio of (18)F-FDG-WBCs compared with (18)F-FDG in all sterile and septic inflammation models (t test: sterile, P = 0.048; E. coli, P = 0.040; P. aeruginosa, P = 0.037). microPET imaging confirmed the greater performance of (18)F-FDG-WBCs versus (18)F-FDG in the sterile inflammation model and in both E. coli and P. aeruginosa septic models. Phosphorimaging analysis showed higher (18)F-FDG-WBC uptake than (18)F-FDG in the sterile inflammation and P. aeruginosa septic models and similar tissue uptake in the E. coli septic model. Time course labeling and TLRC of lysed WBCs demonstrated that (18)F-FDG was retained as (18)F-FDG-6-phosphate inside WBCs for at least 2 h, corresponding to the time frame of analysis. CONCLUSION: (18)F-FDG-WBCs gave better results compared with (18)F-FDG in all sterile and septic inflammation models. These data suggest that (18)F-FDG-WBC PET may be a useful technique for tracking focal inflammatory lesions in the body.

The Role of the Practice of Nuclear Pharmacy in Positron Emission Tomography.

As nuclear medicine evolved from an obscure research tool to a mainstream clinical diagnostic and therapeutic modality, so has the role of the practice of pharmacy in nuclear medicine also evolved. A similar evolution is unfolding today in the practice of positron emission tomography (PET). The skills of many diverse professionals, including pharmacists, are essential for the safe and efficient operation of a modern PET facility. The importance of the role of pharmacists in PET has been increasing as the use of PET radiopharmaceuticals has matured from research to clinical to commercial arenas. While it is clear that pharmacists can contribute clinical and technical skills to the operation of a PET center, perhaps one of the most important factors influencing the increased role of pharmacists in PET is their expertise and experience in the drug regulatory process. The commercial distribution of PET radiopharmaceuticals, primarily [18F]2-fluorodeoxyglucose (FDG), is currently being performed by a variety of corporate and institutional facility partnerships, with the likelihood of several new players entering the marketplace in the near future. This factor has served to dramatically increase the role for nuclear pharmacy in PET. The practice of nuclear pharmacy is a well-established component of PET. The role of nuclear pharmacists in PET is complementary to the many other professionals currently practicing in this specialty. With the rapidly increasing clinical demand for FDG imaging, it is likely that the number of facilities and institutions entering into the commercial distribution of PET radiopharmaceuticals will also increase. Such growth will also serve to solidify and expand the role for the practice of nuclear pharmacy in PET.