Search

Objective: Metastatic lymph node ratio (MLNR) is a known significant predictor of disease-free survival in differentiated thyroid cancer. The authors investigated the ability of preoperative fluorine-18 fluorodeoxyglucose (F-FDG) PET/CT to predict recurrence after surgery with radioactive iodine therapy considering MLNR., Patients and Methods: A total of 274 patients who underwent preoperative PET/CT and surgery with radioactive iodine therapy were enrolled. The tumor-to-liver uptake ratio on PET/CT was calculated by dividing the maximum standardized uptake value of a primary lesion by the mean standardized uptake value of the normal liver. High F-FDG uptake was defined as tumor-to-liver uptake ratio more than the median cutoff value (2.1). MLNR was calculated by dividing the number of metastatic lymph nodes (LNs) by the number of cervical LNs removed. A high MLNR was also defined as one more than a threshold value (0.4), identified by plotting Kaplan-Meier survival curves and comparing them using the log-rank test. The prognostic significances of clinicopathologic variables were analyzed., Results: Fifteen (5.5%) patients developed recurrence in the thyroid bed or in cervical LNs. Cox regression analysis showed that a high MLNR was significantly associated with a worse disease-free survival (odds ratio 6.95; 95% confidence interval: 2.36-20.47; P<0.001). A subgroup analysis of 70 patients with a high MLNR showed that only high F-FDG uptake was significantly associated with a worse disease-free survival (odds ratio 5.77; 95% confidence interval: 1.22-27.16; P=0.027)., Conclusion: High F-FDG uptake of primary lesion on preoperative PET/CT has selective prognostic value according to the extent of metastatic LNs (MLNR>0.4).

Introduction: Lipophilic cations such as phosphonium cations penetrate the hydrophobic barriers of the plasma and mitochondrial membranes and accumulate in the mitochondria in response to negative inner-transmembrane potentials. The present study reports the radiosynthesis and evaluation of (18)F-labeled aliphatic triphenylphosphonium cations as a potential agent for myocardial imaging by using PET., Materials and Methods: (7-[(18)F]fluoroheptyl)triphenylphosphonium salt ([(18)F]3) and (8-[(18)F]fluorooctyl)triphenylphosphonium salt ([(18)F]6) were radiolabeled by means of two-step nucleophilic substitution reactions. We measured the log P value of [(18)F]3 and [F]6 to assess the appropriate range of lipophilicity for their suitability as PET myocardial imaging agents. Normal rats were imaged with microPET after intravenous injection of 37 MBq of [(18)F]3 and [(18)F]6. To determine the pharmacokinetics, a region of interest was drawn around the heart, and time-activity curves of [(18)F]3 and [(18)F]6 were generated to obtain the counts per pixel per second., Results: The radiolabeled compounds [(18)F]3 and [(18)F]6 were synthesized with 18-25% yield. The radiochemical purity was greater than 98% on the basis of the analytical high-performance liquid chromatography system, and the specific activity was greater than 160-170 Ci/mmol. The log P value of the tracers was 2.52 ± 0.01 ([(18)F]3) and 2.91 ± 0.02 ([(18)F]6). Myocardium-to-liver ratios of [(18)F]3 and [(18)F]6 were 2.59 and 1.07, respectively, 10 min after injection, whereas the myocardium-to-lung ratios were 5.57 and 3.35, respectively. In addition, [(18)F]3 and [(18)F]6 showed intense, homogenous uptake in the myocardium., Conclusion: (18)F-labeled aliphatic phosphonium cations [(18)F]3 and [(18)F]6 might have potential as novel myocardial agents for PET and could prove useful in clinical cardiac PET/computed tomography applications.

[11C]Acetate, a radiotracer for PET imaging, is a promising radiopharmaceutical for overcoming the limitation of 2-deoxy-2-[18F]fluoro-D-glucose in a number of cancers. Here, the optimized automatic synthesis of [11C]acetate using an in-house-developed module under different conditions has been reported for routine production. [11C]CO2 was produced in a 16.4 MeV PETtrace cyclotron, and methyl magnesium chloride was used for synthesis. For product purification, ion-exchange solid-phase extraction cartridges were used, connected in series. High-performance liquid chromatography and gas chromatography were used to measure radiochemical and chemical purity. The Limulus amebocyte lysate test and the fluid thioglycollate medium test were performed for quality control of [11C]acetate. The total reaction time of [11C]acetate was within 15 min, and the overall decay-corrected radiochemical yield was 84.33±8.85%. Radiochemical purity was greater than 98% when evaluated on an analytical high-performance liquid chromatography system. No endotoxins or anaerobic bacteria were seen on quality control checks. Optimized production of [11C]acetate was achieved by the in-house module. Radiochemical and biological properties of the [11C]acetate produced were appropriate for clinical PET study.