Great efforts are currently devoted to the development of new approaches for the labeling of cells using appropriate radionuclides. While fluoride-18 and copper-64 have been extensively studied as short-term and intermediate-term trafficking agents, iodide was studied less intensely. Here, we report a new cell labeling agent labeled with $^{131}I$, $[^{131}I]$oleyl-4-iodobenzoate ($[^{131}I]$OIB) for long-term cell trafficking. A precursor of $[^{131}I]$OIB was obtained in two steps, with the yield of 35%. The radiochemical yield of $[^{131}I]$OIB was over 50%. While $[^{131}I]$OIB could label different cells, L6 cells showed the highest cell-labeling efficiency. The $[^{131}I]$OIB-labeled L6 cells were imprinted into a rat heart, and then monitored noninvasively for 2 weeks by gamma camera imaging. We conclude that $[^{131}I]$OIB is a good candidate molecule for a long-term cell trafficking agent.

Azeotropic drying process is routinely applied to enhance nucleophilicity of $[^{18}F]$fluoride ion during the nucleophilic production of PET radiotracers; however, the drying process requires usually 15-25 min. Due to the high demand of employing fluorine-18 ($t_{1/2}=109.8min$) in PET radiopharmaceutical production, several research groups have focused on the method development, obviating tedious removal process of the residual target water ($[^{18}O]H_2O$) for $[^{18}F]$fluoride ion complex to be used in radiofluorination. Some development in radiofluorination in a mixed organic solvent system was demonstrated with various aliphatic substrates, but only kryptand as a phase transfer agent was utilized in the reported method. Here, we extend to investigate the development scope of applicability with basic alkyl ammonium salt as a phase transfer agent through the extensive elution efficiency study and radiofluorination outcome for aliphatic radiofluorination.

${\omega}-[^{18}F]$-Fluorohexadecanoic acid (FHA) has been used for imaging of fatty acid metabolism of myocardium. To increase retention of radiolabeled fatty acid by blocking ${\beta}$-oxidation, methyl branched analogues have been used. In this experiment, we tried to synthesize 18F-labeled ${\alpha}-$, ${\beta}-$ and ${\omega}-FHA$ for imaging of the myocardial fatty acid metabolism. We synthesized ${\alpha}-$, ${\beta}-$ and ${\omega}$-mesylated methyl hexadecanoates and labeled with $^{18}F$ by reacting with $[^{18}F]$TBAF in acetonitrile at $80^{\circ}C$ for 10 min. Methyl ester group was removed by 1 M NaOH at $80^{\circ}C$ for 5 min. The yields of ${\alpha}-[^{18}F]$ and ${\omega}-[^{18}F]FHA$ were 25.5 and 45.5%, respectively [EOS]. However, ${\beta}-[^{18}F]FHA$ was not labeled at all due to a fast elimination reaction. The biodistribution study in ICR-mice showed that ${\omega}-[^{18}F]FHA$ has higher myocardial uptake and lower liver uptake than ${\alpha}-[^{18}F]FHA$. The electron-withdrawing effect of fluorine at ${\alpha}-$ position is believed to be the major factor affecting the biodistribution.

Prostate specific membrane antigen (PSMA) is a cell surface membrane protein, which is overexpressed in most prostate cancer. Recently, PET imaging with $[^{68}Ga]$PSMA-HBED-CC has been widely used for the diagnosis of recurrent prostate cancer and the studies on the diagnostic potential of $^{64}Cu$-labeled PSMA ligands reported actively. In this study, we monitored with biological evaluation in vivo and PET imaging of $^{64}Cu$-labeled PSMA ligand ($[^{64}Cu]$PSMA-617). The radiolabelling efficiency and stability of $[^{64}Cu]$PSMA-617 were confirmed by radio-thin layer chromatography. The radiolabeling efficiency of $[^{64}Cu]$PSMA-617 showed over 95%, and stabilities of intact remained over 98% in both human and mouse serum for 48 h. In normal male mice, in vivo uptake of $[^{64}Cu]$PSMA-617 in several organs was measured at 2, 4, 6, 24, 48 h after injection. Rapid blood clearance was observed for $[^{64}Cu]$PSMA-617. The high uptake was observed in the lung, liver, intestines and kidneys at 2 h postinjection, but was low in the other organs (1-2 %ID/g) at 4 h. The dynamic PET/CT images of 22RV1 tumor-bearing nude mice were acquired during 60 min and additionally acquired 24 h and 48 h after injection. In dynamic PET images, $[^{64}Cu]$PSMA-617 uptake ratio in tumors versus muscle was increased as time elaplsed until 60 minutes and remained in tumors at 48 h. In these results, the PET/CT imaging using $[^{64}Cu]$PSMA-617 in prostate cancer is expected to be useful for the diagnosis and treatment of prostate cancer patients.

In our previous study, tricarbonyl $^{99m}Tc$-labeled TSPO-binding ligand, named $^{99m}Tc$-CB256, having positively charge (+1) was investigated but did not show promising results in in vivo environment despite of a nanomolar binding affinity for TSPO. Because the overall positively charge of $^{99m}Tc$-CB256 would likely interrupt its target protein uptake, we herein designed the neutral tricarbonyl-$^{99m}Tc$ labeled TSPO-binding ligand ($^{99m}Tc$-CB257, 1). $^{99m}Tc$-CB257 was prepared by the facile incorporation of the $[^{99m}Tc(CO)_3]^+$ into a N-(hydroxycarbonylmethyl)-2-picoly moiety in CB257. The radiochemical yield of $^{99m}Tc$-CB257 after HPLC purification was $54.1{\pm}2.4%$ (decay corrected, n = 3). The authentic Re-CB257 (2) was synthesized by using $(NEt_4)_2[Re(CO)_3Br_3]$ in 69.0% yield. The binding affinity of 2 for TSPO was measured in leukocyte and showed approximately 280 times higher than that observed for the positively charged (+1) ligand, Re-CB256 ($K_i=0.57{\pm}0.06nM$ versus $159.3{\pm}8.7nM$, respectively). Our results indicated that 1 can be considered potentially as a new SPECT radiotracer for TSPO-rich cancer and provides the foundation for further in vivo evaluation related with abnormal TSPO-overexpression environments.

$[^{13}N]$Ammonia or $[^{13}N]NH_3$ is one of the most widely used PET tracer for the measurement of MBF. To produce $[^{13}N]NH_3$, devarda's alloy which contains aluminum, copper and zinc is used for the purpose of reduction from $^{13}N$-nitrate/nitrite to $[^{13}N]NH_3$. Since aluminum has neurotoxicity and renal toxicity, the amount of it should be carefully limited for the administration to the human body. Although USP and EP provide a way to identify the aluminum ion concentration, there are some difficulties to perform. Therefore, we tried to develop the modified method for verifying aluminum concentration of test solution. We compared color between test and standard solutions using chrome azurol S in pH 4.6 acetate buffer. We also tested color change of test and standard solutions according to pH, amounts and the order of reagent and time difference These results demonstrated that the color change of the solution can reflect quantitatively measure aluminum ion concentration. We hope the method is to be used effectively and practically in many sites where $[^{13}N]NH_3$ is produced.

We demonstrate a detail protocol for the radiosynthesis of an $^{125}I$-labeled MSTP prosthetic group and its application to the efficient radiolabeling of human serum albumin (HSA). Radioiodination of the precursor (2) was carried out by using $[^{125}I]$NaI and chloramine T as an oxidant at room temperature for 15 min. After HPLC purification of the crude product, the purified $^{125}I$-labeled MSTP ($[^{125}I]1$) was obtained with high radiochemical yield ($73{\pm}5%$, n = 3) and excellent radiochemical purity (>99%). Site-specific reaction between ($[^{125}I]1$) and HSA gave the $^{125}I$-labeled human serum albumin ($[^{125}I]3$) with more than 99% of radiochemical yield as determined by radio-thin-layer chromatography (radio-TLC). These results clearly demonstrate that the present radiolabeling method will be useful for the efficient and convenient radiolabeling of thiol-bearing biomolecules.

The potential health risk from inhalational exposure of diesel exhaust particulates (DEP) has gained considerable scientific interests. However, the long-term in vivo behavior of DEP have not been clearly understood due to the difficulty of accurate analysis of these substances in a living subject. We herein demonstrate a detail protocol for the preparation of radiolabeled DEP using a radioactive-iodine-tagged pyrene analog. The purified $^{125}I$-labeled pyrene ($[^{125}I]1$) was obtained with a good radiochemical yield ($32{\pm}4%$, n=3) and high radiochemical purity (>99%) from the stannylated precursor 2. Next, the purified $[^{125}I]1$ was successfully assembled into the DEP suspension in an efficient manner. The radiolabeled DEP was highly stable in a mouse serum for 7 days without significant deiodination or dissociation of $[^{125}I]1$. These results clearly indicate that the present radiolabeling method will be useful for biodistribution study of carbonaceous particulates in vivo.

Recently, South and North Korea summits agreed to implement the cooperation and promotion of medical healthcare at the third inter-Korean summit in Pyeongyang on September 18, 2018. Therefore, the South Korean government and its affiliated organizations have been looking for ways to establish a specific plan for support and exchanges in the field of healthcare and medical technology. In the background of the above new policy, radiation medicine technology can also contribute to the exchange in the field of healthcare and science & technology for the peaceful coexistence of one Korea. In this review, we analyzed and showed the status of healthcare and radiation medicine infrastructure in North Korea in order to further develop a plan to share the benefits of radiation medicine with North Korea in the exchange of healthcare and science & technology.

$^{211}At$ is an alpha emitting radionuclide, which can be produced using cyclotron with alpha beam. In addition, its strong linear energy transfer and iodine-like chemistry make that $^{211}At$ is one of the most attractive radionuclide in the field of targeted alpha therapy. In this review, production, labeling, and radiopharmaceuticals of $^{211}At$ will be discussed.

Angiogenesis is the new blood vessel formation process and has known to a fundamental event of tumor growth and metastasis. Especially, vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFRs) are the crucial regulators of angiogenesis in tumor. VEGF-A is one of the VEGF family and binds to endothelial cell specific VEGFR1 and VEGFR2, which are associated with tumor growth and tumor angiogenesis. $VEGF_{121}$ is more tumorigenic isomer of VEGF-A. Targeted VEGF or VEGFR molecular imaging has been widely used to enable diagnosis and monitoring of proliferation and development of angiogenic tumors. Therefore, in this review, we have focused on the radioligands with $VEGF_{121}$ for angiogenesis of tumor.

In recent years, many researchers have attempted to make use of 2D nanoparticles as molecular imaging probes since extensive investigations proved that 2D nanoparticles in the body tends to accumulate certain lesions by enhanced permeability and retention (EPR) effect. For example, graphene and carbon nitride which have high surface area and modifiable properties showed good biocompatibility and targetability when it used as imaging probes. However, poor dispersibility in physiological mediums and its uncontrolled size limited its usage in bio-application. Therefore, oxidation process and mechanical exfoliation have been developed for overcoming these problems. In this paper, we highlight the several major methods to synthesize biocompatible 2D nanomaterials like graphene and carbon nitride especially for molecular imaging study including positron emission tomography (PET).

Fluoride is one of most important atoms for both clinical and pharmaceutical usage. Associated with such a strong need, $^{18}F$-fluoride has been widely used as an essential radioisotope. The fluoride always suffers from strong solvation effects through strong hydrogen bonding, which reduce the reactivity of fluoride anion. To enhance the reactivity, the concept of naked fluoride was introduced in the fluorination field. In this essay, I will briefly describe the history of naked fluoride concept and development of naked fluoride sources.