• 대한방사성의약품학회지
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• 제2권1호
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• pp.37-42
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• 2016

The translocator protein (TSPO) has attracted scientist's attention for Positron Emission Tomography (PET) imaging due to correlation with brain cancer, stroke, and neurodegeneration. Recently, GE-180, a novel tricyclic derivative has been developed as a new high affinity agent for the TSPO and evaluated to confirm a possibility for the TSPO ligand. In this highlight review, several studies for the novel TSPO radiotracer are described.

• 대한방사성의약품학회지
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• 제5권1호
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• pp.36-47
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• 2019

Hypoxia-inducible factor-1 ($HIF-1{\alpha}$) is a transcription factor activated in response to low oxygen level, and is highly expressed in many solid tumors. Moreover, $HIF-1{\alpha}$ is a representative biomarker of hypoxia and also helps to maintain cell homeostasis under hypoxic condition. Most solid tumors show hypoxia, which induces poor prognosis and resistance to conventional cancer therapies. Thus, early diagnosis of hypoxia with positron emission tomography (PET) radiotracer would be highly beneficial for management of malignant solid tumors with effective cancer therapy. YC-1 is a most promising candidate among several $HIF-1{\alpha}$ inhibitors. As an effort to develop a hypoxia imaging tool as a PET radiotracer, we designed and synthesized [$^{18}F$]DFYC based on potent derivative of YC-1 and performed preliminary in vitro cell uptake study. [$^{18}F$]DFYC showed a significant accumulation in SKBR-3 cells among other cancer cells, proving as a good lead to develop a hypoxic solid tumor such as breast cancer.

• 한국의학물리학회지:의학물리
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• 제22권4호
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• pp.172-177
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• 2011

본 연구에서는 소동물의 심근에서 $^{68}Ga$-BAPEN PET 영상분석을 통해 심혈 영상 추적자로서의 적용가능성을 보고자 하였다. 소동물용 PET/CT에서 쥐 9마리를 대상으로 120분간의 $^{68}Ga$-BAPEN PET/CT 스캔을 시행하였다. 특별히 킷트를 통해 간편하고 저비용으로 $^{68}Ga$-BAPEN을 합성이 가능하였다. PET 영상은 쥐의 몸통부분에서 $^{68}Ga$-BAPEN의 생체 동적분포를 나타낸다. $^{68}Ga$-BAPEN PET 영상은 처음 수분간 대동맥과 간에서의 섭취가 나타났고 점차 심근에서의 섭취가 이루어졌다. 관심영역은 좌심근, 심혈, 폐, 간에 그렸고 시간-방사능 곡선을 얻었다. 시간-방사능 곡선에서 $^{68}Ga$-BAPEN이 쥐 심근에 잘 결합하는 것을 확인 할 수 있었다. 정확한 약동학적 파라미터 도출을 위한 최소 PET 스캔시간은 타장 기와의 영상 대조도가 일정비에 이르는 주사 후 60분이 적합하였다. 이때 심근의 섭취를 심혈, 간, 폐에서의 섭취로 나누어 얻은 영상 대조도는 각각 1.66, 0.60, 2.82였다. 결론적으로 $^{68}Ga$-BAPEN은 심근 혈류 질환을 진단하기 위한 추적자로서 적합하며 지속적인 연구가 이루어진다면 임상에서의 진단활용에 도움이 될 것이라 예상된다.

• 대한방사성의약품학회지
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• 제3권2호
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• pp.91-97
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• 2017

$^{18}F-THK-5351$ is a PET radiotracer to image the hyperphosphorylated tau fibrillar aggregates in human brain. This protocol describes the optimized radiosynthesis of $^{18}F-THK-5351$ using a commercial GE $TRACERlab^{TM}$ $FX_{FN}$ radiosynthesis module. $^{18}F-THK-5351$ was prepared by nucleophilic [$^{18}F$]fluorination from its protected tosylate precursors, (S)-(2-(2-methylaminopyrid-5-yl)-6-[[2-(tetrahydro-2H-pyran-2-yloxy)-3-tosyloxy]propoxy] quinolone(THK-5352), at $110^{\circ}C$ for 10 min in dimethyl sulfoxide, followed by deprotection with 1 N HCl. The average radiochemical yield of $^{18}F-THK-5351$ was $31.9{\pm}6.7%$(decay-corrected, n = 10), with molar activity of $198.1{\pm}33.9GBq/{\mu}mol$($5.4{\pm}0.9Ci/{\mu}mol$, n = 10). The radiochemical purity was determined to be above 98%. The overall production time including HPLC purification is approximately 70 min. This fully-automated protocol is validated for clinical use.

• 한국의류학회지
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• 제16권1호
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• pp.65-71
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• 1992

The influences of hydrophilic treatment of the PET fabric on soiling and detergency of triolein were studied. The amounts of residual triolein were determined by radiotracer analysis, and distributions of the unsaturated oils on the fabric were evaluated by backscattered electron images. The removal of triolein was increased when the PET fabrics were treated. SRP pretreatment was more effective on the oily soil removal than the of addition of SRP in the detergent. The oily soil of triolein only was packed between the fibers, but mixed soil was distributed around the fibers. When the mixed soil was used, detergent solution could penetrate the continuous interfiber capillaries, this would be one of the reasons that mixed soil was removed rmore extensively.

• 대한방사성의약품학회지
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• 제1권1호
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• pp.15-22
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• 2015

$^{18}F$-labeling reaction of bioactive molecule via click chemistry is widely used to produce $^{18}F$-labeled radiotracer in the field of radiopharmaceutical science and molecular imaging. In particular, bioorthogonal strain-promoted alkyne-azide cycloaddition (SPAAC) reaction has received much attention as an alternative ligation method for radiolabeling bioactive molecules such as peptides, DNA, proteins as well as nanoparticles. Moreover, SPAAC based pretargeting method could provide tumor images successfully on positron emission tomography system using nanoparticle such as mesoporous silica nanoparticles.

• 대한핵의학회지
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• 제38권2호
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• pp.198-204
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• 2004

Tumor cell proliferation is considered to be a useful prognostic indicator of tumor aggressiveness and tumor response to therapy but in vitro measurement of individual proliferation is complex and tedious work. PET imaging provides a noninvasive approach to measure tumor growth rate in situ. Early approaches have used $^{18}F$-FDG or methionine to monitor proliferation status. These 2 tracers detect changes in glucose and amino acid metabolism, respectively, and therefore provide only an indirect measure of proliferation status. More recent studies have focused on DNA synthesis itself as a marker of cell proliferation. Cell lines and tissues with a high proliferation rate require high rates of DNA synthesis. $[^{11}C]Thymidine$ was the first radiotracer for noninvasive imaging of tumor proliferation. The short half-life of $^{11}C$ and rapid metabolism of $[^{11}C]Thymidine$ in vivo make the radiotracer less suitable for routing use. Halogenated thymidine analogs such as 5-iodo-2-deoxyuridine (IUdR) can be successfully used as cell proliferation markers for in vitro studies because these compounds are rapidly incorporated into newly synthesized DNA. IUdR has been evaluated as a potential in vivo tracer in nuclear medicing but the image qualify and the calculation of proliferation rates are impaired by its rapid in vivo degradation. Hence, the thymidine analog $3'-deoxy-3'-^{18}F-fluorothymidine$ (FLT) was recently introduced as a stable proliferation marker with a suitable nuclide half-life and stable in vivo. $[^{18}F]FLT$ is phosphorylated to 3-fluorothymidine monophosphate by thymidine kinase 1 and reflects thymidine kinase 1 activity in proliferating cell. $[^{18}F]FLT$ PET is feasible in clincal use and well correlates with cellular proliferation. Choline is a precursor for the biosynthesis of phospholipids (in particular, phosphatidylcholine), which is the essential component of all eukaryotic cell membranes and $[^{11}C]choline$, which is a new marker for cellular proliferation.

• 핵의학기술
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• 제27권2호
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• pp.111-127
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• 2023

Purpose: Gallium-68 (⁶⁸Ga) is increasingly used in nuclear medicine imaging for various conditions such as lymphoma and neuroendocrine tumors by labeling tracers like Prostate Specific Membrane Antigen (PSMA) and DOTA-TOC. However, compared to Fluorine-18 (¹⁸F) used in conventional nuclear medicine imaging, ⁶⁸Ga has lower spatial resolution and relatively higher Signal to Background Ratio (SBR). Therefore, this study aimed to investigate the optimized parameters and reconstruction methods for PET/CT imaging using the ⁶⁸Ga radiotracer through model-based image evaluation. Materials and Methods: Based on clinical images of ⁶⁸Ga-PSMA PET/CT, a NEMA/IEC 2008 PET phantom model was prepared with a Hot vs Background (H/B) ratio of 10:1. Images were acquired for 9 minutes in list mode using DMIDR (GE, Milwaukee WI, USA). Subsequently, reconstructions were performed for 1 to 8 minutes using OS-EM (Ordered Subset Expectation Maximization) + TOF (Time of Flight) + Sharp IR (VPFX-S), and BSREM (Block Sequential Regularized Expectation Maximization) + TOF + Sharp IR (QCFX-S-400), followed by comparative evaluation. Based on the previous experimental results, images were reconstructed for BSREM + TOF + Sharp IR / 2 minutes (QCFX-S-2min) with varying β-strength values from 100 to 700. The image quality was evaluated using AMIDE (freeware, Ver.1.0.1) and Advanced Workstation (GE, USA). Results: Images reconstructed with QCFX-S-400 showed relatively higher values for SNR (Signal to Noise Ratio), CNR (Contrast to Noise Ratio), count, RC (Recovery Coefficient), and SUV (Standardized Uptake Value) compared to VPFX-S. SNR, CNR, and SUV exhibited the highest values at 2 minutes/bed acquisition time. RC showed the highest values for a 10 mm sphere at 2 minutes/bed acquisition time. For small spheres of 10 mm and 13 mm, an inverse relationship between β-strength increase and count was observed. SNR and CNR peaked at β-strength 400 and then decreased, while SUV and RC exhibited a normal distribution based on sphere size for β-strength values of 400 and above. Conclusion: Based on the experiments, PET/CT imaging using the ⁶⁸Ga radiotracer yielded the most favorable quantitative and qualitative results with a 2 minutes/bed acquisition time and BSREM reconstruction, particularly when applying β-strength 400. The application of BSREM can enhance accurate quantification and image quality in ⁶⁸Ga PET/CT imaging, and an optimization process tailored to each institution's imaging objectives appears necessary.

• Nuclear Medicine and Molecular Imaging
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• 제43권4호
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• pp.253-258
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• 2009

Bone scintigraphy using $^{99m}$Tc-labeled phosphate agents has long been the standard evaluation method for whole skeletal system. However, recent shortage of $^{99m}$Tc supply and advanced positron emission tomography (PET) technology evoked the attention to surrogate radiopharmaceuticals and imaging modalities for bone. Actually, fluorine-18 ($^{18}$F) was the first bone seeking radiotracer before the introduction of $^{99m}$Tc-labeled agents even though its clinical application failed to become pervasive anymore after the rapid spread of Anger type gamma camera systems in early 1970s. However, rapidly developed PET technology made us refocus on the usefulness of $^{18}$F as a PET tracer. Early study comparing $^{18}$F-Na PET scan and planar bone scintigraphy reported that PET has higher sensitivity and specificity in the diagnosis of metastatic bone lesions than planar bone scan. Subsequent reports comparing between PET and both planar and SPECT bone image also revealed better results of PET scan in similar study groups. Rapid clinical application of PET/CT also accumulated considerable amount of experiences in skeletal evaluation and this modality is known to have better diagnostic power than stand alone PET system as well as bone scan. Furthermore $^{18}$F-Na PET/CT revealed better or at least equal results in detection of primary and metastatic bone lesions compared with CT and MRI. Therefore, it is obvious that $^{18}$F-Na PET/CT has potential to become new imaging modality for practical skeletal evaluation so continuous and careful evaluation of this modality and radiopharmaceutical must be required.

• 대한방사성의약품학회지
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• 제2권2호
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• pp.69-72
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• 2016

Since the translocator protein (TSPO) is involved in neurodegeneration diseases, many scientists' interest has been focused on the development of a ligand targeting TSPO. A novel compound based on pyrazolo[1,5 -a] pyrimidine structure, DPA-714, has been studied and considered as a TSPO ligand with high affinity. In this highlight review, several researches for the novel radioligand for the translocator protein are illustrated.