• The Korean Journal of Nuclear Medicine Technology
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• v.28 no.1
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• pp.41-47
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• 2024

Purpose: ¹⁸F-FET, a radiopharmaceutical based on a Tyrosine amino acid derivative using the Sodium-Potassium Pump-independent Transporter (System L) for non-invasive evaluation of primary, recurrent, and metastatic brain tumors, exhibits distinct characteristics. Unlike the widely absorbed ¹⁸F-FDG in both tumor and normal brain tissues, ¹⁸F-FET demonstrates specific uptake only in tumor tissue while almost negligible uptake in normal brain tissue. This study aims to compare and evaluate the usefulness of ¹⁸F-FDG and ¹⁸F-FET Brain PET/CT quantitative analysis in brain tumor diagnosis. Materials and Methods: In 46 patients diagnosed with brain gliomas (High Grade: 34, Low Grade: 12), Brain PET/CT scans were performed at 40 minutes after ¹⁸F-FDG injection and at 20 minutes (early) and 80 minutes (delay) after ¹⁸F-FET injection. SUV_max and SUV_peak of tumor areas corresponding to MRI images were measured in each scan, and the SUV_max-to-SUV_peak ratio, an indicator of tumor prognosis, was calculated. Differences in SUV_max, SUV_peak, and SUV_max-to-SUV_peak ratio between ¹⁸F-FDG and ¹⁸F-FET early/delay scans were statistically verified using SPSS (ver.28) package program. Results: SUV_max values were 3.72±1.36 for ¹⁸F-FDG, 4.59±1.55 for ¹⁸F-FET early, and 4.12±1.36 for ¹⁸F-FET delay scans. The highest SUV_max was observed in ¹⁸F-FET early scans, particularly in HG tumors (4.85±1.44), showing a slightly more significant difference (P<0.0001). SUV_peak values were 3.33±1.13 for ¹⁸F-FDG, 3.04±1.11 for ¹⁸F-FET early, and 2.80±0.96 for ¹⁸F-FET delay scans. The highest SUV_peak was in ¹⁸F-FDG scans, while the lowest was in ¹⁸F-FET delay scans, with a more significant difference in HG tumors (P<0.001). SUV_max-to-SUV_peak ratio values were 1.11±0.09 for ¹⁸F-FDG, 1.54±0.22 for ¹⁸F-FET early, and 1.48±0.17 for ¹⁸F-FET delay scans. This ratio was higher in ¹⁸F-FET scans for both HG and LG tumors (P<0.0001), but there was no statistically significant difference between ¹⁸F-FET early and delay scans. Conclusion: This study confirms the usefulness of early and delay scans in ¹⁸F-FET Brain PET/CT examinations, particularly demonstrating the changes in objective quantitative metrics such as SUV_max, SUV_peak, and introducing the SUV_max-to-SUV_peak ratio as a new evaluation metric based on the degree of tumor malignancy. This is expected to further contributions to the quantitative analysis of Brain PET/CT images.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.7 no.2
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• pp.147-152
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• 2021

C-11 Radiolabeled amino acid-based radiopharmaceuticals such as [¹¹C]MET for brain tumor PET imaging have limitations due to their short half-life (20 min). F-18 radiolabeled amino acid derivatives have been developed to overcome for the short half-life, one of which is [¹⁸F]FET. Brain tumor imaging using [¹⁸F]FET showed high uptake in tumor region and no non-specific uptake in inflammatory tissue, which was useful in discriminating the difference between inflammation and tumor especially. In this study, [¹⁸F]FET was synthesized using an automatic synthesis module and quality tests were carried out including enantiomeric purity analysis with reference compounds. Radiochemical yield was 50.3 ± 4.9% (n=7, decay-corrected) with molar activity of 76 ± 17 GBq/mmol. The radiochemical purity of >99%. Enantiomeric purity of [¹⁸F]FET using chiral HPLC analysis showed >99%, which was confirmed by co-injection with the L-FET and D-FET authentic standards. [¹⁸F]FET was prepared with high radiochemical yield and molar activity including no racemate mixture.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.91-96
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• 2005

O-(3-[$^{18}$F]Fluoropropyl)-L-tyrosine (L-[$^{18}$F]FPT) was synthesized by nucleophilic radiofluorination followed by acidic hydrolysis of protective groups and evaluated with 9 L tumor bearing rat. L-[$^{18}$F]FPT is an homologue of O-(2-[$^{18}$F]fluoroethyl)-L-tyrosine (L-[$^{18}$F]FET) which recently is studied as a tracer for tumor imaging using positron emission tomography (PET). [$^{18}$F]FPT was directly prepared from the precursor of O-(3-ptoluenesulfonyloxypropyl)- N-(tert-butoxycarbonyl)-L-tyrosine methyl ester. FPT-PET image was obtained at 60 min in 9 L tumor bearing rats. The radiochemical yield of [$^{18}$F]FPT was 0-45% (decay corrected) and the radiochemical purity was more than 95% after HPLC purification. The total time elapsed for the synthesis of [$^{18}$F]FPT was 100 min from EOB (End-of-bombardment). A comparison of uptake studies between [$^{18}$F]FPT and [$^{18}$F]FET was performed. In biodistribution, [$^{18}$F]FPT showed similar pattern with [$^{18}$F]FET in various tissues, but [$^{18}$F]FPT showed low uptake in brain. Furthermore, [$^{18}$F]FPT showed higher tumor-to-brain ratio than [$^{18}$F]FET. In conclusion, [$^{18}$F]FPT seems to be more useful amino acid tracer than [$^{18}$F]FET for brain tumors imaging with PET.

• Laboraroty Animal Research
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• v.34 no.4
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• pp.248-256
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• 2018

O-2-$^{18}F$-fluoroethyl-l-tyrosine ($[^{18}F]FET$) has been widely used for glioblastomas (GBM) in clinical practice, although evaluation of its applicability in non-clinical research is still lacking. The objective of this study was to examine the value of $[^{18}F]FET$ for treatment evaluation and prognosis prediction of anti-angiogenic drug in an orthotopic mouse model of GBM. Human U87MG cells were implanted into nude mice and then bevacizumab, a representative anti-angiogenic drug, was administered. We monitored the effect of anti-angiogenic agents using multiple imaging modalities, including bioluminescence imaging (BLI), magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET/CT). Among these imaging methods analyzed, only $[^{18}F]FET$ uptake showed a statistically significant decrease in the treatment group compared to the control group (P=0.02 and P=0.03 at 5 and 20 mg/kg, respectively). This indicates that $[^{18}F]FET$ PET is a sensitive method to monitor the response of GBM bearing mice to anti-angiogenic drug. Moreover, $[^{18}F]FET$ uptake was confirmed to be a significant parameter for predicting the prognosis of anti-angiogenic drug (P=0.041 and P=0.007, on Days 7 and 12, respectively, on Pearson's correlation; P=0.048 and P=0.030, on Days 7 and 12, respectively, on Cox regression analysis). However, results of BLI or MRI were not significantly associated with survival time. In conclusion, this study suggests that $[^{18}F]FET$ PET imaging is a pertinent imaging modality for sensitive monitoring and accurate prediction of treatment response to anti-angiogenic agents in an orthotopic model of GBM.

• 대한핵의학회:학술대회논문집
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• 2003.11a
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• pp.11.1-11.1
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• 2003

• Nuclear Medicine and Molecular Imaging
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• v.40 no.5
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• pp.263-270
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• 2006

Purpose: Several radioisotope-labeled thymidine derivatives such as $[^{11}C]$thymidine was developed to demonstrate cell proliferation in tumor. But it is difficult to track metabolism with $[^{11}C]$thymidine due to rapid in vivo degradation and its short physical half-life. 3'-$[^{18}F]$fluoro-3'-deoxythymidine ($[^{18}F]$FLT) was reported to have the longer half life of fluorine-18 and the lack of metabolic degradation in vivo. Here, we described the synthesis of the 3'-$[^{18}F]$fluoro-3'-deoxythymidine ($[^{18}F]$FLT) and compared with $([^{18}F]FET)\;and\;([^{18}F]FDG)$ in cultured 9L cell and obtained the biodistribution and PET image in 9L tumor hearing rats. Material and Methods: For the synthesis of $[^{18}F]$FLT, 3-N-tert-butoxycarbonyl-(5'-O-(4,4'-dimet hoxytriphenylmethyl)-2'-deoxy-3'-O-(4-nitrobenzenesulfonyl)-${\beta}$-D-threopentofuranosyl)thymine was used as a FLT precursor, on which the tert-butyloxycarbonyl group was introduced to protect N3-position and nitrobenzenesulfonyl group. Radiolabeling of nosyl substitued precursor with $^{18}F$ was performed in acetonitrile at $120^{\circ}C$ and deproteced with 0.5 N HCI. The cell uptake was measured in cultured 9L glioma cell. The biodistribution was evaluated in 9L tumor bearing rats after intravenous injection at 10 min, 30 min, 60 min and 120 min and obtained PET image 60 minutes after injection. Results: The radiochemical yield was about 20-30% and radiochemical purity was more than 95% after HPLC purification. Cellular uptake of $[^{18}F]$FLT was increased as time elapsed. At 120 min post-injection, the ratios of tumor/blood, tumor/muscle and tumor/brain were $1.61{\pm}0.34,\;1.70{\pm}0.30\;and\;9.33{\pm}2.22$, respectively. The 9L tumor was well visualized at 60 min post injection in PET image. Conclusion: The uptake of $[^{18}F]$FLT in tumor was higher than in normal brain and PET image of $[^{18}F]$FLT was acceptable. These results suggest the possibility of $[^{18}F]$FLT at an imaging agent for brain tumor.

• 대한핵의학회:학술대회논문집
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• 2002.11a
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• pp.23.2-23.2
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• 2002

• Asian Journal of Business Environment
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• v.4 no.3
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• pp.13-18
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• 2014

Purpose - This study examines students' perspectives (stream-wise) of parameters affecting education quality in an affiliated undergraduate engineering institution in NCR, Haryana. Research design, data, and methodology - This study involves descriptive research and data collection using a structured questionnaire based on the Likert scale. The sample comprises 500 student respondents. For data analysis, an f-test was performed using high quality SPSS software. Results - For "Selection" and "Personality Development & Industry Exposure," the analysis of variance revealed a statistical difference between the mean values of the groups. Whereas, for "Academic Excellence," "Infrastructure," "Placements," and "Management & Administration," the analysis of variance revealed no statistical difference between the mean values of the groups. Conclusions - Students' perceptions about the "Selection" and "Personality Development & Industry Exposure" change according to the various specializations they opt for in their undergraduate engineering education in Haryana. Whereas, for "Academic Excellence," "Infrastructure," "Placements," and "Management & Administration," the perceptions of the students do not vary because of the different specializations they have opted for in their undergraduate engineering education.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.1
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• pp.39-43
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• 2008

Purpose: We evaluated whether it was necessary to perform whole body acquisition of $^{18}F$-FDG PET/CT including whole skull and lower extremity (LE) distal to mid-thigh (MT) in patients with multiple myeloma (MM). Materials and Methods: Thirty patients underwent 45 whole body $^{18}F$-FDG PET/CT scans including skull and LE distal to MT. PET scans were divided by 2 subgroups according to the presence of abnormal focal $^{18}F$-FDG uptake in skull or LE distal to MT. Clinical characteristics including age, sex, and stages were compared between the 2 subgroups. Results: Of total 45 whole body PET/CT scans, focally increased abnormal FDG uptake in the skull or LE distal to MT suggesting myeloma involvement was found in 22 scans (48.9%) of 14 patients (46.7%). Skull lesions were more frequently observed than LE lesions distal to MT on PET (86.4% vs. 40.9%, p<0.005). There were no significant differences in age, sex, initial Durie/Salmon stage, and tumor burden at the time of PET scan suggested by serum hemoglobin level, serum calcium level, serum and urine paraprotein level, and serum creatinine level between the two subgroups. The presence of the skull or LE distal MT lesions on PET did not affect on the Durie/Salmon plus stage except only 1 case (1/22, 4.5%, p>0.05). Conclusion: Abnormal lesions in the skull or LE distal to MT on $^{18}F$-FDG PET/CT did not affect significantly on the tumor burden and Durie/Salmon plus stage of MM. Therefore, torso PET acquisition including head may be sufficient for evaluating patients with MM.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.514-522
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• 2000

In this thesis, a two-dimensional active phased array antenna without phase shifter is studied for two-dimensional beam scanning. A designed two-dimensional oscillator-type active array antenna, radiation elements and the oscillator circuits were combined with via-hole and coupled by slot on the opposite ground plane. The operating characteristics are analyzed and experimentally demonstrated , The two-dimensional $4\times4$ elements were designed for the proper coupling strengths and coupling phases by adjusting the width, length and offset position of slot-lines. The fabricated active phased array antenna shows the beam shift characteristics capable of scanning from $-17^{\circ}$ to $18^{\circ}$ with respect to broadside in one dimension, from $-5^{\circ}$ to $10^{\circ}$ in two dimension. The experimental results show that it is possible to use the oscillator-type active phased array antenna as a two-dimensional planar array antenna.