• Journal of radiological science and technology
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• v.40 no.1
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• pp.79-85
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• 2017

The purpose of this study was to measure contrast to noise ratio (CNR) and signal to noise ratio (SNR) according to change of reconstruction from region of interest (ROI) in breast positron emission tomography-computed tomography (PET-CT), and to analyze the CNR and SNR statically. We examined images of breast PET-CT of 100 patients in a University-affiliated hospital, Seoul, Korea. Each patient's image of breast PET-CT were calculated by using ImageJ. Differences of CNR and SNR among four reconstruction algorithms were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p<0.05). We have analysis socio-demographical variables, CNR and SNR according to reconstruction images, 95% confidence according to CNR and SNR of reconstruction and difference in a mean of CNR and SNR. SNR results, with the quality of distributions in the order of PSF_TOF, Iterative and Iterative-TOF, FBP-TOF. CNR, with the quality of distributions in the order of PSF_TOF, Iterative and Iterative-TOF, FBP-TOF. CNR and SNR of PET-CT reconstruction methods of the breast would be useful to evaluate breast diseases.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.776-780
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• 2017

To avoid imaging artifacts and interpretation mistakes, an improvement of the uniformity in gamma camera systems is a very important point. We can expect excellent uniformity using cadmium zinc telluride (CZT) photon counting detector (PCD) because of the direct conversion of the gamma rays energy into electrons. In addition, the uniformity performance such as integral uniformity (IU), differential uniformity (DU), scatter fraction (SF), and contrast-to-noise ratio (CNR) varies according to the energy window setting. In this study, we compared a PCD and conventional scintillation detector with respect to the energy windows (5%, 10%, 15%, and 20%) using a $^{99m}Tc$ gamma source with a Geant4 Application for Tomography Emission simulation tool. The gamma camera systems used in this work are a CZT PCD and NaI(Tl) conventional scintillation detector with a 1-mm thickness. According to the results, although the IU and DU results were improved with the energy window, the SF and CNR results deteriorated with the energy window. In particular, the uniformity for the PCD was higher than that of the conventional scintillation detector in all cases. In conclusion, our results demonstrated that the uniformity of the CZT PCD was higher than that of the conventional scintillation detector.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2367-2370
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• 2014

"Cat's eye"-shaped $[^{57}Co]CoO@SiO_2$ core-shell nanostructure was prepared by the reverse microemulsion method combined with radioisotope technique to investigate a potential imaging agent for a single photon emission computed tomography (SPECT) in nuclear medicine. The core cobalt oxide nanorods were obtained by thermal decomposition of $Co-(oleate)_2$ precursor from radio isotope Co-57 containing cobalt chloride and sodium oleate. The $SiO_2$ coating on the surface of the core cobalt oxide nanorods was produced by hydrolysis and a condensation reaction of tetraethylorthosilicate (TEOS) in the water phase of the reverse microemulsion system. In vivo test, micro SPECT image was acquired with nude mice after 30 min of intravenous injection of $[^{57}Co]CoO@SiO_2$ core-shell nanostructure.

• The Korean Journal of Nuclear Medicine
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• v.17 no.1
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• pp.55-62
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• 1983

In 16 volunteers without clinical or laboratory evidence of liver disease, liver volume was determined using single-photon emission computed tomography(ECT). This technique provided excellent object contrast between the liver and its surroundings and permitted calculation of liver volume without geometric assumptions about the liver's configuration. Reproducibility of results was satisfactory, with a root-me an-square error of less than 2% between duplicate measurements in 16 individuals. The volume measurements were validated by the use of phantoms.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3943-3948
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• 2022

Single-photon emission computed tomography is one of the reliable pin-by-pin verification techniques for spent-fuel assemblies. One of the challenges with this technique is to increase the total fuel assembly verification speed while maintaining high verification accuracy. The aim of the present study, therefore, was to develop an artificial intelligence (AI) algorithm-based tomographic image analysis technique for partial-defect verification of fuel assemblies. With the Monte Carlo (MC) simulation technique, a tomographic image dataset consisting of 511 fuel-rod patterns of a 3 × 3 fuel assembly was generated, and with these images, the VGG16, GoogLeNet, and ResNet models were trained. According to an evaluation of these models for different training dataset sizes, the ResNet model showed 100% pattern estimation accuracy. And, based on the different tomographic image qualities, all of the models showed almost 100% pattern estimation accuracy, even for low-quality images with unrecognizable fuel patterns. This study verified that an AI model can be effectively employed for accurate and fast partial-defect verification of fuel assemblies.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1527-1532
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• 2023

The noise reduction algorithm using the non-local means (NLM) approach is very efficient in nuclear medicine imaging. In this study, the applicability of the NLM noise reduction algorithm in single-photon emission computed tomography (SPECT) images with a brain phantom and the optimization of the NLM algorithm by changing the smoothing factors according to various reconstruction methods are investigated. Brain phantom images were reconstructed using filtered back projection (FBP) and ordered subset expectation maximization (OSEM). The smoothing factor of the NLM noise reduction algorithm determined the optimal coefficient of variation (COV) and contrast-to-noise ratio (CNR) results at a value of 0.020 in the FBP and OSEM reconstruction methods. We confirmed that the FBP- and OSEM-based SPECT images using the algorithm applied with the optimal smoothing factor improved the COV and CNR by 66.94% and 8.00% on average, respectively, compared to those of the original image. In conclusion, an optimized smoothing factor was derived from the NLM approach-based algorithm in brain SPECT images and may be applicable to various nuclear medicine imaging techniques in the future.

• Journal of Gastric Cancer
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• v.18 no.3
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• pp.218-229
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• 2018

Purpose: This study investigated whether the metabolic avidity of primary tumors and/or metastatic lymph nodes (LNs) measured by $^{18}F$-fluorodeoxyglucose ($^{18}F-FDG$) positron emission tomography/computed tomography (PET/CT) was related to survival after surgery in patients with advanced gastric cancer (AGC). Materials and Methods: One hundred sixty-eight patients with AGC who underwent preoperative $^{18}F-FDG$ PET/CT and curative resection were included. The $^{18}F-FDG$ avidity of the primary gastric tumor and LNs was determined quantitatively and qualitatively. The diagnostic performance of $^{18}F-FDG$ PET/CT was calculated, and the prognostic significance of $^{18}F-FDG$ avidity for recurrence-free survival (RFS) and overall survival (OS) was assessed. Results: In all, 51 (30.4%) patients experienced recurrence, and 32 (19.0%) died during follow-up (median follow-up duration, 35 months; range, 3-81 months); 119 (70.8%) and 33 (19.6%) patients showed $^{18}F-FDG$-avid primary tumors and LNs, respectively. $^{18}F-FDG$ PET/CT showed high sensitivity (73.8%) for the detection of advanced pathologic T ($pT{\geq}3$) stage and high specificity (92.2%) for the detection of advanced pN (${\geq}2$) stage. $^{18}F-FDG$ avidity of LNs was significantly associated with RFS (P=0.012), whereas that of primary tumors did not show significance (P=0.532). Univariate and multivariate analyses revealed that $^{18}F-FDG$ avidity of LNs was an independent prognostic factor for RFS (hazard ratio=2.068; P=0.029). Conclusions: $^{18}F-FDG$ avidity of LNs is an independent prognostic factor for predicting RFS. Preoperative $^{18}F-FDG$ PET/CT can be used to determine the risk and prognosis of patients with AGC after curative resection.

• Journal of Gynecologic Oncology
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• v.29 no.6
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• pp.98.1-98.13
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• 2018

Objective: We describe a systematic review and meta-analysis of the performance of ${18}F$-fluorodeoxyglucose ($^{18}F-FDG$) positron emission tomography/computed tomography (PET/CT) for detecting metastasis in ovarian cancer. Methods: MEDLINE and Embase were searched for diagnostic accuracy studies that used $^{18}F-FDG$ PET or PET/CT for pre-treatment staging, using surgical findings as the reference standard. Sensitivities and specificities were pooled and plotted in a hierarchic summary receiver operating characteristic plot. Potential causes of heterogeneity were explored through sensitivity analyses. Results: Eight studies with 594 patients were included. The overall pooled sensitivity and specificity for metastasis were 0.72 (95% confidence interval [CI]=0.61-0.81) and 0.93 (95% CI=0.85-0.97), respectively. There was considerable heterogeneity in sensitivity ($I^2=97.57%$) and specificity ($I^2=96.74%$). In sensitivity analyses, studies that used laparotomy as the reference standard showed significantly higher sensitivity and specificity (0.77; 95% CI=0.67-0.87 and 0.96; 95% CI=0.92-0.99, respectively) than those including diagnostic laparoscopy (0.62; 95% CI=0.46-0.77 and 0.84; 95% CI=0.69-0.99, respectively). Higher specificity was shown in studies that confirmed surgical findings by pathologic evaluation (0.95; 95% CI=0.90-0.99) than in a study without pathologic confirmation (0.69; 95% CI=0.24-1.00). Studies with a lower prevalence of the FDG-avid subtype showed higher specificity (0.97; 95% CI=0.94-1.00) than those with a greater prevalence (0.89; 95% CI=0.80-0.97). Conclusion: Pre-treatment $^{18}F-FDG$ PET/CT shows moderate sensitivity and high specificity for detecting metastasis in ovarian cancer. With its low false-positive rate, it can help select surgical approaches or alternative treatment options.

• Journal of the Korean Orthopaedic Association
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• v.56 no.5
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• pp.398-403
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• 2021

Purpose: A biopsy is needed to diagnose soft tissue tumors. However, it is extremely difficult to pinpoint the site of a tumor due to the heterogeneity of sarcomas. Thus, even when an open biopsy is conducted, it is difficult to diagnose a soft tissue tumor. In such cases, an ultrasound (US)-guided biopsy is used to improve the diagnostic accuracy. This study evaluated the accuracy of US-guided biopsy for a diagnosis of soft tissue tumors found initially in a magnetic resonance (MR) perfusion and assessed the availability of positron emission tomography-computed tomography (PET-CT) for a diagnosis of soft tissue tumors. Materials and Methods: From January 2014 to December 2018, the US-guided biopsy was performed on 152 patients with a suspected soft tissue tumor found in an MR perfusion and 86 cases were definitively diagnosed with a soft tissue tumor. The accuracy of the US-guided biopsy was assessed retrospectively. Among the 86 cases, only MR perfusion was used before the biopsy in 50 cases, while both MR perfusion and PET-CT was conducted on 36 cases. The accuracy was analyzed to determine if the PET-CT could improve the precision of a biopsy. Results: From 86 cases, 34 out of 50 cases, in which only MR perfusion had been conducted, matched the result of the definitive diagnosis and the US-guided biopsy. 32 out of 36 cases, in which both PET-CT and MR perfusion were conducted, matched the definitive diagnosis and the US-guided biopsy. These results show significant differences in the accuracy of US-guided biopsy. In the case of soft tissue sarcomas, 6 out of 12 cases, in which only MR perfusion had been conducted, matched the result of the definitive diagnosis and the US-guided biopsy. 17 out of 18 cases, in which both PET-CT and MR perfusion were conducted, matched the definitive diagnosis. Moreover US-guided biopsy also showed significant differences in the accuracy of US-guided biopsy. Conclusion: In diagnosing soft tissue tumors, a US-guided biopsy is a well-known tool for its high accuracy. However, the heterogeneity of sarcoma makes it difficult to locate the exact site for a biopsy using only MR perfusion. Thus, the use of PET-CT will meaningfully improve the accuracy of a diagnosis by precisely targeting the site for the US-guided biopsy.

• Journal of Biomedical Engineering Research
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• v.26 no.5
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• pp.283-294
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• 2005

The Center for Imaging Human Structures (CIH) was established in December 2002 to develop new diagnostic imaging techniques and to make them available to the greater community of biomedical and clinical researchers at Sungkyunkwan University. CIH has been involved in 5 specific activities to provide solutions for early diagnosis and improved treatment of human diseases. The five area goals include: 1) development of a digital mammography system with computer aided diagnosis (CAD); 2) development of digital radiological imaging techniques; 3) development of unified medical solutions using 3D image fusion; 4) development of multi-purpose digital endoscopy; and, 5) evaluation of new imaging systems for clinical application