• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.808-809
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• 2006

The decrease of the distance between particle centers due to the growth of the sinter necks can be explained by the well known two-particle model. Unfortunately this model fails to provide a comprehensive description of the processes for 3D specimens. Furthermore, there is a significant discrepancy between the calculated and the measured shrinkage because particle rearrangements are not considered. Only the recently developed analysis of the particle movements inside of 3D specimens using micro focus computed tomography $({\mu}CT)$, combined with photogrammetric image analysis, can deliver the necessary experimental data to improve existing sintering theories. In this work, ${\mu}CT$ analysis was applied to spherical copper powders. Based on photogrammetric image analysis, it is possible to determine the positions of all particle centers for tracking the particles over the entire sintering process and to follow the formation and breaking of the particle bonds. In this paper, we present an in-depth analysis of the obtained data. In the future, high resolution synchrotron radiation tomography will be utilized to obtain in-situ data and images of higher resolution.

• Korean Journal of Radiology
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• 제1권1호
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• pp.51-55
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• 2000

Objective: To determine the accuracy of CT and positron emission tomography (PET) in the diagnosis of recurrent uterine cervical cancer. Materials and Methods: Imaging findings of CT and PET in 36 patients (mean age, 53 years) in whom recurrent uterine cervical cancer was suspected were analyzed retrospectively. Between October 1997 and May 1998, they had undergone surgery and/or radiation therapy. Tumor recurrence was confirmed by pathologic examination or follow-up studies. Results: In detecting recurrent uterine cervical cancer, the sensitivity, specificity, and accuracy of CT were 77.8%, 83.3%, and 80.5%, respectively, while for PET, the corresponding figures were 100%, 94.4%, and 97.2%. The Chi-square test revealed no significant difference in specificity (p = .2888), but significant differences in sensitivity (p = .0339) and accuracy (p = .0244). Conclusion: PET proved to be a reliable screening method for detecting recurrent uterine cervical cancer, but to determine the anatomical localization of recurrent tumors, and thus decide an adequate treatment plan, CT was eventually needed.

• 대한방사선방어학회:학술대회논문집
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• 대한방사선방어학회 2009년도 추계 학술발표
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• pp.46-47
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• 2009

• Radiation Oncology Journal
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• 제29권4호
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• pp.277-282
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• 2011

Purpose: This study was performed to evaluate the change in the lumpectomy cavity volumes before and after whole breast radiation therapy (WBRT) and to identify factors associated with the change of volume. Materials and Methods: From September 2009 to April 2010, the computed tomography (CT) simulation data from 70 patients obtained before and after WBRT was evaluated. The lumpectomy cavity volumes were contoured based on surgical clips, seroma, and postoperative changes. Significant differences in the data from pre-WBRT CT and post-WBRT CT were assessed. Multiple variables were examined for correlation with volume reduction in the lumpectomy cavity. Results: The mean and median volume reduction in the lumpectomy cavity after WBRT were 17.6 $cm^3$ and 16.1 $cm^3$, respectively with the statistical significance (p < 0.001). The volume reduction in the lumpectomy cavity was inversely correlated with time from surgery to radiation therapy (R = 0.390). The presence of seroma was significantly associated with a volumetric change in the lumpectomy cavity after WBRT (p = 0.011). Conclusion: The volume of lumpectomy cavity reduced significantly after WBRT. As the time from surgery to the start ot WBRT increased, the volume reduction in the lumpectomy cavity during WBRT decreased. A strong correlation was observed between the presence of seroma and the reduced volume. To ensure appropriate coverage and to limit normal tissue exposure during boost irradiation in patients who has seroma at the time of starting WBRT, repeating CT simulation at boost planning is suggested.

• Journal of Digital Convergence
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• 제10권11호
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• pp.449-457
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• 2012

The purpose of this study is to investigate the relationship between radiation origin and health professionals, and to reduce exposed dose of radiation through efficient management. Increasing exposed dose of radiation to health professionals are caused by the increase of PET/CT use and a radioactive isotope. Hence, in this study, space dose from each origin of radiation generating was analyzed and the use of personnel protective clothing and shields was compared. As a result of this study, we confirmed that the exposed dose of radiation was much higher in case of wearing personnel protective clothing(0.5 mm pb) than no wearing personnel protective clothing under high energy gamma radiation(511 keV) of the position emitter($^{18}F$).

• Korean Journal of Radiology
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• 제23권5호
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• pp.517-528
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• 2022

Due to its excellent diagnostic performance, CT is the mainstay of diagnostic test in adults with suspected acute appendicitis in many countries. Although debatable, extensive epidemiological studies have suggested that CT radiation is carcinogenic, at least in children and adolescents. Setting aside the debate over the carcinogenic risk of CT radiation, the value of judicious use of CT radiation cannot be overstated for the diagnosis of appendicitis, considering that appendicitis is a very common disease, and that the vast majority of patients with suspected acute appendicitis are adolescents and young adults with average life expectancies. Given the accumulated evidence justifying the use of low-dose CT (LDCT) of only 2 mSv, there is no reasonable basis to insist on using radiation dose of multi-purpose abdominal CT for the diagnosis of appendicitis, particularly in adolescents and young adults. Published data strongly suggest that LDCT is comparable to conventional dose CT in terms of clinical outcomes and diagnostic performance. In this narrative review, we will discuss such evidence for reducing CT radiation in adolescents and young adults with suspected appendicitis.

• Radiation Oncology Journal
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• 제33권2호
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• pp.126-133
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• 2015

Purpose: To evaluate the outcomes of adjuvant radiotherapy (RT) and to analyze prognostic factors of survival in the International Federation of Gynecology and Obstetrics (FIGO) IB-IIA uterine cervical cancer. Materials and Methods: We retrospectively reviewed the medical records of 148 patients with FIGO IB-IIA uterine cervical cancer who underwent surgery followed by adjuvant RT at the Yonsei Cancer Center between June 1997 and December 2011. Adjuvant radiotherapy was delivered to the whole pelvis or an extended field with or without brachytherapy. Among all patients, 57 (38.5%) received adjuvant chemotherapy either concurrently or sequentially. To analyze prognostic factors, we assessed clinicopathologic variables and metabolic parameters measured on preoperative 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT). To evaluate the predictive performance of metabolic parameters, receiver operating characteristic curve analysis was used. Overall survival (OS) and disease-free survival (DFS) were analyzed by the Kaplan-Meier method. Results: The median follow-up period was 63.2 months (range, 2.7 to 206.8 months). Locoregional recurrence alone occurred in 6 patients, while distant metastasis was present in 16 patients, including 2 patients with simultaneous regional failure. The 5-year and 10-year OSs were 87.0% and 85.4%, respectively. The 5-year and 10-year DFSs were 83.8% and 82.5%, respectively. In multivariate analysis, pathologic type and tumor size were shown to be significant prognostic factors associated with both DFS and OS. In subset analysis of 40 patients who underwent preoperative PET/CT, total lesion glycolysis was shown to be the most significant prognostic factor among the clinicopathologic variables and metabolic parameters for DFS. Conclusion: Our results demonstrated that adjuvant RT following hysterectomy effectively improves local control. From the subset analysis of preoperative PET/CT, we can consider that metabolic parameters may hold prognostic significance in early uterine cervical cancer patients. More effective systemic treatments might be needed to reduce distant metastasis in these patients.

• Journal of the Korean Society of Radiology
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• 제7권5호
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• pp.365-369
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• 2013

Intravenous injection is administered with radioactive medical isotopes to detect disease on Positron Emission Tomography (PET). In this case, typically, $^{18}FDG$ (Fluorodeoxyglucose) is used as a radioactive medicine. Cassette equipment is needed to synthesize deoxyglucose with $^{18}F$, produced by medical cyclotron. Production of radioactive medicine creates a lot of radiation, thus Hot Cell is used to shield a secondary radiation. We measured the radiation dosage flowing out of the hot cell during synthesis of $^{18}FDG$ or distribution. The purpose of this study is to provide the information of radiation dosage regarding the occupational exposure that unintentionally occurs during the synthesis of $^{18}FDG$. In conclusion, we confirmed the radiation dosage out of the hot cell during the $^{18}FDG$ synthesis. Especially, we observed that the radiation flowed out through the lead window, attached as a view port. Thus, it is considered that the improvement of a lead window is necessary in order to decrease the occupational exposure during the $^{18}FDG$ synthesis.

• The Journal of Korean Society for Radiation Therapy
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• 제22권1호
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• pp.19-24
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• 2010

Purpose: To study the efficacy of marker match with using kilovoltage (KV) X-ray among multiple image guidance that referring tree fiducial marker in radiation therapy for prostate cancer patients. Materials and Methods: KV two-dimantional images (anterior-posterior, right-left) and cone-beam CT volumetric images were acquired after setup for patients with three fiducial markers. Compare the position of the fiducial marker of reference plan computed tomography (CT) and of KV, CBCT images; then decide the shift score of X, Y, and Z. This study executed 5 times on 10 patients and analyzed the shift value. Results: In the radiation therapy using fiducial marker, The function of marker match showed the same direction tendency as the CBCT, and showed X, Y, Z difference of about 0.6, 0.7, and 0.8 (unit: mm). Conclusion: Comparing to this, the result of shift value using 2D marker match showed less than 1.0 mm difference. The function of marker match is considered more useful in time-wise and effective dose rather than CBCT. Therefore, Both methods are used to treat patients for prostate cancer.

• Asian Pacific Journal of Cancer Prevention
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• 제14권5호
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• pp.2925-2929
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• 2013

Objective: To explore the relationships between primary tumor $^{18}F$-FDG uptake measured as the SUVmax and local extension, and nodal or distant organ metastasis in patients with NSCLC on pretreatment PET-CT. Methods: 93 patients with NSCLC who underwent $^{18}F$-FDG PET-CT scans before the treatment were included in the study. Primary tumor SUVmax was calculated; clinical stages, presence of local extension, nodal and distant organ metastases were recorded. The patients with SUVmax${\geq}2.5$ were divided into low and high SUVmax groups by using the median SUVmax. The low SUVmax group consisted of 45 patients with SUVmax<10.5, the high SUVmax group consisted of 46 patients with SUVmax${\geq}10.5$. Their data were compared statistically. Results: 91 cases with SUVmax${\geq}2.5$ were included for analysis. The mean SUVmax in patients without any metastasis was $7.42{\pm}2.91$ and this was significantly lower than that ($12.18{\pm}4.94$) in patients with nodal and/or distant organ metastasis (P=0.000). In the low SUV group, 19 patients had local extension, 22 had nodal metastasis, and 9 had distant organ metastasis. In the high SUV group, 31 patients had local extension, 37 had nodal metastasis, and 18 had distant organ metastases. There was a significant difference in local extension (P =0.016), distant organ metastasis (P =0.046), and most significant difference in nodal metastasis rate (P =0.002) between the two groups. In addition, there was a moderate correlation between SUVmax and tumor size (r = 0.642, P<0.001), tumor stage (r = 0.546, P<0.001), node stage (r = 0.388, P<0.001), and overall stage (r = 0.445, P= 0.000). Conclusion: Higher primary tumor SUVmax predicts higher extensional or metastatic potential in patients with NSCLC. Patients with higher SUVmax may need a close follow-up and more reasonable individual treatment because of their higher extensional and metastatic potential.