Nam-Gil Choi

Working memory dysfunction associated with brain functional deficits and cellular metabolic changes in patients with generalized anxiety disorder.

Generalized anxiety disorder (GAD) is associated with brain functional and morphological changes in connected with emotional dysregulation and cognitive deficit. This study dealt with the neural functional deficits and metabolic abnormalities in working memory (WM) task with emotion-inducing distractors in patients with GAD. Fourteen patients with GAD and 14 healthy controls underwent functional magnetic resonance imaging (fMRI) and proton magnetic resonance spectroscopy ((1)H-MRS) at 3T. In response to the emotional distractors in WM tasks, the patients concurrently showed higher activity in the hippocampus and lower activities in the superior occipital gyrus, superior parietal gyrus, dorsolateral prefrontal cortex (DLPFC) and precentral gyrus compared to the controls. MRS revealed significantly lower choline/creatine (Cho/Cr) and choline/N-acetylaspartate (Cho/NAA) ratios in the DLPFC. In particular, the Cho ratios were positively correlated with the brain activities based on blood oxygenation level-dependent signal change in the DLPFC. This study provides the first evidence for the association between the metabolic alterations and functional deficit in WM processing with emotion-inducing distractors in GAD. These findings will be helpful to understand the neural dysfunction in connection with WM impairment in GAD.

Evaluation on Usefulness of Applying Body-fix to Four Dimensional Radiation Therapy

This study investigates the usefulness of body fix in 4DRT on Liver cancer trying to find tumor tissue`s volume and located variations, absorbed dose on tumor and normal tissues. Test subjects 23 patients were agreed these test. These patient`s have a 4 dimensional CT scan. We make an acquisition on patients CT image by two types -put on the body fix or not-. Average tumor volume reduced by 0.17% on GTV and 3.2% on CTV and PTV. Tumor`s variation reduces 29.8%(anterior and posterior, AP) and 5.31% (upper and lower, UL). The absorbed tumor doses under put on the body fix was a little higher(1.3%) than other. Normal tissues`(normal liver, stomach, Rt. kidney, spinal cord) absorbed dose could be reduced approximately 5%. Therefore, using body fix on 4DRT for liver cancer patient is considered effectively.

Evaluation of Radiation Dose and Image Quality Between Manual and Automatic Exposure Control Mode According to Body Mass Index in Cardiac CT

This study included 198 patients who underwent prospectively electrocardiogram-triggered high-pitch spiral mode(FLASH mode) in cardiac CT for health check: 123 patients who underwent manual exposure control(Group A) and 75 patients who underwent automatic exposure control(Group B). Patients were classified according to BMI grades: Grade 1, Grade 2, Grade 3, Grade 4. Radiation dose, objective and subjective image quality between two groups were compared. In Group B, tube voltage were significantly decreased in all BMI grades. Both and effective dose were significantly reduced in the BMI Grade 1, 3, and 4 whereas they were slightly reduced in the Grade 2(p>0.05), SNR was significantly decreased in the Grade 1 and increased in the Grade 3(p0.05). CNR was significantly decreased in the Grade 1(p0.05). The subjective image quality showed no significant difference in all BMI Grades between the two groups(p>0.05). Automatic exposure control can lead to a significant reduction of radiation exposure dose without degradation of subjective image quality.

Effects of Radiation Dose and Image Quality at the Coronary Angiography

The aim of this study was to assess the effect of exposure factors such as kVp and mA applied by BMI on the image quality and patients absorbed dose of Coronary angiography in CT. Each data sets were into 4groups with different exposure values : Group A at 100kVp, 240mAs, Group B at 120kVp, 240mAs, Group C at 100kVp, 270mAs and Group D at 120kVp, 270mAs, and the mean of the scores of 4 groups was calculated for image quality as 4grades that is, 1(poor), 2(fair), 3(good) and 4(very good). Patient absorbed dose was calculated as DLP on the monitor. In case of absorbed dose, deviation in 2groups at 100kVp was 5.6 , 11 , was at 120kVp(DLP) with p0.05), and the image quality was sufficient for diagnosis. As we applying coronary angiography, the selection of adequate exposure factors considering BMI identified might be effective for reduction of patient absorbed dose, improvement of image quality and diagnostic accuracy.

The clinical usefulness of 64 channel MDCT and 128 channel DSCT in coronary CT angiography

This study was retrospectively to compare the exposure dose and the imaging quality in coronary CT angiography by using the 64 channel multidetector computed tomography and the 128 channel DSCT. Effective dose was calculated dose length product (DLP) by multiplied the convention factor of chest (0.017). Imaging quality was assessed by radiologists using the 5-point Likert scale. The DLP was ranged from 851 to (mean: 17.23 mSv) in the 64 channel MDCT and from 82 to (mean: 1.58 mSv) in the of 128 channel DSCT, respectively. The score of imaging quality was respectively in 64 channel MDCT and in the 128 channel DSCT. The exposure dose of 128 channel DSCT has decreased 1ess 1/10. The score of imaging quality was significant difference between two modalities and the frequency (>4 good) in the 128 channel DSCT is about three times than that of the 64 channel MDCT. Therefore, the 128 channel DSCT in coronary CT angiography is clinically more effective modality for both investigators and patients.

Correlations Analysis of the Entrance Surface Dose according to the BMI at Computed Tomography and Angiography in Cardiovascular Examination

Background/Objectives: The purpose of this study was to investigate the correlation between the entrance surface dose (ESD) and the patient’s body mass index (BMI) in coronary angiography (CAG) of the cardiovascular center and coronary computed tomography angiography (CCTA). Methods/Statistical analysis: This study was conducted on 300 patients (CAG 100 persons; CTA 200 persons), who underwent CAG and CCTA in this hospital from December 2012 to March 2017. To analyze the ESD, the CTDIvol value was obtained from CCTA, and the air kerma value was obtained from CAG for retrospective analysis. CCTA was conducted using the prospective ECG gating technique (PGT) and the retrospective ECG gating technique (RGT). Findings: In the cardiovascular lesion examinations, PGT showed a higher ESD compared to RGT, but the difference was not statistically significant (403.8±118.7 vs. 384.7±117.4, P=0.553). In the correlation between BMI and ESD, there were statistically significant differences among the three groups (PGT, RGT, and CAG) (p<0.05). In the linear relationship examined with a scatter plot, the dose in CAG increased with the increase in BMI (R2=0.144, p<0.001), but the doses in PGT (R2=0.04, p<0.05) and RGT (R2=0.144, p<0.05) decreased with the increase in BMI. Improvements/Applications: Although the dose of CAG tended to increase with the increase in the patient’s BMI, the dose of CCTA tended to decrease inversely. Therefore, BMI may be used as the criterion for the selection of an appropriate examination considering the exposure dose.

Clinical Usefulness of 99m Tc-DMSA Renal SPECT Using High Sensitivity-All Purpose Collimator for Pediatric Patients

신장의 기능을 정량분석 할 수 있는 99m Tc-DMSA 평면 영상은 단층영상에 비해 병소의 위치 정보에 한계가 있다. 따라서 광자 신호에 민감한 범용성 collimator로 교체하여 SPECT 방식으로 임상실험을 시행한 후, 진단의 정확도와 검사 소요시간을 분석하여 임상적용 가능성을 평가하였다. 10명의 실험대상에게 방사성의약품(1.0-1.2 MBq/kg)을 정맥주사하고, 이중 검출기 감마카메라를 이용하여 planar scan (high resolution (HR)-mode, 256×256, 50 kcts/view, 4 image)과 SPECT (HR / high sensitive (HS)-mode, 128×128, step and shoot, 180°, variable sec/angle, total 64 frame, OSEM reconstruction)를 시행하였다. 획득한 데이터를 분석 프로그램을 이용하여 비교한 결과, 실험 방법에 따라서 total counts는 high sensitive-mode SPECT가 대략 1.8-5.6 배 정도 많았고, counts를 이용한 상대신장기능은 모든 실험에서 유의한 수준 범위에서 차이가 없었으며(p=0.96), 검사 소요시간은 39%정도 단축되었다. 그러므로 고감도 범용성 collimator를 이용한 99m Tc-DMSA renal SPECT는 planar scan에 비하여 신장의 기능을 정량분석 할 수 있고, 병변의 위치에 대한 정보를 보다 정확하게 진단할 수 있으며, 동시에 검사 소요시간을 단축시킬 수 있으므로 임상적으로 유용하게 활용할 수 있을 것으로 사료된다.

Analysis of Fine Needle Aspiration Results of Thyroid Nodules in Ultrasonography

본 연구는 직장건강검진 수검자의 갑상샘 초음파 검사에서 발견된 결절 중 1 cm 보다 큰 결절이거나 초음파상 악성을 시사하는 경우의 세침흡인세포검사 결과를 1군으로, 결절의 크기와 상관없이 초음파상 악성을 시사하는 경우의 세침흡인세포검사 결과를 2군으로 나누어 세침흡인세포검사가 필요한 결절 양상 에 대해 비교⋅분석하였다. 1군에서 15.8%가 악성이었고 2군에서는 28%에서 악성으로 나왔다. 악성을 시 사하는 소견은 양성과 악성 간의 통계학적으로 유의한 차이가 있었고 결절의 크기가 1 cm 이상이지만 고 위험 인자를 동반하지 않으면서 초음파검사 결과 스폰지(spongiform) 형태 소견을 보일 때에는 거의 대부 분 양성이므로 세침흡인세포검사가 불필요하다고 사료되었다. 이러한 초음파 소견의 의미는 갑상샘 결절 에 대한 세침흡인세포검사가 필요한지 여부를 결정하는데 중요한 근거가 된다. 현재 갑상샘 결절에 대한 세침흡인세포검사 시행은 결절의 크기가 1 cm 이상이면 스폰지 형태라도 환자의 불안감에 편승하여 행하 여지는 경우가 흔하다. 그러나 양성과 악성 결절을 감별하는데 있어서 갑상샘 초음파 소견을 정확히 숙지 한다면 불필요한 세침흡인세포검사를 줄일 수 있을 것으로 사료된다.

Radiation Treatment Planning Evaluation by Internal Target Volume Settings

본 연구에서는 내부표적체적을 통한 방사선치료계획을 분석하여 호흡연동방사선치료에 주로 이용되는 호기상태의 치료계획체적과 비교·분석하여 정상조직이 받은 선량을 알아보았다. 2013년 12월부터 2014년 6월까지 모 대학교병원 방사선종양학과에서 복부부위에 호흡연동방사선치료를 받은 환자 25명을 대상으 로 하였으며, 암의 종류는 liver(64%), CBD(8%), gastric(8%), GB(8%), pancreas(8%), SMA(4%)이었 다. ITV와 PTV 체적의 평균치는 471.44 cm , 425.48 cm 로 체적의 증가를 알 수 있었고, PTV구간에서 ITV구간으로 선택한 구간의 증가로 인해 정상조직체적 또한 증가함을 알 수 있었다. 그리고 정상조직체적 의 증가, target volume 증가, 치료조사야 면적증가의 차이와 정상조직이 받은 선량평균치의 차이에서는 right kidney가 유의한 증가를 보였다. 호흡평균치에 따른 정상조직이 받은 선량평균치의 차이는 없었고 target moving과 정상조직의 선량평균치의 차이에서는 both kidney가 유의한 차이를 나타내었다. 결론적 으로 PTV구간과 ITV구간 체적 설정을 통한 치료방법이 모두 정상조직의 보호선량에 적합하였으며, 처방 선량의 95% 이상이 분포하였으므로 환자의 치료목적에 따라 선택적으로 사용되어도 무방할 것이라 사료된다.

Study on Knowledge and Safety Management of Radiation Workers

This study has been carried out to find out current status of understanding radiation safety expertise by workers under the present training scheme and to minimize radiation risks at work as well as to refurbish training systems for mitigation of uneasiness of the people at large in near future. Questionnaire survey asking 30 items was carried out during 3 months from May to July, 2013. The number of the overall respondents were about 500. Overall scores of hath degree of the basic knowledge and of the attitude related with radiation safety could he procured through analysis of the questionnaire data. Results were as followings: The workers of the higher academic level, the larger of the accumulated training time and the worker`s personal antecedents, the more accredited license holders showed the larger scores of the basic knowledge of radiation as well as the attitude related with the radiation safety. The group having higher basic knowledge also showed the higher score in attitude related with radiation safety. The overall scores obtained from the radiation workers in industrial sector were relatively lower, in general, than those of the other sectors. These results suggest that the training program might better be separately implemented. A specific training program implementation might be desirable particularly for the workers in industrial sectors so as not only to reduce radiation risks of workers but also to mitigate the uneasiness arising among the people at large.