달라지는 2014학년도 수능시험 개편 방안

최홍윤 한국교육과정평가원 2011 교육광장 Vol.39 No.-

Deep-Learning-Based Molecular Imaging Biomarkers: Toward Data-Driven Theranostics

최홍윤 한국의학물리학회 2019 의학물리 Vol.30 No.2

Deep learning has been applied to various medical data. In particular, current deep learning models exhibit remarkable performance at specific tasks, sometimes offering higher accuracy than that of experts for discriminating specific diseases from medical images. The current status of deep learning applications to molecular imaging can be divided into a few subtypes in terms of their purposes: differential diagnostic classification, enhancement of image acquisition, and image-based quantification. As functional and pathophysiologic information is key to molecular imaging, this review will emphasize the need for accurate biomarker acquisition by deep learning in molecular imaging. Furthermore, this review addresses practical issues that include clinical validation, data distribution, labeling issues, and harmonization to achieve clinically feasible deep learning models. Eventually, deep learning will enhance the role of theranostics, which aims at precision targeting of pathophysiology by maximizing molecular imaging functional information.

Parametric Cerebrovascular Reserve Images Using Acetazolamide 99mTc-HMPAO SPECT: A Feasibility Study of Quantitative Assessment

최홍윤,유민영,천기정,강건욱,정준기,이동수 대한핵의학회 2013 핵의학 분자영상 Vol.47 No.3

Purpose Basal/acetazolamide stress 99mTc-HMPAO singlephoton emission computed tomography (SPECT) has been widely used for evaluation of hemodynamics; however,qualitative and subjective visual assessment of cerebrovascular reserve (CVR) has been performed in clinical settings. The aim of this study was to generate parametric CVR images and evaluate its feasibility of quantification. Methods Basal/acetazolamide stress 99mTc-HMPAO SPECT data from 17 patients who underwent bypass surgery or percutaneous transluminal angioplasty were used. Spatial normalization was performed and parametric CVR images were generated using relative CVR (rCVR) of each voxel proportional to CVR of the whole brain. Binary parametric maps to show area of relatively reduced CVR were generated also using threshold of rCVR < 90 %. We calculated rCVR of internal carotid artery (ICA) using the parametric CVR images and probabilistic maps for ICA territory. Pre- and postprocedural parametric CVR images were obtained and quantitative rCVRs were compared. The rCVRs were evaluated according to visual grades for regional decreased CVR. Results Postprocedural rCVR obtained from parametric CVR images increased significantly from preprocedural rCVR. The rCVR was significantly correlated with visual grades of reduced CVR for each side of ICA territories. Conclusions We generated parametric CVR images for basal/acetazolamide stress 99mTc-HMPAO SPECT. As a quantitative measurement, rCVR obtained from the parametric image was feasibly assessed hemodynamic abnormalities with preserved anatomical information.

Tc-99m Hydroxymethylene Diphosphonate (HMDP) Renal Uptake as a Surrogate Marker of Postoperative Impairment of the Glomerular Filtration Rate in Renal Tumor Patients Following Nephron-Sparing Surgery

최홍윤,이원우,소영,하승균,변석수,김상은 대한핵의학회 2014 핵의학 분자영상 Vol.48 No.4

P u r p o s e : We i n v e s t i g a t ed Tc - 9 9mhydroxymethylene diphosphonate (HMDP) scintigraphy findingsin renal tumor patients from the perspective of postoperativerenal dysfunction following nephron-sparing surgery(NSS). Methods: Forty-three renal tumor patients (M:F =28:15, age 53.9±12.5 years) who had undergone Tc-99mHMDP scintigraphy after NSS were enrolled. The patientswere divided into HMDP+ or HMDP− groups by visual assessment,and the asymmetric index (ASI) was calculatedusing a region-of-interest analysis. In 16 patients, the totaland split glomerular filtration rate (GFR) was assessed usingTc-99m diethylenetriaminepentaacetic acid (DTPA) scintigraphyat baseline and at 3 and 6months post-NSS. Results: HighTc-99m HMDP uptake was observed in the operated kidneys,but this did not persist later than 7 days post-NSS. Split GFRof the operated kidneys at baseline (58.5±9.3 ml/min) wassignificantly reduced at 6 months post-NSS (40.1±5.9 ml/min, p<0.001) in only those who showed intense uptake ofTc-99m HMDP. Declines in both total GFR (p=0.010 and p=0.002 for 3 and 6 months, respectively) and split GFR of theoperated kidneys (p<0.001 and p<0.001 for 3 and 6 months,respectively) were clearly evidenced at 3 and 6 months post-NSS only in patients with high Tc-99m HMDP in the operatedkidneys. The ASI was negatively correlated with %change inthe split GFR of these operated kidneys at 6 months post-NSS(rho =−0.578, p=0.0304). Conclusions: Tc-99m HMDP uptakewithin 1 week following NSS is a surrogate marker ofGFR impairment over 6 months post-NSS.

신용평가를 위한 신경망 Clustering기법의 적용

최홍윤,정윤,김정원,최종욱 한국경영과학회 1994 한국경영과학회 학술대회논문집 Vol.- No.2

핵의학 : Deep learning-based imaging biomarker - How deep learning reshapes nuclear medicine

최홍윤 대한방사선방어학회 2019 대한방사선방어학회 학술발표회 논문요약집 Vol.2019 No.04

직선수로에 설치된 교각 주변의 흐름에 관한 수치해석

최홍윤(Hong-Yun Choi),노경범(Kyong-Bum Roh),진영훈(Young-Hoon Jin),박성천(Sung-Chun Park) 대한토목학회 2006 대한토목학회 학술대회 Vol.2006 No.10

Radiomics in Oncological PET/CT: a Methodological Overview

하승균,최홍윤,팽진철,천기정 대한핵의학회 2019 핵의학 분자영상 Vol.53 No.1

Radiomics is a medical imaging analysis approach based on computer-vision. Metabolic radiomics in particular analyses the spatial distribution patterns of molecular metabolism on PET images. Measuring intratumoral heterogeneity via image is one of the main targets of radiomics research, and it aims to build a image-based model for better patient management. The workflow of radiomics using texture analysis follows these steps: 1) imaging (image acquisition and reconstruction); 2) preprocessing (segmentation & quantization); 3) quantification (texture matrix design & texture feature extraction); and 4) analysis (statistics and/or machine learning). The parameters or conditions at each of these steps are effect on the results. In statistical testing or modeling, problems such as multiple comparisons, dependence on other variables, and high dimensionality of small sample size data should be considered. Standardization of methodology and harmonization of image quality are one of the most important challenges with radiomics methodology. Even though there are current issues in radiomics methodology, it is expected that radiomics will be clinically useful in personalized medicine for oncology.

A Negative Correlation Between Blood Glucose Level and 68 Ga-DOTA-TOC Uptake in the Pancreas Uncinate Process

오동규,최홍윤,팽진철,강건욱,천기정 대한핵의학회 2022 핵의학 분자영상 Vol.56 No.1

Purpose 68 Ga-DOTA-TOC uptake in the pancreas uncinate process is often found due to physiologic expression of somatostatin receptors (SSTR). We investigated the association of physiologic 68 Ga-DOTA-TOC uptake in the pancreas uncinate process with blood glucose level. Methods 68 Ga-DOTA-TOC PET scans acquired from 44 patients (male:female = 20:24, age = 50.8 ± 14.8y [mean ± SD]) were retrospectively analyzed. The blood glucose level (BGL) was examined before 68 Ga-DOTA-TOC injection. Patients diagnosed with diabetes mellitus and patients with BGL over 200 mg/dl were excluded. 68 Ga-DOTA-TOC uptake was measured by the maximum standardized uptake values (SUVmax). Additionally, SSTR-positive volume (SV) in the pancreas uncinate process was measured with two different thresholds: by SUV cutoff of 2.5 ( SV2.5) and 40% of SUVmax ( SV40%). These measurements on 68 Ga-DOTA-TOC PET were correlated with BGL. Results The mean of SUVmax of the pancreas uncinate process was 6.51 ± 2.04. SV2.5 was 17.81 ± 7.14 cm3, and SV40% was 18.20 ± 8.83 cm3. A significant negative correlation was found between SUVmax of the pancreas uncinate process and BGL (r = -0.37, p = 0.01). The ratio between SUVmax of the pancreas uncinate process and SUVmean of the pancreas body also showed a significance negative correlation with BGL (r = -0.40, p = 0.01). SV2.5 (r = 0.27, p = 0.07) and SV40% (r = -0.151, p = 0.32) were not significantly correlated with BGL. Conclusion Physiologic 68 Ga-DOTA-TOC uptake in the pancreas uncinate process was negatively correlated with BGL. Our results suggested that glycemia could affect physiologic uptake of 68 Ga-DOTA-TOC.

Spatial Normalization Using Early-Phase [18F]FP-CIT PET for Quantification of Striatal Dopamine Transporter Binding

배성우,최홍윤,위원석,팽진철,천기정,강건욱,이동수 대한핵의학회 2020 핵의학 분자영상 Vol.54 No.6

Purpose The precise quantification of dopamine transporter (DAT) density on N-(3-[18F]Fluoropropyl)-2β-carbomethoxy- 3β-(4-iodophenyl) nortropane positron emission tomography ([18F]FP-CIT PET) imaging is crucial to measure the degree of striatal DAT loss in patients with parkinsonism. The quantitative analysis requires a spatial normalization process based on a template brain. Since the spatial normalization method based on a delayed-phase PET has limited performance, we suggest an early-phase PET-based method and compared its accuracy, referring to the MRI-based approach as a gold standard. Methods A total of 39 referred patients from the movement disorder clinic who underwent dual-phase [18F]FP-CIT PET and took MRI within 1 year were retrospectively analyzed. The three spatial normalization methods were applied for quantification of [18F]FPCIT PET-MRI-based anatomical normalization, PET template-based method based on delayed PET, and that based on early PET. The striatal binding ratios (BRs) were compared, and voxelwise paired t tests were implemented between different methods. Results The early image-based normalization showed concordant patterns of putaminal [18F]FP-CIT binding with anMRI-based method. The BRs of the putamen from the MRI-based approach showed higher agreement with early image- than delayed imagebased method as presented by Bland-Altman plots and intraclass correlation coefficients (early image-based, 0.980; delayed image-based, 0.895). The voxelwise test exhibited a smaller volume of significantly different counts in putamen between brains processed by early image and MRI compared to that between delayed image and MRI. Conclusion The early-phase [18F]FP-CIT PET can be utilized for spatial normalization of delayed PET image when theMRI image is unavailable and presents better performance than the delayed template-based method in quantitation of putaminal binding ratio.