종양환자의 진료에 있어서 양전자방출 단층촬영술(Positron Emission Tomography, PET)의 유용성에 대한 고찰

최재걸,송문갑 고려대학교 의과대학 1998 고려대 의대 잡지 Vol.35 No.2

Positron emission tomography(PET) is a diagnostic method that creates high resolution, 3 dimensional tomographic images of the distribution of positron emitting radionuclide in the human body. The radionuclide compounds used include substrates, ligands, drugs. antibodies, neurotransmitters and other biomolecules that are tracer for specific biological processes. Thus the resulting PET images can be considered images of these biochemical or physiological processes(functional images). Positron emission tomography is now primarily used in oncological indications owing to the successful application of fluoline-18 fluo-rodeoxyglucose(FDG) in increasing number of clinical indications at different stages of diagnosis, and for staging and follow-up. This review will discuss detailed clinical applications based on current achievements in respect of various organs and tumors.

역문서빈도로 가중된 부속단어를 이용한 FastText 워드 임베딩

최재걸,이상웅 한국차세대컴퓨팅학회 2019 한국차세대컴퓨팅학회 논문지 Vol.15 No.3

Word Embedding is important in natural language processing, and word2vec is known as a representative algorithm. Word2vec and many other dictionary based word-imbedding algorithms have limitations in creating word vectors only for words used in learning, because they does not use the words’ morphological feature. FastText is a proposed algorithm to solve this problem, word embedding in a combination of sub-words, thus creating a word vector for words that have never been used in learning. Because FastText uses morphological features, it has strengths in syntactic and weekness in semantic compared to word2vec. In this paper, the method of improving FastText is presented by using the inverse document frequency of the subword, and was intended to overcome the weakness in the semantic part of FastText. The results of the experiment show that there has been improvement in semantic tests with little loss in syntactic tests. this method can be applied to any word embedding algorithms using subwords. The probabilistic FastText designed to distinguish multi-sense words and was also tested with the inverse document frequency, and the results confirmed that the performance is improved. 워드 임베딩은 자연어처리 분야에서 중요한 기술로, word2vec이 대표적인 알고리즘으로 알려져 있다. word2vec을 비롯한 사전기반의 워드 임베딩 알고리즘들은 단어의 형태소특징을 사용하지 않는 방식, 즉 단어를 하나의 개체로 사용하기 때문에 학습에 사용된 단어에 대해서만 단어 벡터를 만들 수 있는 한계를 가지고 있다. FastText는 이 문제를 해결하기 위해 제안된 알고리즘으로, 부속단어들의 조합으로 워드 임베딩을 하며, 이에 따라 학습에 사용된 적이 없는 단어에 대해서도 단어 벡터를 만들 수 있다. FastText는 형태소적 특징을 사용하기 때문에, word2vec 방식에 비하여 구문적 부분에서는 강점이 있고, 의미적 부분에서는 약점이 있다. 이 논문에서는 부속단어의 역문서빈도를 이용하여 FastText를 개선하는 방법을 제시하며, FastText가 가지고 있는 의미적 부분에서의 약점을 극복하고자 한다. 실험결과는 구문적 부분에서의 손실이 거의 없이 의미적부분에서 개선이 있었음을 보여준다. 또한 이 방법은 부속단어를 이용한 워드 임베딩에 모두 적용할 수 있다. 중의어를 구별하여 워드 임베딩하기 위해 고안된 확률적 FastText에도 역문서 빈도를 적용 실험하고, 결과를 통해 성능이 향상되었음을 확인하고자 한다.

신경정신 의학분야의 방사성동위원소 표지 cDNA 마이크로어레이

최재걸,신경호,이민수,김명곤 대한핵의학회 2003 핵의학 분자영상 Vol.37 No.1

Microarray technology allows the simultaneous analysis of gene expression patterns of thousands of genes, in a systematic fashion, under a similar set of experimental conditions, thus making the data highly comparable. In some cases arrays are used simply as a primary screen leading to downstream molecular characterization of individual gene candidates. In other cases, the goal of expression profiling is to begin to identify complex regulatory networks underlying developmental processes and diseases states. Microarrays were originally used with cell lines or other simple model systems, More recently, microarrays have been used in the analysis of more complex biological tissues including neural systems and the brain. The application of cDNA arrays in neuropsychiatry has lagged behind other fields for a number of reasons. These include a requirement for a large amount of input probe RNA in fluorescent-glass based array systems and the cellular complexity introduced by multicellular brain and neural tissues. An additional factor that impacts the general use of microarrays in neuropsychiatry is the lack of availability of sequenced clone sets from model systems. While human cDNA clones have been widely available, high quality rat, mouse, and drosophilae, among others are just becoming widely available. A final factor in the application of cDNA microarrays in neuropsychiatry is cost of commercial arrays. As academic microarray facilitates become more commonplace custom made arrays will become more widely available at a lower cost allowing more widespread application. In summary, microarray technology is rapidly having an impact on many areas of biomedical research. Radiosotope-nylon based microarrays offer alternatives that may in some cases be more sensitive, flexible, inexpensive, and universal as compared to other array formats such as fluorescent-glass arrays. in some situations of limited RNA or exotic species, radioactive membrane microarrays may be the most practical experimental approach in studying psychiatric and neurodegenerative disorders, and other complex questions in the brain. (Korean J Nucl Med 2003;37:43-52)

초록집 : 99mTc - DTPA 및 Gamma Scintillation Camera를 이용한 사구체 여과율의 측정

최재걸,이민재,백세현 대한핵의학회 1992 핵의학 분자영상 Vol.26 No.1

제46차 대한핵의학회 추계학술대회 : 일반연제 ; PET 및 PET-CT 정도관리를 위한 실태조사연구

최재걸,이병일,김경민,황경훈,이재성,김진수,김병일,정용현,범희승 대한핵의학회 2007 핵의학 분자영상 Vol.41 No.5

안와 종양의 전산화 단층촬영 소견

최재걸 대한영상의학회 1987 대한영상의학회지 Vol.23 No.2

The development of computed tomography [provided a noninvasive safe technique for imaging the orbit in any plane exquisitely demonstrating its normal anatomy as well as its pathologic process. The orbit is an ideal structure to be examined by CT because of large difference of absortion values between the intraorbgital fat, muscle, optic nerve and vessels. In this study, the authors reviewed CT findings of 66 pathologically proven orbital tumors and tumorous conditions among the total of 98 cases who had taken orbital CT scan because of exophthalmos, ocular pain, diplopia and other ophthalmologic symptoms suggesting orbital masses during the period of 3 years. RESULT : 1. Exact tumor detecton and localization was possible in 63 cases. Thus the detection rate was 95% with CT scan. 2. Among 36 males and 30 females, their age ranged from 10 months to 72 years. 3. Intraocular tumors were 10 cases. Retinoblastoma occurred wholly in the young children under 5 years and combined with alcification in 57%. Choroidal melanoma occurred wholly in adults. 4. Intraconal tumor were 9 cases. Vascular tumors were the most frequent and well enhancing mass. 5. The tumors arising inthe extraconal region were pseudotumor, lymphoma, dermoid cyst, metastasis, adenoid cystic carcinoma and teratoma. 6. The lesions arising from extraorbital region were PNS cancer, mucocele, lid cancer, fibrous dysplasia and neurofibromatosis. 7. Thin slice thickness of the transverse axial scan and reconstruction of image in various planes provide better 3 dimensional image and are useful for the evaluation of the characteristics of the mass and its relation to other structures. 8. Contrast enhanement is useful in differentiation of vascular tumors and other nonvascular tumors, and evaluation of the scleral thickening in pseudotumors. Evaluation of tumor extension is also possible with contrast enhancement, but in extraconal mass contrast enhacement was not helpful. 9. The CT is the method of choic in the detection and differential diagnosis of t

담관낭종의 방사선학적 고찰

최재걸 대한영상의학회 1986 대한영상의학회지 Vol.22 No.4

The authors have experienced 11 cases of radiologically or surgically proven choledochal cyst during the period of 4 years. and reviewed radiological and clinical features. The results are as follows : 1. The sex ration of female to male was 2.7 : 1 . Four were children under 10, and seven were adults over 30 years of age. 2. The most frequent symptom was abdominal pain (45%) , which was followed by jaundice(36%) and palpable abdominal mass(27%). 3. Morphologically, 4 cases were type A of Kimura classification (segmental cystic dilatation involiving common bile duct : pure type A of Alonso-Lej). The other 7 patients showed some dilatation in the intrahepatic bile ductsas well : i.e. type A' of Kimura classification. 4. The union between the common bile and main pancreatic ducts was at a high position in 5 of 6 patients in whom both ducts were adequately opacified with ERCP, PTC and/or operative cholangiography, forming an abnormally long common channel. 5. Associated choledoch lithiasis was reported with increasing frequency. We experienced 4 cases (36.3%) which had multiple stones in the choledochal cyst. 6. Adenocarcinoma were combined in 2 patients : both were females of 38 and 45 years of age. 7. Ten cases were correctly diagnosed preoperatively with ultrasonography. Specific ultrasound diagnosis of a choledochal cyst could be made by identifying two bile ducts entering into the large cyst which was separted from the gallbladder and extended deep onto the porta hepatis. Dilatation of intrahepatic ducts.

동위원소 뇌혈관 촬영술을 이용한 뇌사의 판정

최재걸,이민재 ( Jae Gol Choe,Min Jae Lee ) 대한핵의학회 1992 핵의학 분자영상 Vol.26 No.2

Evidence - Based Medicine 에 대한 소개

최재걸(Jae Gol Choe) 대한핵의학회 2001 핵의학 분자영상 Vol.35 No.4

EBM is “the conscientious, explicit and judicious use of current best evidence in making decisions about the care of the individual patient. It means integrating individual clinical expertise with the best available external clinical evidence from systematic research.” EBM is the integration of clinical expertise, patient values, and the best evidence into the decision making process for patient care. The practice of EBM is usually triggered by patient encounters which generate questions about the effects of therapy, the utility of diagnostic tests, the progriosis of diseases, or the etiology of disorders. The best evidence is usually found in clinically relevant research that has been conducted using sound methodology. Evidence-based medicine requires new skills of the clinician, including efficient literature-searching, and the application of formal rules of evidence in evaluating the clinical literature. Evidence-based medicine converts the abstract exercise of reading and appraising the literature into the pragmatic process of using the literature to benefit individual patients while simultaneously expanding the clinician's knowledge base. This review will briefly discuss about concepts of evidence medicine and method of critical appraisal of literatures. (Korean J Nucl Med 200135:224-230)

감마카메라 정도관리 실태 조사

최재걸 ( Jae Gol Choe ),조철우 ( Cheol Woo Joh ) 대한핵의학회 2008 핵의학 분자영상 Vol.42 No.4