• 한국의학물리학회지:의학물리
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• 제25권1호
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• pp.53-63
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• 2014

본 연구에서는 호흡 동조 구동 팬톰을 이용하여 5가지의 호흡패턴에 따른 4DCT와 Slow-CT의 내부표적체적(ITV) 변화를 비교 분석하였다. 각 호흡패턴마다 호흡주기 1~4초와 표적 진폭 1~3 cm를 적용하여 4DCT와 Slow-CT를 각 3회 촬영하였다. 촬영한 영상들은 Eclipse 치료계획 시스템으로 표적을 윤곽 묘사하고 내부표적체적(ITV) 길이와 체적을 측정하였으며, 4DCT, Slow-CT의 ITV 길이와 체적의 평균값을 이론값과 비교하여 분석하였다. 4DCT에서의 ITV 길이와 체적은 호흡주기가 길수록, 표적 진폭이 짧을수록 이론값과의 차이가 감소하는 경향을 보였다. Slow-CT에서는 표적 진폭이 커질수록 4DCT와 마찬가지로 이론값과의 차이가 커졌으나 호흡주기에 따른 ITV 길이와 체적의 변화는 호흡주기 1초에서 가장 이론값 비슷하였고 2~4초 내에서는 재현성의 변화가 근소했다. 호흡패턴에 따라서는 4DCT, Slow-CT 모두 ITV 길이와 체적에 대해 A패턴에서 가장 높은 재현성을 보였고, B, C, D패턴은 서로 비슷한 차이를 보였으며 E패턴은 다른 네 패턴에 비해 이론값과의 차이가 가장 컸다. 4DCT에 대한 Slow-CT의 ITV 길이와 체적의 차이는 모든 호흡패턴에 대하여 호흡주기가 길수록, 표적 진폭이 클수록 증가하였다. 4DCT와 Slow-CT 영상간의 ITV 길이 및 체적에 대한 재현성을 비교했을 때 Slow-CT가 4DCT에 비해 평균적으로 약 22% 낮았으며, 호흡패턴에 따라 상, 하 방향에 대해 표적의 재현성이 달라졌다. A, B, C패턴의 경우 상, 하 방향으로 3 mm, E패턴은 상 방향에 비해 하 방향에서 5 mm의 차이를 보인 반면에 D패턴에서는 상 방향으로는 차이가 없었으나 하 방향으로 1.45 cm의 차이가 났다. 따라서 4DCT에 대하여 Slow-CT에 표적 움직임을 고려한 여유를 설정할 경우에는 호흡패턴에 따라 상, 하 방향에 다른 여유를 정의해야 한다고 판단된다. 향후 환자의 호흡신호를 바탕으로 CT 영상을 분석할 때 본 연구에서 수행한 데이터가 유용하게 사용될 것으로 사료된다.

• Radiation Oncology Journal
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• 제22권1호
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• pp.55-63
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• 2004

목적 : 방사선치료계획용 전산화단층활영(computerized tomography, 이하 CT) 시 주사시간이 종양부피의 재현성에 미치는 영향을 살펴보고자 하였다. 대상 및 방법 : 인공호흡기의 환기작용에 의해 세로방향의 왕복 운동을 하는 N자형 모형을 제작하였고, 호흡주기를 T로 하였을 때 주사시간을 상대적으로 각각 0.33, 0.50, 0.67, 0.75, 1.00, 1.33, 그리고 1.53 T로 설정하고 CT촬영을 시행하였다. 또한 2002년 3월 19일부터 2002년 5월 21일까지 서울아산병원 방사선종양학과에서 정위방사선수술(stereotactic radiosurgery)을 시행받은 비소세포성 폐암 환자 3명을 대상으로, 주사시간이 빠른 CT (LightSpeed, GE Medical Systems, 주사시간 0.8초)와 느린 CT (IQ Premier, Picker, 주사시간 2.0초)를 각각 $1\~4$회 시행하였다. 각각의 slice에서, N자형 모형의 왕복 운동이 CT 영상에 반영된 좌우방향 선분의 길이를 측정하여 치료계획용 CT 촬영이 모형의 움직임을 반영하는 정도를 측정하였다. 환자를 대상으로 한 연구에서는 정위적 체부 고정틀을 이용하여, 빠른 CT 및 느린 CT의 종양을 하나의 CT 영상조합에서 재구성하여 종양의 체적과 장경을 측정하여 비교하였다. 결과 : 모형실험에서 주사시간에 비례하여, 세로방향 운동을 CT 촬영에서 반영하는 정도는 증가하였으며 1.00 T 이상에서는 일정한 양상을 보였다 주사시간 1.00 T 이상에서 얻어진 결과를 기준으로, 1.00 T 미만의 주사시간을 가지는 CT촬영에서 모형운동을 반영하지 못하는 비율이 각각 $0.33\;T:\;30\%,\;0.50\;T:\;27\%,\;0.67\;T:\;20\%,\;0.75\;T:\;7.0\%$로 측정되었다. 또한 투시검사로 측정한 종양의 세로 방향 움직임이 각각 3 mm, 5 mm, 10 mm이었던 각각의 환자에서 느린 CT에서 얻어진 종양의 세로방향 장경이 빠른 CT에 비해 $5.3\%\;17\%,\;23\%$ 증가하였다. 결론 : 주사시간을 환자의 호흡주기 이상으로 하는 경우 setup margin만을 고려하여 계획용표적체적(planning target volume, PTV)을 정의할 수 있으므로 정상 폐조직에 조사되는 방사선량을 줄여 치료효율을 향상시킬 수 있을 것으로 생각된다.

• Annals of Clinical Neurophysiology
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• 제9권2호
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• pp.102-104
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• 2007

Spinocerebellar ataxia type 2 (SCA2) is characterized by progressive cerebellar ataxia and slow saccades. A 40-year-old woman presented with progressive gait disturbance and ataxia over 15 years. Neurologic examination revealed scanning speech, ataxia, and hyporeflexia. Brain CT showed diffuse atrophy of the cerebellum. Electronystagmography demonstrated slowed saccades with normal accuracy and delayed latency. The diagnosis of SCA2 was confirmed by the genetic test. Documentation of slow saccades may help differentiation among SCA subgroups.

• 한국축산식품학회지
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• 제36권5호
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• pp.650-655
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• 2016

This study investigated the effects of artificial supercooling followed by still air freezing (SSF) on the qualities of pork loin. The qualities of pork frozen by SSF were compared with the fresh control (CT, stored at 4℃ for 24 h), slow freezing (SAF, still air freezing) and rapid freezing (EIF, ethanol immersion freezing) treatments. Compared with no supercooling phenomena of SAF and EIF, the extent of supercooling obtained by SSF treatment was 1.4℃. Despite that SSF was conducted with the same method with SAF, application of artificial supercooling accelerated the phase transition (traverse from -0.6℃ to -5℃) from 3.07 h (SAF) to 2.23 h (SSF). The observation of a microstructure indicated that the SSF prevented tissue damage caused by ice crystallization and maintained the structural integrity. The estimated quality parameters reflected that SSF exhibited superior meat quality compared with slow freezing (SAF). SSF showed better water-holding capacity (lower thawing loss, cooking loss and expressible moisture) and tenderness than SAF, and these quality parameters of SSF were not significantly different with ultra-fast freezing treatment (EIF). Consequently, the results demonstrated that the generation of supercooling followed by conventional freezing potentially had the advantage of minimizing the quality deterioration caused by the slow freezing of meat.

• The Korean Journal of Ecology
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• 제28권4호
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• pp.181-188
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• 2005

Methods used to study carbon sequestration by soil aggregates have often excluded the concentric spatial variability and other dynamic processes that contribute to resource accessibility and solute transport within aggregates. We investigated the spatial gradients of carbon (C) and nitrogen (N) from the exterior to interior layers within macroaggregates, $6.3\sim9.5$ mm, sampled from conventional tillage (CT) and no tillage (NT) sites of a Hoytville silt clay loam. Spatial gradients in C accumulation within macroaggregates were related to the differences in C dynamics by determining the sizes and the turnover rates of fast C and slow C pools in the concentric layers of aggregates. Aggregate exteriors contained more labile C and were characterized by greater C mineralization rates than their interiors in both management systems. In contrast, C in the interior layers of aggregates was more resistant in both systems. These results indicated the spatial differentiation of C dynamics within macroaggregates, i.e., exterior layers as a reactive site and interior layers as a protective site. Greater total C distribution in the exterior layers of NT aggregates indicated more influx of C from the macropores in interaggregate space than C. mineralization (net gain of C), whereas lower C distribution within the exterior layers of CT aggregates indicated net loss of C by greater C mineralization than C influx. We found total C increased approximately 1.6-fold by the conversion of CT soils to NT management systems for a period of 36 years. Differences in total accumulation and the spatial distribution of C within aggregates affected by management were attributed to the differences in aggregate stability and pore networks controlling the spatial heterogeneities of resource availability and microbial activity within aggregates.

• Nuclear Medicine and Molecular Imaging
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• 제42권sup1호
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• pp.116-120
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• 2008

Prostate cancer is the second leading cause of cancer death of men in western countries and the death related to this disease in Korea is also getting increased. Although anatomic imaging tools such as transrectal US or MRI have been playing a great role in detection of primary prostate lesion, the evaluation of regional lymph node or distant organ metastasis using these modalities is not successful. $^{18}F-FDG-PET$ scan is emerging diagnostic tool for various malignancies. Considering the usual characteristics of prostate cancer such as slow growing and osteoblastic metastasis, the application of FDG PET scan to this disease might be limited. However, in advanced prostate cancer refractory to chemotherapy, FDG PET scan show strong FDG uptake and SUV changes in serial PET scan can be a good indicator of treatment response. Although FDG PET can be useful only in limited cases of prostate cancer, its indication can be widened in future owing to rapid technical improvement and accumulated experiences in this field.

• Journal of Digestive Cancer Research
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• 제5권1호
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• pp.55-57
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• 2017

A 64-year-old man was admitted due to jaundice for 2 weeks. Radiologic findings revealed biliary stricture at the hepatic hilum with intrahepatic duct dilation suggesting Bismuth type IV Klatskin tumor. Jaundice improved spontaneously several days after hospitalization. Surgical treatment was considered but he only wanted to observe without specific treatment. Ten months later, he was re-admitted due to the recurrence of jaundice. Computed tomography (CT) showed no significant difference compared to previous results. Serum cancer antigen 19-9 and Immunoglobulin G4 were normal. Endoscopic forcep biopsy during endoscopic retrograde cholagiopancreatography (ERCP) revealed chronic inflammation. After steroid use under possible diagnosis of IgG4 related cholangiopathy, biliary stricture improved slightly. Four years later, he was hospitalized with the occurrence of acute cholangitis. Endoscopic retrograde biliary drainage was performed following endobiliary forcep biopsy. Pathology revealed well-differentiated adenocarcinoma at this time. Combined chemotherapy based on gemcitabine and cisplatin was performed. Six months later, CT revealed partial response.

• 제어로봇시스템학회논문지
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• 제22권8호
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• pp.597-602
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• 2016

In image guided surgery, a patient registration process is a critical process for the successful operation, which is required to use pre-operative images such as CT and MRI during operation. Though several patient registration methods have been studied, we concentrate on one method that utilizes 3D surface measurement data in this paper. First, a hand-held 3D surface measurement device measures the surface of the patient, and secondly this data is matched with CT or MRI data using optimization algorithms. However, generally used ICP algorithm is very slow without a proper initial location and also suffers from local minimum problem. Usually, this problem is solved by manually providing the proper initial location before performing ICP. But, it has a disadvantage that an experience user has to perform the method and also takes a long time. In this paper, we propose a method that can accurately find the proper initial location automatically. The proposed method finds the proper initial location for ICP by converting 3D data to 2D curvature images and performing image matching. Curvature features are robust to the rotation, translation, and even some deformation. Also, the proposed method is faster than traditional methods because it performs 2D image matching instead of 3D point cloud matching.

• 한국방사선학회논문지
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• 제17권1호
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• pp.141-148
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• 2023

CT에서 대수적재구성기법은 잡음에 강점을 가지는 재구성기법으로 알려져 있다. 대수적재구성기법에서 반복 횟수는 계산 시간을 결정하는 중요한 인자 중의 하나이다. 그러나 반복 횟수에 대한 기준이 연구되어 있지만 수백 번 이상의 반복을 수행하게 되어 현실적으로 사용하기에는 무리가 있었다. 본 연구에서는 반복 횟수를 결정할 수 있는 현실적인 방법을 제시하였다. 반복 횟수에 따라 단면 영상의 품질이 천천히 개선된다는 것을 이용하였다. 반복 횟수를 절대치 평균 오차의 차이 𝜖 < 0.001 로 선택하였다. 잡음이 없는 경우는 Shepp-Logan 두부 팬텀을 이용하였고 잡음이 있는 경우는 Geant4를 이용하여 다양한 입사광자에 대해 360, 720, 1,440개의 투영을 얻었다. 정지 조건에서 10회 내외의 반복으로 우수한 단면 영상을 획득하였다. 수 백회 이상을 반복하는 최적 영상기반의 방법에 비해 현실적으로 적용 가능성이 높은 방법이 될 수 있을 것이다.

• 대한두개안면성형외과학회지
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• 제16권2호
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• pp.67-72
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• 2015

Background: A schwannoma is a benign, slow-growing peripheral nerve sheath tumor that originates from Schwann cells. Orbital schwannomas are rare, accounting for only 1% of all orbital neoplasms. In this study, we retrospectively review orbital schwannomas and characterize clinical, radiologic, and histologic features of this rare entity. Methods: A retrospective review was performed to identify patients with histologically confirmed orbital schwannoma, among a list of 437 patients who had visited our hospital with soft tissue masses within the orbit as the primary presentation between 2010 and 2014. Patient charts and medical records were reviewed for demographic information, relevant medical and family history, physical examination findings relating to ocular and extraocular sensorimotor function, operative details, postoperative complications, pathologic report, and recurrence. Results: Five patients (5/437, 1.1%) were identified as having histologically confirmed orbital schwannoma and underwent complete excision. Both computed tomography (CT) and magnetic resonance imaging (MRI) studies were not consistent in predicting histologic diagnosis. There were no complications, and none of the patients experienced significant scar formation. In two cases, patients exhibited a mild postoperative numbness of the forehead, but the patients demonstrated full recovery of sensation within 3 months after the operation. None of the five patients have experienced recurrence. Conclusion: Orbital schwannomas are relatively rare tumors. Preoperative diagnosis is difficult because of its variable presentation and location. Appropriate early assessment of orbital tumors by CT or MRI and prompt management is warranted to prevent the development of severe complications. Therefore, orbital schwannomas should be considered in the differential diagnosis of slow-growing orbital masses.