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황기환,고대식,전계석,Hwang, Ki-Hwan,Ko, Dae-Sik,Jun, Kye-Suk 한국음향학회 1997 韓國音響學會誌 Vol.16 No.1
본 논문에서는 음향-광 효과를 이용한 STAM 시스템으로부터 얻을 수 있는 토모그라픽 영상의 분해능을 해석하였다. 이를 위하여 BFP 토모그라픽 복원 알고리즘을 이용하여 초음파변환기 회전장치와 시료 회전장치에 대한 측방향과 축방향 분해능을 해석하였다. Matlab을 이용한 분석결과, 축방향 분해능은 두 회전장치 모두 약 1.5 파장정도로 좋은 분해능을 나타내었다. 측방향 분해능은 시료 회전장치인 경우 x와 yqkdgid에서 0.53 파장의 동일한 분해능을 보였으며 초음파변환기 회전장치인 경우에는 x와 yqkdgid에서 각각 0.56 및 0.70 파장의 분해능을 나타내었다. 결과적으로 STAM 시스템은 시료회전장치를 사용할 때 더 좋은 분해능을 얻을 수 있음을 보였다. In this paper, we analyzed the resolution of tomographic images which can be obtained with Scanning Tomographic Acoustic Microscope(STAM) utilizing the acousto-optic effect. To realize this, lateral and depth resolutions of both ultrasonic transducer and specimen rotating device are obtained by using BFP tomographic reconstruction algorithm. Simulation results show that both rotating devices have a good depth resolution of $1.5{\lambda}$. For the lateral resolution, the specimen rotating device produces $0.53{\lambda}$ in the x and y directions and the transducer rotating device produces $0.56{\lambda}$ and $0.70{\lambda}$ in the x and y directions respectively. These results imply that the specimen rotating device is more suitable for STAM system construction.
황기환,김태민,박철기,장종희,정태영,김진희,남도현,김세혁,유헌,홍용길,김은영,이동은,주정남,김유정,최기영,최병세,강석구,김정훈,김채용 대한암학회 2020 Cancer Research and Treatment Vol.52 No.2
Purpose We investigated the efficacy of temozolomide during and after radiotherapy in Korean adults with anaplastic gliomas without 1p/19q co-deletion. Materials and Methods This was a randomized, open-label, phase 2 study and notably the first multicenter trial for Korean grade III glioma patients. Eligible patients were aged 18 years or older and had newly diagnosed non-co-deleted anaplastic glioma with an Eastern Cooperative Oncology Group performance status of 0-2. Patients were randomized 1:1 to receive radiotherapy alone (60 Gy in 30 fractions of 2 Gy) (control group, n=44) or to receive radiotherapy with concurrent temozolomide (75 mg/m2/day) followed by adjuvant temozolomide (150-200 mg/m2/day for 5 days during six 28-day cycles) (treatment group, n=40). The primary endpoint was 2-year progression-free survival (PFS). Seventy patients (83.3%) were available for the analysis of the isocitrate dehydrogenase 1 gene (IDH1) mutation status. Results The two-year PFS was 42.2% in the treatment group and 37.2% in the control group. Overall survival (OS) did not reach to significant difference between the groups. In multivariable analysis, age was a significant risk factor for PFS (hazard ratio [HR], 2.08; 95% confidence interval [CI], 1.04 to 4.16). The IDH1mutation was the only significant prognostic factor for PFS (HR, 0.28; 95% CI, 0.13 to 0.59) and OS (HR, 0.19; 95% CI, 0.07 to 0.50). Adverse events over grade 3 were seen in 16 patients (40.0%) in the treatment group and were reversible. Conclusion Concurrent and adjuvant temozolomide in Korean adults with newly diagnosed nonco- deleted anaplastic gliomas showed improved 2-year PFS. The survival benefit of this regimen needs further analysis with long-term follow-up at least more than 10 years.
황기환,고대식,전계석 慶熙大學校 材料科學技術硏究所 1992 材料科學技術硏究論集 Vol.5 No.-
In this paper, using the spectra and the reflection coefficient of surface acoustic wave:SAW, the surface breaking crack-depth is estimated by computer simulation and the experiment. In order to perform this experiment, two type shaped flows half-penny and rectangular of line-crack have been made in the surface of aluminium. Measuring results, for half-penny type, the reflection coefficient have been in proportion to the surface breaking crack-depth. When the spectrum analyzer was used, the spectra analysis method for line crack of rectangular type was measured the average deviation 8.7% to the surface breaking crack-depth.
황기환,김현,김종찬,전계석,Hwang, Ki-Hwan,Kim, Hyun,Kim, Jong-Chan,Jun, Kye-Suk 한국음향학회 1998 韓國音響學會誌 Vol.17 No.8
본 논문에서는 다층구조물에 대한 토모그라픽 영상을 복원하기 위해 기존의 SLAM 시스템에 쿼드러쳐 검출기와 시료회전장치를 부가하여 STAM 시스템을 구성하고 BFP 알 고리즘을 이용하여 영상복원 프로그램을 개발하였다. 본 실험에서는 시료로서 알루미늄을 사용하여 2개 층이 서로 다른 패턴을 갖는 불균질 층을 만들고 그 사이를 물로써 채워진 다 층구조물을 구성하였으며 또한 불균질 층 간격을 각각 8λ, 10λ 그리고 12λ가 되도록 제 작하였다. 이들 시료는 STAM 시스템에서 4중 프로젝션(0°, 90°, 180°, 270°)시켜 토모 그라픽 데이터를 획득하고 이를 영상처리하여 토모그라픽 영상을 복원하였다. 영상분석 결 과, 본 STAM 시스템은 4중 프로젝션시 12λ의 불균질 층 간격에서 높은 분해능의 토모그 라픽 영상을 얻을 수 있었고 각 층에 대한 위치를 결정할 수 있었다.
황기환,전계석,Hwang, Ki-Hwan,Jun, Kye-Suk 한국음향학회 1997 韓國音響學會誌 Vol.16 No.3
본 논문에서는 SLAM(Scanning Laser Acoustic Microscope) 시스템을 이용하여 고체 내부에 발생한 크랙의 깊이를 측정하는 방법을 연구하였다. SLAM 시스템은 초음파의 투과계수에 따른 그림자 영상을 재생시키므로 크랙 깊이에 대한 정확한 측정방법이 요구된다. 이를 위하여 시료에 초음파를 사각으로 입사시켜 얻은 SLAM 영상의 그림자영역과 시료내의 초음파 모드 변환에 대한 기하학적 구조를 이용하여 크랙의 깊이를 측정할 수 있는 방법을 제안하고 실험을 통하여 확인하였다. 실험을 위하여 알루미늄에 서로 다른 깊이로 수직형 라인-크랙의 결함을 갖는 시료를 가공하였고 시료에 초음파를 사각 입사시키기 위하여 20$^{\circ}$ 각도로 웨지를 제작하였다. 실험 결과, 크랙의 깊이가 증가할수록 SLAM 영상의 그림자 영역이 비례적으로 증가함을 보였고, 결함의 깊이에 대한 측정치와 실제치를 비교한 결과 약 6% 이하의 측정오차를 보였다. In this paper, we studied the configuration and depth measurement method of the crack in the interior of solid with scanning laser acoustic microscope. Precision measurement method of crack depth is required in SLAM because that system reconstructs the shadow image to the transmission coefficient. We proposed this method that used geometrical structure to the shadow area of SLAM images obtained from oblique incidence and the mode conversion of ultrasound in specimen and then experimented it. For this experiment, we fabricated various specimens which had the vertical line-crack with different depth and made the wedge as 20$^{\circ}$ for oblique incidence. Experimental results showed that the shadow area of SLAM images were proportional to the depth of crack. Measured depth error to the crack was less than 6% compared with practical crack depth.
CT Fluoroscopy-guided Aspiration of Intracerebral Hematomas: Technique and Outcomes
황기환,Gyojun Hwang,권오기,Jae Seung Bang,오창완 대한뇌혈관외과학회 2015 Journal of Cerebrovascular and Endovascular Neuros Vol.17 No.1
Objective:The authors evaluated the feasibility and targeting accuracy of CT fluoroscopy (CTF)-guided catheter placement and aspiration of intracerebral hematoma (ICH)s. Materials and Methods:Nine patients (mean age, 63.3 ± 15.3 years) were treated by CTF-guided hematoma aspiration under local anesthesia. The targeting errors in the lesion center, volume of the aspirated hematoma, accuracy of the final catheter position, procedure time, and clinical outcomes were evaluated. Results:All catheters were successfully placed in the center of the hematoma. The mean volume of the aspirated hematoma was 20.6 ± 8.8 mL (pre-treatment, 44.7 ± 20.1 mL; post-treatment, 24.1 ± 13.8 mL). The average procedure time was 25.1 minutes (range, 18-32 minutes). In one case with a scanty residual hematoma, the catheter was removed at the end of the procedure. In the remaining eight cases, the catheter was left in the residual hematoma for drainage and all catheter tips were accurately located in the final position. There were no procedure-related complications, including rebleeding and infection. Conclusion:CTF-guided ICH aspiration is a feasible, quick, and accurate procedure which could substitute for stereotactic methods. The accurate catheter position provided by real-time observation enables an effective aspiration and drainage of hematomas.