Tc-99m-MIBI 심근 SPECT에서 재구성필터의 차단주파수에 의한 인위적 관류결손의 정량적 평가

곽철은,정준기,이명철,Kwark, Cheol-Eun,Chung, June-Key,Lee, Myung-Chul 대한의용생체공학회 1995 의공학회지 Vol.16 No.2

Tc-99m-MIBI 심근 SPECT에서 심근조직에 비하여 간섭취가 상대적으로 높고 이들이 서로 가까이에 위치해 있는 경우 단축단면상의 하위부 또는 하위중격부에서 발생하는 인위적 관류결손의 정도와 여과기의 차단주파수의 관계를 분석하였다. 이러한 영향은 단축단면상 뿐만 아니라 심근 극성지도에서도 관찰되는데, 심근단층상에서 계수분포가 균일하지 못하고 간과 같이 특정부위에 방사능의 집적도가 높은 경우 단층상 재구성시 차단 파수의 적절한 설정에 따라 이 효과를 줄일 수 있는 방법을 제안하였다. 본 연구에서 분석에 사용된 여과기는 저역통과여과기로 이를 사용하는 경우에는 차단주파수를 0.4Nyquist 이상으로 하면 인위적 관류결손의 정도를 충분히 줄일 수 있었다. 그러나 높은 차단주파수에서는 심근영상의 균일도가 떨어지고 배후방사능 및 기타 잡음요인이 효과적으로 제거되지 않기 때문에 적절한 차단주파수의 설정이 중요하며, 본 연구에 사용된 영상에서 여과방법에 따른 원주프로필의 변화가 미세하여 후처리방법을 사용하여 분석하였다. 또한 역투사방법이 비선형적이므로 특정 영상보다는 다양한 간-심근 방사능비에 따른 영상을 분석하여 비선형성을 배제한 연구가 향후 진행되어야 한다. Tc-99m-MIBI (Sestamibi) myocardial SPECT along with TI-201 tomographic Imaging has demonstrated wide application and high image quality sufficient for the diagnosis of myocardial perfusion defect, which consequently reflects regional myocardial blood flow. The qualitative values of myocardial SPECT with Tc-99m-MIBI as well ds the quantitative cases depend in some degree on the reconstruction techniques of multiple projections. Filtered backprojection (FBP) Is the common standard method for reconstruction rather than the complicated and time-consuming arithmetic methods. In FBP it is known that the distribution of radioactivity in reconstructed transverse slices varies with the selected litter parameters such as cutoff frequencies and order (Butterworth case) The cutoff frequencies used in clinicAl practice partially remove and decrease the true radioactive distribution and alter the pixel counts, which lead to underestimation of true counts in specific myocardial regions. In this study, we have investigated the effect of cutoff frequencies of reconstruction filter on the artifactually induced perfusion defects, which are often demonstrated near inferior and/or inferoseptal cardiac walls due to the intense hepatic uptake of Tc-99m-MIBI. A computerized method for Identifying the relative degree of artifactual perfusion defect and for comparing those degrees along with the relative amount of hepatic uptake to myocardium was developed and patient images were studied to observe the quantitative degree of underestimation of myocardial perfusion, and to propose some reasonable threshold of cutoff frequency in the diagnosis of perfusion defect quantitatively. We concluded that from the quantitative viewpoint cutoff frequencies may be used as high as possible with the sacrifice of homogeneity of image quality, and those frequencies lower than the common 0.3 Wyquist frequency would reveal severe degradation of radioactive distribution near inferior and/or inferoseptal myocardium when applying Butterworth or low pass filter.

소형 계수용 및 영상용 감마프로브 시스템의 설계와 성능평가

양묘근,곽철은,심용걸,김희중,최용,정준기,이명철,고창순,Yang, Myo-Geun,Kwark, Cheol-Eun,Sim, yong-Geol,Kim, Hee-Joung,Choi, Yong,Chung, Jung-Key,Lee, Myung-Chul,Koh, Chang-Soon 대한의용생체공학회 1997 의공학회지 Vol.18 No.3

As a microimaging device detecting gamma rays emitted from small lesions or tumors during operation, the intraoperative surgical probe has been proposed and is now under development. We have designed a multipurpose portable gamma prove system and evaluated the performance both for the absolute counting purpose of residual radioactivities and for the localizing capability of gamma events using the NaI(Tl) crystal and two types of photomultiplier tubes(PMTs). Counting efficiencies in the range of routine clinical use of radiation dose were measured using the assembly of single channel PMTs and 0.5 inch thick NaI(Tl) crystal of 1 inch diameter. The positioning of gamma events for imaging purpose requires the multiple channel PMTs with appropriate positioning electronics. We have designed a simple and reliable positioning circuit based on the concept of modified Anger. In preliminary experiments using the multiple channel PMT of 3 inch diameter and the dim lighth source, we were able to trace and localize the correct position with reduced positioning error by the use of two multiplier/divider chipset and simplified peripherals. The energy resolutions for the counting gamma probe measured as full width at half maximum(FWHM) for Cs-137, F-18, Tc-99m were 12%, 13%, and 36%, respectively. The spatial resolution for the imaging gamma probe measured as FWHM for green LED was 2.9 mm. The results indicate that the currently developing probe is very promising and could be very useful for many applications in nuclear medicine. Future studies will include developing collimators, improving interface hardwares, and evaluating the system with clinical data.

갑상선 호르몬의 외부정도 관리 분석 - 1989년 9월부터 1990년 8월까지 첫해 시행 결과 -

이동수,조보연,곽철은,서일택,정준기,이명철,고창순 ( Dong Soo Lee,Bo Youn Cho,Cheol Eun Kwark,Il Taek Seo,June Key Chung,Myung Chul Lee,Chang Soon Koh ) 대한핵의학회 1991 핵의학 분자영상 Vol.25 No.2

금속 물성이 CORONA 방전 메카니즘에 미치는 영향에 관한 연구

신민철(Min Cheol Schin),곽철은(Cheol Eun Kwark),이충웅(Choong Woong Lee) 대한전자공학회 1990 대한전자공학회 학술대회 Vol.1990 No.11

82Sr/82Rb 발생기의 제조 및 정상인 심근의 양전자 단층촬영상

정재민,정준기,이동수,곽철은,이경한,이명철,고창순 ( Jae Min Jeong,June Key Chung,Dong Soo Lee,Cheol Eun Kwark,Kyung Han Lee,Myung Chul Lee,Chang Soon Koh ) 대한핵의학회 1994 핵의학 분자영상 Vol.28 No.3

A Sr/Rb generator was prepared by loading Sr to preconditioned tin dioxide column. The generator was eluted by normal saline with flow rate up to 8ml/min, and the eluted radioactivity was monitored by dose calibrator. Radioactivity began to come out at 5ml and reached to peak around 9ml. The total eluted radioactivity increased linearly with flow rate, and the maximum obtained radioactivity was 35mCi at 8ml/min. The Rb preparation was proven to be free from both strontium radioactivity and pyrogen. The Rb was injected to normal female valunteer and positron emission tomographic image of heart was obtained successfully.

정상 한국 성인에서 혈청 암태아성항원의 경계치 및 이에 영향을 미치는 인자

김선욱,정준기,이동수,곽철은,정재민,김명기,이명철,고창순,이형기,유근영,안윤옥,김종순 ( Sun Wook Kim,June Key Chung,Dong Soo Lee,Cheol Eun Kwark,Jae Min Jeong,Myung Ki Kim,Myung Chul Lee,Chang Soon Koh,Hyung Kee Lee,Keun Young Yoo,Yoon Ok 대한핵의학회 1994 핵의학 분자영상 Vol.28 No.3

Carcinoembryonic Antigen is one of most frequent.ly checked tumor markers in cancer management. We performed statistical analysis with serum CEA data of 2626 persons who received regular health examination and were thought to be free of active disease to determine the cutoff values of serum CEA level in normal Korean adults and to study the factors influencing serum (:EA levels in normal subjects. 1) The cutoff values of serum CEA in normal Korean adults in general were 9.28ng/ ml for men, 5.90 ng/ml for women. 2) Serum CEA level was influenced by age, present smoking history, sex, and abnormal findings in chest X ray. 3) Serum CEA level had no correlation with the history of amount of alcohol consumption or obesity. 4) Cutoff values of serum CEA in normal Korean adults were tabulated according to age, sex, and smoking histor y. Serum CEA level was influenced by age, sex, present smoking history and abnormal findings in chest X ray and cutoff values of serum CEA were tabulated according to age, sex, and smoking history.

Tc-99m-MIBI 심근 SPECT 의 분절 육안 분석시 판독자간의 일치도

여정석,이동수,이경한,김종호,손경수,조성욱,곽철은,정준기,이명철,서정돈,고창순 ( Jeong Seok Yeo,Dong Soo Lee,Kyung Han Lee,Jong Ho Kim,Kyung Soo Shon,Sung Wook Cho,Cheol Eun Kwark,June Key Chung,Myung Chul Lee,Jeong Don Seo,Chang Soon 대한핵의학회 1994 핵의학 분자영상 Vol.28 No.3

The accuracy of dipyridamole stress/rest 99mTc-MIBI myocardial imaging for detection of ischemia depends on reproducible image interpretation. To evaluate the reproducibility of visual assessment, agreement in interpretation among two independent obervers, blinded to clinieal data, was evaluated in SPECT images of 131 patients (94 males, 38 fe- males, mean age 58+7 yr) with suspected coronary artery disease who underwent both dipyridamole st,ress/rest 99mTc-MJBI myocardial SPECT and coronary angiography, The left ventricle was divided into twenty-nine segments in stress and rest SPECT images and each segment was visually graded according to a five point scale (segmental score : O=normal, 1 =equivocal, 2=mild decrease, 3=severe decrease and 4=absent uptake). Overall concordance of segmental scoring between the two observers was 80%. The Pear- sons correlat.ion coefficient (r) of the segmental scores for stress and rest images were 0.67 and 0.65, respectively, while the difference in score between the two images showed a correlat,ion of 0.45 (all p<0,001). Agreement between two observers in final SPECT diagnosis as absence or presence of disease was 93%. The degree of agr eement in segmental scoring showed no difference between patients with or without agreement as to the presence of disease. Therefore it appeared that cases with inconcordant diagnosis between the 2 observers were mainly due to a difference in individual threshold for interpretating the significance of a particular decreased uptake area rather (han to a difference in perceiving the degree of the hypoactivity, Thus, establishment of individual optimum thresholds in visual interpretation of myocardial SPECT may be helpful to improve reproducibility and acruracy of scan ditagnosis.

뇌 PET 과 MR 영상의 자동화된 3차원적 합성기법 개발

이명철(Myung Chul Lee),정준기(June Key Chung),이동수(Dong Soo Lee),곽철은(Cheol Eun Kwark),이재성(Jae Sung Lee),박광석(Kwang Suk Park) 대한핵의학회 1998 핵의학 분자영상 Vol.32 No.5

N/A Purpose: Cross-modality coregistration of positron emission tomography (PET) and magnetic resonance imaging (MR) could enhance the clinical information. In this study we propose a refined technique to improve the robustness of registration, and to implement more realistic visualization of the coregistered images. Materials and Methods: Using the sinogram of PET emission scan, we extracted the robust head boundary and used boundary-enhanced PET to coregister PET with MR. The pixels having 10% of maximum pixel value were considered as the boundary of sinogram. Boundary pixel values were exchanged with maximum value of sinogram. One hundred eighty boundary points were extracted at intervals of about 2 degree using simple threshold method from each slice of MR images. Best affined transformation between the two point sets was performed using least square fitting which should minimize the sum of Euclidean distance between the point sets. We reduced calculation time using pre-defined distance map. Finally we developed an automatic coregistration program using this boundary detection and surface matching technique. We designed a new weighted normalization technique to display the coregistered PET and MR images simultaneously. Results: Using our newly developed method, robust extraction of head boundary was possible and spatial regishation was successfully performed. Mean displacement error was less than 2.0mm. In visualization of coregistered images using weighted normalization method, structures shown in MR image could be realistically represented. Conclusion: Our refined technique could practically enhance the performance of automated three dimensional coregistration.

99mTc - MIBI 심근 SPECT에서 180도와 360도 데이터 집적의 비교

고창순(Chang Soon Koh),이명철(Myung Chul Lee),정준기(June Key Chung),이동수(Dong Soo Lee),곽철은(Cheol Eun Kwark),현인영(In Young Hyun),강건욱(Keon Wook Kang) 대한핵의학회 1995 핵의학 분자영상 Vol.29 No.4

N/A We compared the influences of reconstruction methods using 180°or 360°data upon contrasts and discriminating capability and diagnostic accuracy in Tc-99m-MIBI stress/rest myocardial SPECT, We reviewed SPECT images reconstructed only with 180°projection data or with 360°data in 18 patients and in 11 normal subjects. To compare counts of surface structures and deep structures, we measured apex/posterior wall ratios in 11 normal subjects. To compare the contrasts of images, we measured apex/ventricle ratios. To compare contrasts between normal and diseased myocardial segments, we measured count ratios of defect and normal segments in 4 patients who had single coronary artery diseases. To compare diagnostic accuracy, we scored SPECT images made with 180°and 360°ata segmentally. Sensitivity and specificity for the diagnosis of coronary artery disease and for the diseased arteries with both 180°and 360°SPECT images. If involvled coronary arteries had more narrowing than 50% in coronary angiogram, we considered them as diseased arteries. Apex/posterior wall ratios were not different significantly in normal subjects. Apex/ventricle ratios in normal subjects were different, significantly between 180°and 360°SPECT images. Defect/normal ratios were different significantly between 180°and 360°SPECT images in single vessel disease patients. The overall diagnostic accurracy was the same between 180°and 360°data collection. Sensitivity was 94% and specificity was 91% for both types of data collection in this sample population. Sensitivity and specificity of each coronary artery territory were not significantly different between the images made with 180°and 360° data. The images made with 180°data had better contrast between ventricle and myocardium and between hypoperfused and normal myocardium, though no difference was found between the ratios of the myocardial counts of surface and deep structures. However, diagnostic sensitivities of diseased artery territories were not different significantly and so were overall diagnostic accuracy between both methods of making images with 180°and 360°data

소아 폐쇄성 요로질환에서 이뇨 신 신티그라피의 정량적 분석

고창순(Chang Soon Koh),이명철(Myung Chul Lee),정준기(June Key Chung),이동수(Dong Soo Lee),최창운(Chang Woon Choi),최용(Yong Choi),이경한(Kyung Han Lee),곽철은(Cheol Eun Kwark),김종호(Jong Ho Kim),최황(Hwang Choi) 대한핵의학회 1993 핵의학 분자영상 Vol.27 No.2

N/A Differentiating the various causes of hydronephrosis from that of obstruction can be very difficult. The decision-marking process for those instances of urinary tract dilatation that require surgical correction and those that do not is based in part on the findings of diuresis renography. The methodology for performing this test has differed among nuclear medicine practitioners and the surgical findings are occasionally discrepant from the diuretic renogram interpretation. Consequently we made an automatic computer software program that calculates the slope of the response curve. The quantitative indices, such as the injection and response t1/2 by linear-fitting and monoexponential-fitting, were compared with the visual assessment of the diuretic cinerenography and clinical outcome in 50 children (62 kidneys) with ureteropelvic junction obstruction. Pooled diuresis renogram data indicated that: (1) Visual evaluation of the diuretic cinerenography is a sensitive (87%, 54/62) tool to differentiate obstruction in suspected ureteropelvic junction obstruction. (2) The cut-off value (maximum washout t1/2 with non- obstruction) of injection and response t1/2 by linear-fitting were 40 min. (3) The sensitivity and specificity using injection and response t1/2 by linear-fitting for obstruction were 89%(23/26) and 100%(30/30), respectively. (4) Response t1/2 as well as injection t1/2 by monoexponential-fitting do not stratify children with possible ureteropelivic junction obstruction. In conclusion, quantitative assessment of diuretic renography as well as visual assessment of diuretic cinerenography correlate well with surgical and clinical outcome of suspected ureteropelvic junction obstruction.