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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.
송인찬,곽철은,민병구,Song, In-Chan,Kwack, Cheol-Eun,Min, Byoung-Goo 대한의용생체공학회 1990 의공학회지 Vol.11 No.2
As a part of the study on ultrasonic tissue characterization, conventional ultrasonic imaging system is interfaced to the personal computer to acquire raw ultrasonic signal. One approach for tissue charaterization is performed using the attenuation map to the conventional images and the resulting attenuation map images are compared and inspected inside the region of interest from the viewpoint of pattern analysis. Currently, these methods are applied and modified to effectively find out the differences between the normal control and the patients with liver cirrhosis.
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.