• 전자공학회논문지C
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• 제34C권4호
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• pp.26-35
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• 1997

This paper proposes a multi-bit $\Sigma\Delta$ modulator arcitecture which eliminates signal clipping problem. To avoid signal clipping, the output values of intgrators are monitored and modified by a reference value. This oepration is recorded as a digital code to restore actual signal value. Due to the digital code, the substraction of feedback value from the multi-bit quantizer can be calculated by a digital adder and this simplifies dAC operation making the accurate DAC of conventional multi-bit $\Sigma\Delta$ modulator scheme unnecessary. These features make N-th modulator can be implemented by sharing an integrator among N stages to decrease the required chip area. As an experimental example, a 4th order .sum..DELTA. modulator with oversampling ratio of 64 was simulated to show over 130 DB SNR at rail-to-rail input sinusoidal signal.

• Tuberculosis and Respiratory Diseases
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• 제46권1호
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• pp.116-121
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• 1999

Unilateral hypoplasia of the pulmonary artery is an uncommon anomaly, which commonly develops in combination with congenital cardiovascular defects such as tetralogy of Fallot, patent ductus arteriosus and septal defect of atrium or ventricle, but may also present as an isolated lesion. We have recently experienced a case of the left pulmonary artery hypoplasia in adult by chance of during the general health screen, which diagnosed by chest X-ray, chest spiral CT, lung perfusion and ventilation scan, digital substraction angiogram and bronchoscopy, then presented hereby with the review of relevant literature.

• 대한전자공학회논문지
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• 제26권2호
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• pp.132-139
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• 1989

본 연구에서는 심장의 박동영상을 방사선 투시법으로 관찰하여 심장질환을 진단하기 위한 실시간 처리 심장 디지탈 감산 조영 영상기법(cardiac digital subtraction angiography)을 개발하여 임상실험을 시행하였다. 평균 1초에 1번의 심장박동에 따른 주변부위의 운동에 의한 오차의 영향을 감소하면서, 좌심실 박동상을 32프레임까지 실시간으로 감산 처리하는 고속기억(512X512 해상도와 256 gray level) 및 고속 데이타링크 시스템과 프로세서를 개발하였다. 기억된 영상을 컴퓨터에 입력하고, 심장의 경계면을 Dynamic Programming을 사용하여 검출하고, 부피를 구하여 심장의 박동에 따른 최대부피(ESV)와 박동후 최소부피(ESV), 최대와 최소부피의 비율(EF)로서 표시되는 심박출계수 등 심장의 좌심실기능을 나타내는 생리계수를 영상으로 부터 구하는 알고리듬을 개발해서 임상실험을 시행하였다.

• Journal of Periodontal and Implant Science
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• 제32권1호
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• pp.199-211
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• 2002

Digital substraction technique and computer-assisted densitometirc analysis detect minor change in bone density and thus increase the diagnostic accuracy. This advantage as well as high sensitivity and objectivity which precludes human bias have drawn interest in radiologic research area. The objectives of this study are to verify if Radiographic density can be recognized in linear pattern when density profile of standard periapical radiograph with the aluminium stepwedge as the reference, was investigated under varies circumstances which can be encountered in clinical situations, and in addition to that to obtain mutual relationship between the existing standard radiographic system, and future digital image systems, by confirming the corelationship between the standard radiograph and Digora system which is a digital image system currently being used. In order to make quantitative analysis of the bone tissue, digital image system which uses high resolution automatic slide scanner as an input device, and Digora system were compared and analyzed using multifunctional program, Brain3dsp. The following conclusions were obtained. 1. Under common clinical situation that is 70kVp, 0.2 sec., and focal distance 10cm, Al-Equivalent image equation was found to be Y=11.21X+46.62 $r^2=0.9898$ in standard radiographic system, and Y=12.68X+74.59, $r^2=0.9528$ in Digora system, and linear relation was confirmed in both the systems. 2. In standard radiographic system, when all conditions were maintained the same except for the condition of developing solution, Al-Equivalent image equation was Y=10.07X+41.64, $r^2=0.9861$ which shows high corelationship. 3. When all conditions were maintained the same except for the Kilovoltage peak, linear relationship was still maintained under 60kVp, and Al-Equivalent image equation was Y=14.60X+68.86, $r^2=0.9886$ in the standard radiograhic system, and Y=13.90X+80.68, $r^2=0.9238$ in Digora system. 4. When all conditions were maintained the same except for the exposure time which was varied from 0.01 sec. to 0.8 sec., Al-Equivalent image equation was found to be linear in both the standard radiographic system and Digora system. The R-square was distributed from 0.9188 to 0.9900, and in general, standard radiographic system showed higher R-square than Digora system. 5. When all conditions were maintained the same except for the focal distance which was varied from 5cm to 30cm, Al-Equivalent image equation was found to be linear in both the standard radiographic system and Digora system. The R-square was distributed from 0.9463 to 0.9925, and the standard radiographic system had the tendency to show higher R-square in shorter focal distances.

• Archives of Reconstructive Microsurgery
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• 제13권2호
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• pp.130-135
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• 2004

Purpose : To observe the patency of anastomosis site and the findings of circulation of grafted fibula in osteonecrosis of femoral head treated with vascularized fibular graft by use of digital subtraction angiography. Materials and Methods : 17 cases of 11 patients who underwent vascularized fibula graft for osteonecrosis of femoral head. We performed digital subtraction angiography(DSA) for them at second week postoperatively in 12 cases, at sixth week in 1 case, at sixth month in 2 cases, at twelfth month in 1 case, and eighteenth month in 1 case which had been got DSA at second week before. We observe the patency of pedicle, and the circulation of grafted fibula such as periosteal and intraosseous vessels with time. Results : All cases except one which were thought failure of selective angiogram showed good passage of blood flow through anstomosed pedicle on DSA. We found the differences in appearance of circulation of grafted fibula with time. DSA at 2nd and 6th week postoperatively revealed both of periosteal and intraosseous vessels along the fibula and blood pooling at the tip of fibula. DSA at 6th month showed maintenance of periosteal and intraosseous vessels along the fibula but did not clearly reveal blood pooling at the tip of fibula. The findings of DSA at 12th and 18th month were similar each other. The periosteal vessels were not seen as the grafted fibular bone were incorporated into surrounding femoral bone but intraosseous vessels were still seen. Conclusion : It was thought that DSA could be used for evaluation of the status of pedicle including anastomsed site and vessels of grafted fibula with time. The periosteal vessels of fibula were decreased with time but intraosseous vessels were still seen until 18th month after vascularized fibula graft.

• The Korean Journal of Pain
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• 제20권1호
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• pp.26-30
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• 2007

Background: Epidural steroid injections (ESI) are a common treatment for spinal disorders. Previous research has shown that aspiration of the syringe is not a sensitive test for placement of an intravascular needle. Serious complications have been reported from injection of steroids and local anesthetics into the vascular space. In addition to safety concerns, the efficacy may decline with partial injection outside the desired epidural location. We hypothesized that incidence of vascular problems is increased in patients who undergo spine surgery compared with the patients who don't undergo spine surgery. We investigated the incidence of vascular problems during lumbosacral transforaminal ESI and we compared the difference of vascular problems between the patients who undergo spinal surgery and those patients who don't undergo spinal surgery. Methods: Two hundreds and three patients were consecutively recruited and they received 299 fluoroscopically guided lumbosacral transforaminal ESIs. Injection of contrast was performed under live dynamic fluoroscopy with using digital substraction analysis. The observed uptake pattern was classified into one of three categories: flashback, aspirated, and positive contrast with negative flashback and aspiration. Results: The vascular incidence rate was 20.4%. Transforaminal ESIs performed at S1 had avascular incidence rate of 27.8% compared with 17.7% for all the other lumbar injection sites. The sensitivity of spontaneous observation of blood in the needle hub or blood aspirate for predicting an intravascular injection in lumbar transforaminal ESIs was 70.4%. Conclusions: There is a high incidence of intravascular problems when performing transforaminal ESIs, and this is significantly increased in patients with previous spine surgery. Using a flash or blood aspiration to predict an intravascular injection is not sensitive therefore; a negative flash or aspiration is not reliable. Fluoroscopically guided procedures without contrast confirmation are prone to instill medications intravascularly. This finding confirms the need for not only fluoroscopic guidance, but also for contrast injection instillation when performing lumbosacral transforaminal ESIs, and especially for patients with previous spine surgery.

• 구강회복응용과학지
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• 제28권1호
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• pp.1-13
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• 2012

짧은 임플란트는 상악동이나 하치조신경 등의 해부학적 구조물이 있거나 심한 치조골 흡수로 인해 제한적인 치조제 높이를 가지는 부위에서 사용되고 있다. 본 연구는 길이 10 mm 이하의 임플란트에서 임플란트의 길이, 직경, 식립 부위, 골이식술 유무, 보철물의 연결고정 유무가 임플란트의 생존율과 변연골 흡수에 미치는 영향을 알아보고자 하였다. 원광대학교 치과병원 임플란트센터에서 길이 10 mm 이하의 임플란트를 식립한 137명의 환자, 227개 임플란트를 대상으로 진료 기록부를 통해 임플란트의 길이, 직경, 식립 위치, 골이식 유무, 보철물의 연결고정 유무를 조사하였다. 변연골 흡수량은 Emago advanced v5.6(Oral diagnostic systems, Amsterdam, The Netherlands) 프로그램을 이용하여 측정하였다. 총 227개의 임플란트 중 8개가 실패하여, 전체 짧은 임플란트의 생존율은 96.5 %로 나타났다. 골이식 부위와 상악에 식립된 경우 더 높은 실패율을 보이는 경향이 있었으며, 임플란트의 길이와 직경은 변연골 흡수량에 영향을 미치지 않았다. 실패 요인을 조사하였을 때, 상악의 불량한 골질과 골이식 유무가 임플란트의 더 높은 실패율에 영향을 미쳤다. 10 mm 이하 임플란트에서 길이, 직경, 식립 부위, 골이식술과 보철물의 연결 고정은 임플란트 생존율과 변연골 흡수량에 영향을 끼치지 않았다.