• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.4
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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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• v.46 no.1
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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.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.2
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• pp.132-139
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• 1989

We have designed a real-time Cardiac digital substraction angiography system (C-DSA) and tested the system for the diagnosis of Cardiac patients. The system was developed by interfacing a radiographic angiography system to a computerized motional image analysis system. This new cardiac DSA can perform the real time processing of averaging and subtraction of the 32 image frames to measure the volume changes of the left ventricle after elimination of motional artrifacts, caused by the heart contraction of beats per minute in average. Each frame has a resolution of 512 x 512 pixels and 256 gray levels. Two image data with maximal and minimal volume were moved to the interfaced IBM PC computer system by high speed computer link line for computation of the heart's contraction parameters. First, the boundary of the left ventricule was detected using a dynamic programming of the gray levels, and its volume was computered to determine the parameters, such as the maximal volume of end-diastolic volume (EDV), the minimal volume of end systolic volume (ESV), and ejection fraction (EF).

• Journal of Periodontal and Implant Science
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• v.32 no.1
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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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• v.13 no.2
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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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• v.20 no.1
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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.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.1
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• pp.1-13
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• 2012

Short implants are used in parts which have anatomical structures like maxillary sinus, inferior alveolar nerve and limited alveolar height due to severe alveolar bone resorption. In these case, there are no need of additional bone augmentation so there are advantages like reduced entire treatment time, reduced patient's discomfort and protection of important anatomical structures. The aim of this study is, in implants whose length is less than 10mm, to analyze the impact of implant length, diameter, location of implant placement, presence of bone graft, presence of prosthesis splinting on survival rates and marginal bone resorption. The samples used in this study were 227 implants, less than 10mm, placed in 137 patients in Wonkwang university dental hospital implant center. From dental charts the information about implant length, diameter, location of implant placement, presence of bone graft, presence of prosthesis splinting were obtained. Emago advanced v5.6(Oral diagnostic systems, Amsterdam, The Netherlands)program was used to measure the amount of marginal bone resorption. Out of total 227 implants, resulting in 96.5 % of survival rate. There was a tendency toward higher failure rates for the maxilla and bone graft site. No significant difference in marginal bone resorption was found associated with length of implants(p>0.05) and neither with the diameter of implants. Among the risk factors examined, more failure rates of short implants can be attributed to poor bone quality in the maxilla and presence of bone graft. At implants under 10mm, length, diameter, location of implant placement, bone graft and splinting of prosthesis didn't affect marginal bone loss.