• Imaging Science in Dentistry
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• 제51권1호
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• pp.41-47
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• 2021

Purpose: This study aimed to compare the accuracy of 3-dimensional(3D) printed models derived from multidetector computed tomography (MDCT) and cone-beam computed tomography (CBCT) systems with different fields of view (FOVs). Materials and Methods: Five human dry mandibles were used to assess the accuracy of reconstructions of anatomical landmarks, bone defects, and intra-socket dimensions by 3D printers. The measurements were made on dry mandibles using a digital caliper (gold standard). The mandibles then underwent MDCT imaging. In addition, CBCT images were obtained using Cranex 3D and NewTom 3G scanners with 2 different FOVs. The images were transferred to two 3D printers, and the digital light processing (DLP) and fused deposition modeling (FDM) techniques were used to fabricate the 3D models, respectively. The same measurements were also made on the fabricated prototypes. The values measured on the 3D models were compared with the actual values, and the differences were analyzed using the paired t-test. Results: The landmarks measured on prototypes fabricated using the FDM and DLP techniques based on all 4 imaging systems showed differences from the gold standard. No significant differences were noted between the FDM and DLP techniques. Conclusion: The 3D printers were reliable systems for maxillofacial reconstruction. In this study, scanners with smaller voxels had the highest precision, and the DLP printer showed higher accuracy in reconstructing the maxillofacial landmarks. It seemed that 3D reconstructions of the anterior region were overestimated, while the reconstructions of intra-socket dimensions and implant holes were slightly underestimated.

• Journal of Preventive Medicine and Public Health
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• 제30권1호
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• pp.195-207
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• 1997

High price equipment is one of the major factors that increases national health expenditure in developed countries. Computerized Tomography(CT), one of the important high price equipment, has been concerns of health service researchers and policy makers in many countries. In Korea, CT, first introduced in 1984, have spreaded nationwide with rapid speed. Though the Committee for Approving Import of High Price Medical Equipment, founded in 1981, tried to regulate the introduction of high price medical equipment including CT, the effort resulted in failure. The exact situation of diffusion of the high price equipment, however, was not yet investigated. We aimed at the description of the diffusion of CT in Korea and analysis of influencing factors on hospitals for the adoption of CT. We mainly used the database of CT, made in 1996 by the National Federation of Medical Insurance for the purpose of insurance payment for CT. Also characteristics of hospitals were gathered from yearbooks published by the central and local governments and by the Korean Hospital Association. We calculated the cumulative number of the CT per one million population year by year. In turn, multiple linear logistic regression was done to find out the contributing factors for the adoption of CT by each hospital. In the logistic regression model, it is regarded as dependent factor whether a hospital retained CT or not in 1988 and 1993. The major categories of the independent factors were hospital characteristics, environmental factors and competitive conditions of hospitals at the period of the adoption. The results are as follows: Number of CT scanners per one million persons in Korea marked more higher level compared with those of most OECD countries. Major influencing factors on the adoption of CT scanners were hospital characteristics, such as hospital referral level, and competitive condition of hospitals, such as number of CT scanners per 10,000 persons in each district where the hospital was located. In Korea, CT diffused with rather rapid speed, comparable with those of the United States and Japan. The major factors contributing on the adoption of CT for hospitals were competitive condition and hospital characteristics rather than regional health care need for CT. In conclusion, a kind of regulating mechanism would be necessary for the prevention of the indiscreet adoption and inefficient use of high price equipment including CT.

• Journal of Korean Dental Science
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• 제15권1호
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• pp.1-8
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• 2022

Purpose: Intraoral scanners, desktop scanners, and cone-beam computed tomography (CBCT) are being used in a complementary way for diagnosis and treatment planning. Limited patient-based results are available about dimensional reproducibility among different three-dimensional imaging systems. This study aimed to evaluate dimensional reproducibility among patient-derived digital models created from an intraoral scanner, desktop scanner, and two CBCT systems. Materials and Methods: Twenty-nine arches from sixteen patients who were candidates for implant treatments were enrolled. Different types of CBCT systems (KCT and VCT) were used before and after the surgery. Polyvinylsiloxane impressions were taken on the enrolled arches after the healing period. Gypsum casts were fabricated and scanned with an intraoral scanner (CIOS) and desktop scanner (MDS). Four test groups of digital models, each from CIOS, MDS, KCT, and VCT, respectively, were compared to the reference gypsum cast group. For comparison of linear measurements, intercanine and intermolar widths and left and right canine to molar lengths were measured on individual gypsum cast and digital models. All measurements were triplicated, and the averages were used for statistics. Bland-Altman plots were drawn to assess the degree of agreement between each test group with the reference gypsum cast group. A linear mixed model was used to analyze the fixed effect of the test groups compared to the reference group (α=0.05). Result: The Bland-Altman plots showed that the bias of each test group was -0.07 mm for CIOS, -0.07 mm for MDS, -0.21 mm for VCT, and -0.25 mm for KCT. The linear mixed model did not show significant differences between the test and reference groups (P>0.05). Conclusion: The linear distances measured on the digital models created from CIOS, MDS, and two CBCT systems showed slightly larger than the references but clinically acceptable reproducibility for diagnosis and treatment planning.

• Imaging Science in Dentistry
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• 제47권1호
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• pp.11-15
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• 2017

Purpose: This study was performed to investigate the intra- and inter-observer variability in linear measurements with axial images obtained by PreXion (PreXion Inc., San Mateo, USA) and i-CAT(Imaging Sciences International, Xoran Technologies Inc., Hatfield, USA) CBCT scanners, with different voxel sizes. Materials and Methods: A cylindrical object made from nylon with radiopaque markers (phantom) was scanned by i-CAT and PreXion 3D devices. For each axial image, measurements were taken twice in the horizontal(distance A-B) and vertical (distance C-D) directions, randomly, with a one-week interval between measurements, by four oral radiologists with five years or more experience in the use of these measuring tools. Results: All of the obtained linear measurements had lower values than those of the phantom. The statistical analysis showed high intra- and inter-observer reliability (p=0.297). Compared to the real measurements, the measurements obtained using the i-CAT device and PreXion tomography, on average, revealed absolute errors ranging from 0.22 to 0.59 mm and from 0.23 to 0.63 mm, respectively. Conclusion: It can be concluded that both scanners are accurate, although the linear measurements are underestimations, with no significant differences between the evaluators.

• 대한방사선기술학회지:방사선기술과학
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• 제8권2호
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• pp.29-45
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• 1985

Computed Tomography Scanner (CT) is highly expensive in operation as well as purchasing. That reason may cause not only to increase the burden of patients but also to waste the capital resources leading to financial difficulties. However the numbers of CT installed throughout the country is increasing, because of efficiency in medical care, patient's concern, competitions among the hospitals within the same area. In the non-Metropolitan area the scanners were expected to be less utilized and less profitable. Nine hospitals equipped with the CT were studied on the utilization of that equipment during the period from November 1984 to February 1985 in non-Metropolitan area and break-even point in one hospital was analyzed for estimating profitabilities. The results were as follows ; 1. Among those nine hospitals, four hospitals had less than 400 beds, which is one of the restrictive minimum standards on the installation of Whole-body Computed Tomography Scanner. 2. The operating time during the normal operation period was longer than those of any other studies, but the accumulated down time was also longer than those of any other studies. The average number of scanning per week for each CT was 45, while the estimated number of for the break-even point was 56.7 cases. 3. When the downtime was excluded in calculating the average operation would be much closer to the cases for the break-even point. Therefore the break-down of the equipment was to be a main cause of the low profitability. 4. The average scanning rate for head area was 33.6%, however three of the nine hospitals showed about 20%. 5. If scanning ratio for the body parts excepting head was increased, the number of scanning for the break-even point would be diminished. 6. The small size hospital especially located near the Metropolitan area showed largest loss in the CT operation. In purchasing the highly expensive equipments in hospitals, demand should be taken into account and planning is recommended.

• 대한치과교정학회지
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• 제50권1호
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• pp.13-25
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• 2020

Objective: The aim of this study was to compare the accuracy and reliability of measurements performed using two different software programs on digital models generated using two types of plaster model scanners (a laser scanner and a computed tomography [CT] scanner). Methods: Thirty plaster models were scanned with a 3Shape laser scanner and with a Flash CT scanner. Two examiners performed measurements on plaster models by using digital calipers and on digital models by using Ortho Analyzer (3Shape) and Digimodel^® (OrthoProof) software programs. Forty-two measurements, including tooth diameter, crown height, overjet, overbite, intercanine and intermolar distances, and sagittal relationship, were obtained. Results: Statistically significant differences were not found between the plaster and digital model measurements (ANOVA); however, some discrepancies were clinically relevant. Plaster and digital model measurements made using the two scanning methods showed high intraclass coefficient correlation values and acceptable 95% limits of agreement in the Bland-Altman analysis. The software used did not influence the accuracy of measurements. Conclusions: Digital models generated from plaster casts by using laser and CT scanning and measured using two different software programs are accurate, and the measurements are reliable. Therefore, both fabrication methods and software could be used interchangeably.

• Tuberculosis and Respiratory Diseases
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• 제57권6호
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• pp.515-521
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• 2004

With the increasing resolution of modern CT scanners, analysis of the larger numbers of images acquired in a lung screening exam or diagnostic study is necessary, which also needs high accuracy and reproducibility. Recent developments in the computerized analysis of medical images are expected to aid radiologists and other healthcare professional in various diagnostic tasks of medical image interpretation. This article is to provide a brief overview of some of computer-aided diagnosis schemes in chest CT.

• 대한의용생체공학회:의공학회지
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• 제41권4호
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• pp.147-153
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• 2020

This study was to evaluate the usability of self-developed phantom for evaluating automatic exposure control (AEC) using three-dimensions (3D) printer. 3D printer of fused deposition modeling (FDM) type was utilized to make the self-developed AEC phantom and image acquisitions were conducted by two different type of scanners. The self-developed AEC phantom consisted of four different size of portions. As a result, two types of phantom (pyramid and pentagon shape) were created according to the combination of the layers. For evaluating the radiation dose with the two types of phantom, the values of tube current, computed tomography dose index volume (CTDIvol), and dose length product (DLP) were compared. As a result, it was confirmed that the values of tube current were properly reflected according to the thickness, and the CTDIvol and DLP were not significantly changed regardless of AEC functions of different scanners. In conclusion, the self-developed phantom by using 3D printer could assess whether the AEC function works well. So, we confirmed the possibility that a self-made phantom could replace the commercially expensive AEC performance evaluation phantom.

• 대한소아치과학회지
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• 제49권1호
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• pp.57-64
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• 2022

콘빔 전산화 단층촬영(CBCT)은 치열을 왜곡시켜 추가 치열 이미지가 필요하다. 치열 이미지로 주로 사용되는 석고 모형을 대신해 구강 스캐너로 CBCT의 치열 이미지를 보완할 때의 임상적 활용 가능성을 평가하였다. 만 12 - 18세의 20명에게 상악에 대한 석고 모형, 구강 스캔 이미지, CBCT이미지를 획득하였다. 비교를 위해 두 종류의 구강 스캐너를 이용하였는데, 그 중 하나의 구강 스캐너로는 전악을 3분할하여 각각을 스캔한 후 이들을 병합해 전악 이미지를 획득하는 방법을 추가로 시행하였다. 구강 스캐너를 이용해 얻은 가상 골격-치열 하이브리드 이미지를 석고 모형을 통해 얻은 이미지와 중첩하여 각 기준점에서의 좌표 값의 차이와 거리를 측정하였다. 결과적으로 구강 스캐너로 분할하여 스캔하는 방법을 시행했을 때 평균 거리 2 ㎛를 보여 가장 적게 나타났다. 구강 스캐너를 적절히 이용하면 가상 골격-치열 하이브리드 이미지를 위한 치열 이미지로 훌륭히 활용될 수 있을 것이다.

• 대한방사선기술학회지:방사선기술과학
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• 제33권3호
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• pp.231-237
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• 2010

CT장치는 많은 발전과 임상적 유용성이 향상되고, 의료영상 진단 장치로 중요성을 확립하였다. 그러나 이용률과 보급률이 더욱 증가되고 있는 실정에서 CT에 의한 진단은 환자의 피폭선량이 비교적 높은 검사이기 때문에 이 점에 있어서도 관심이 증가하고 있다. 이에 본 연구에서는 이용량이 계속 증가될 것이므로 이에 따른 방사선 피폭도 증가할 것으로 예상되므로 우리나라에서 시행되는 CT검사건수 및 CT 검사에 의한 집단실효선량을 추정하고자 한다. DLP(총 선량의 측정값)는 의료기관에서 사용하고 있는 장비의 각각의 검사 영상에 대하여 평균의 선량을 적용하고 계산하여 조사하였으며, CT검사건수는 의료보험심사평가원의 2008년도 발표 자료를 참고로 하여 의료기관 종별로 3년간 검사 통계를 EUR 16262에서 제시된 부위에 준하여 조사하였다. CT장비의 도입규제 완화정책으로 2010년 3월 말 현재 국내에서 총 1,825대를 보유하고 있고, 인구 백만 명 당 36.8대이다. 의료기관별 CT장치의 설치비율이 의원급에서는 570대로 2.1 %, 병원 급에서 52.5 %의 기관이 보유하고 있다. 종합전문요양기관은 기관 당 장치가 3.84대이며, 종합병원은 1.44대를 보유하고 있다. 1996년 건강보험급여가 실시된 이후 CT진료비 청구건수와 진료비용은 10년(2006) 만에 5배에 가깝게 급증하고 있다. 2007년 전국에서 실시한 CT검사건수는 329만 건이었다. 인구 천 명당 검사건수는 68건이었다. 부위별 검사건수는 복부와 골반검사가 가장 많았다. 집계결과를 2007년도 통계청 우리나라 총 인구는 48,456,000명을 이용하여 연간으로 추계한 총 집단실효선량을 나누어 구한 국민 1인 당 선량은 0.952 mSv로 추정되었다. CT검사는 앞으로도 증가가 예상되며, 투시 등 응용도 확대될 것으로 생각된다. 그러나 한편으로 장치의 발전도 눈부실 것이며, 환자 각자의 체격에 따라 자동적으로 가장 적합한 검사조건을 선택할 수 있는 장치가 개발되어 피폭의 최적화가 기대된다.