• Restorative Dentistry and Endodontics
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• 제42권4호
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• pp.273-281
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• 2017

Objectives: The aims of this study were to quantify tug-back by measuring the pulling force and investigate the correlation of clinical tug-back pulling force with in vitro gutta-percha (GP) cone adaptation score using micro-computed tomography (${\mu}CT$). Materials and Methods: Twenty-eight roots from human single-rooted teeth were divided into 2 groups. In the ProTaper Next (PTN) group, root canals were prepared with PTN, and in the ProFile (PF) group, root canals were prepared using PF (n = 14). The degree of tug-back was scored after selecting taper-matched GP cones. A novel method using a spring balance was designed to quantify the tug-back by measuring the pulling force. The correlation between tug-back scores, pulling force, and percentage of the gutta-percha occupied area (pGPOA) within apical 3 mm was investigated using ${\mu}CT$. The data were analyzed using Pearson's correlation analysis, one-way analysis of variance (ANOVA) and Tukey's test. Results: Specimens with a strong tug-back had a mean pulling force of 1.24 N (range, 0.15-1.70 N). This study showed a positive correlation between tug-back score, pulling force, and pGPOA. However, there was no significant difference in these factors between the PTN and PF groups. Regardless of the groups, pGPOA and pulling force were significantly higher in the specimens with a higher tug-back score (p < 0.05). Conclusions: The degree of subjective tug-back was a definitive determinant for master cone adaptation in the root canal. The use of the tug-back scoring system and pulling force allows the interpretation of subjective tug-back in a more objective and quantitative manner.

• Journal of Periodontal and Implant Science
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• 제48권4호
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• pp.202-212
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• 2018

Purpose: Bone-to-implant contact (BIC) is difficult to measure on micro-computed tomography (CT) because of artifacts that hinder accurate differentiation of the bone and implant. This study presents an advanced algorithm for measuring BIC in micro-CT acquisitions using a spiral scanning technique, with improved differentiation of bone and implant materials. Methods: Five sandblasted, large-grit, acid-etched implants were used. Three implants were subjected to surface analysis, and 2 were inserted into a New Zealand white rabbit, with each tibia receiving 1 implant. The rabbit was sacrificed after 28 days. The en bloc specimens were subjected to spiral (SkyScan 1275, Bruker) and round (SkyScan 1172, SkyScan 1275) micro-CT scanning to evaluate differences in the images resulting from the different scanning techniques. The partial volume effect (PVE) was optimized as much as possible. BIC was measured with both round and spiral scanning on the SkyScan 1275, and the results were compared. Results: Compared with the round micro-CT scanning, the spiral scanning showed much clearer images. In addition, the PVE was optimized, which allowed accurate BIC measurements to be made. Round scanning on the SkyScan 1275 resulted in higher BIC measurements than spiral scanning on the same machine; however, the higher measurements on round scanning were confirmed to be false, and were found to be the result of artifacts in the void, rather than bone. Conclusions: The results of this study indicate that spiral scanning can reduce metal artifacts, thereby allowing clear differentiation of bone and implant. Moreover, the PVE, which is a factor that inevitably hinders accurate BIC measurements, was optimized through an advanced algorithm.

• 한국정밀공학회지
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• 제26권8호
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• pp.126-131
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• 2009

Acetabular dysplasia is a condition defined by inadequate development of an individual's acetabulum. Individual diversity of the symptoms in this disease needs safe and accurate preoperative planning. Technologies that utilize multidimensional image information are thus important. The assessment method by Janzen et al. was suggested a coefficient method in evaluation of acetabular dysplasia. In this study, we applied it, using a three-dimensional computed tomography (3D CT) on the koreans. 19 cases of the normal hips and 4 cases of the acetabular dysplasia were investigated to evaluate the proved method; 3D CT was used to define the geometric center of the femoral head and to measure center edge angles at $10^{\circ}$ rotational increments around the acetabular rim. Mean and standard deviation in CEAs (Center Edge Angle) of normal 19 hips at $10^{\circ}$ rotational increments from anterior to posterior rim were determined, and termed as a 'normal curve'. Then this normal values were compared with the CEA data measured from 4 cases of acetabular dysplasia patiens. Quantative comparison of the CEA values between the normal cases and dysplasia cases was successfully demonstrated, and thus, we claim that this simple CT method of assessing acetabular dysplasia can be well applicable to diagnosis, quantification and surgical planning for adult acetabular dysplasia patients.

• Archives of Plastic Surgery
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• 제32권4호
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• pp.467-473
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• 2005

Calvarial bone grafting in craniomaxillofacial trauma and facial reconstructive surgery is now widely recognized and accepted as a standard procedure. One of the commonly reported problems of calvarial bone graft is the contour defect caused by partial resorption of the graft. But, there are few reports that discuss the fate of the calvarial bone graft based on the quantitative data. In this article, the changes of grafted calvarial bone were evaluated using 3-dimensional computed tomography(CT). 9 patients were observed with the CT scans at 2mm thickness immediately after operation and at the time of last follow-up. The area of the bone defect was segmented on the 3-dimensional CT image and calculated by AnalyzeDirect 5.0 software. The immediate postoperative bone defect area of the recipient site and the donor site were $612.9mm^2$ and $441.5mm^2$, respectively, which became $1028.1mm^2$ and $268.8mm^2$, respectively at the last follow-up. In conclusion, the bone defect area was less increased on the donor site of calvarial bone graft than on the recipient site. And the CT scan is a valuable imaging method to assess and follow-up the clinical outcome of calvarial bone grafting.

• Journal of Korean Neurosurgical Society
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• 제44권1호
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• pp.15-18
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• 2008

Objective : C2 laminar screw fixation is considered as an excellent alternative to Magerl's transfacetal approach or Harms construct for the atlantoaxial stabilization. However, to our knowledge, there is no report on the feasibility of the new approach to Korean population. We investigated morphometric parameters of the dorsal arch of the C2 to provide the quantitative data for the feasibility of laminar screw fixation. Methods : One-hundred-and-two patients' cervical computed tomography had been reconstructed and investigated on the anatomical parameters related with C2 laminar screw placement. Sixty patients were male and forty-two patients were female. Measurements included the laminar thickness and slope, spino-laminar angle, and maximal screw length. Results : Ages ranged from 20 to 81 and the mean age was 48.4. Mean laminar thickness was 5.7 mm (${\pm}1.0$) (5.8 mm in male and 5.4 mm in female). Fifty-one patients (50%) had a laminar thickness smaller than 5.5 mm at least unilaterally, therefore the patients were considered as inappropriate candidates for the laminar screw fixation in the smaller side of the laminae. Mean value of maximal length of screw was 33.3 mm (34.3 mm in male and 31.9 mm in female). Mean spino-laminar angle was $43.2^{\circ}$ and mean slope angle was $32.9^{\circ}$. Conclusion : Half of patients had inappropriate laminar profiles to accommodate a 3.5 mm screw in at least one side of the axis. The three-dimensional computed tomography reconstruction is mandatory for the preoperative assessment for the feasibility of the C2 lamina.

• Journal of Korean Neurosurgical Society
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• 제54권5호
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• pp.384-389
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• 2013

Objective : Use of quantitative computed tomography (CT) to evaluate bone mineral density was suggested in the 1970s. Despite its reliability and accuracy, technical shortcomings restricted its usage, and dual-energy X-ray absorptiometry (DXA) became the gold standard evaluation method. Advances in CT technology have reduced its previous limitations, and CT evaluation of bone quality may now be applicable in clinical practice. The aim of this study was to determine if the Hounsfield unit (HU) values obtained from CT correlate with patient age and bone mineral density. Methods : A total of 128 female patients who underwent lumbar CT for back pain were enrolled in the study. Their mean age was 66.4 years. Among them, 70 patients also underwent DXA. The patients were stratified by decade of life, forming five age groups. Lumbar vertebrae L1-4 were analyzed. The HU value of each vertebra was determined by averaging three measurements of the vertebra's trabecular portion, as shown in consecutive axial CT images. The HU values were compared between age groups, and correlations of HU value with bone mineral density and T-scores were determined. Results : The HU values consistently decreased with increasing age with significant differences between age groups (p<0.001). There were significant positive correlations (p<0.001) of HU value with bone mineral density and T-score. Conclusion : The trabecular area HU value consistently decreases with age. Based on the strong positive correlation between HU value and bone mineral density, CT-based HU values might be useful in detecting bone mineral diseases, such as osteoporosis.

• 대한의용생체공학회:의공학회지
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• 제24권5호
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• pp.473-480
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• 2003

반복법을 사용한 영상재구성은 기존의 여과역투사 방법에 비해 윌등한 장점을 가지고 있으므로 방출 전산화단층촬영에 있어 매우 중요한 역할을 해왔다. 그러나, 반복법을 사용한 영상재구성법은 데이터의 투사 및 역투사 계산의 반복으로 이루어져 있으므로 한 영상을 재구성하는데 필요한 계산량은 알고리즘의 구현을 위해 사용된 투사기 및 역투사기의 성능에 크게 좌우된다. 본 연구에서는 투사기 및 역투사기를 구현하기 위한 대표적 방법들의 성능을 정량적으로 비교한다. 각 구현방법에 있어서 투사-역투사 계산에 필요한 연산량을 줄이기 위해 이전에 계산된 결과들을 재사용함으로써 불필요하게 반복되는 연산들을 최소화하도록 하는 방법에 고찰한다. 실험결과에 의하면 선추적법은 연산속도 면에서 다른 방법에 비해 우수할 뿐 아니라, 정확성이 높은 개선된 영상을 제공하는 것으로 나타났다.

• Investigative Magnetic Resonance Imaging
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• 제20권4호
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• pp.241-249
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• 2016

Purpose: To evaluate the added value of diffusion weighted imaging (DWI) to computed tomography (CT) for detecting pancreatic abnormality in patients with clinically suspected acute pancreatitis (AP). Materials and Methods: 203 patients who underwent abdomen CT and subsequent DWI to do a workup for epigastric pain were analyzed. Two blinded radiologists independently performed an interval reading based on CT image sets first, then based on combined CT and DWI image sets. The diagnostic criterion on DWI was the increased signal intensity in the pancreas to that of the spleen. For quantitative analysis, the third radiologist measured ADC value of the pancreas in each patient. Results: For AP (n = 43), the sensitivity for detecting pancreatic abnormality increased, from 42% to 70% for reader 1 (P < 0.05) and from 44% to 72% for reader 2 (P < 0.05). For borderline pancreatitis (n = 42), the sensitivity also increased, from 10% to 26% for reader 1 (P < 0.05) and from 7% to 29% for reader 2 (P < 0.05). The mean ADC values (unit, ${\times}10^{-3}mm^2/s$) were significantly different among the three groups (for AP, $1.09{\pm}0.16$; for borderline pancreatitis, $1.28{\pm}0.2$; for control, $1.46{\pm}0.15$, P < 0.05). Conclusion: Sensitivity for detecting pancreatic abnormality increased significantly after adding DWI to CT in patients with clinically suspected AP.

• 대한방사선기술학회지:방사선기술과학
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• 제36권2호
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• pp.141-148
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• 2013

CT 검사 시 뇌출혈의 부위는 심각한 정도에 따라 인지하기 어려운 경우도 있으며, 응급상황에서 숙련이 되지 않은 의료진에게는 부담을 준다. 응급상황에서 검사와 동시에 뇌출혈부위를 자동으로 빨리 파악하고 정량적인 정보를 제공하는 보조적인 역할은 필요하며, 컴퓨터를 이용한 자동 검출 및 인식 시스템은 출혈부위 진단에 매우 큰 도움을 줄 수 있다. 본 연구에서는 출혈부위를 문턱치값 처리, 모폴로지 연산, 원형률 계산을 접목하여 뇌 출혈부위의 자동검출에 성공하였고 검출 후보군에서 잘 못 선정된 영역을 판정하기위한 주성분분석을 이용한 분류기 개발에 성공하였다. 개발된 시스템을 응급상황의 뇌출혈 환자에게 적용한다면 의료진에게 수술계획을 위한 유용한 정보가 될 것으로 사료된다.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2003년도 제120회 추계학술대회 제 5차 한ㆍ일 치과보존학회 공동학술대회
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• pp.547-547
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• 2003

The aim of this study was to compare the effects of three Ni-Ti instruments on leaning ability by evaluating the volumetric and morphological changes in the apical 6mm of the root canals before and after preparation, using three-dimensionally reconstructed root canals of extracted human teeth. Forty-five teeth were used in this study. They were opened the chambers and removed the all pulp remnants ultrasonically. Subsequently, the canal wall was coated with silver paste and prepared using ProTaper, ProFile and GT rotary files according to the manufacturers instructions. Before and after root canal preparation, all the specimens were scanned with micro computed tomography and examined the differences in dentine volume removed, canal straightening, the proportion of the unchanged area and canal transportation. Quantitative analysis revealed that instrumentation increased in canal volume ranging between 0.081 and $1.866{\;}\textrm{mm}^3$. On average, the large apical preparation produced by ProTaper demonstrated smaller proportions of unchanged surface areas compared to the two other instruments in small canals. But in large canals like maxillary central incisor, the preparation of ProTaper instruments was not enough. ProTaper instrument was tended to increase more in canal volume as compared with the other two instruments but unchanged area was no significant difference. These results showed that three instruments had similar preparation ability and micro computed tomography in combination with the coated wall of root canal using silver paste is a nondestructive and valuable tool to study root canal geometry and changes after preparations in detail.