• Proceedings of the Korean Society of Medical Physics Conference
• /
• 1999.11a
• /
• pp.266-267
• /
• 1999

• Imaging Science in Dentistry
• /
• v.33 no.4
• /
• pp.211-215
• /
• 2003

Purpose: To assess the radiographic findings of odontogenic cysts showing displacement of the mandibular canal using computed tomographic (CT) and panoramic images. Materials and Methods : CT and panoramic images of 63 odontogenic cysts (27 dentigerous, 16 odontogenic keratocysts, and 20 radicular cysts) were analyzed to evaluate the following parameters: the dimension and shape of the cysts, and the effect of the cysts on the mandibular canal and cortical plates. Results: Of the 63 cysts examined in the study, 35 (55.6%) showed inferior displacement of the mandibular canal and 46 (73.0%) showed perforation of the canal. There were statistically significant differences between CT and panoramic images in depicting displacement and perforation of the mandibular canal. Cortical expansion was seen in 46 cases (73.0%) and cortical perforation in 23 cases (36.5%). The radicular cysts showed cortical expansion and perforation less frequently than the other cyst groups. Conclusion: Large cysts of mandible should be evaluated by multiplanar CT images inorder to detect the mandibular canal and cortical bone involvement.

• Tuberculosis and Respiratory Diseases
• /
• v.56 no.4
• /
• pp.343-347
• /
• 2004

Congenital bronchial atresia is a rare anomaly, which results from a congenital focal obliteration of a proximal segmental or subsegmental bronchus, with normal development of the distal structures. The short atretic segment leads to the accumulation of mucus within the distal bronchi, forming a bronchocele and air trapping of the alveoli supplied by these bronchi. The diagnostic CT features include the presence of a branching opacity and the bronchocele, which radiate from the hilum and are surrounded by an area of hyperlucency.

• Imaging Science in Dentistry
• /
• v.37 no.1
• /
• pp.45-51
• /
• 2007

Purpose : This study aimed to identify the range of normal facial asymmetry using three-dimensional CT and to develop a simple method of diagnosis of facial asymmetry. Materials and Methods : Twenty eight adults with normal occlusion (16 males and 12 females; mean age 24 years and 1 month) were selected whose faces were assessed to be symmetric by an orthodontist. Three-dimensional reconstructions were obtained utilizing spiral CT scans and an oral and maxillofacial radiologist evaluated nineteen anatomic landmarks in three-dimensional coordinates. Facial asymmetry index of each landmark was caluculated. Results : The range of normal facial asymmetry of each landmark was identified using mean and standard deviation of facial asymmetry index. Conclusions : The range of normal facial asymmetry identified in this study may be used as a diagnostic standard for facial asymmetry analysis.

• Journal of the Korean Institute of Gas
• /
• v.15 no.4
• /
• pp.39-43
• /
• 2011

In this study, the stress and deformation behavior characteristics of a flexible joint for a gas pipe have been analyzed by a finite element method. These characteristic results may investigate the strength safety analysis of a flexible joint, which is composed by a spiral corrugation pipe or a rectangular corrugation model and a plane pipe. The FEM computed results show that an optimized spiral corrugation pipe model is a inclined angle of $4.7^{\circ}$ and a corrugation height of 1.5mm. And also, a rectangular corrugation pipe model of $90^{\circ}$ is recommended in strength safety rather than a spiral corrugation pipe with an inclined angle. Thus, a corrugated pipe for an increased strength safety is to recommend a reduced pitch and curvature radius of an inclined corrugation.

• Journal of Veterinary Clinics
• /
• v.30 no.4
• /
• pp.268-272
• /
• 2013

The purpose of this study was to assess the effects of reconstruction kernel, and slice thickness on the accuracy of spiral CT-based volume assessment over a range of object sizes typical of synthetic simulated tumor. Spiral CT scanning was performed at various reconstruction kernels (soft tissue, standard, bone), and slice thickness (1, 2, 3 mm) using a phantom made of gelatin and 10 synthetic simulated tumors of different sizes (diameter 3.0-12.0 mm). Three-dimensional volume assessments were obtained using an automated software tool. Results were compared with the reference volume by calculating the percentage error. Statistical analysis was performed using ANOVA and setting statistical significance at P < 0.05. In general, smaller slice thickness and larger sphere diameters produced more accurate volume assessment than larger slice thickness and smaller sphere diameter. The measured volumes were larger than the actual volumes by a common factor depending on slice thickness; in 100HU simulated tumors that had statistically significant, 1 mm slice thickness produced on average 27.41%, 2 mm slice thickness produced 45.61%, 3 mm slice thickness produced 93.36% overestimates of volume. However, there was no statistically significant difference in volume error for spiral CT scans taken with techniques where only reconstruction kernel was changed. These results supported that synthetic simulated tumor size, slice thickness were significant parameters in determining volume measurement errors. For an accurate volumetric measurement of an object, it is critical to select an appropriate slice thickness and to consider the size of an object.

• Journal of Radiation Protection and Research
• /
• v.30 no.3
• /
• pp.113-119
• /
• 2005

The computed tomogrpahy(CT) provides a high quality in images of human body but contributes to the relatively high patient dose. The frequency of CT examination is increasing and, therefore, the concerns about the patient dose are also increasing. In this study the experimental determination of patient dose was performed by using a physical anthropomorphic phantom and thermoluminescent dosimeter(TLD). The measurements were done for the both axial and spiral scan mode. As a result the effective doses for each scan mode were 17.78mSv and 10.01 mSv respectively and the fact that the degree of the reduction in the patient dose depends on the pitch scan parameter was confirmed. The measurement methods suggested in this study can be applied for the reassessment of the patient dose when the technique in CT equipment is developed or the protocol for CT scanning is changed.

• Imaging Science in Dentistry
• /
• v.34 no.1
• /
• pp.13-18
• /
• 2004

Purpose : This study was to evaluate the influence of slice thickness of computed tomography (CT) and rapid protyping (RP) type on the accuracy of 3-dimensional medical model. Materials and Methods: Transaxial CT data of human dry skull were taken from multi-detector spiral CT. Slice thickness were 1, 2, 3 and 4 mm respectively. Three-dimensional image model reconstruction using 3-D visualization medical software (V-works /sup TM/ 3.0) and RP model fabrications were followed. 2-RP models were 3D printing (Z402, Z Corp., Burlington, USA) and Stereolithographic Apparatus model. Linear measurements of anatomical landmarks on dry skull, 3-D image model, and 2-RP models were done and compared according to slice thickness and RP model type. Results: There were relative error percentage in absolute value of 0.97, 1.98,3.83 between linear measurements of dry skull and image models of 1, 2, 3 mm slice thickness respectively. There was relative error percentage in absolute value of 0.79 between linear measurements of dry skull and SLA model. There was relative error difference in absolute value of 2.52 between linear measurements of dry skull and 3D printing model. Conclusion: These results indicated that 3-dimensional image model of thin slice thickness and stereolithographic RP model showed relative high accuracy.

• Tuberculosis and Respiratory Diseases
• /
• v.70 no.1
• /
• pp.10-20
• /
• 2011

Various diseases can diffusely involve central airways, including the trachea and main stem bronchi. Central airway abnormalities are frequently not apparent or are overlooked on chest radiographs, even though the patient may have significant symptoms. Recent advances in spiral and multi-detector computed tomography (CT) with multi-planar reconstruction and three-dimensional demonstration, including virtual bronchoscopy, allow for excellent display of central airway anatomy and abnormalities with visualization of accurate locations of lesions. Early detection and proper diagnosis of airway diseases based on various radiographic findings will help determine appropriate treatment, including surgical planning and evaluation of treatment response. Herein we describe and illustrate the imaging findings of a wide spectra of diffuse central airway diseases.

• Tuberculosis and Respiratory Diseases
• /
• v.59 no.5
• /
• pp.473-479
• /
• 2005

Background : A pulmonary embolism often presents with nonspecific symptoms and signs. However, a delayed diagnosis can result in catastrophic outcome. The majority of preventable deaths associated with a pulmonary embolism can be ascribed to a missed diagnosis rather than to the failure of existing treatments. Therefore, accurate and rapid diagnostic methods are essential for the management of a pulmonary embolism. The recent generation of multidetector-row spiral CT scanners appears to outperform other imaging modalities in detecting a central and peripheral pulmonary embolism. However, there are some variations in the interpretations of the findings between observers. This study examined the inter-observer differences of the diagnoses in patients with a pulmonary embolism. Method : 64 patients who were diagnosed with a pulmonary embolism either clinically or with spiral chest CT from 2002 to 2004, were included. Two thoracic radiologists interpreted the multidetector-row spiral CT in terms of the diagnosis of a pulmonary embolism and the location of the thrombus independently. Among 64 patients, 14 patients were excluded because there was no evidence of a pulmonary embolism or there was different interpretation of the pulmonary embolism between radiologists. A clinical diagnosis was based on "Rules for predicting the probability of embolism". Results : The mean score of the patients according to the Wells method was $3.91{\pm}0.30$ (0-9). The accordance of the radiologists was 95% in the main, 85% in the lobar, 91.2% in the segmental, and 96% in the sub-segmental pulmonary arteries. After excluding the negative interpretation from both radiologists, their agreement was 76.2%(${\kappa}.$ 0.83) in the main, 57.6%(${\kappa}.$ 0.63) in the lobar, 51.5%(${\kappa}.$ 0.63) in the segmental, and 34.6%(${\kappa}.$ 0.49) in the sub-segmental pulmonary arteries. Conclusion : Chest CT has been recently applied to patients suspected of having a pulmonary embolism. It was found that spiral CT is a rapid test for diagnosing a thrombus, and there was reliable accordance between the observers from the area of the large pulmonary arteries. However, there was a lack of agreement between the observers in diagnosing thrombi located distal to the sub-segmental arteries.