• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.111-120
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• 2010

Purpose: This investigation was designed to evaluate the condyle position and the symmetry of the both condyle heads at the maximum intercuspal position on the sagittal CT image of the temporomandibular joint. Materials and Methods: Cone-beam CT was used to assess 400 joints in 100 symptom and 100 symtom-free subject(100 male, 100 female). Three independent observers(dentists) determined the positions classified with Anterior Position(AP), Middle Position(MP), and Posterior Position(PP), and the symmetry of the both condyle. Results: According to gender, the mean percentages of AP, MP, and PP were 48.5, 28.5, and 23 in male group, and 34, 38, and 28 in female group. The symmetry of condylar heads was more common than asymmetry in the both of groups. In the respect of symptom or symptom-free, the mean percentages of AP, MP, and PP were 44.5, 34, and 21.5 in the symptom-free group, and 37, 33.5, and 29.5 in the symptom group. The symmetry of condylar heads was more common in the symptom-free group, but the asymmetry of condylar heads was more common in the symptom group. Conclusions: These data might serve as useful criteria for the clinical assessment of condyle position at the maximum intercuspal position optained by Cone-beam CT.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.35 no.1
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• pp.21-25
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• 2009

Objective: The purpose of this study is to determine the prevalence of sinus disease and abnormalities in patients scheduled for dental implant in maxillary posterior area using cone beam CT. Patients and Method: One hundred five maxillary sinuses in eighty-seven patients who underwent cone beam CT for dental implant in maxillary posterior area were included. Any patients who had previous history of sinus operations were not included. The sinus abnormalities were classified as follows ; normal (membrane thickness <2 mm), mucosal thickening (membrane thickness ${\geq}$ 2 mm and < 6 mm), partial opacification (membrane thickness > 6 mm but not full), full opacification and mucous retention cyst. The relationship between the remaining bone height, sinus symptoms and maxillary sinus abnormality was statistically surveyed. Results: Of 105 maxillary sinuses in 87 patients, 80 (76%) maxillary sinuses showed abnormalities ; 4 of 4 symptomatic patients and 76 of 101 asymptomatic patients. Mucosal thickening was the most common sinus abnormality. Only 3 (4%) of 80 maxillary sinus abnormalities were caused by the odontogenic origin. The prevalence of maxillary sinus abnormalities was higher in the symptomatic group than asymptomatic one (p<0.05). Conclusion: Maxillary sinus abnormalities were very common in the patients who were planning implantation in maxillary posterior areas. This result supports that thorough evaluation for maxillary sinus is recommended when implant treatment is planned for those areas.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.1
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• pp.15-21
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• 2012

Purpose: Image Guided Radiation Therapy (IGRT) has been carried out using On-Board Imager system (OBI) in Asan Medical Center. For this reason, This study was to analyze and evaluate the impact on Cone-Beam CT according to variation of material and respiration. Materials and Methods: This study was to acquire and analyze Cone-Beam CT three times for two material: Cylider acryl (lung equvalent material, diameter 3 cm), Fiducial Marker (using clinic) under Motion Phantom able to adjust respiration pattern randomly was varying period, amplitude and baseline vis-a-vis reference respiration pattern. Results: First, According to a kind of material, when being showed 100% in the acryl and 120% in the Fiducial Marker under the condition of same movement of the motion phantom. Second, According to the respiratory alteration, when being showed 1.13 in the baseline shift 1.8 mm and 1.27 in the baseline shift 3.3 mm for acryl. when being showed 1.01 in 1 sec of period and 1.045 in 2.5 sec of period for acryl. When being showed 0.86 in 0.7 times the standard of amplitude and 1.43 in 1.7 times the standard of amplitude for acryl. when being showed 1.18 in the baseline shift 1.8 mm and 1.34 in the baseline shift 3.3 mm for Fiducial Marker. when being showed 1.0 in 1 sec of period and 1.0 in 2.5 sec of period for Fiducial Marker. When being showed 0.99 in 0.7 times the standard of amplitude and 1.66 in 1.7 times the standard of amplitude for Fiducial Marker. Conclusion: The effect of image size of CBCT was 20% in the case of Fiducial marker. The impact of changes in breathing pattern was minimum 13% - maximum 43% for Arcyl, min. 18% - max. 66% for Fiducial marker. This difference makes serious uncertainty. So, Must be stabilized breathing of patient before acquiring CBCT. also must be monitored breathing of patient in the middle of acquire. If you observe considerable change of breathing when acquiring CBCT. After Image Guided, must be need to check treatment site using fluoroscopy. If a change is too big, re-acquiring CBCT.

• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.141-147
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• 2009

This paper presents a new fast algorithm, rotation-based method (RBM), for the reconstruction of 3 dimensional image for cone beam computerized tomography (CB CT) system. The system used cone beam has less exposure time of radioactivity than fan beam. The Three-Pass Shear Matrices (TPSM) is applied, that has less transcendental functions than the one-pass shear method to decrease a time of calculations in the computer. To evaluate the quality of the 3-D images and the time for the reconstruction of the 3-D images, another 3-D images were reconstructed by the radon transform under the same condition. For the quality of the 3-D images, the images by radon transform was shown little good quality than REM. But for the time for the reconstruction of the 3-D images REM algorithm was 35 times faster than radon transform. This algorithm offered $4{\sim}5$ frames a second. It meant that it will be possible to reconstruct the 3-D dynamic images in real time.

• Journal of Radiation Protection and Research
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• v.40 no.1
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• pp.17-24
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• 2015

To improve accuracy of dose calculation on kilovoltage cone beam computed tomography (kV CBCT) images, a custom-made phantom was fabricated to acquire an accurate CT number to electron density curve by full scatter of cone beam x-ray. To evaluate the dosimetric accuracy, 9 volumetric modulated arc therapy (VMAT) plans for head and neck (HN) cancer and 9 VMAT plans for lung cancer were generated with an anthropomorphic phantom. Both CT and CBCT images of the anthropomorphic phantom were acquired and dose-volumetric parameters on the CT images with CT density curve (CTCT), CBCT images with CT density curve ($CBCT_{CT}$) and CBCT images with CBCT density curve ($CBCT_{CBCT}$) were calculated for each VMAT plan. The differences between $CT_{CT}$ vs. $CBCT_{CT}$ were similar to those between $CT_{CT}$ vs. $CBCT_{CBCT}$ for HN VMAT plans. However, the differences between $CT_{CT}$ vs. $CBCT_{CT}$ were larger than those between $CT_{CT}$ vs. $CBCT_{CBCT}$ for lung VMAT plans. Especially, the differences in $D_{98%}$ and $D_{95%}$ of lung target volume were statistically significant (4.7% vs. 0.8% with p = 0.033 for $D_{98%}$ and 4.8% vs. 0.5% with p = 0.030 for $D_{95%}$). In order to calculate dose distributions accurately on the CBCT images, CBCT density curve generated with full scatter condition should be used especially for dose calculations in the region of large inhomogeneity.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.3
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• pp.1649-1654
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• 2013

Objective: This work aimed to evaluate the safety and clinical efficacy of transcatheter arterial chemoembolization (TACE) combined with c-arm cone-beam CT guided synchronous radiofrequency ablation (RFA) in treatment of large hepatocellular carcinoma (HCC). Methods: 21 patients with large HCC were studied from January 2010 to March 2012. TACE combined with synchronous C-arm cone-beam CT guided RFA were performed on a total of 25 lesions. Conventional imaging examination (CEUS, enhanced CT or MRI) and AFP detection were regularly conducted to evaluate the technical success rate of combined treatment, complications, treatment response, time without disease recurrence and survival rate. Results: The technical success rate of combined treatment was 100%, without any significant complication. After 1 month, there were 19 cases with complete response and 2 cases with partial response, with an complete response rate of 90.4% (19/21) and a clinical effective rate of 100% (21/21). The complete response rates of single nodular lesions (100%, 17/17) was significantly higher than that of multiple nodular lesions (50%, 2/4) (P<0. 05). During 2 to 28 months of follow-up, in 19 cases with complete response, the average time without disease recurrence was $10.8{\pm}6$ months. The total survival rates of 6, 12 and 18 months in 21 patients were 100%, respectively. Conclusion: TACE combined with synchronous C-arm CT guided RFA is safe and effective for treatment of large HCC. The treatment efficacy for single nodular lesion is better than that for multiple nodular lesions.

• The Journal of the Korean dental association
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• v.53 no.12
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• pp.967-974
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• 2015

Purpose: This study was performed to investigate the characteristics of mandibular incisive canal (MIC) in Korean population. Materials and methods: A total of 97 subjects (60 males and 37 females) who underwent cone-beam computed tomography were included in the study. The anatomic features of MIC was assessed according to gender. Length, diameter and distance to inferior, lingual and buccal border were measured at the origin and the terminal. Also the distribution of MIC at each tooth position was evaluated. Results: Of 97 patients included, 75(77.3%) presented bilateral MIC and 13(13.4%) presented unilateral MIC. Of 194 hamimandibles, MIC was detected in 102(85%) sites in male and 61(82.4%) sites in female. Gender and side showed no statistically significant differences in detectability. The length, diameter and distance to adjacent structures were bigger in male than in female except the distance to lingual border. MIC travelled anteriorly in a slightly downward and lingual direction and usually terminated between the first premolar and the canine. On cross-sectional view, MIC showed individually scattered distribution both buccolingually and superoinferiorly. Conclusion: MIC is well detected with cone-beam computed tomography. Considered that the length and the location of MIC has large variations between individuals, its localization using cone-beam CT is highly recommended before performing surgical procedures such as implant placement and bone harvesting.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.433-438
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• 2015

To evaluate the radiation exposure level based on radiation workers' locations in dental radiography, the radiation dose rate in the radiographic room, lead glass, and operation system was measured. To that end, various devices were used, such as a Standard(Max-GLS, Shinhung), a panorama (PCH-2500, Vatech), a cephalometric radiography (PCH-2500), and a cone beam CT (PHT-30LFO, Vatech), as well as a PM1405 equipment as a radiation meter. Radiography conditions were set the same as the factors used in the clinical setting. As the result, the cone beam CT turned out the highest with 98 uSv and the standard showed the lowest level with 0.4 uSv/h. The panorama was measured to be higher than the Cephalo due to its different focus mode. On the lead glass surface and in the operation stand, the oral radiography device, panoramic, and Cephalo all were measured below the recording level. However, the cone beam CT was measured to have the leakage dose. Thus, radiation involved workers should be equipped with appropriate protection tools and reduce radiography time as much as possible. In addition, the structure of the radiation chamber should be also designed efficiently. Dental radiography has continued to grow in recent years, so it is necessary take appropriate protection measures for patients and radiation workers.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.2
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• pp.78-86
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• 2010

Introduction: Cone beam computed tomography (CBCT) has various advantages and is used favorably in many fields in dentistry. Especially, CBCT is being used as basic diagnostic tool for 3-dimensional analysis in orthognathic patient. Two-dimensional cephalograms can be synthesized from CBCT digital imaging and communications in medicine (DICOM) data. In this study, conventional cephalograms and CBCT were taken simultaneously, and representative landmarks were located and analyzed in its accuracy and reproducibility. Materials and Methods: Ten patients who had orthognathic surgery in Wonkwang University Daejeon Dental Hospital participated in this study. For each patient, CBCT and conventional cephalogram was taken. By using Ondemand (Cybermad, Korea), 2-dimensional cephalograms was established on CBCT. In addition, 19 landmarks were designated and measured by 3 orthodontists twice a week. After these landmarks were transferred to a coordinate, distance of landmark and axis, standard error, distribution degree were measured, compared and analyzed. Results: Comparing the CT ceph group and conventional cephalogram group, CT ceph group had shown shorter distance of landmark and axis in S, Hinge axis, Bpt, Ba, Or, Corpus left. Standard error of the mean shows that CT ceph group has better reproducibility in Or, Corpus left, Hinge axis at X axis and Na, U1R, U1T, Bpt, PNS, Ba Corpus left, Hinge axis at Y axis. In both groups, mean error was less than 1.00 mm, no significant difference were found between CT ceph group and conventional cephalogram group in all measurements. Furthermore, comparing two groups, each 17 landmarks out of 19 had its characteristic in distribution degree. Conclusion: No significant difference were found between CBCT composed cephalographic radiograph and conventional cephalograghic radiograph, clinical application may be possible if improved.

• Restorative Dentistry and Endodontics
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• v.45 no.4
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• pp.46.1-46.8
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• 2020

Objectives: This study aimed to investigate the incidence and location of the second mesiobuccal root (MB2) canal in maxillary molars with the aid of various measuring points and lines using cone-beam computed tomography (CT). Materials and Methods: A total of 205 images of patients who underwent cone-beam CT examinations between 2011 and 2015 as part of their dental diagnosis and treatment were included. There were 76 images of the maxillary first molar and 135 images of the maxillary second molar. Canal orifices were detected at -1 mm from the top of the pulpal floor on cone-beam CT images. Image assessment was performed by 2 observers in reformatted image planes using software. Assessments included measurement of the distance between the MB1 and MB2 canals, and the angles between the lines connecting the MB1-MB2 and distobuccal (DB)-palatal (P) canals. The data were analyzed using the student's t-test. Results: The prevalence of the MB2 canal was 86.8% in the first molar and 28.9% in the second molar. The angle between the lines connecting the MB1-MB2 and DB-P canals was 2.3° ± 5.7° in the first molar and -3.95° ± 7.73° in the second molar. The distance between the MB1 and MB2 canals was 2.1 ± 0.44 mm in the first molar and 1.98 ± 0.42 mm in the second molar. Conclusions: The angles between the lines connecting the MB1-MB2 and DB-P canals was almost parallel. These findings may aid in the prediction of the location of the MB2 canal orifice.