• Journal of Korean Dental Science
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• v.3 no.2
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• pp.12-19
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• 2010

Despite the latest advancement made in its techniques and devices/apparatuses and the resulting rising expectation in the field of dental surgery, apicoectomy performed in the molar teeth remains a technical challenge and lacks evidence substantiated by long-term follow-up studies. This study sought to investigate the treatment outcomes and post-operative success rate in the root-end resected molar teeth accompanied by a high level of surgical risks due to their close proximity to the mandibular canal and maxillary sinus. A total of 68 patients who received treatment at Livingwell Dental Hospital between 2004 and 2010 and underwent apical surgery in the maxillary or mandibular molar area were enrolled in this study. A total of 160 roots collected from 75 molar teeth were subjected to surgical endodontic treatment and subsequently evaluated clinically as well as radiographically. Based on the results of the study, the clinical success rate was found to be 78.8% in cases involving radiological healing. Likewise, 90.7% of the roots recorded a robust clinical survival rate, but with incomplete healing as shown by radiography. The results indicate that the apical procedure involving molar teeth is a prognosis-friendly method that promises positive outcomes and higher success rate based on long-term follow-up observations.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.39
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• pp.2.1-2.6
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• 2017

Background: All clinicians are aware of the difficulty of installing a dental implant in posterior maxilla because of proximate position of maxillary sinus, insufficient bone width, and lower bone density. This study is to examine which factors will make the implantation in the posterior maxilla more difficult, and which factors will affect the postoperative implant stability in this region. Methods: Five hundred seventy-three fixtures on the maxilla posterior were included for this study from all the patients who underwent an installation of the dental implant fixture from January 2010 to December 2014 at the Department of Oral and Maxillofacial Surgery in Pusan National University Dental Hospital (Yangsan, Korea). The postoperative implant stability quotient (ISQ) value, fixture diameter and length, presence of either bone graft or sinus lift, and graft material were included in the reviewed factors. The width and height of the bone bed was assessed via preoperative cone beam CT image analysis. The postoperative ISQ value was taken just before loading by using the OsstellTM $mentor^{(R)}$ (Integration Diagnostics AB, Gothenburg, Sweden). The t test and ANOVA methods were used in the statistical analysis of the data. Results: Mean ISQ of all the included data was 79.22. Higher initial bone height, larger fixture diameter, and longer fixture length were factors that influence the implant stability on the posterior edentulous maxilla. On the other hand, the initial bone width, bone graft and sinus elevation procedure, graft material, and approach method for sinus elevation showed no significant impact associated with the implant stability on the posterior edentulous maxilla. Conclusions: It is recommended to install the fixtures accurately in a larger diameter and longer length by performing bone graft and sinus elevation.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.1
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• pp.17-25
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• 2016

Purpose : The purpose of this study is to evaluate the variability of tumor motion and respiration pattern in lung cancer patients undergoing Stereotactic Body RadioTherapy(SBRT) by using On-Board imager (OBI) system and Real-time Position Management (RPM) System. Materials and Methods : This study population consisted of 60 lung cancer patient treated with stereotactic body radiotherapy (48 Gy / 4 fractions). Of these, 30 were treated with gating (group 1) and 30 without gating(group2): typically the patients whose tumors showed three-dimensional respiratory motion > 10 mm were selected for gating. 4-dimensional Computed Tomography (4DCT). Cone Beam CT (CBCT) and Fluoroscopy images were used to measure the tumor motion. RPM system was used to evaluate the variability of respiration pattern on SBRT for group1. Results : The mean difference of tumor motion among 4DCT, CBCT and Fluoroscopy images in the cranio-caudal direction was 2.3 mm in group 1, 2. The maximum difference was 12.5 mm in the group 1 and 8.5 mm in group 2. The number of treatment fractions that patient's respiration pattern was within Upper-Lower threshold on SBRT in group 2 was 31 fractions. A patient who exhibited the most unstable pattern exceeded 108 times in a fraction Conclusion : Although many patients in group 1 and 2 kept the reproducibility of tumor motion within 5 mm during their treatment, some patients exhibited variability of tumor motion in the CBCT and Fluoroscopy images. It was possible to improve the accuracy of dose delivery in SBRT without gating for lung cancer patient by using RPM system.

• Journal of radiological science and technology
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• v.36 no.2
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• pp.123-129
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• 2013

This study investigated the rate of setup variance by the rotating unbalance of gantry in image-guided radiation therapy. The equipments used linear accelerator(Elekta Synergy TM, UK) and a three-dimensional volume imaging mode(3D Volume View) in cone beam computed tomography(CBCT) system. 2D images obtained by rotating $360^{\circ}$and $180^{\circ}$ were reconstructed to 3D image. Catpan503 phantom and homogeneous phantom were used to measure the setup errors. Ball-bearing phantom was used to check the rotation axis of the CBCT. The volume image from CBCT using Catphan503 phantom and homogeneous phantom were analyzed and compared to images from conventional CT in the six dimensional view(X, Y, Z, Roll, Pitch, and Yaw). The variance ratio of setup error were difference in X 0.6 mm, Y 0.5 mm Z 0.5 mm when the gantry rotated $360^{\circ}$ in orthogonal coordinate. whereas rotated $180^{\circ}$, the error measured 0.9 mm, 0.2 mm, 0.3 mm in X, Y, Z respectively. In the rotating coordinates, the more increased the rotating unbalance, the more raised average ratio of setup errors. The resolution of CBCT images showed 2 level of difference in the table recommended. CBCT had a good agreement compared to each recommended values which is the mechanical safety, geometry accuracy and image quality. The rotating unbalance of gentry vary hardly in orthogonal coordinate. However, in rotating coordinate of gantry exceeded the ${\pm}1^{\circ}$ of recommended value. Therefore, when we do sophisticated radiation therapy six dimensional correction is needed.

• Radiation Oncology Journal
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• v.27 no.1
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• pp.42-48
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• 2009

Purpose: The introduction of image guided radiation therapy/four-dimensional radiation therapy (IGRT/4DRT) potentially increases the accumulated dose to patients from imaging and verification processes as compared to conventional practice. It is therefore essential to investigate the level of the imaging dose to patients when IGRT/4DRT devices are installed. The imaging dose level was monitored and was compared with the use of pre-IGRT practice. Materials and Methods: A four-dimensional CT (4DCT) unit (GE, Ultra Light Speed 16), a simulator (Varian Acuity) and Varian IX unit with an on-board imager (OBI) and cone beam CT (CBCT) were installed. The surface doses to a RANDO phantom (The Phantom Laboratory, Salem, NY USA) were measured with the newly installed devices and with pre-existing devices including a single slice CT scanner (GE, Light Speed), a simulator (Varian Ximatron) and L-gram linear accelerator (Varian, 2100C Linac). The surface doses were measured using thermo luminescent dosimeters (TLDs) at eight sites-the brain, eye, thyroid, chest, abdomen, ovary, prostate and pelvis. Results: Compared to imaging with the use of single slice non-gated CT, the use of 4DCT imaging increased the dose to the chest and abdomen approximately ten-fold ($1.74{\pm}0.34$ cGy versus $23.23{\pm}3.67$cGy). Imaging doses with the use of the Acuity simulator were smaller than doses with the use of the Ximatron simulator, which were $0.91{\pm}0.89$ cGy versus $6.77{\pm}3.56$ cGy, respectively. The dose with the use of the electronic portal imaging device (EPID; Varian IX unit) was approximately 50% of the dose with the use of the L-gram linear accelerator ($1.83{\pm}0.36$ cGy versus $3.80{\pm}1.67$ cGy). The dose from the OBI for fluoroscopy and low-dose mode CBCT were $0.97{\pm}0.34$ cGy and $2.3{\pm}0.67$ cGy, respectively. Conclusion: The use of 4DCT is the major source of an increase of the radiation (imaging) dose to patients. OBI and CBCT doses were small, but the accumulated dose associated with everyday verification need to be considered.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.4
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• pp.437-448
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• 2021

The purpose of this study is to analyze morphological characteristics of maxillary primary molar's root and root canal. 268 children aged 3 - 7 years (175 boys, 93 girls) who had CBCT (152 children) and 3D CT (116 children) taken in Seoul National University Dental Hospital from January 2006 to April 2020 were included. The number of roots and root canals were analyzed in 1002 teeth without any root resorption or periapical pathologies. Curvature, angulation, length of root and root canal, as well as cross-sectional shapes of the root canal were analyzed in 218 teeth. By using Mimics and 3-Matics software, volume, surface area, and volume ratio of root canal was analyzed in 48 teeth. More than half of maxillary primary molars have 3 roots and 3 root canals. The degree of symmetry of root canal type was about 0.63 (Cohen's kappa coefficient). The most frequent shape of roots and canals was linear in 1^st primary molars and curved in 2^nd primary molars. Angulation, length of root and root canals was the largest on palatal roots. Most teeth showed ovoid or round shapes at apex. The largest root canal volume, surface area, volume ratio was found in the palatal roots.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.27-33
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• 2007

Purpose: We have performed SRS (stereotactic radiosurgery) for avm (arterry vein malformation) and brain cancer. In order to verify dose and localization of SRS, dose distributions from TPS ($X-Knife^{(R)}$ 3.0, Radionics, USA) and GafChromic $EBT^{(R)}$ film in a head phantom were compared. Materials and Methods: In this study, head and neck region of conventional humanoid phantom was modified by substituting one of 2.5 cm slap with five 0.5 cm acrylic plates to stack the GafChromic $EBT^{(R)}$ film slice by slice with 5 mm intervals. Four films and five acrylic plates were cut along the contour of head phantom in axial plane. The head phantom was fixed with SRS head ring and adapted SRS localizer as same as real SRS procedure. CT images of the head phantom were acquired in 5 mm slice intervals as film interval. Five arc 6 MV photon beams using the SRS cone with 2 cm diameter were delivered 300 cGy to the target in the phantom. Ten small pieces of the film were exposed to 0, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900 cGy, respectively to calibrate the GafChromic $EBT^{(R)}$ film. The films in the phantom were digitized after 24 hours and its linearity was calibrated. The pixel values of the film were converted to the dose and compared with the dose distribution from the TPS calculation. Results: Calibration curve for the GafChromic $EBT^{(R)}$ film was linear up to 900 cGy. The R2 value was better than 0.992. Discrepancy between calculated from $X-Knife^{(R)}$ 3.0 and measured dose distributions with the film was less than 5% through all slices. Conclusion: It was possible to evaluate every slice of humanoid phantom by stacking the GafChromic EBT film which is suitable for 2 dimensional dosimetry, It was found that film dosimetry using the GafChromic $EBT^{(R)}$ film is feasible for routine dosimetric QA of stereotactic radiosurgery.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.345-354
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• 2014

Purpose : We evaluated the usefulness of $Fraxion^{(R)}$ system and s-thermoplastic mask by analyzing setup error when stereotactic radiousurgery (SRS) was treated for brain metastasis. Materials and Methods : 6 patients who received definite diagnosis as brain metastasis between May 2014 and October 2014 were selected. 3 patients were immobilized s-thermoplastic mask and mouthpiece (group1), while $Fraxion^{(R)}$ system was used for the other 3 patients (group2). Cone Beam Computerized Tomography (CBCT) scan was acquired to register planning CT scan. The registration offset was compared for each group. We compared and reported the errors using maximum, minimum, mean, and standard deviation of registration offsets. Furthermore, We used the same method as patient specific quality assurance to verify absorbed dose of PTV. Results : The setup error which is registration offset was reduced 83% in x, 40% in y, and 92% in z-direction when $Fraxion^{(R)}$ system was used compared to the case of using s-thermoplastic mask and mouthpiece. In addition, using $Fraxion^{(R)}$ system showed improved results in rotational components, pitch (rotation along x-axis), roll (y), and yaw (z) which were reduced 64, 88, and 87% respectively compared to the case of using s-thermoplastic mask and mouthpiece. In dosimetry results, when s-thermoplastic mask and mouthpiece used, absorbed dose was reduce 83% compared to before and after registration. However, using $Fraxion^{(R)}$ system showed only 1.9%. All percentage were calculated with respect to average value. Conclusion : Using $Fraxion^{(R)}$ system including mouthpiece, Fraxion frame, frontpiece, and thermoplastic mask, showed better repeatability and precision compared to using s-thermoplastic mask and mouthpiece, which is consequently considered as more improved immobilization system.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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• pp.38.1-38.10
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• 2016

Background: The aims of this study are to evaluate the lip morphology and change of lip commissure after mandibular setback surgery (MSS) for class III patients and analyze association between the amount of mandibular setback and change of lip morphology. Methods: The samples consisted of 14 class III patients treated with MSS using bilateral sagittal split ramus osteotomy. Lateral cephalogram and cone-beam CT were taken before and about 6 months after MSS. Changes in landmarks and variables were measured with 3D software program $Ondemand^{TM}$. Paired and independent t tests were performed for statistical analysis. Results: Landmarks in the mouth corner (cheilion, Ch) moved backward and downward (p < .005, p < .01). However, cheilion width was not statistically significantly changed. Landmark in labrale superius (Ls) was not altered significantly. Upper lip prominence angle (ChRt-Ls-$ChLt^{\circ}$) became acute. Landmarks in stomion (Stm), labrale inferius (Li) moved backward (p < .005, p < .001). Lower lip prominence angle (ChRt-Li-$ChLt^{\circ}$) became obtuse (p < .001). Height of the upper and lower lips was not altered significantly. Length of the upper lip vermilion was increased (p =< 0.01), and length of the lower lip vermilion was decreased (p < .05). Lip area on frontal view was not statistically significantly changed, but the upper lip area on lateral view was increased and change of the lower lip area decreased (p > .05, p < .005). On lateral view, upper lip prominent point (UP) moved downward and stomion moved backward and upward and the angle of Ls-UP-Stm ($^{\circ}$) was decreased. Lower lip prominent point (LP) moved backward and downward, and the angle of Stm-LP-Li ($^{\circ}$) was increased. Li moved backward. Finally, landmarks in the lower incisor tip (L1) moved backward and upward, but stomion moved downward. After surgery, lower incisor tip (L1) was positioned more superiorly than stomion (p < .05). There were significant associations between horizontal soft tissue and corresponding hard tissue. The posterior movement of L1 was related to statistically significantly about backward and downward movement of cheilion. Conclusions: The lip morphology of patients with dento-skeletal class III malocclusion shows a significant improvement after orthognathic surgery. Three-dimensional lip morphology changes in class III patients after MSS exhibited that cheilion moved backward and downward, upper lip projection angle became acute, lower lip projection angle became obtuse, change of upper lip area on lateral view was increased, change of lower lip area decreased, and morphology of lower lip was protruding. L1 was concerned with the lip tissue change in statistically significant way.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.35-46
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• 2021

Purpose : By comparing and analyzing treatment plans using abdominal compression and The Continuous Positive Air Pressure(CPAP) during SABR of lung cancer, we try to contribute to the improvement of radiotherapy effect. Materials & Methods : In two of the lung SABR patients(A, B patient), we developed a SABR plan using abdominal compression device(the Body Pro-Lok, BPL) and CPAP and analyze the treatment plan through homogeneity, conformity and the parameters proposed in RTOG 0813. Furthermore, for each phase, the X, Y, and Z axis movements centered on PTV are analyzed in all 4D CTs and compared by obtaining the volume and average dose of PTV and OAR. Four cone beam computed tomography(CBCT) were used to measure the directions from the center of the PTV to the intrathoracic contacts in three directions out of 0°, 90°, 180° and 270°, and compare the differences from the average distance values in each direction. Result : Both treatment plans obtained using BPL and CPAP followed recommendations from RTOG, and there was no significant difference in homogeneity and conformity. The X-axis, Y-axis, and Z-axis movements centered on PTV in patient A were 0.49 cm, 0.37 cm, 1.66 cm with BPL and 0.16 cm, 0.12 cm, and 0.19 cm with CPAP, in patient B were 0.22 cm, 0.18 cm, 1.03 cm with BPL and 0.14 cm, 0.11 cm, and 0.4 cm with CPAP. In A patient, when using CPAP compared to BPL, ITV decreased by 46.27% and left lung volume increased by 41.94%, and average dose decreased by 52.81% in the heart. In B patient, volume increased by 106.89% in the left lung and 87.32% in the right lung, with an average dose decreased by 44.30% in the stomach. The maximum difference of A patient between the straight distance value and the mean distance value in each direction was 0.05 cm in the a-direction, 0.05 cm in the b-direction, and 0.41 cm in the c-direction. In B patient, there was a difference of 0.19 cm in the d-direction, 0.49 cm in the e-direction, and 0.06 cm in the f-direction. Conclusion : We confirm that increased lung volume with CPAP can reduce doses of OAR near the target more effectively than with BPL, and also contribute more effectively to restriction of tumor movement with respiration. It is considered that radiation therapy effects can be improved through the application of various sites of CPAP and the combination with CPAP and other treatment machines.