• The Journal of Korean Society for Radiation Therapy
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• 제26권1호
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• pp.137-147
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• 2014

Purpose : The purpose of this study is to verify the accuracy of dose delivery according to the patient's breathing cycle in Gated Volumetric Modulated Arc Therapy Materials and Methods : TrueBeam STxTM(Varian Medical System, Palo Alto, CA) was used in this experiment. The Computed tomography(CT) images that were acquired with RANDO Phantom(Alderson Research Laboratories Inc. Stamford. CT, USA), using Computerized treatment planning system(Eclipse 10.0, Varian, USA), were used to create VMAT plans using 10MV FFF with 1500 cGy/fx (case 1, 2, 3) and 220 cGy/fx(case 4, 5, 6) of doserate of 1200 MU/min. The regular respiratory period of 1.5, 2.5, 3.5 and 4.5 sec and the patients respiratory period of 2.2 and 3.5 sec were reproduced with the $QUASAR^{TM}$ Respiratory Motion Phantom(Modus Medical Devices Inc), and it was set up to deliver radiation at the phase mode between the ranges of 30 to 70%. The results were measured at respective respiratory conditions by a 2-Dimensional ion chamber array detector(I'mRT Matrixx, IBA Dosimetry, Germany) and a MultiCube Phantom(IBA Dosimetry, Germany), and the Gamma pass rate(3 mm, 3%) were compared by the IMRT analysis program(OmniPro I'mRT system software Version 1.7b, IBA Dosimetry, Germany) Results : The gamma pass rates of Case 1, 2, 3, 4, 5 and 6 were the results of 100.0, 97.6, 98.1, 96.3, 93.0, 94.8% at a regular respiratory period of 1.5 sec and 98.8, 99.5, 97.5, 99.5, 98.3, 99.6% at 2.5 sec, 99.6, 96.6, 97.5, 99.2, 97.8, 99.1% at 3.5 sec and 99.4, 96.3, 97.2, 99.0, 98.0, 99.3% at 4.5 sec, respectively. When a patient's respiration was reproduced, 97.7, 95.4, 96.2, 98.9, 96.2, 98.4% at average respiratory period of 2.2 sec, and 97.3, 97.5, 96.8, 100.0, 99.3, 99.8% at 3.5 sec, respectively. Conclusion : The experiment showed clinically reliable results of a Gamma pass rate of 95% or more when 2.5 sec or more of a regular breathing period and the patient's breathing were reproduced. While it showed the results of 93.0% and 94.8% at a regular breathing period of 1.5 sec of Case 5 and 6, it could be confirmed that the accurate dose delivery could be possible on the most respiratory conditions because based on the results of 100 patients's respiratory period analysis as no one sustained a respiration of 1.5 sec. But, pretreatment dose verification should be precede because we can't exclude the possibility of error occurrence due to extremely short respiratory period, also a training at the simulation and careful monitoring are necessary for a patient to maintain stable breathing. Consequently, more reliable and accurate treatments can be administered.

• Journal of Yeungnam Medical Science
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• 제4권1호
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• pp.1-15
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• 1987

Magnetic Resonance (M.R.) is rapidly emerging technique that provides high quality images and potentially provides much more diagnostic information than do conventional imaging modalities. M.R.I. is conceptually quite different from currently used imaging methods. The complex nature of M.R.I. allows a great deal of flexibility in image product ion and available information, and key points are as follows. 1. M.R.I. offers a non-invasive technique with which to gene rate in vivo human images without ionizing radiation and with no known adverse biological effects. 2. Imaging mechanism of M.R.I. is quite different from conventional imaging modality and for more accurate diagnostic application, It is necessary for physician to understand imaging mechanism of M.R.I. 3. M.R. makes available basic chemical parameters that may provide to be useful for diagnostic medical imaging and more specific pathophysiologic information which are not available by alternate techniques. 4. M.R. can be produced by number of different methods. This flexibility allows the imaging technique to be applicated for particular clinical purpose. Multiplanar and three dimensional imaging may extend the imaging process beyond the single section available with current CT. 5. Future directions include efforts to; a. Further development of hard ware b. More fasternning scan time c. Respiratory and cardiac gated imaging d. Imaging of additional nuclei except hydrogen e. Further development of contrast media f. M.R. in vivo spectroscopy g. Real time M.R. imaging.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제41권
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• pp.51.1-51.8
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• 2019

Purpose: It has been reported before that the amount of pharyngeal airway space (PAS) significantly decreases following mandibular setback (MS) surgery in patients with mandibular prognathism (MP). Further, MP patients with an anterior open-bite (AOB) presentation may show a larger decrease in PAS compared with those without AOB. However, studies on postoperative PAS changes in MP patients with AOB remain rare. This study sought to evaluate changes in PAS and hyoid bone positioning following MS surgery in MP patients with and without AOB. Patients and methods: Twenty patients who underwent two jaw surgery involving MS movement were included. Patients were divided into a non-AOB group (n = 10; overbite > 2 mm) and an AOB group (n = 10; overbite < - 4 mm). Three-dimensional changes in PAS and hyoid bone positioning were compared and statistically evaluated pre- and postoperatively using computed tomography (CT). Results: The mean magnitude of MS was 6.0 ± 2.8 mm and 5.6 ± 3.2 mm in the non-AOB group and AOB group, respectively. The oropharyngeal volume and upper hypopharyngeal volume were significantly reduced after surgery in both the groups (p = 0.006 and p = 0.003), while the retroglossal cross-sectional area was significantly reduced only in the AOB group (p = 0.028). Although the AOB group showed a larger decrease in PAS, the difference was not statistically significant between the groups. The position of the hyoid bone showed significant posterior and inferior displacement only in the AOB group, while the vertical displacement of the hyoid bone showed a statistically significant difference between the two groups. Conclusion: PAS was significantly decreased after MS in both the groups, while only the AOB group presented a statistically significant reduction in the retroglossal cross-sectional area. Vertical displacement of the hyoid bone showed a statistically significant difference between the groups, while the PAS change was not. Surgeons should be aware of potential postoperative airway problems that may arise when performing MS surgeries.

• The korean journal of orthodontics
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• 제42권4호
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• pp.159-168
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• 2012

Objective: The aims of this study were to investigate mandibular deformation under clenching and to estimate its effect on the stability of orthodontic mini-implants (OMI). Methods: Three finite element models were constructed using computed tomography (CT) images of 3 adults with different mandibular plane angles (A, low; B, average; and C, high). An OMI was placed between #45 and #46 in each model. Mandibular deformation under premolar and molar clenching was simulated. Comparisons were made between peri-orthodontic mini-implant compressive strain (POMI-CSTN) under clenching and orthodontic traction forces (150 g and 200 g). Results: Three models with different mandibular plane angles demonstrated different functional deformation characteristics. The compressive strains around the OMI were distributed mesiodistally rather than occlusogingivally. In model A, the maximum POMI-CSTN under clenching was observed at the mesial aspect of #46 (1,401.75 microstrain [${\mu}E$]), and similar maximum POMI-CSTN was observed under a traction force of 150 g (1,415 ${\mu}E$). Conclusions: The maximum POMI-CSTN developed by clenching failed to exceed the normally allowed compressive cortical bone strains; however, additional orthodontic traction force to the OMI may increase POMI-CSTN to compromise OMI stability.

• The Journal of Advanced Prosthodontics
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• 제6권5호
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• pp.361-371
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• 2014

PURPOSE. In case of large horizontal discrepancy of alveolar ridge due to severe resorption, cantilevered crown is usually an unavoidable treatment modality. The purpose of this study was to evaluate the clinical criteria for the placement of the aforementioned implant crown. MATERIALS AND METHODS. The mandible model with 2 mm thick cortical bone and cancellous bone was fabricated from CT cross-section image. An external connection type implant was installed and cantilevered crowns with increasing offset of 3, 4, 5, 6, and 7 mm were connected. Vertical load and $30^{\circ}$ oblique load of 300 N was applied and stress around bone and implant component was analyzed. A total of 14 cases were modeled and finite element analysis was performed using COSMOS Works (Solid works Inc, USA). RESULTS. As for the location of the vertical load, the maximum stress generated on the lingual side of the implant became larger according to the increase of offset distance. When the oblique load was applied at $30^{\circ}$, the maximum stress was generated on the buccal side and its magnitude gradually decreased as the distance of the offset load increased to 5 mm. After that point, the magnitude of implant component's stress increased gradually. CONCLUSION. The results of this study suggest that for the patient with atrophied alveolar ridge following the loss of molar teeth, von-Mises stress on implant components was the lowest under the $30^{\circ}$ oblique load at the 5 mm offset point. Further studies for the various crown height and numbers of occusal points are needed to generalize the conclusion of present study.

• Journal of Chest Surgery
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• 제42권5호
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• pp.653-656
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• 2009

The entrapment of the popliteal artery is a rare cause of ischemia of the lower extremities among young males. The development of local occlusive or aneurysmal changes of the popliteal artery is caused by abnormal anatomic relationships between vascular and musculo-tendinous structures in the popliteal fossa. An 18-year-old male visited our outpatient clinic with the chief complaint of claudication in his right calf. Three dimensional CT angiography showed an occlusion of the popliteal artery and less opacified arteries of the right leg. Intraoperatively, the popliteal artery was compressed by an accessory muscle band arising from the medial head of the gastrocnemius. After release of the muscle band, thrombectomy with endarterectomy was done. Three years after surgery, he is doing well without any problems.

• Journal of Oral Medicine and Pain
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• 제24권1호
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• pp.69-80
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• 1999

OBJECTIVES: This study was designed to measure the minimal cross-sectional areas and volumes of the pharynx in snoring patients and normal subjects and to see if there is an increase in the minimal cross-sectional areas and volumes of the pharynx with advancement of the mandible. METHODS: The pharyngeal computed tomography and 3-dimensional reconstruction were used to measure the cross-sectional areas and volumes of the nasopharynx, oropharynx, and hypopharynx with the jaw in normal position and in protrusive position in 7 patients with snoring and 7 control subjects while they were awake. RESULTS: The oropharynx was revealed to have the most narrow site in the pharynx and there was a tendency for the snorers to have a smaller nasopharyngeal and oropharyngeal cross-sectional area than normal subjects but not statistically significant. There were no significant differences in the volumes of the nasopharynx and oropharynx between the two groups. With advancement of the jaw the minimal cross-sectional area of oropharynx was significantly increased, and the volume was also increased but not significantly. The minimal cross-sectional areas and volumes of nasopharynx as well as hypopharynx were not significantly influenced by the advancement of the mandible. CONCLUSIONS: There was a tendency for snorers to have a smaller oropharynx than normal subjects and the oropharyngeal lumen was increased with the advancement of the mandible in both snorers and normal subjects.

• Imaging Science in Dentistry
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• 제40권4호
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• pp.179-185
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• 2010

Purpose : Cortical bone thickness is one of the important factor in mini-implant stability. This study was performed to investigate the buccal cortical bone thickness at every interdental area as an aid in planning mini-implant placement. Materials and Methods : Two-dimensional slices at every interdental area were selected from the cone-beam computed tomography scans of 20 patients in third decade. Buccal cortical bone thickness was measured at 2, 4, and 6 mm levels from the alveolar crest in the interdental bones of posterior regions of both jaws using the plot profile function of $Ez3D2009^{TM}$ (Vatech, Yongin, Korea). The results were analyzed using by Mann-Whitney test. Results : Buccal cortical bone was thicker in the mandible than in the maxilla. The thickness increased with further distance from the alveolar crest in the maxilla and with coming from the posterior to anterior region in the mandible (p<0.01). The maximum CT value showed an increasing tendency with further distance from the alveolar crest and with coming from posterior to anterior region in both jaws. Conclusion : Interdental buccal cortical bone thickness varied in both jaws, however our study showed a distinct tendency. We expect that these results could be helpful for the selection and preparation of mini-implant sites.

• Journal of Digital Contents Society
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• 제11권4호
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• pp.553-559
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• 2010

By applying the various reformation techniques by using a circle raw data of after computed tomography image in the patient enforcing the spine screw fixation, this research tried to look into the various information including the exact location of the position of the screw spike and accuracy of an operation. In a clinical, by applying the or multi planar reformatting(MPR), that is the re-composition technique used mainly, maximum intensity projection (MIP), and volume rendering technique(VRT) and transformation removal from a register modifying VRT, video data were compared and were analyzed by the quantitative method and qualitative method. It is judged as the transformation volume rendering technique of the re-composition technique which is most useful in minimizing the artifact shadow by the exact location of the position of a screw and metal among the analysis and evaluation result computed tomography image reformation technique of the reformation image after the spine screw fixation.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제40권
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• pp.30.1-30.6
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• 2018

Background: The purpose of the present study was to investigate the differences in the position and shape of the anterior loop of the inferior alveolar nerve (ALIAN) in relation to the growth pattern of the mandibular functional subunit. Methods: The study was conducted on 56 patients among those who had undergone orthognathic surgery at the Gangnam Severance Hospital between January 2010 and December 2015. Preoperative computerized tomography (CT) images were analyzed using the Simplant OMS software (ver.14.0 Materialise Medical, Leuven, Belgium). The anterior and inferior lengths of ALIAN (dAnt and dInf) and each length of the mandibular functional subunits were measured. The relationship between dAnt, dInf, and the growth pattern of the mandibular subunits was analyzed. Results: The length of the anterior portion of ALIAN (dAnt) reached 3.34 ± 1.59 mm in prognathism and 1.00 ± 0.97 mm in retrognathism. The length of the inferior portion of ALIAN (dInf) reached 6.81 ± 1.33 mm in prognathism and 5.56 ± 1.34 mm in retrognathism. The analysis of Pearson's correlation coefficiency on all samples showed that the lengths of functional subunits were positively correlated with the loop depth. The length of the symphysis area in prognathic patients was positively correlated with the anterior loop depth (p = 0.005). Conclusions: Both the anterior and inferior length of ALIAN are longer in prognathic patients. Especially, it seems to be associated with the growth of the symphysis area.