• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.294-300
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• 2010

Purpose: The template-guided implant surgery offers several advantages over the traditional approach. The purpose of this study was to evaluate the accuracy of coordinate synchronization procedure with 5-axis milling machine for surgical template fabrication by means of reverse engineering through universal CAD software. Materials and methods: The study was performed on ten edentulous models with imbedded gutta percha stoppings which were hidden under silicon gingival form. The platform for synchordination was formed on the bottom side of models and these casts were imaged in Cone beam CT. Vectors of stoppings were extracted and transferred to those of planned implant on virtual planning software. Depth of milling process was set to the level of one half of stoppings and the coordinate of the data was synchronized to the model image. Synchronization of milling coordinate was done by the conversion process for the platform for the synchordination located on the bottom of the model. The models were fixed on the synchordination plate of 5-axis milling machine and drilling was done as the planned vector and depth based on the synchronized data with twist drill of the same diameter as GP stopping. For the 3D rendering and image merging, the impression tray was set on the conbeam CT and pre- and post- CT acquiring was done with the model fixed on the impression body. The accuracy analysis was done with Solidworks (Dassault systems, Concord, USA) by measuring vector of stopping’s top and bottom centers of experimental model through merging and reverse engineering the planned and post-drilling CT image. Correlations among the parameters were tested by means of Pearson correlation coefficient and calculated with SPSS (release 14.0, SPSS Inc. Chicago, USA) ($\alpha$ = 0.05). Results: Due to the declination, GP remnant on upper half of stoppings was observed for every drilled bores. The deviation between planned image and drilled bore that was reverse engineered was 0.31 (0.15 - 0.42) mm at the entrance, 0.36 (0.24 - 0.51) mm at the apex, and angular deviation was 1.62 (0.54 - 2.27)$^{\circ}$. There was positive correlation between the deviation at the entrance and that at the apex (Pearson Correlation Coefficient = 0.904, P = .013). Conclusion: The coordinate synchronization 5-axis milling procedure has adequate accuracy for the production of the guided surgical template.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.85-92
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• 2020

Purpose: To find out the advantages of thermoplastic bolus compared to conventional bolus, which is mainly used in clinical practice, We evaluated Two cases in terms of dose and location reproducibility to assess Usability of thermoplastic Bolus for skin VMAT radiotherapy. Materials and Methods: Two patient's treated with left breast skin lesion were simulated using thermoplastic Bolus and planned with 2arc VMAT. the prescription dose was irradiated to 95% or more of the target volume. We evaluated The reproducibility of the bolus position by measuring the length of the air gap in the CBCT (Cone Beam CT) image. to evaluate dose reproducibility, we compared The dose distribution in the plan and CBCT and measured in vivo for patient 2. Results: The difference between the air gap in patient 1's simulation CT and the mean air gap (M1) during 10 treatments in the CBCT image was -0.42±1.24mm. In patient 2, the difference between the average air gap between the skin and the bolus (M2) during 14 treatments was -1.08±1.3mm, and the air gap between the bolus (M3) was 0.49±1.16. The difference in the dose distribution between Plan CT and CBCT was -1.38% for PTV1 D95 and 0.39% for SKIN (max) in patient 1. In patient 2, PTV1 D95 showed a difference of 0.63% and SKIN (max) -0.53%. The in vivo measurement showed a difference of -1.47% from the planned dose. Conclusion: thermoplastic Bolus is simpler and takes less time to manufacture compared to those produced by 3D printer. Also compared to conventional bolus, it has high reproducibility in the set-up side and stable results in terms of dose delivery.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.3
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• pp.334-343
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• 2018

The purpose of this study was to investigate the cause of eruption disturbance in the maxillary central incisor and establish the effective treatment plan by analyzing the vertical distance, angulation of long axis and root development of the tooth with eruption disturbance using the cone-beam CT. The average age of 134 patients diagnosed with unilaterally impacted maxillary central incisor was 7.9 years old and the male was 2.1 times higher than the female. The most common cause of eruption disorder was physical obstruction, especially mesiodens and odontoma. Of the teeth with unilateral eruption disorder, 78 cases erupted spontaneously and 56 cases erupted non-spontaneously after removal of physical obstruction. The possibility of spontaneous or non-spontaneous eruption in the unilaterally impacted maxillary central incisor depended on several factors, such as vertical distance, angulation of long axis and root development of unerupted tooth. The spontaneous eruption of the impacted maxillary cental incisor was most frequent at the angulation of long axis of 50 to 90 degrees, which is similar to the angulation of long axis of the normally erupted maxillary central incisor. In addition, the spontaneous eruption period of impacted maxillary central incisor was more influenced by the vertical distance than the angulation of long axis and the root development. Most of the teeth that showed non-spontaneous eruption had orthodontic traction, and these teeth were usually erupted within about 12 months. The period treated with orthodontic traction was no statistical significance with the vertical distance, the angulation of long axis, and the root development. This study will provide information on the cause of unilaterally impacted maxillary cental incisor and help to establish the future treatment plan.

• The Journal of Korean Society for Radiation Therapy
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• v.22 no.1
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• pp.19-24
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• 2010

Purpose: To study the efficacy of marker match with using kilovoltage (KV) X-ray among multiple image guidance that referring tree fiducial marker in radiation therapy for prostate cancer patients. Materials and Methods: KV two-dimantional images (anterior-posterior, right-left) and cone-beam CT volumetric images were acquired after setup for patients with three fiducial markers. Compare the position of the fiducial marker of reference plan computed tomography (CT) and of KV, CBCT images; then decide the shift score of X, Y, and Z. This study executed 5 times on 10 patients and analyzed the shift value. Results: In the radiation therapy using fiducial marker, The function of marker match showed the same direction tendency as the CBCT, and showed X, Y, Z difference of about 0.6, 0.7, and 0.8 (unit: mm). Conclusion: Comparing to this, the result of shift value using 2D marker match showed less than 1.0 mm difference. The function of marker match is considered more useful in time-wise and effective dose rather than CBCT. Therefore, Both methods are used to treat patients for prostate cancer.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.4
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• pp.607-618
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• 2008

This study three-dimensionally and histologically assessed the effect of Emdogain$^{(R)}$ on periodontal healing in replanted teeth in three beagle dogs which were 1 to 2 years old, weighing from 10 to 13 ㎏. Twelve maxillary and mandibular incisors were intentionally extracted and replanted after 15(Group I), 30(Group II) and 60(Group III) minutes of air dry storage with and without the application of Emdogain$^{(R)}$. The following conclusions could be drawn from the present investigation. 1. Increased incidence of inflammatory healing response in periodontal tissue was proportional to air dry time in Both control and experimental group(P<0.001). 2. Treatment Group showed lower inflammatory root resorption, especially there were statically significant in Group I, III(P<0.001, Group II : P=0.093). 3. Inflammatory root resorption were mainly occurred in apical third(14, 15-16 section)(P<0.05, 0.001), and cervical third(1 section)(P<0.05). 4. In view of horizontal section of long tooth axis, Main root resorption area were 1, 4, 5 line area(bucco-lingual area)(p<0.01).

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.5
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• pp.2393-2398
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• 2012

Objectives: The purpose of this study was to evaluate the geometric accuracy of thoracic anatomic landmarks as target surrogates of intrapulmonary tumors for manual rigid registration during image-guided radiotherapy (IGRT). Methods: Kilovolt cone-beam computed tomography (CBCT) images acquired during IGRT for 29 lung cancer patients with 33 tumors, including 16 central and 17 peripheral lesions, were analyzed. We selected the "vertebrae", "carina", and "large bronchi" as the candidate surrogates for central targets, and the "vertebrae", "carina", and "ribs" as the candidate surrogates for peripheral lesions. Three to six pairs of small identifiable markers were noted in the tumors for the planning CT and Day 1 CBCT. The accuracy of the candidate surrogates was evaluated by comparing the distances of the corresponding markers after manual rigid matching based on the "tumor" and a particular surrogate. Differences between the surrogates were assessed using 1-way analysis of variance and post hoc least-significant-difference tests. Results: For central targets, the residual errors increased in the following ascending order: "tumor", "bronchi", "carina", and "vertebrae"; there was a significant difference between "tumor" and "vertebrae" (p = 0.010). For peripheral diseases, the residual errors increased in the following ascending order: "tumor", "rib", "vertebrae", and "carina"; There was a significant difference between "tumor" and "carina" (p = 0.005). Conclusions: The "bronchi" and "carina" are the optimal surrogates for central lung targets, while "rib" and "vertebrae" are the optimal surrogates for peripheral lung targets for manual matching of online and planned tumors.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.71-78
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• 2021

Purpose: To evaluate the inter-fractional position and respiratory reproducibility of lung and liver tumors using pressure conserving type(P-type) abdominal compressor in volumetric modulated arc therapy(VMAT). Materials and methods: Six lung cancer patients and three liver cancer patients who underwent VMAT using a P-type abdominal compressor were included in this study. Cone-beam computed tomography(CBCT) images were acquired before each treatment and compared with planning CT images to evaluate the inter-fractional position reproducibility. The position variation was defined as the difference of position shift values between target matching and bone matching. 4-dimensional cone-beam computed tomography(4D CBCT) images were acquired weekly before treatment and compared with planning 4DCT images to evaluate the inter-fractional respiratory reproducibility. The respiratory variation was calculated by the magnitude of excursions by breathing. Results: The mean ± standard deviation(SD) of overall position variation values, 3D vector in the three translational directions were 1.1 ± 1.4 mm and 4.5 ± 2.8 mm for the lung and liver, respectively. The mean ± SD of respiratory variation values were 0.7 ± 3.4 mm (p = 0.195) in the lung and 3.6 ± 2.6 mm (p < 0.05) in the liver. Conclusion: The use of P-type compressor in lung and liver VMAT was effective for stable control of inter-fractional position and respiratory variation by reproduction of abdominal compression. Appropriate PTV margin must be considered in treatment planning, and image guidance before each treatment are required in order to obtain more stable reproducibility

• Journal of the Korean Society of Radiology
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• v.18 no.6
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• pp.733-740
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• 2024

Panoramic radiography is a technique that captures high-resolution images of the oral and dental areas of a patient, providing comprehensive information about the patient's entire dental condition in a single image. While panoramic radiography uses much less radiation compared to cone-beam CT (CBCT), the issue of patient radiation exposure cannot be overlooked. This study aimed to measure the entrance surface dose of radiation-sensitive tissues, such as the thyroid and eyes, during panoramic radiography, and to calculate the equivalent dose and effective dose from the measured absorbed dose to compare and analyze it with the dose limits. The experiment was conducted using the Rayscan α-OCL (Ray Co., Ltd. Gyeonggi-do, Korea) dental panoramic X-ray system. The phantom used was a head and neck phantom (Model PH-47, Kyoto Kagaku, Japan), which has an attenuation coefficient similar to that of human tissue. During panoramic radiography, the entrance surface dose was measured for radiation-sensitive tissues like the thyroid and lens. The entrance surface dose measured were 31.36 µGy for the thyroid, 25.70 µGy for the left lens, and 25.13 µGy for the right lens, respectively. To verify the differences in radiation doses for each site, a one-way ANOVA was performed, and a significant difference between groups was confirmed. A post-hoc test classified the left and right lenses into the same group, while the thyroid was classified into a different group. From the measured entrance surface dose, the equivalent doses for the left and right lenses were calculated to be 27.50 µSv and 27.13 µSv, respectively. The equivalent dose and effective dose for the thyroid were 31.36 µSv and 1.2544 µSv, respectively.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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• pp.15.1-15.6
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• 2016

Background: The utilization of a cone-beam computed tomography (CT)-assisted surgical template allows for predictable results because implant placement plans can be performed in the actual surgery. In order to assess the accuracy of the CT-guided surgery, angular errors and shoulder/apex distance errors were evaluated by data fusion from before and after the placement. Methods: Computer-guided implant surgery was performed in five patients with 19 implants. In order to analyze differences of the implant fixture body between preoperative planned implant and postoperative placed implant, angular error and distance errors were evaluated. Results: The mean angular errors between the preoperative planned and postoperative placed implant was $3.84^{\circ}{\pm}1.49^{\circ}$; the mean distance errors between the planned and placed implants were $0.45{\pm}0.48mm$ horizontally and $0.63{\pm}0.51mm$ vertically at the implant neck and $0.70{\pm}0.63mm$ horizontally and $0.64{\pm}0.57mm$ vertically at the implant apex for all 19 implants. Conclusions: It is important to be able to utilize these methods in actual clinical settings by improving the various problems, including the considerations of patient mouth opening limitations, surgical guide preparation, and fixation.

• Journal of Korean Neurosurgical Society
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• v.63 no.2
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• pp.237-247
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• 2020

Objective : Fixation of the C1-2 segment is challenging because of the complex anatomy in the region and the need for a high degree of accuracy to avoid complications. Preoperative 3D-computed tomography (CT) scans can help reduce the risk of complications in the vertebral artery, spinal cord, and nerve roots. However, the patient may be susceptible to injury if the patient's anatomy does not match the preoperative CT scans. The intraoperative 3D image-based navigation systems have reduced complications in instrument-assisted techniques due to greater accuracy. This study aimed to compare the radiologic outcomes of C1-2 fusion surgery between intraoperative CT image-guided operation and fluoroscopy-guided operation. Methods : We retrospectively reviewed the radiologic images of 34 patients who underwent C1-2 fusion spine surgery from January 2009 to November 2018 at our hospital. We assessed 17 cases each of degenerative cervical disease and trauma in a study population of 18 males and 16 females. The mean age was 54.8 years. A total of 139 screws were used and the surgical procedures included 68 screws in the C1 lateral mass, 58 screws in C2 pedicle, nine screws in C2 lamina and C2 pars screws, four lateral mass screws in sub-axial level. Of the 34 patients, 19 patients underwent screw insertion using intraoperative mobile CT. Other patients underwent atlantoaxial fusion with a standard fluoroscopy-guided device. Results : A total of 139 screws were correctly positioned. We analyzed the positions of 135 screws except for the four screws that performed the lateral mass screws in C3 vertebra. Minor screw penetration was observed in seven cases (5.2%), and major pedicle screw penetration was observed in three cases (2.2%). In one case, the malposition of a C2 pedicle screw was confirmed, which was subsequently corrected. There were no complications regarding vertebral artery injury or onset of new neurologic deficits. The screw malposition rate was lower (5.3%) in patients who underwent intraoperative CT-based navigation than that for fluoroscopy-guided cases (10.2%). And we confirmed that the operation time can be significantly reduced by surgery using intraoperative O-arm device. Conclusion : Spinal navigation using intraoperative cone-beam CT scans is reliable for posterior fixation in unstable C1-2 pathologies and can be reduced the operative time.