• Journal of Radiation Protection and Research
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• v.46 no.4
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• pp.151-159
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• 2021

Background: Computed tomography (CT) is one of the crucial diagnostic tools in modern medicine. However, careful monitoring of radiation dose for CT patients is essential since the procedure involves ionizing radiation, a known carcinogen. Materials and Methods: The most desirable CT dose descriptor for risk analysis is the organ absorbed dose. A variety of CT organ dose calculators currently available were reviewed in this article. Results and Discussion: Key common elements included in CT dose calculators were discussed and compared, such as computational human phantoms, CT scanner models, organ dose database, effective dose calculation methods, tube current modulation modeling, and user interface platforms. Conclusion: It is envisioned that more research needs to be conducted to more accurately map CT coverage on computational human phantoms, to automatically segment organs and tissues for patient-specific dose calculations, and to accurately estimate radiation dose in the cone beam computed tomography process during image-guided radiation therapy.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.1-5
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• 2007

Purpose: The accuracy and advantages of OBI(On Board Imager) against the conventional method like film and EPID for the setup error correction were evaluated with the analysis of the accumulated data which were produced in the process of setup error correction using OBI. Materials and Methods: The results of setup error correction using OBI system were analyzed for the 130 patients who had been planned for 3 dimensional conformal radiation therapy during March 2006 and May 2006. Two kilo voltage images acquired in the orthogonal direction were fused and compared with reference setup images. The setup errors in the direction of vertical, lateral, longitudinal axis were recorded and calculated the distance from the isocenter. The corrected setup error were analyzed according to the lesion and the degree of shift variations. Results: There was no setup error in the 41.5% of total analyzed patients and setup errors between 1mm and 5mm were found in the 52.3%. 6.1% patients showed the more than 5mm shift and this error were verified as a difference of setup position and the movement of patient in a treatment room. Conclusion: The setup error analysis using OBI in this study verified that the conventional setup process in accordance with the laser and field light was not enough to get rid of the setup error. The KV images acquired using OBI provided good image quality for comparing with simulation images and much lower patients' exposure dose compared with conventional method of using EPID. These advantages of OBI system which were confirmed in this study proved the accuracy and priority of OBI system in the process of IGRT(Image Guided Radiation Therapy).

• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.65-71
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• 2018

Purpose : Standardized pillow may not support patient's individual cervical spine thoroughly when head and neck radiation therapy with $Tomotherapy^{(R)}$. Therefore, the purpose of this study was to make a comparative analysis for the difference of using standardized pillow only and using customized cervical spine immobilizer with standardized pillow. Materials and Methos : The head and neck cancer patients who are treated image-guided radiation therapy(IGRT) with $Tomotherapy^{(R)}$ were divided into two groups, 20 patients using standardized pillow only, and 20 patients using customized cervical spine immobilizer with standardized pillow. We achieved 20 mega-voltage computed tomography(MVCT) image per patient, compared curvature of the cervical spine in MVCT with curvature of the cervical spine in CT-simulation. Results : Results of comparative analysis were curvature consistency 95.9 %, maximum error of distance 41.9 mm, average distance error per fractionation 19.4 mm, average standard deviation 1.34 mm in case of using standardized pillow only, curvature consistency 98.9 %, maximum error of distance 12.9 mm, average distance error per fractionation 5.8 mm, average standard deviation 0.59 mm in case of using customized cervical spine immobilizer with standardized pillow. Conclusion : Using customized cervical spine immobilizer shows higher reproducibility and low distance error, therefore customized cervical spine immobilizer could be useful for head and neck cancer patients who need radiation therapy.

• The Journal of Korean Society for Radiation Therapy
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• v.32
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• pp.73-83
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• 2020

Purpose: The purpose of this study is to confirm the matching of the electron density between tissue and gas due to variation of abdominal gas volume in MRgART (Magnetic Resonance-guided Adaptive Radiation Therapy) for pancreatic cancer patients, and to confirm the effect on the dose change and treatment time. Materials and Methods: We compared the PTV and OAR doses of the initial plan and the AGC(Abdominal gas correction) plans to one pancreatic cancer patient who treated with MRgART using the ViewRay MRIdian System (Viewray, USA) at this clinic. In the 4fx AGC plans, Beam ON(%) according to the patient's motion error was checked to confirm the effect of abdominal gas volume on treatment time. Results: Comparing the Initial plan with the average value of AGC plan, the dose difference was -7 to 0.1% in OAR and decreased by 0.16% on average, and in PTV, the dose decreased by 4.5% to 5.5% and decreased by 5.1% on average. In Adaptive treatment, as the abdominal gas volume increased, the Beam ON(%) decreased. Conclusion: Abdominal gas volume variation causes dose change due to inaccurate electron density matching between tissue and gas. In addition, if the abdominal gas volume increases, the Beam ON(%) decreases, and the treatment time may increase due to the motion error of the patient. Therefore, in MRgART, it is necessary to check the electron density matching and minimize the variability of the abdominal gas.

• Journal of Biomedical Engineering Research
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• v.28 no.5
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• pp.676-683
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• 2007

A non-invasive respiratory gated radiotherapy system like those based on external anatomic motion gives better comfortableness to patients than invasive system on treatment. However, higher correlation between the external and internal anatomic motion is required to increase the effectiveness of non-invasive respiratory gated radiotherapy. Both of invasive and non-invasive methods need to track the internal anatomy with the higher precision and rapid response. Especially, the non-invasive method has more difficulty to track the target position successively because of using only image processing. So we developed the system to track the motion for a non-invasive respiratory gated system to accurately find the dynamic position of internal structures such as the diaphragm and tumor. The respiratory organ motion tracking apparatus consists of an image capture board, a fluoroscopy system and a processing computer. After the image board grabs the motion of internal anatomy through the fluoroscopy system, the computer acquires the organ motion tracking data by image processing without any additional physical markers. The patients breathe freely without any forced breath control and coaching, when this experiment was performed. The developed pattern-recognition software could extract the target motion signal in real-time from the acquired fluoroscopic images. The range of mean deviations between the real and acquired target positions was measured for some sample structures in an anatomical model phantom. The mean and max deviation between the real and acquired positions were less than 1mm and 2mm respectively with the standardized movement using a moving stage and an anatomical model phantom. Under the real human body, the mean and maximum distance of the peak to trough was measured 23.5mm and 55.1mm respectively for 13 patients' diaphragm motion. The acquired respiration profile showed that human expiration period was longer than the inspiration period. The above results could be applied to respiratory-gated radiotherapy.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.7-18
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• 2017

Purpose: A QA Set was established to verify the movement accuracy of image-guided 6DoF Couch and to evaluate its usefulness. Materials and Methods: Two sets of linear accelerators equipped with 6DoF Couch and CBCT were used. Using the established QA Set, each CBCT image was obtained over 15 times through the Penta-Guide Phantom installed with off-set shift values along six translational (Translation; TX, TY, TZ) and rotational (Rotation, Pitch; RX, Roll; RY, Yaw; RZ) directions. Using this method, we compared the reference image and the registration image, and we analyzed the error calculated by measuring the positional accuracy of the modified 6DoF Couch. Results: The Air Cavity corresponding to the Pixel of the reference image and the registration image were all contained between 30 and 66, and the revealing high registration accuracy. Error between the modified off-set value of 6DoF Couch and the measured value along translational directions were $0.25{\pm}0.18mm$ in the TX direction, $0.25{\pm}0.25mm$ in the TY direction, and $0.36{\pm}0.2mm$ in the TZ direction. Misalignments along the rotational axis were $0.18{\pm}0.08^{\circ}$ in the RX direction, $0.26{\pm}0.09^{\circ}$ in the RY direction, and $0.11{\pm}0.08^{\circ}$ in the RZ direction, it was corrected precisely for any value. Conclusion: Using the YCC QA Set, we were able to verify the error of 6DoF Couch along both the translational and rotational directions in a very simple method. This system would be useful in performing Daily IGRT QA of 6DoF Couch.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.47 no.6
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• pp.438-444
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• 2021

Objectives: Loss of the interdental papilla is multi-factorial and creates a multitude of problems. Autogenous connective tissue/biomaterial-based regeneration has been attempted for decades to reconstitute the black space created due to the loss of papilla. The aim of this present study was to regenerate papillary recession defects using an amnion-chorion membrane (ACM) allograft and to evaluate the clinical outcome up to six months postoperatively. Materials and Methods: Twenty patients with 25 Nordland and Tarnow's Class I/II interdental papillary recession defects were treated with ACM and coronal advancement of the gingivo-papillary unit via a semilunar incision on the labial aspect followed by a sulcular incision in the area of interest. A photographic image analysis was carried out using the GNU Image Manipulation software program from the baseline to three and six months postoperatively. The black triangle height (BTH) and the black triangle width (BTW) were calculated using the pixel size and were then converted into millimeters. The mean and standard deviation values were determined at baseline and then again at three and six months postoperatively. The probability values (P<0.05 and P≤0.01) were considered statistically significant and highly significant, respectively. An analysis of variance and post hoc Bonferroni test were carried out to compare the mean values. Results: Our evaluation of the BTH and BTW showed a statistically and highly significant difference from the baseline until both three and six months postoperatively (P=0.01). A post hoc Bonferroni test disclosed a statistically significant variance from the baseline until three and six months postoperatively (P<0.05) and a non-significant difference from three to six months after the procedure (P≥0.05). Conclusion: An ACM allograft in conjunction with a coronally advanced flap could be a suitable minimally invasive alternative for papillary regeneration.

• Tuberculosis and Respiratory Diseases
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• v.48 no.3
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• pp.357-364
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• 2000

Background : Complicated exudative pleural fluid collections have traditionally been treated by either closed tube thoracostomy drainage or by open surgical drainage. Complete drainage is important in order to control pleural sepsis, restore pulmonary function, and entrapment. Recently intracavitary fibrinolytic therapy has been advocated as a method to facillitate drainage of complicated exudative pleural effusion and to allow enzymatic debridemant of the restrictive fibrinous sheets covering the pleural surface. The purpose of this study is to prospectively evaluate the effects of image-guided catheter drainage with high dose urokinase(UK) instillation in the treatment of complicated pleural effusions. Patients : Twenty complicated pleural effusion patients that poorly respond to image-guided drainage were allocated to receive UK. There were 8 pneumonia and 12 tuberculosis. Methods : Drugs were diluted in 250 mL normal saline and were infused intrapleurally through the chest tube or pig-tail catheter in a daily dose of 250,000 IU of UK. Response was assessed by clinical outcome, fluid drainage, chest radiography, pleural ultrasound and/or computed tomography. Results : The mean UK instillation time was $1.63{\pm}0.10$. The mean volume drained UK instillation was $381.3{\pm}314.4\;mL$, and post-UK was $321.6{\pm}489.5\;mL$. The follow up duration after UK therapy was mean $212.9{\pm}194.5$ days. We had successful results in 19 cases (95.0%). There were 12 pleural thickenings (60.0%), 2 markedly decreased effusions (10.0%) and 5 cases of no thickening or effusion. There was recurrence after treatment in only one patient(5%) with complicated pleural effusiondue to tuberculosis. Conclusions : Image-guided drainage with high dose UK instillation (250,000 U/day) in complicated pleural effusion is a safe and more effective method than closed thoracostomy drainage. And this management, in turn, can obviate surgery in most cases.

• Journal of Radiation Protection and Research
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• v.35 no.2
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• pp.63-68
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• 2010

The ultimate goal of radiation treatment is to use enough radiation dosage in order to examine a tumor while protecting normal tissue. Respiratory guided radiotherapy is being clinically implemented to examine a given stabilized area in order to compensate for the problems of patient breathing. This study investigates the effects of breathing movements on 40 patients with liver cancer through the actual radiation therapy plan using 4D-CT and respiratory guided radiotherapy using RPM. Using a commercial RPM respiratory gating system 4D-CT, we acquired 4D CT on multislice helical CT scanners that use different approaches to 4D CT image reconstruction. The results from analyzing forty patients according to age and direction showed no relationship between gender and transition change. The mean left-right, anteroposterior, and craniocaudal total movements were $3.19{\pm}1.29$, $5.44{\pm}2.07$, and $12.54{\pm}4.70$ mm, respectively. Changes were the largest with CC directions and as patients advanced in age, movements were larger. Therefore, as changes occur in treatment areas because of movements caused from breathing, respiratory gating system is put into operation to revise movement and can increase the radiotherapeutics effects in treating liver cancer.

• The Journal of Korean Society for Radiation Therapy
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• v.35
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• pp.41-51
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• 2023

Purpose: This study compares and analyzes the image quality of 3D-CBCT(Cone Beam Computed-Tomography) and Gated CBCT according to baseline changes during SBRT(Stereotactic Body RadioTherapy) in lung cancer patients to find a useful CBCT method for correcting movement due to breathing Materials and methods : Insert a solid tumor material with a diameter of 3 cm into the QUASAR^TM phantom. 4-Dimentional Computed-Tomography(4DCT) images were taken with a speed of the phantom at period 3 sec and a maximum amplitude of 20 mm. Using the contouring menu of the computerized treatment planning system Eclipse^TM Gross Tumor Volume was outlined on solid tumor material. Set-up the same as when acquiring a 4DCT image using Truebeam STx^TM, breathing patterns with baseline changes of 1 mm, 3 mm, and 5 mm were input into the phantom to obtain 3D-CBCT (Spotlight, Full) and Gated-CBCT (Spotlight, Full) images five times repeatedly. The acquired images were compared with the Signal-to-Noise Ratio(SNR), Contrast-to-Noise Ratio(CNR), Tumor Volume Length, and Motion Blurring Ratio(MBR) based on the 4DCT image. Results: The average Signal-to-Noise Ratio, Contrast-to-Noise Ratio, Tumor Volume Length and Motion Blurring Ratio of Spotlight Gated CBCT images were 13.30±0.10%, 7.78±0.16%, 3.55±0.17%, 1.18±0.06%. As a result, Spotlight Gated-CBCT images according to baseline change showed better values than Spotligtht 3D-CBCT images. Also, the average Signal-to-Noise Ratio, Contrast-to-Noise Ratio, Tumor Volume Length and Motion Blurring Ratio of Full Gated CBCT images were 12.80±0.11%, 7.60±0.11%, 3.54±0.16%, 1.18±0.05%. As a result Full GatedCBCT images according to baseline change showed better values than Full 3D-CBCT images. Conclusion : Compared to 3D-CBCT images, Gated-CBCT images had better image quality according to the baseline change, and the effect of Motion Blurring Artifacts caused by breathing was small. Therefore, it is considered useful to image guided using Gated-CBCT when a baseline change occurs due to difficulty in regular breathing during SBRT that exposes high doses in a short period of time