• The Journal of Korean Society for Radiation Therapy
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• v.28 no.2
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• pp.149-159
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• 2016

Purpose : To evaluate the usefulness of the breathing exercise,we analyzed the change in the RPM signal and the diaphragm imagebefore 4D respiratory gated radiation therapy planning of lung cancer patients. Materials and Methods : The breathing training was enforced on 11 patients getting the 4D respiratory gated radiation therapy from April, 2016 until August. At the same time, RPM signal and diaphragm image was obtained respiration training total three steps in step 1 signal acquisition of free-breathing state, 2 steps respiratory signal acquisition through the guide of the respiratory signal, 3 steps, won the regular respiration signal to the description and repeat training. And then, acquired the minimum value, maximum value, average value, and a standard deviation of the inspiration and expiration in RPM signal and diaphragm image in each steps. Were normalized by the value of the step 1, to convert the 2,3 steps to the other distribution ratio (%), by evaluating the change in the interior of the respiratory motion of the patient, it was evaluated breathing exercise usefulness of each patient. Results : The mean value and the standard deviation of each step were obtained with the procedure 1 of the RPM signal and the diaphragm amplitude as a 100% reference. In the RPM signal, the amplitudes and standard deviations of four patients (36.4%, eleven) decreased by 18.1%, 27.6% on average in 3 steps, and 2 patients (18.2%, 11 people) had standard deviation, It decreased by an average of 36.5%. Meanwhile, the other four patients (36.4%, eleven) decreased by an average of only amplitude 13.1%. In Step 3, the amplitude of the diaphragm image decreased by 30% on average of 9 patients (81.8%, 11 people), and the average of 2 patients (18.2%, 11 people) increased by 7.3%. However, the amplitudes of RPM signals and diaphragm image in 3steps were reduced by 52.6% and 42.1% on average from all patients, respectively, compared to the 2 steps. Relationship between RPM signal and diaphragm image amplitude difference was consistent with patterns of movement 1, 2 and 3steps, respectively, except for No. 2 No. 10 patients. Conclusion : It is possible to induce an optimized respiratory cycle when respiratory training is done. By conducting respiratory training before treatment, it was possible to expect the effect of predicting the movement of the lung which could control the patient's respiration. Ultimately, it can be said that breathing exercises are useful because it is possible to minimize the systematic error of radiotherapy, expect more accurate treatment. In this study, it is limited to research analyzed based on data on respiratory training before treatment, and it will be necessary to verify with the actual CT plan and the data acquired during treatment in the future.

• Radiation Oncology Journal
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• v.21 no.1
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• pp.44-65
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• 2003

Purpose : To conduct nationwide surgery on the principles In radiotherapy for rectal center, and develop the framework of a database of Korean Patterns of Care Study. Materials and Methods : A consensus committee was established to develop a tool for measuring the Patterns in radiotherapy Protocols for rectal cancer. The Panel was composed of radiation oncologists from 18 hospitals in Seoul Wetropolltan area. The committee developed a survey format to analyze radiation oncologist's treatment principles for rectal cancer. The survey items developed for measuring the treatment principles were composed of 1) 8 eliglblllty criteria, 2) 20 Items for staging work-ups and prognostic factors, 3) 7 Items for principles of combined surgery and chemotherapy, 4) 9 patient set-ups, 5) 19 determining radiation fields, 6) S radiotherapy treatment pians, 7) 4 physicalilaboratory examination to monitor a patient's condition during treatment, and 8) 10 follow-up evaluations. These items were sent to radiation oncoioglsts In charge of gastrolntestlnal malignancies in all hospitals (48 hospitals) In Korea to which 30 replies were received (63$\%$). Results : Most of the surrey Items were replied to without no major between the repliers, but with the fellowing items only 50$\%$ of repliers were in agreement : 1) Indications of preoperative radiation, 2) use of endorectal ultrasound, CT scan, and bone scan for staging work-ups, 3) principles of combining chemotherapy with radiotherapy, 4) use of contrast material for small bowel delineation during simulation, 5) determination of field margins, and 6) use of CEA and colonoscopy for follow-up evaluations. Conclusions : The Items where considerable disaggrement was shown among the radiation oncologists seemed to make no serious difference In the treatment outcome, but a practical and reasonable consensus should be reached by the committee, with logical processes of agreement. These Items can be used for a basic database for the Patterns of Care Study, which will survey the practical radiotherapy Patterns for rectal cancer in Korea.

• Progress in Medical Physics
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• v.26 no.3
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• pp.143-152
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• 2015

In this study, we aim to design the architecture of the kV imaging system for tumor tracking in the dual-head gantry system and analyze its accuracy by simulations. We established mathematical formulas and algorithms to track the tumor position with the two-pair kV imaging systems when they are in the non-orthogonal positions. The algorithms have been designed in the homogeneous coordinate framework and the position of the source and the detector coordinates are used to estimate the tumor position. 4D XCAT (4D extended cardiac-torso) software was used in the simulation to identify the influence of the angle between the two-pair kV imaging systems and the resolution of the detectors to the accuracy in the position estimation. A metal marker fiducial has been inserted in a numerical human phantom of XCAT and the kV projections were acquired at various angles and resolutions using CT projection software of the XCAT. As a result, a positional accuracy of less than about 1mm was achieved when the resolution of the detector is higher than 1.5 mm/pixel and the angle between the kV imaging systems is approximately between $90^{\circ}$ and $50^{\circ}$. When the resolution is lower than 1.5 mm/pixel, the positional errors were higher than 1mm and the error fluctuation by the angles was greater. The resolution of the detector was critical in the positional accuracy for the tumor tracking and determines the range for the acceptable angle range between the kV imaging systems. Also, we found that the positional accuracy analysis method using XCAT developed in this study is highly useful and will be a invaluable tool for further refined design of the kV imaging systems for tumor tracking systems.

• Journal of Radiation Protection and Research
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• v.27 no.1
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• pp.37-49
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• 2002

The accuracy of radiation dose delivery to target volume is one of the most important factors for good local control and less treatment complication. In vivo dosimetry is an essential QA procedure to confirm the radiation dose delivered to the patients. Transmission dose measurement is a useful method of in vivo dosimetry and it's advantages are non-invasiveness, simplicity and no additional efforts needed for dosimetry. In our department, in vivo dosimetry system using measurement of transmission dose was manufactured and algorithms for estimation of transmission dose were developed and tested with phantom in various conditions successfully. This system was applied in clinic to test stability, reproducibility and applicability to daily treatment and the accuracy of the algorithm. Transmission dose measurement was performed over three weeks. To test the reproducibility of this system, X-tay output was measured before daily treatment and then every hour during treatment time in reference condition(field size; $10 cm{\times} 10 cm$, 100 MU). Data of 11 patients whose pelvis were treated more than three times were analyzed. The reproducibility of the dosimetry system was acceptable with variations of measurement during each day and over 3 week period within ${\pm}2.0%$. On anterior- posterior and posterior fields, mean errors were between -5.20% and +2.20% without bone correction and between -0.62% and +3.32% with bone correction. On right and left lateral fields, mean errors were between -10.80% and +3.46% without bone correction and between -0.55% and +3.50% with bone correction. As the results, we could confirm the reproducibility and stability of our dosimetry system and its applicability in daily radiation treatment. We could also find that inhomogeneity correction for bone is essential and the estimated transmission doses are relatively accurate.

• Radiation Oncology Journal
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• v.27 no.4
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• pp.194-200
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• 2009

Purpose: This aim of this study was to evaluate changes in gastric volume and organ position as a result of delayed gastric emptying after a subtotal gastrectomy performed as part of the treatment of stomach cancer. Materials and Methods: The medical records of 32 patients who underwent concurrent chemoradiotherapy after a subtotal gastrectomy from March 2005 to December 2008 were reviewed. Of these, 5 patients that had more than 50 cc of residual gastric food detected at computed tomography (CT) simulation, were retrospectively enrolled in this study. Gastric volume and organ location was measured from CT images obtained before radiotherapy, twice weekly. In addition, authors evaluated the change of radiation dose distribution to planning the target volume and normal organ in a constant radiation therapy plan regardless of gastric volume variation. Results: A variation in the gastric volume was observed during the radiotherapy period (64.2~340.8 cc; mean, 188.2 cc). According to the change in gastric volume, the location of the left kidney was shifted up to 0.7 - 2.2 cm (mean, 1.2 cm) in the z-axis. Under-dose to planning target volume (V43, 79.5${\pm}$10.4%) and over-dose to left kidney (V20, 34.1${\pm}$12.1%; Mean dose, 23.5${\pm}$8.3 Gy) was expected, given that gastric volume change due to delayed gastric emptying wasn't taken into account. Conclusion: This study has shown that a great change in gastric volume and left kidney location may occur during the radiation therapy period following a subtotal gastrectomy, as a result of delayed gastric emptying. Detection of patients who experienced delayed gastric emptying and the application of gastric volume variation to radiation therapy planning will be very important.

• Journal of the Korean Geographical Society
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• v.28 no.4
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• pp.285-297
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• 1993

For the application of the diffusion equation, slope height and maximum slope angle are calculated from the plotted slope profile. Using denudation rate as a solution for the diffusion equation, an apparent age index can be calculated, which is the total amount of denudation through total time. Plots of slope angle versus slope height and apparent age index versus slope height are useful for determining relative or absolute ages and denudation rates. Mathematical simulation plots of slope angle versus slope height can generate equal denudation-rate lines for a given age. Mathematical simulations of slope angle versus age for a given slope height, for equal denudation-rate at a particular profile site, and for comparing to other sites having controlled ages.

• Radiation Oncology Journal
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• v.16 no.1
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• pp.71-79
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• 1998

Purpose : The objective of this study is to introduce our installation of a non-commercial 3D Planning system, Plunc and confirm it's clinical applicability in various treatment situations. Materials and Methods : We obtained source codes of Plunc, offered by University of North Carolina and installed them on a Pentium Pro 200MHz (128MB RAM, Millenium VGA) with Linux operating system. To examine accuracy of dose distributions calculated by Plunc, we input beam data of 6MV Photon of our linear accelerator(Siemens MXE 6740) including tissue-maximum ratio, scatter-maximum ratio, attenuation coefficients and shapes of wedge filters. After then, we compared values of dose distributions(Percent depth dose; PDD, dose profiles with and without wedge filters, oblique incident beam, and dose distributions under air-gap) calculated by Plunc with measured values. Results : Plunc operated in almost real time except spending about 10 seconds in full volume dose distribution and dose-volume histogram(DVH) on the PC described above. As compared with measurements for irradiations of 90-cm 550 and 10-cm depth isocenter, the PDD curves calculated by Plunc did not exceed $1\%$ of inaccuracies except buildup region. For dose profiles with and without wedge filter, the calculated ones are accurate within $2\%$ except low-dose region outside irradiations where Plunc showed $5\%$ of dose reduction. For the oblique incident beam, it showed a good agreement except low dose region below $30\%$ of isocenter dose. In the case of dose distribution under air-gap, there was $5\%$ errors of the central-axis dose. Conclusion : By comparing photon dose calculations using the Plunc with measurements, we confirmed that Plunc showed acceptable accuracies about $2-5\%$ in typical treatment situations which was comparable to commercial planning systems using correction-based a1gorithms. Plunc does not have a function for electron beam planning up to the present. However, it is possible to implement electron dose calculation modules or more accurate photon dose calculation into the Plunc system. Plunc is shown to be useful to clear many limitations of 2D planning systems in clinics where a commercial 3D planning system is not available.

• Radiation Oncology Journal
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• v.28 no.4
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• pp.231-237
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• 2010

Purpose: We investigated the effect of location changes in the inferior border of the belly board (BB) aperture by adding a bladder compression device (BCD). Materials and Methods: We respectively reviewed data from 10 rectal cancer patients with a median age 64 years (range, 45~75) and who underwent computed tomography (CT) simulation with the use of BB to receive pelvic radiotherapy between May and September 2010. A CT simulation was again performed with the addition of BCD since small bowel (SB) within the irradiated volume limited boost irradiation of 5.4 Gy using the cone down technique after 45 Gy. The addition of BCD made the inferior border of BB move from symphysis pubis to the lumbosacral junction (LSJ). Results: Following the addition of BCD, the irradiated volumes of SB and the abdominopelvic cavity (APC) significantly decreased ($174.3{\pm}89.5mL$ vs. $373.3{\pm}145.0mL$, p=0.001, $1282.6{\pm}218.7mL$ vs. $1,571.9{\pm}158mL$, p<0.001, respectively). Bladder volume within the treated volume increased with BCD ($222.9{\pm}117.9mL$ vs. $153.7{\pm}95.5mL$, p<0.001). The ratio of irradiated bladder volume to APC volume with BCD ($33.5{\pm}14.7%$) increased considerably compared to patients without a BCD ($27.5{\pm}13.1%$) (p<0.001), and the ratio of irradiated SB to APC volume decreased significantly with BCD ($13.9{\pm}7.6%$ vs. $24.2{\pm}10.2%$, p<0.001). The ratios of the irradiated SB volume and irradiated bladder volume to APC volume negatively correlated (p=0.001). Conclusion: This study demonstrated that the addition of BCD, which made the inferior border of BB move up to the LSJ, increased the ratio of the bladder to APC volume and as a result, decreased the irradiated volume of SB.

• The korean journal of orthodontics
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• v.39 no.4
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• pp.203-212
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• 2009

Objective: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion in a self-drilling manner. Methods: A 3D finite element method was used to simulate the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) into 1 mm thick cortical bone. The shape and dimension of thread groove in the center of the cortical bone produced by the cutting flute at the apical of the microimplant was obtained from animal test using rabbit tibias. A total of 3,600 analysis steps was used to calculate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. Results: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, were observed in the peri-implant bone along the whole length of the microimplant. Level of strains in the vicinity of either the screw tip or the valley part were similar. Conclusions: Bone strains from a microimplant insertion in a self-drilling manner might have a negative impact on the physiological remodeling of cortical bone.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.121-123
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• 2002

The design of an air seat cushion for preventing decubitus ulcer includes many design factors such as the even distribution of interface pressure, the minimization of mean and peak interface pressure values, and the reduction of interface shear force and pressure gradient. It involves the anatomic condition of plegia's buttock as well as air pressure in air cells of cushion. As a result, a suitable design of the cushion satisfying the all requirements is a difficult problem. Therefore, an appropriate and effective numerical tool to develop an air cushion orthosis is required. The purpose of the present study was to develop an air seat cushion orthosis having optimized air cells for evenly distributed interface pressure between the buttock and cushion surface. For the purpose, an advanced finite element (FE) model for the design of air cushion was developed. Since the interface pressure and shear force behavior, as well as stress analyses were primary concern, a FE air cell model was developed and verified by the experiments. Then, the interactions of two cells were checked. Also, the human part of the developed numerical model includes every material property and geometry related to buttock and femoral parts. For construction of dimension data of buttock and femoral parts, CT scans were performed. A commercial FE program was employed for the simulation representing the seating process on the orthosis. Then, sensitive analyses were performed with varying design parameters. A set of optimal design parameters was found satisfying the design criteria of the orthosis. The results were utilized to produce a prototype of the orthosis. Experimentally, the buttock interface pressure distributions from the optimized and previous ones were compared. The new seat orthosis showed a significantly improved interface pressure characteristics compared to the most popular one in the market. The new orthosis will be used for the development of the AI(artificial intelligent) controlled seat orthosis fur prevention of decubitus ulcer fur various plegic patients and the elderly.