• Radiation Oncology Journal
• /
• v.15 no.4
• /
• pp.297-303
• /
• 1997

Purpose : To evaluate the prognostic factors for disease-free survival and long-term results of radiotherapy for pituitary adenoma. Methods and Materials : The study involved a retrospective review of out-come in a series of 27 patients with pituitary adenoma, between 1984 and 1995 at Paik hospital. The study included 20 patients treated with surgery and postoperative radiotherapy and 7 with radiotherapy alone. The patients were followed for 12-146 months (median : 97 months). Seventeen were men and 10 were women. The numbers of functioning and nonfunctioning pituitary adenorna were 22 and 5 respectively and those of microadenoma and macroadenoma were 4 and 23 respectively. The radiation doses of 5040-5580cGy (median : 5040cGy) were deliverd over 5-7 weeks, using 4MV LINAC. The prognostic factors were analyzed by log-rank test. Results: For radiation therapy alone, the 5YSR was 100% and progression free survival rate was 85.8%, The tumor was controlled in 6/7 (85.8%). For surgery and postoperative radiotherapy. the 5YSR, progression free survival rate and local control rate were 95%, 84.8%, and 89.5% respectively. The parameters of tumor size, hormone secretion, radiation dose. radiotherapy field size were evaluated in a uni- and multivariate analysis and all the factors were not statisticaIty significant (P>0.05). Eleven of 12 (92%) with visual field defect experienced normalization or improvement, and 5 for 7 evaluabie patients with hyperprolactinoma achived normalization in 4 and decrement in S patients. Only 2 patients developed mild degree of Panhypopituitarism. Conclusion: The radiotherapy appears to be effective in controiling clinical symptoms and signs resulting from pituitary adenoma. Local control rate with radiotherapy alone or with surgery and postoperative radiotherauy was comparable. There was a trend toward high recurrence rate in Patients with nonfunctioning or prolactin secretion tumor and larger radiation field sizes.

• Radiation Oncology Journal
• /
• v.15 no.4
• /
• pp.339-348
• /
• 1997

Purpose : To evaluate the role of postoperative radiation therapy after curative resection of sigmoid colon cancer Materials and Methods : From 1988 to 1993, a total of 93 Patients with curative resectable sigmoid colon cancer of modified Astler-Coiler (MAC) stage B2, B3, C2, C3 was divided into two groups on the basis of those who received radiation treatment and those who did not. Forty-three patients who treated by surgery alone were classified as postop RT (-) group The remaining 50 patients who underwent postoperative radiotherapy were classified as postop RT (+) group. In all patients in Postop RT (+) group. radiation therapy was delivered using 4 or 10 MV linear accelerators to treat the tumor bed with approximately 5cm margin to a total dose 50.4-61Gy(median 54Gy) in 1.8Gy per fraction. Thirty-two patients were treated. with 5-Fluorouracil based adjuvant chemotherapy at least 3 cycles. but these was no significant difference between two groups. Treatment failure Pattern, 5-year local failure-free survival rates (LFFS), and 5-year disease-free survival rates (DFS) were compared between two groups. Result : Five year LFFS and DFS were $85.1\%,\;68.5\%$, respectively, In Postop RT (-) group, LFFS was $76.2\%$ compared with $91.7\%$ in Postop RT (+) group. Improved LFFS and DFS were seen for patients with stage C3 sigmoid colon carcinoma with postoperative radiation therapy compared with postop RT (-) group (P=0.01, p=0.06 respectively), in stage B3, LFFS washigher in postop RT (+) group than that in Postop RT (-) group. although itwas not significant. Especially, local control was higher in stage 74 inpostop RT (+) group than that in postop RT (-) group, Conclusion : This studv showed significantly improved LFFS and DFS in MAC Stage C3 and improved tendency of LFFS and DFS in MAC Stage B3 disease. Large scale prospective study is required to verify the role of adjuvant radiation therapy in resectable sigmoid colon cancer.

• Radiation Oncology Journal
• /
• v.16 no.2
• /
• pp.195-202
• /
• 1998

Purpose : In order to obtain basic data for treatment plan in radiosurgery, we measured small fields of 6 MV X-rays and compared the measured data with our Monte Carlo simulations for the small fields. Materials and Methods : The small fields of 1.0, 2.0 and 3.0 cm in diameter were used in this study. Percentage depth dose (PDD) and beam Profiles of those fields were measured and calculated. A small semiconductor detector, water phantoms, and a remote control system were used for the measurement Monte Carlo simulations were Performed using the EGS4 code with the input data prepared for the energy distribution of 6 MV X-rays, beam divergence, circular fields and the geometry of the water phantoms. Results : In the case of PDD values, the calculated values were lower than the measured values for all fields and depths, with the differences being 0.3 to 5.7% at the depths of 20 to 20.0 cm and 0.0 to 8.9% at the surface regions. As a result of the analysis of beam profiles for all field sizes at a depth of loom in water phantom, the measured 90% dose widths were in good agreement with the calculated values, however, the calculated Penumbra radii were 0.1 cm shorter than measured values. Conclusion : The measured PDDs and beam profiles agreement with the Monte Carlo calculations approximately. However, it is different when it comes to calculations in the area of phantom surface and penumbra because the Monte Carlo calculations were performed under the simplified geometries. Therefore, we have to study how to include the actual geometries and more precise data for the field area in Monte Carlo calculations. The Monte Carlo calculations will be used as a useful tool for the very complicated conditions in measurement and verification.

• Korean Journal of Heritage: History & Science
• /
• v.52 no.4
• /
• pp.170-183
• /
• 2019

Fiber scutching refers to the process of extracting fibers from plants by separating or extracting fibers from the raw materials. As the definition of the term implies, the "Fiber Scutching" is performed on plants with advanced bast fiber as the primary material processing technique performed on plant materials. Some of the most popular phosphorus plants are ramie, hemp, flax, and the paper mulberry, which have a long history of cultivation and a wide range of distribution, making them very universal as a material supporting human life and culture. This study was described in Oju-yeonmunjangjeon-sango but was designed to re-examine the method of breaking dried stalks, which is currently unused in Korea, to examine the feasibility and characteristics of the technology. As a result of sampling and experimenting with hemp bast using the method recorded in the literature, hemp fiber was actually produced. The criteria for removing the shell from the hemp stem were the degree of discoloration and drying, and only when the stalk was completely discolored to yellow could segregation of the stalk from the shell be performed. The amount of sunlight and temperature were conditions that accelerated drying. However, if exposed for a long time, it is confirmed that hemp bast will be in a suitable condition to process, regardless of the amount of sunlight and temperature. 'Breaking of dried stalks', which utilizes the physical power of 'threshing with a flail' is considered a core process of the fiber scutching technique in 'Yukjin' in Hamgyeong-do. The bark and the core of the hemp were separated by tapping, the bast was thinly split, and the shell was peeled off, making it suitable for collecting with thread. The method of collecting the fibers by applying physical power causes downing on the fibers, which is to be generally avoided in the manufacture of bast fabric woven hemp or ramie. However, Hamgyeong-do's fiber scutching method seems to have applied this principle to the method of making fragile fabrics by using it in reverse. This method is distinct from the steaming or boiling of the stalks' in Andong, Korea, and it is similar to the Western method of spinning fabrics.

• Radiation Oncology Journal
• /
• v.15 no.1
• /
• pp.71-78
• /
• 1997

Purpose : To collect beam data for dynamic wedge fields using conventional measurement tools without the multi-detector system, such as the linear diode detectors or ionization chambers. Materials and Methods : The accelerator CL 2100 C/D has two photon energies of 6MV and 15MV with dynamic wedge an91es of 15o, 30o, 45o and 60o. Wedge transmission factors, percentage depth doses(PDD's) and dose Profiles were measured. The measurements for wedge transmission factors are performed for field sizes ranging from $4\times4cm^2\;to\;20\times20cm^2$ in 1-2cm steps. Various rectangular field sizes are also measured for each photon energy of 6MV and 15MV, with the combination of each dynamic wedge angle of 15o 30o. 45o and 60o. These factors are compared to the calculated wedge factors using STT(Segmented Treatment Table) value. PDD's are measured with the film and the chamber in water Phantom for fixed square field. Converting parameters for film data to chamber data could be obtained from this procedure. The PDD's for dynamic wedged fields could be obtained from film dosimetry by using the converting parameters without using ionization chamber. Dose profiles are obtained from interpolation and STT weighted superposition of data through selected asymmetric static field measurement using ionization chamber. Results : The measured values of wedge transmission factors show good agreement to the calculated values The wedge factors of rectangular fields for constant V-field were equal to those of square fields The differences between open fields' PDDs and those from dynamic fields are insignificant. Dose profiles from superposition method showed acceptable range of accuracy(maximum 2% error) when we compare to those from film dosimetry. Conclusion : The results from this superposition method showed that commissionning of dynamic wedge could be done with conventional dosimetric tools such as Point detector system and film dosimetry winthin maximum 2% error range of accuracy.

• The Journal of Korean Society for Radiation Therapy
• /
• v.16 no.1
• /
• pp.1-9
• /
• 2004

Purpose : The aim of this study is to investigate the properties of small field size and to measure the penumbra and central axis depth dose varying to the jaw setting and off axis distance for indicate this data to small field sizes radiation therapy. Material and methods : The percentage depth dose, beam profile and central axis output dose was measured by farmer type ion chamber and pinpoint chamber using Primart linac with 6MV energy. Beam quality and penumbra variations according to the central axis shift, from center to every 2cm outside increment, and field size, from $1{\times}1cm$ to $10{\times}10cm$ was investigated and compared with that of the standard geometrical condition's results Results : The differences of measured values between two ion chamber was about $37\%$ at 10cm depth with $1{\times}1cm$ field sizes but as field size increased this differences was diminished gradually. Measured data from various off axis distance with the different asymmetric collimations are not changed significantly but as size decreased the dose variation was increased and at $1{\times}1cm$ field size dose difference among off axis distance was as much as $13\%$, and as shallower the measured depth the central axis dose variations among the OAD was increased, penumbra was not changed noticeably depending on off axis distance but the percentage of penumbra from its initial field sizes was strongly dependant on field sizes and penumbra occupation rates of its own field sizes ranging from $6\%$ at $10{\times}10cm$ to $50\%$ at $1{\times}1cm$ field size. Conclusion : For imrt treatment, there are several numbers of different gentry angles with beams of nonuniform fluences are required and several complex factors involved. Among them the characteristics of beam output varying to the geometrical setting and design of collimators are of important to attaining a good treatment results. As mentioned in results the differences of measured values are changed significantly depends on ion chamber volume, depths and field size. For providing quality radiation treatment, especially at small field size, those factor's should have considering deliberately.

• Progress in Medical Physics
• /
• v.23 no.2
• /
• pp.114-122
• /
• 2012

For the determination of absorbed dose to water from a linear accelerator photon beams, it needs a exposure calibration factor $N_x$ or air kerma calibration factor $N_k$ of air ionization chamber. We used the exposure calibration factor $N_x$ to find the absorbed dose calibration factors of water in a reference source through the TG-21 and TRS-277 protocol. TG-21 used for determine the absorbed dose in accuracy, but it required complex calculations including the chamber dependent factors. The authors obtained the absorbed dose calibration factor $N_{dw}{^{Co-60}}$ for reduce the complex calculations with unknown $N_{dw}$ only with $N_x$ or $N_k$ calibration factor in a TM31010 (S/N 1055, 1057) ionization chambers. The results showed the uncertainty of calculated $N_{dw}$ of IC-15 which was known the $N_x$ and $N_{dw}$ is within -0.6% in TG-21, but 1.0% in TRS-277. and TM31010 was compared the $N_{dw}$ of SSDL to that of PSDL as shown the 0.4%, -2.8% uncertainty, respectively. The authors experimented with good agreement the calculated $N_{dw}$ is reliable for cross check the discrepancy of the calibration factor with unknown that of TM31010 and IC-15 chamber.

• Radiation Oncology Journal
• /
• v.20 no.3
• /
• pp.193-198
• /
• 2002

Purpose : Oligodendrogliomas (ODG) are a rare, slow growing, tumor in the brain, which can be cured by complete surgical resection, but as yet it is not known if postoperative adjuvant radiation therapy (RT) is essential, We analyzed the treatment results of patients with irradiated ODG to investigate the efficacy of RT in terms of survival rates and other influencing prognostic factors. Methods and Materials : Between March 1983 and December 1997, 42 patients with ODG were treated with RT at our hospital. The RT was peformed dally at a dose of $1.8\~2.0\;Gy$, at 5 fractions per week, to a total dose of between 39.6 Gy and 64.8 Gy (mean 53.3 Gy). The ages of the patients ranged between 5 and 62 years, with a median age of 39 years. The mean follow-up period was 63.4 months (8-152 months). The Kaplan-Meier method was used to assess the survival, and 5 year survival rates (5-YSR). Log rank tests and Cox regression analyses were used to define the significance of prognostic factors. Results : The majority of ODG in this study were located in the cerebral hemisphere $(83.3\%)$. ODG are slightly more common in men than women, and commonly occurs in middle age, between the 3rd and 4th decades. It has been recommended that RT is commenced within 4 weeks following surgery (5-YSR; $86\%\;vs.\;49\%;\;p<0.03$). Histologically well differentiated, as opposed to poorly differentiated, tumors were found to have a more favorable prognosis (p<0.02). The actuarial 5-YSR was $65.3\%$ (median survival 90 months). 5-YSR for the various extents of surgical excision, followed by external RT, was superior to that of biopsy only followed by external RT $(69.9\%\;vs.\;25.6\%,\;p<0.01)$. Tumor size and location, overall elapsed irradiation days, age, sex, whole brain irradiation as a course of treatment and chemotherapy, had no influence on the 5-YSR (p>0.05). Conclusion : A local involved field irradiation with conventional fractionation, commencing within 4 weeks following surgical excision of the tumor, was beneficial for the 5-YSR, but a total radiation dose exceeding 60 Gy did not improve the 5-YSR.

• Journal of Korea Water Resources Association
• /
• v.52 no.10
• /
• pp.743-752
• /
• 2019

The flow in the meandering channel is characterized by the spiral motion of secondary currents that typically cause the erosion along the outer bank. Hydraulic structures, such as spur dike and groyne, are commonly installed on the channel bottom near the outer bank to mitigate the strength of secondary currents. This study is to investigate the effects of submerged vanes installed in a $90^{\circ}$ meandering channel on the development of secondary currents through three-dimensional numerical modeling using the hybrid RANS/LES method for turbulence and the volume of fluid method, based on OpenFOAM open source toolbox, for capturing the free surface at the Froude number of 0.43. We employ the second-order-accurate finite volume methods in the space and time for the numerical modeling and compare numerical results with experimental measurements for evaluating the numerical predictions. Numerical results show that the present simulations well reproduce the experimental measurements, in terms of the time-averaged streamwise velocity and secondary velocity vector fields in the bend with submerged vanes. The computed flow fields reveal that the streamwise velocity near the bed along the outer bank at the end section of bend dramatically decrease by one third of mean velocity after the installation of vanes, which support that submerged vanes mitigate the strength of primary secondary flow and are helpful for the channel stability along the outer bank. The flow between the top of vanes and the free surface accelerates and the maximum velocity of free surface flow near the flow impingement along the outer bank increases about 20% due to the installation of submerged vanes. Numerical solutions show the formations of the horseshoe vortices at the front of vanes and the lee wakes behind the vanes, which are responsible for strong local scour around vanes. Additional study on the shapes and arrangement of vanes is required for mitigate the local scour.

• The Journal of Korean Society for Radiation Therapy
• /
• v.34
• /
• pp.51-60
• /
• 2022

Objectives: The purpose is to evaluate dosimetric performance and delivery efficiency of VMAT with Halcyon LINAC for double target spine SBRT Materials and Methods: 12 patients with spine oligometastases were retrospectively studied. Single-isocenter spine SBRT plans was established using Halcyon® with Dual Layer MLC and Truebeam® with High Definition MLC. All patients' plans were created in Eclipse TPS through the identical conditions and optimization. C.I, H.I, G.I (Gradient Index), maximal and volumetric doses to spinal cord and low dose area were evaluated for comparison of both plans. Also, total MU and BOT(Beam On Time) were evaluated. Results: Halcyon plans was no Statistical differences in C.I and H.I. However, the average of G.I was 4.64 for Halcyon, which decreased to 5.5% compared to Truebeam (P<0.001). Halcyon plans demonstrated statistically significant reduced G.I. The average of 50% and 25% isodose volume was 487.56 cc (-3.82%, P<0.001), 1859.45 cc (-4.75%, P<0.001) in Halcyon, respectively. Significantly reduced low dose spill were observed in Halcyon plans. In the evaluation of the spinal cord, the average of Dmean and V10 of Halcyon plans in the sample group with an overlap volume of less than 1 cc was 6.802 Gy (-3.504%, P=0.067), 5.766±1.683 cc (-8.199%, P=0.002), respectively. Halcyon plans demonstrated statistically significant reduced D_mean and V10. For delivery efficiency, MU and BOT(maximum dose rate for each machine), on average, increased in Halcyon plans. However, the average of BOT(800MU/min for each machine) was 648.33 sec for Halcyon (-1.74%, P<0.001). Conclusion: Halcyon plan for double-target spine SBRT demonstrated advantages in the low dose area with a steep dose gradient, while having dosimetrically equivalent target dose distribution and spinal cord protective effect. As a result, Halcyon LINAC produced a dosimetrically improved plan for double-target spine SBRT.