• Progress in Medical Physics
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• v.12 no.2
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• pp.125-131
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• 2001

We was investigate the dosimetric characteristics of the virtual wedge and it compared to the conventional fixed wedge. Also we was evaluate the quality factor of the experimental multi-channel dosimetry system for virtual wedge. Recently virtual wedge technique and wedge fraction methods are available through the computer controlled asymmetric collimator or the independent jaw in medical linear accelerator for radiation therapy. The dosimetric characteristics are interpreted by radiation field analyzer RFA-7 system and PTW-UNIDOS system. Experimental multi-channel dosimetry system for virtual wedge was consists of the electrometer, the solid detector and array phantom. The solid detectors were constructed using commercially diodes for the assessment of quality assurance in radiotherapy. And it was used for the point dose measuring and field size scanning. The semiconductor detector and ion chamber were positioned at a dmax, 5 cm, 10 cm, 20 cm depth and its specific ratio was determined using a scanning data. Wedge angles in fixed and virtual type are compared with measurements in water phantom and it is shown that the wedge angle 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$were agree within 1$^{\circ}$ degree in 6, 10 MV photon beams. In PDD and beam flatness, experimental multi-channel disimetry system was capable of reproduceing the measured values usually to within $\pm$2.1% the statistical uncertainties of the data. It was used to describe dosimetric characteristics of virtual wedge in clinical photon beams. Also we was evaluate optimal use of the virtual wedge and improve the quality factor of the experimental multi-channel dosimetry system for virtual wedge.

• Journal of the Korean Magnetics Society
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• v.25 no.6
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• pp.208-218
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• 2015

Recently, radiation therapy is used in the CT existing conventional two-dimensional radiation image, and set the size and location of the tumor in a manner that the image is going to change the treatment plan. After using the simulation using CT, radiation therapy it is four-dimensional or three-dimensional treatment made possible. and radiation therapy became the more effective ever before. High technology radiation therapy such as the treatment of SRS,IMRT, IGRT, SBRT, is a need to try contemplating the possibility to apply appropriate analysis and situation, so it has its own characteristics. and then it is believed that it is necessary to analyze and try it worries the proper applicability of the situation. The configuration of the various treatment that is applicable in many hospitals is necessary to try to determine how to practically apply the patients. Critical organs surrounding tumor give a small dose to avoid side effects and then the tumor has the therapeutic effect by providing a larger dose than before the radiation treatment.

• Journal of Life Science
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• v.26 no.9
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• pp.1088-1096
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• 2016

Despite that moderate hyperthermia can exert various antitumor activities such as direct cytotoxic effects on tumor cells, effects on tumor vasculatures and immunological effects, hyperthermia has been usually combined with radiotherapy or chemotherapy due to its limited efficacy in cancer treatment, showing some positive clinical benefits with generally well-tolerated side effects. Since heat shock responses itself can interfere with the anti-tumor effects of hyperthermia, not all of these studies might have demonstrated positive clinical outcomes in cancer patients. Therefore, the negative anti-tumor effect of hyperthermia should be reduced to enhance the effectiveness of hyperthermia. Although the responses to heat stress of tumor tissues containing vessels, immune cells, connective tissues as well as cancer cells, are very complicated, it is needed to study in the near future if some clinically available drugs, which can modulate heat stress responses, can improve the efficacy of hyperthermia in patients with cancer. In this review, the effect of clinical hyperthermia centered on non-invasive external hyperthermia using radiofrequency at moderate temperature will be discussed, since it is the state-of-the-art technology in the current clinical practice of hyperthermia, and a moderate operational temperature is used to increase the therapeutic effectiveness of conventional therapy without additional toxicity to normal tissues.

• Progress in Medical Physics
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• v.13 no.3
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• pp.109-113
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• 2002

In recent years, the radiotherapy equipment has become much more sophisticated, and with the complication comes an increased set of quality assurance (QA) responsibilities. Today's computer controlled linear accelerator requiring QA of not only the radiation integrity, but also the mechanical accuracy of the linear accelerator. The existing QA sheets are adequate for acceptance testing and commissioning but those sheets are somewhat descriptive form for routine QA. establishing the QA sheets for a facility are more efficient if the sheets could estimate the long-term stability for the result of QA. We are going to develope new prototype of mechanical QA sheet to visualize and to verify long-term stability of mechanical QA for clinical linear accelerator. The items included in mechanical QA sheet were 1) gantry rotation, 2) collimator rotation, 3) couch rotation, 4) optical distance indicator (ODI), and 5) laser alignment. We compared new prototype sheet with conventional sheet for several hospitals in Korea for those items. The QA acceptance criteria in this study mainly followed published recommendations. The contents of test for mechanical QA are the following. Confirm that the digital and/or mechanical gantry angle readouts are correct. Verify that digital and/or mechanical readouts of collimator angle agree with the true angle, as determined with the protractor. Measure the light field using a graph paper and compare with the digital readouts. Confirm digital readout accuracy. Verify that the sagittal laser, the left and right lasers, and the ceiling laser intersect at the isocenter. In the design of new QA sheet, we emphasized the representation of the long-term stability of mechanical QA by using Excel program. By using the new prototype QA sheet, we simplified and visualized the mechanical QA process, and could estimate the long-term stability of mechanical error of linear accelerator.

• Progress in Medical Physics
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• v.17 no.1
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• pp.6-16
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• 2006

The goal of this study was to develop new indices for effectively evaluating the dose coverage and homogeneity based on the target-volume dose-volume histogram (TV-DVH) of intensity-modulated radio-therapy treatment plans. A new coverage Index and a new homogeneity index were developed by integrating a modified TV-DVH and by fitting a TV-DVH with a modified step function, respectively. The coverage index, named the l-index, indicates whether the dose coverage for the target volume is adequate based on user-defined criteria. A lower l-index indicates higher dose coverage of the tumor volume. The index for assessing dose homogeneity in a target volume, named the n-index, is more accurate than the conventional method in evaluating the dose homogeneity in a tumor volume. The baseline treatment plan for a target volume coverage and homogeneity is discussed. The proposed simple indices have been demonstrated to be effective in evaluating the dose coverage and homogeneity for TV-DVHs.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.333-338
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• 2019

In the field of radiotherapy, the Quality Assurance(QA) procedure to verify the safety of treatment is considered to be very important. However, due to various problems of the conventional dosimeters used for the QA, researches on these dosimeters have been actively carried out to replace them. In this study, to maximize the sensitivity by visible light(VL) emitted from phosphors, blended hybrid sensors were fabricated by blending various weight percent(wt%) of $Gd_2O_2S:Tb$ which is a phosphor with excellent fluorescence efficiency into $PbI_2$. Then, the electrical properties to high energy radiation from the blended sensors and the pure $PbI_2$ sensor were compared and evaluated. As a result of the sensitivity evaluation, the sensor of 3wt% showed the highest value with more than 40% difference from the other sensors, and gradual decreasing in sensitivity was observed with increasing wt% except for the sensor of 3wt%. Also, in the reproducibility evaluation, the pure $PbI_2$ sensor exhibited a large variation in coefficient of variation(CV)>0.015, while all the blended sensors showed CV<0.015.

• Journal of the Korean Society of Radiology
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• v.17 no.7
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• pp.1091-1097
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• 2023

Bolus is used in radiation therapy to prescribe an even dose to the tumor when the skin surface is inclined or has irregularities. At this time, the dose to the skin surface increases. Due to the patient's unique body structure and irregular skin, voids may occur between the bolus and the skin, which may reduce the accuracy of treatment. Therefore, in this study, the existing bolus and the self-produced bolus through 3D printing were applied to the nasal area, and the difference between the surface dose after treatment plan and the dose directly measured with an Optically Stimulated luminescence(OSL) dosimeter was compared to the existing bolus. The bolus rate was 97%, PLA 100.33%, ePETELA 75A 100.53%, and ePETELA 85A 100.36%. It was confirmed that there was little error in the measurement values and treatment plan values for each material. In addition, compared to when applying a conventional bolus, a difference of -3% to +0.5% for a 3D printed bolus can be confirmed, so a customized bolus produced through 3D printing can complement the shortcomings of the existing bolus. It is believed that there will be.

• Progress in Medical Physics
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• v.19 no.4
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• pp.263-268
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• 2008

The application of a respiratory gated radiotherpy method to the lung radiation surgery was evaluated compared with the conventional method in which the whole tumor motion range is considered in the delineation of PTV (Planning target volume). The four dimensional CT simulation images were acquired for the five NSCLC (Non-small cell lung cancer) patients for radiation surgery. The respiratory gated plan was prepared with the 50% phase CT images and the conventional method was planned based on the ITV (Internal target volume) which include all the target volumes created in each phase CT images within a whole respiratory period. The DVH (Dose volume histogram) of OAR (Organ at risk) which calculated in each method was compared for the evaluation of the plan properness. The relative decrease of OARs' DVH were verified in the application of respiratory gated method. The average decrease rate were $16.88{\pm}9.97%$ in the bronchus, $34.13{\pm}19.15%$ in the spinal cord, $28.42{\pm}18.49%$ in the chest wall and $32.48{\pm}16.66%$ in the lung. Based on these results, we can verified the applicability and the effectiveness of the respiratory gated method in the lung radiation surgery.

• Radiation Oncology Journal
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• v.26 no.4
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• pp.237-246
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• 2008

Purpose: Three-dimensional conformal radiation therapy (3DCRT) and intensity-modulated radiation therapy (IMRT) were found to reduce the incidence of acute and late rectal toxicity compared with conventional radiation therapy (RT), although acute and late urinary toxicities were not reduced significantly. Acute urinary toxicity, even at a low-grade, not only has an impact on a patient's quality of life, but also can be used as a predictor for chronic urinary toxicity. With bladder filling, part of the bladder moves away from the radiation field, resulting in a small irradiated bladder volume; hence, urinary toxicity can be decreased. The purpose of this study is to evaluate the impact of bladder volume on acute urinary toxicity during RT in patients with prostate cancer. Materials and Methods: Forty two patients diagnosed with prostate cancer were treated by 3DCRT and of these, 21 patients made up a control group treated without any instruction to control the bladder volume. The remaining 21 patients in the experimental group were treated with a full bladder after drinking 450 mL of water an hour before treatment. We measured the bladder volume by CT and ultrasound at simulation to validate the accuracy of ultrasound. During the treatment period, we measured bladder volume weekly by ultrasound, for the experimental group, to evaluate the variation of the bladder volume. Results: A significant correlation between the bladder volume measured by CT and ultrasound was observed. The bladder volume in the experimental group varied with each patient despite drinking the same amount of water. Although weekly variations of the bladder volume were very high, larger initial CT volumes were associated with larger mean weekly bladder volumes. The mean bladder volume was $299{\pm}155\;mL$ in the experimental group, as opposed to $187{\pm}155\;mL$ in the control group. Patients in experimental group experienced less acute urinary toxicities than in control group, but the difference was not statistically significant. A trend of reduced toxicity was observed with the increase of CT bladder volume. In patients with bladder volumes greater than 150 mL at simulation, toxicity rates of all grades were significantly lower than in patients with bladder volume less than 150 mL. Also, patients with a mean bladder volume larger than 100 mL during treatment showed a slightly reduced Grade 1 urinary toxicity rate compared to patients with a mean bladder volume smaller than 100 mL. Conclusion: Despite the large variability in bladder volume during the treatment period, treating patients with a full bladder reduced acute urinary toxicities in patients with prostate cancer. We recommend that patients with prostate cancer undergo treatment with a full bladder.

• Radiation Oncology Journal
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• v.15 no.1
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• pp.49-56
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• 1997

Purpose : To evaluate the pathologic effects of preoperative radiotherapy o the resectable distal rectal cancer, we analyzed the results of postoperative pathologic findings for the patients with preoperative radiotherapy ant surgery Materials and Methods: From July 1995 to April 1996, we treated sixteen patients of resectable rectal cancer with preoperative radiation therapy and curative surgery At diagnosis, Thomas Jefferson (TJ) system was used for the clinical stage of the Patients. We treated the patients with conventional radiation therapy of 4500~5000cGy before surgery. The surgery was carried out 4 weeks after completion of radiation therapy. Modified Astler Coller (MAC) system was used for the postoperative pathologic stage. We analyzed the pathologic stages and findings according to preoperative clinical stage and compared with those of the control group in similar clinical stages. Result : All patients were treated with sphincter preservation surgery after Preoperative radiation therapy. Pathoiogic complete response (CR) was shown in 1 case $(6.3\%)$. We compared the results between preoperative radiation therapy group (Preop.RT group) and surgery only group (control group). In TJ stage II, among nine patients of Preop.RT group, 8 patients $(88.9\%)$ were in MAC stage 8 except 1 CR patient, but among 17 patients of control group. 11 patients$(64.7\%)$ were in MAC stage B and 6 Patients $(35.3\%)$ in MAC stage C. In TJ stage III, among 7 patients of Preop.RT group, 4 patients $(57.1\%)$ were in MAC stage B and 3 patients$(42.9\%)$ in MAC stage C. Among 14 Patients of control group, 4 patients $(28.6\%)$ were in MAC stage B and 10 Patients $(71.4\%)$ in MAC stage C. Above results showed that postoperative Pathologic stage was decreased in Preop.RT group with statistical significance (P=0.049). The postoperative Pathologic findings (blood vessel invasion. Iymphatic vessel invasion, perineural invasion) were decreased in the Preop.RT group compared with those of control group. But statistical significance was found only in Iymphatic vessel invasion (p=0.019). Conclusion : The Postoperative pathologic stages and adverse Prognostic pathologic findings were decreased in preoperative radiation therapy group. The Iymphatic vessel invasion and MAC stage C findings were abruptly decreased in Preoperative radiation therapy group. The preoperative radiation therapy was found to be effective in resectable rectal cancer. The patients group in our study was very small and long term follow up was not done. Therefore, further study about this issues is needed.