• Progress in Medical Physics
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• v.18 no.2
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• pp.93-97
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• 2007

This study was designed to evaluate radiosurgery technique using multiple noncoplanar arc therapy with intensity modulated fine MLC shaped photon beam. The stereotactic radiosurgery was performed with 6-MV X-ray beams from a Clinac 21EX LINAC (Varian, Palo Alto, CA, USA) with a MLC-120, which features a full $40{\times}40cm$ field and is the first MLC for general use that offers 0.5 cm resolution for high precision treatment of small and irregular fields. We used a single isocenter and five gantry-couch combinations with a set of intensity modulated arc therapy. We investigated dosimetric characteristics of 2 cm sized spherical target volume with film (X-OMAT V2 film, Kodak Inc, Rochester NY, USA) dosimetry within $25{\times}25cm$ acrylic phantom. A simulated single isocentric treatment using inversely Planned 3D radiotherapy planning system demonstrated the ability to conform the dose distribution to an spherical target volume. The 80% dose level was adequate to encompass the target volume in frontal, sagittal, and transverse planes, and the region between the 40% and 80% isodose lines was $4.0{\sim}4.5mm$ and comparable to the dose distribution of the Boston Arcs. We expect that our radiosurgery technique could be a treatment option for irregular-shaped large intracranial target.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.571-575
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• 2016

Monte Carlo simulations are widely used as the most accurate technique for dose calculation in radiation therapy. In this paper, the GATE6(Geant4 Application for Tomographic Emission ver.6) code was employed to calculate the dosimetric performance of the photon beams from a linear accelerator(LINAC). The treatment head of a Varian 21EX Clinac was modeled including the major geometric structures within the beam path such as a target, a primary collimator, a flattening filter, a ion chamber, and jaws. The 6 MV photon spectra were characterized in a standard $10{\times}10cm^2$ field at 100 cm source-to-surface distance(SSD) and subsequent dose estimations were made in a water phantom. The measurements of percentage depth dose and dose profiles were performed with 3D water phantom and the simulated data was compared to measured reference data. The simulated results agreed very well with the measured data. It has been found that the GATE6 code is an effective tool for dose optimization in radiotherapy applications.

• Radiation Oncology Journal
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• v.12 no.1
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• pp.117-121
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• 1994

In spite of remarkable improvement of surgical skills and anesthesia, local failure still occurred in 36-45$ \% $ of locally advanced colorectal cancer after curative resection with or without pre-or post-operative irradiation. Intraoperative radiation therapy(IORT) is the ideal modality which resectable lesions are removed surgically 3nd the remaining cancer nests are sterilized by irradiation during a surgical procedure. Therefore, the excellent local control without the damage of the adjacent normal tissues can be achieved. In IORT, judicious set up of the treatment cone on the treatment surface of the patient is required for accurate and homogenous dose distribution within treatment field, especially on the slopping surface of sacrum and pelvic sidewall which are the common sites of the local recurrence in rectal cancer. For this purpose, adequate co-ordination of gantry rotation and table tilting are essential. Adjusting gantry rotation is not difficult but tilting of the table is impossible inconventional treatment couch. Department of Therapeutic Radiology in Yeungnam University Medical Center developed the IORT table for colorectal cancer which is easy to set up and detach on the Linac treatment couch within 5 minutes. The range of tilting with head-up and head-down is about 30 degree which is efficient and easy-to-use, not only for IORT but also for colorectal surgery. So far, authors performed IORT with newly developed treatment table in 2 patients with rectal cancer and we found that this newly developed table could contribute in improving the dose distribution of IORT and surgical procedure for colorectal cancer.

• Radiation Oncology Journal
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• v.20 no.4
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• pp.391-395
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• 2002

Purpose : To confirm the accuracy of the radiation dose at the isocenter by the standard linear accelerator-based stereotactic radiosurgery technique which was developed at Seoul National University Hospital. Materials and Methods : Radiation dosimetry was undertaken during standard 5-arc radiosurgery using 6 MV X-ray beam from CL2100C linac. The treatment head was attached with circular tertiary collimators of 10 and 20 mm diameter. We measured the absorbed dose at the isocenter of a multi-purpose phantom using two kinds of detector : a 0.125 co ionization chamber and a silicon diode detector. Results : The dose differences at each arc plane between the planned dose and the measured dose at the isocenter raged from $-0.73\%\;to\;-2.69\%$ with the 0.125 cc ion chamber, and from $-1.29\%\;to\;-2.91\%$ with the diode detector during radiosurgery with the tertiary collimator of 20 mm diameter. Those with the 10-mm tertiary collimator ranged from $-2.39\%\;to\;-4.25\%$ with the diode. Conclusion : The dose accuracy at the isocenter was ${\pm}3\%$. Therefore, further efforts such ws modification in processing of the archived image through DICOM3.0 format are required to lessen the dose difference.

• Radiation Oncology Journal
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• v.11 no.2
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• pp.431-437
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• 1993

An important problem in radiosurgery is the utilization of the proper beam parameters, to which dose shape is sensitive. Streotactic radiosurgery techniques for a linear accelerator typically, use circular radiation fields with multiple arcs to produce an spherical radiation distribution. Target volumes are irregular in shape for a certain case, and spherical distributions can irradiate normal tissues to high dose as well as the target region. The current improvement to dose distribution utilizes treating multiple isocenters or weighting various arcs to change treatment volume shape. in this paper another promising study relies upon dynamically shaping the treatment beam to fit the beam's eye view of the target. This conformal irradiation technique was evaluated by means of visual three dimensional dose distribution, dose volume histograms to the target volume and surrounding normal brain. It is shown that using even less arcs than multiple isocenter irradiation technique, the conformal therapy yields comparable dose gradients and superior homogeneity of dose within the target volume.

• Journal of the Korean Society of Radiology
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• v.10 no.4
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• pp.233-239
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• 2016

Comparison of the dose aspect that radiation therapy treatments using IMRT, tomotherapy, mArc (modulated arc therapy). The experimental subject is non-small cell lung cancer patient. The prescription dose is 58.0 Gy to the volume of PTV(planning target volume). and spinal cord, esophagus, and liver organ is the normal organ(OAR, organ at risk). Average PTV value is 57.60 Gy in mArc and 61.04 Gy in tomotherapy and 58.95 Gy in IMRT. The average dose of the Esophagus is 2.84 Gy in m-Arc, 5.14 Gy in tomotherapy, 1.84 Gy in IMRT. The average dose of the Liver is 19.44 Gy in m-Arc, 12.22 Gy in tomotherapy, 21.97 Gy in IMRT. The average dose of the Spinal cord is 5.72 Gy in m-Arc, 7.08 Gy in tomotherapy, 6.15 Gy in IMRT. Results of this study is no significant difference between mArc and tomotherapy and Linac based IMRT in dose study and also, mArc's dose coverage and dose volume histogram is better than IMRT and tomotherapy. but, This study is limited to a disease of cancer. in addition, fewer number of groups. The wide range the more research can be developed patient-specific treatment techniques and be applied to the patients

• Journal of Radiation Protection and Research
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• v.34 no.3
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• pp.107-114
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• 2009

A Compton camera, which is based on Compton kinematics, is a very promising gamma-ray imaging device in that it could overcome the limitations of the conventional gamma-ray imaging devices. In the present study, the image quality of a rotating Compton camera was evaluated by using 4-D Monte Carlo simulation technique and the applicability to nuclear industrial applications was examined. It was found that Compton images were significantly improved when the Compton camera rotates around a gamma-ray source. It was also found that the 3-D imaging capability of a Compton camera could enable us to accurately determine the 3-D location of radioactive contamination in a concrete wall for decommissioning purpose of nuclear facilities. The 4-D Monte Carlo simulation technique, which was applied to the Compton camera fields for the first time, could be also used to model the time-dependent geometry for various applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1777-1783
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• 2014

In this paper, we designed and fabricated a high-speed semiconductor sensor for use in power control devices and analyzed the characteristics with pulsed radiation tests. At first, radiation sensitive circular Si PIN diodes with various diameters(0.1 mm ~5.0 mm) were designed and fabricated using Si epitaxial wafer, which has a $42{\mu}m$ thick intrinsic layer. The reverse leakage current of the diode with a radius of 2 mm at a reverse bias of 30 V was about 20.4 nA. To investigate the characteristic responses of the developed diodes, the pulsed gamma-radiation tests were performed with the intensity of 4.88E8 rad(Si)/sec. From the test results showing that the output currents and the rising speeds have a linear relationship with the area of the sensors, we decided that the optimal condition took place at a 2 mm diameter. Next, for the selected 2 mm diodes, dose rate tests with a range of 2.47E8 rad(Si)/sec to 6.21E8 rad(Si)/sec were performed. From the results, which showed linear characteristics with the radiation intensity, a large amount of photocurrent over 60mA, and a high speed response under 350ns without saturation, we can conclude that the our developed PIN diode can be a good candidate for the sensor of power control devices.

• The Korean Journal of Food & Health Convergence
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• v.4 no.1
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• pp.15-22
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• 2018

A radiation dosimeter is important to assess quality assurance (QA) of radiation therapy devices and to estimate the radiation dose in vivo dosimetry. Recently, optically stimulated luminescence detector (OSLD) is widely used in clinical filed. Therefore, the purpose of this study is to evaluate dose, energy, and angular dependence of OSLD and EBT3 film. The absorbed dose in clinical linear accelerator (Linac) beam is calibrated for dose per monitor unit (MU). Dose, energy, and angular dependence of OSLD and EBT3 film are estimated after the calibration procedure. The absorbed dose is measured at 50, 100, 150, and 200 cGy in an 6 MV X-ray beam for dose dependence. A dose of 150 cGy is delivered to OSLD and EBT3 film with 6 and 10 MV photon energies for energy dependence. For measurements of angular dependence, angular positions of gantry are $0^{\circ}{\pm}80^{\circ}$ with 6 MV at 150 cGy. The results of dose dependence is linear for OSLD and EBT3 film. For the results of energy dependence, errors were 0.39% and 0.03% for OSLD and EBT3 film, respectively. The results of dose for angular is decreased from $0^{\circ}$ to ${\pm}80^{\circ}$ for both OSLD and EBT3 film. When angle of $0^{\circ}$ is normalized to 1, and the dose is decreased to 60 and 66% at $80^{\circ}$ for OSLD and EBT3 film, respectively. Dose and energy dependence of OSLD and EBT3 film are measured within the recommendation of manufacturer. Angular dependence is increased from $0^{\circ}$ to ${\pm}80^{\circ}$ for OSLD and EBT3 film. The characteristics of OSLD and EBT3 film are similar and expected to useful for clinical field.

• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.229-238
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• 2021

The selective permeate transport characteristics of iodine ion at follicle cell membrane model in thyroid which irradiated by high energy x-ray(linac 6 MV) was investigated. The follicle cell membrane model used in this experiment was a polysulfonated copolymerized membrane of poly(4-vinylpyridine-co-acrylonitrile:VP-AN). The difference of membrane thickness [2 mole AN%(w/w)], fixed carrier concentration[VP-AN%(w/w)], OH- concentration were occurred at difference of I- concentration and quantity of thyroid hormone, respectively. The tensile strength in fixed carrier concentration[VP-AN% (w/w): 0-62 %] of irradiated membrane was found to be decreased about 1.2-1.8 times than non-irradiated membrane. The I- selective permeate initial flux with increase of membrane thickness [2mole AN%(w/w)], fixed carrier concentration[VP-AN%(w/ w)], OH- concentration in irradiated membrane were found to be decreased about 2.1-4.5 times, about 2.2-2.5 times, about 2.1-2.67 times than non-irradiated membrane, respectively. As a result, the quantity of thyroid hormone was decreased at irradiated membrane than non-irradiated membrane. The decrease of thyroid hormone was occurred at hypothyroidism and hyperthyroidism, thyroid cancer, and so on. As the thyroid hormone in cell membrane model were abnormal, cell damages were appeared at cell.