• The Journal of Korean Society for Radiation Therapy
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• v.16 no.1
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• pp.57-65
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• 2004

Introduction : The phantom that includes high density materials such as steel was custom-made to fix lung and bone in order to evaluation inhomogeneity correction at the time of conducting radiation therapy to treat lung cancer. Using this, values resulting from the inhomogeneous correction algorithm are compared on the 2 and 3 dimensional radiation therapy planning systems. Moreover, change in dose calculation was evaluated according to inhomogeneous by comparing with the actual measurement. Materials and Methods : As for the image acquisition, inhomogeneous correction phantom(Pig's vertebra, steel(8.21g/cm3), cork(0.23 g/cm3)) that was custom-made and the CT(Volume zoom, Siemens, Germany) were used. As for the radiation therapy planning system, Marks Plan(2D) and XiO(CMS, USA, 3D) were used. To compare with the measurement value, linear accelerator(CL/1800, Varian, USA) and ion chamber were used. Image, obtained from the CT was used to obtain point dose and dose distribution from the region of interest (ROI) while on the radiation therapy planning device. After measurement was conducted under the same conditions, value on the treatment planning device and measured value were subjected to comparison and analysis. And difference between the resulting for the evaluation on the use (or non-use) of inhomogeneity correction algorithm, and diverse inhomogeneity correction algorithm that is included in the radiation therapy planning device was compared as well. Results : As result of comparing the results of measurement value on the region of interest within the inhomogeneity correction phantom and the value that resulted from the homogeneous and inhomogeneous correction, gained from the therapy planning device, margin of error of the measurement value and inhomogeneous correction value at the location 1 of the lung showed $0.8\%$ on 2D and $0.5\%$ on 3D. Margin of error of the measurement value and inhomogeneous correction value at the location 1 of the steel showed $12\%$ on 2D and $5\%$ on 3D, however, it is possible to see that the value that is not correction and the margin of error of the measurement value stand at $16\%$ and $14\%$, respectively. Moreover, values of the 3D showed lower margin of error compared to 2D. Conclusion : Revision according to the density of tissue must be executed during radiation therapy planning. To ensure a more accurate planning, use of 3D planning system is recommended more so than the 2D Planning system to ensure a more accurate revision on the therapy plan. Moreover, 3D Planning system needs to select and use the most accurate and appropriate inhomogeneous correction algorithm through actual measurement. In addition, comparison and analysis through TLD or film dosimetry are needed.

• The Journal of Korean Society for Radiation Therapy
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• v.18 no.1
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• pp.35-41
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• 2006

Purpose: A various find of radiotherapy treatment plans have been made to determine appropriate doses for breasts, chest walls and loco-regional lymphatics in the radiotherapy of breast cancers. The aim of this study was to evaluate the optimum radiotherapy plan technique method by analyzing dose distributions qualitatively and quantitatively. Materials and Methods: To evaluate the optimum breast cancer radiotherapy plan technique, the traditional method(two dimensional method) and computed tomography image are adopted to get breast volume, and they are compared with the three-dimensional conformal radiography (3DCRT) and the intensity modulated radiotherapy (IMRT). For this, the regions of interest (ROI) such as breasts, chest walls, loco-regional lymphatics and lungs were marked on the humanoid phantom, and the computed tomography(Volume, Siemens, USA) was conducted. Using the computed tomography image obtained, radiotherapy treatment plans (XiO 5.2.1, FOCUS, USA) were made and compared with the traditional methods by applying 3DCRT and IMRT. The comparison and analysis were made by analyzing and conducting radiation dose distribution and dose-volume histogram (DVH) based upon radiotherapy techniques (2D, 3DCRT, IMRT) and point doses for the regions of interest. Again, treatment efficiency was evaluated based upon time-labor. Results: It was found that the case of using 3DCRT plan techniques by getting breast volume is more useful than the traditional methods in terms of tumor delineation, beam direction and confirmation of field boundary. Conclusion: It was possible to present the optimum radiotherapy plan techniques through qualitative and quantitative analyses based upon radiotherapy plan techniques in case of breast cancer radiotherapy. However, further studies are required for the problems with patient setup reproducibility arising from the difficulties of planning target volume (PVT) and breast immobilization in case of three-dimensional radiotherapy planning.

• Progress in Medical Physics
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• v.23 no.3
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• pp.162-168
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• 2012

In proton therapy, in vivo dose verification is one of the most important parts to fully utilize characteristics of proton dose distribution concentrating high dose with steep gradient and guarantee the patient safety. Currently, in order to image the proton dose distribution, a prompt gamma distribution detection system, which consists of an array of multiple CsI(Tl) scintillation detectors in the vertical direction, a collimator, and a multi-channel DAQ system is under development. In the present study, the optimal design of prompt gamma distribution detection system was studied by Monte Carlo simulations using the MCNPX code. For effective measurement of high-energy prompt gammas with enough imaging resolution, the dimensions of the CsI(Tl) scintillator was determined to be $6{\times}6{\times}50mm^3$. In order to maximize the detection efficiency for prompt gammas while minimizing the contribution of background gammas generated by neutron captures, the hole size and the length of the collimator were optimized as $6{\times}6mm^2$ and 150 mm, respectively. Finally, the performance of the detection system optimized in the present study was predicted by Monte Carlo simulations for a 150 MeV proton beam. Our result shows that the detection system in the optimal dimensions can effectively measure the 2D prompt gamma distribution and determine the beam range within 1 mm errors for 150 MeV proton beam.

• Bulletin of the Society of Naval Architects of Korea
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• v.24 no.4
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• pp.19-36
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• 1987

In this research the coupling problem between the elastic structure and the fluid, specially the hydroelastic harmonic vibration problem, is studied. In order to couple the domains, i.e., the structural domain and the fluid domain, the boundary integral method(direct boundary integral formulation) is used in the fluid domain in combination with the finite element method for the structure. The boundary integral method has been widely developed to apply it to the hydroelastic vibration problem. The hybrid boundary integral method using eigenfunctions on the radiation boundaries and the boundary integral method using the series form image-functions to replace the even bottom and free surface boundaries in case of high frequencies have been developed and tested. According to the boundary conditions and the frequency ranges the different boundary integral methods with the different idealizations of the fluid boundaries have been studied. Using the same interpolation functions for the pressure distribution and the displacement the two domains have been coupled and using Hamilton principle the solution of the hydroelastic have been obtained through the direct minimizing process. It has become evident that the finite-boundary element method combining with the eigenfunction or the image-function method give good results in comparison with the experimental ones and the other numerical results by the finite element method.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.8 no.2
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• pp.113-118
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• 2022

Gadolinium neutron capture therapy (Gd-NCT) is a precision radiation therapy that kills cancer cells using the neutron capture reaction that occurs when ¹⁵⁷Gd hits thermal neutrons. ¹⁵⁷Gd has the highest thermal neutron capture cross section of 254,000 barns among stable isotopes in the periodic table. Another stable isotope, ¹⁵⁵Gd, also has a high thermal neutron trapping area (~ 60,700 barns), so gadolinium that exists in nature can be used as a Gd-NCT drug. Gd-NCT is a mixed kinetic energy of low-energy and high-energy ionizing particles, which can be uniformly distributed throughout the tumor tissue, thereby solving the disadvantage of heterogeneous dose distribution in tumor tissue. The Gd complexes of small-sized molecule are widely used as contrast agents for magnetic resonance imaging (MRI) in clinical practice. Therefore, these compounds can be used not only for diagnosis but also therapy when considering the concept of Gd-NCT. This multifunctional trial can look forward to new medical advance into NCT clinical practices. In this review, we introduce gadolinium compounds suitable for Gd-NCT and describe the necessity of image guided Gd-NCT.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.748-751
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• 2000

Microlens made by laser radiation method have advantages in the easiness of their fabrication. The process is based on the projection of a chromium-on-quartz reticle on to the Polymer using a pulsed 248nm KrF excimer laser. Fabrication process is a fluence-dependent rate and density. The lens shape is defined by a rotationally symmetric sluence distribution with smooth radial variation in the image plane of the reticle. A typical lens of 50㎛ diameter was fabricated by irradiating 2000 laser pulses within 40 seconds. The experimental results show microlens fabrication by UV laser is possible and well worth studying further.

• Transactions on Electrical and Electronic Materials
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• v.18 no.1
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• pp.35-41
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• 2017

This study looks at optimizinge light redistribution to improve the overall illuminance uniformity of commercial IRED modules. To obtain uniform illumination over a prescribed rectangular area, a freeform surface lens was evaluated using TracePro. The LED light overall illuminance uniformity regulated in KSC 7658 was verified using Relux software. Experimental test results showed 0.81 overall illuminance uniformity for rectangular light distribution of LED lights having a radiation angle of $80^{\circ}$. After fabricating prototype IRED lights based on these simulation results, illuminance performance was observed when used as actual IRED lighting with a nighttime CCTV system. Image observation photographs of the prototype $80^{\circ}$ rectangular IRED lights confirmed that object images can be seen clearly owing to high overall illuminance uniformity, and that dark regions of the CCTV screen were not shown.

• Journal of Radiation Protection and Research
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• v.20 no.1
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• pp.25-36
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• 1995

The purpose of this research is to develop stereotactic localization and radiation measurement system for the efficient and precise radiosurgery. The algorithm to obtain a 3-D stereotactic coordinates of the target has been developed using a Fisher CT or angio localization. The procedure of stereotactic localization was programmed with PC computer, and consists of three steps: (1) transferring patient images into PC; (2) marking the position of target and reference points of the localizer from the patient image; (3) computing the stereotactic 3-D coordinates of target associated with position information of localizer. Coordinate transformation was quickly done on a real time base. The difference of coordinates computed from between Angio and CT localization method was within 2 mm, which could be generally accepted for the reliability of the localization system developed. We measured dose distribution in small fields of NEC 6 MVX linear accelerator using various detector; ion chamber, film, diode. Specific quantities measured include output factor, percent depth dose (PDD), tissue maximum ratio (TMR), off-axis ratio (OAR). There was small variation of measured data according to the different kinds of detectors used. The overall trends of measured beam data were similar enough to rely on our measurement. The measurement was performed with the use of hand-made spherical water phantom and film for standard arc set-up. We obtained the dose distribution as we expected. In conclusion, PC-based 3-D stereotactic localization system was developed to determine the stereotactic coordinate of the target. A convenient technique for the small field measurement was demonstrated. Those methods will be much helpful for the stereotactic radiosurgery.

• Journal of Radiation Protection and Research
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• v.29 no.4
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• pp.231-236
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• 2004

An imaging plate(IP) detector, a two-dimensional digital radiation detector that can acquire image of radioactivity distribution in a sample, has been applied in many fields; for industrial radiography, medical diagnosis, X-ray diffraction test, etc. In this study, the possibility of IP detector to be used lot measuring radioactivity of sample is explored using its high sensitivity, higher spatial resolution, wider dynamic range and screen uniformity for several kinds radiations. First, the IP detector is applied to measure the surface uniformity for area source. Surface uniformity is measured rapidly and nondestructively by measuring the radioactivity distribution of common standard area source$(^{241}Am)$. Next, the IP is employed to study the possibility of measuring an extremely low-level activity of environmental sample. For this study the screen uniformity, shield effect of background radiation, linear dynamic range and fading effect of the IP detector is investigated. The potato, banana, radish and carrot samples are chosen to measure ultra low-level activity of $^{40}K$ isotope. The efficiency calibration of IP detector is carried out using the standard source.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.77-84
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• 2017

Purpose: To evaluate the image quality improvement and dosimetric effects on virtual monochromatic images of a Dual Source-Dual Energy CT(DS-DECT) for radiotherapy planning. Materials and Methods: Dual energy(80/Sn 140 kVp) and single energy(120 kVp) scans were obtained with dual source CT scanner. Virtual monochromatic images were reconstructed at 40-140 keV for the catphan phantom study. The solid water-equivalent phantom for dosimetry performs an analytical calculation, which is implemented in TPS, of a 10 MV, $10{\times}10cm^2$ photon beam incident into the solid phantom with the existence of stainless steel. The dose profiles along the central axis at depths were discussed. The dosimetric consequences in computed treatment plans were evaluated based on polychromatic images at 120 kVp. Results: The magnitude of differences was large at lower monochromatic energy levels. The measurements at over 70 keV shows stable HU for polystyrene, acrylic. For CT to ED conversion curve, the shape of the curve at 120 kVp was close to that at 80 keV. 105 keV virtual monochromatic images were more successful than other energies at reducing streak artifacts, which some residual artifacts remained in the corrected image. The dose-calculation variations in radiotherapy treatment planning do not exceed ${\pm}0.7%$. Conclusion: Radiation doses with dual energy CT imaging can be lower than those with single energy CT imaging. The virtual monochromatic images were useful for the revision of CT number, which can be improved for target coverage and electron densities distribution.