• Journal of The Korean Radiological Technologist Association
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• v.29 no.1
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• pp.291-291
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• 2003

• Radiation Oncology Journal
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• v.10 no.2
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• pp.147-153
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• 1992

It is ideal thing to compensate tissue deficit without skin contamination in curvatured irradiation field of high energy photon beam. The 3-dimensional compensating technique utilizing tissue equivalent materials to ensure an adequate dose distribution and skin sparing effect was described. This compensator was made of paraffin ($70\%$) and stearin wax ($30\%$) compound. The parameters for evaluation of the effect on skin dose in application of compensator were considered in the size of the field, the thickness of the compensator and the source-to-axis distance. The results are as follows; the skin doses were not changed even though application of the compensator, but depended on the field size and the source-to-axis distance, and the skin doses were only slightly changed within $1\%$ relative errors as increasing the thickness of the compensator in these experiments.

• Progress in Medical Physics
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• v.15 no.2
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• pp.105-111
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• 2004

The parallel plate detector with dielectric film for dosimetry was designed to measure detection characteristic of 6 MV X-ray with medical linear accelerator. PTFE film was inserted into FEP films that are made by two one-side metal coated materials for ion source. The thicknesses of PTFE dielectric film was 100 ${\mu}{\textrm}{m}$ and the thickness of FEP dielectric film was 100 ${\mu}{\textrm}{m}$, respectively. This detector was fixed by two acrylic plate for physical hardness ad geometrical consistency. The geometrical condition for measurement with parallel-plate for detector was below; SSD=100 cm and the 5 cm depth between detector and phantom surface The major parameter of detector characteristics such as zero drift current, leakage current, charge response by applied voltage, reproducibility, linearity, TMR measurement, dose rate effect were measured. The zero drift currents are 8.3 pA and leakage currents are 10 pA. The charge response of applied voltage is showing linearity in 414 voltage. The measurement deviation of reproducibility in this detector is within 1% for dose and the linearity of applied dose shows in this detector. The TMR curves in phantom between this parallel plate detector and reference detector are matched within 3% deviation from maximum dose depth to 7.5 cm depth. It is considered that this dosimetric system is satisfactory for the purpose of the constancy check of the 6 MV x-ray from medical linear accelerator.

• Journal of radiological science and technology
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• v.41 no.3
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• pp.249-254
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• 2018

In this study, we evaluated the DAP(Dose Area Product) reduction effect of the newly developed IRIS collimator by measuring the DAP of the Rectangle collimator and the IRIS collimator depending on the field, SID(Source to Image recpetor Distance) change, and AEC mode use. The results were as follows. The IRIS collimator decreased DAP by 34.91, 29.33, and 29.04%, respectively, compared to the Rectangle collimator when the field was increased to $8{\times}8$, $12{\times}12$, $16{\times}16inch$. And also, when the SID was increased to 100, 120 and 140 cm, the IRIS collimator decreased DAP by 10.73, 33.68 and 46.22%, respectively, compared to the Rectangle collimator. In AEC mode and none-AEC mode, DAP in IRIS collimator was reduced by 32.71 and 21.69%, respectively, compared with the Rectangle type. The IRIS collimator can reduce DAP by 29.62% on average compared to Rectangle type, which is statistically significant. These results suggest that the newly developed IRIS collimator can be used in medical field to alleviate radiation exposure.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.133-137
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• 2017

The purpose of this study was to validate for GATE (Geant4 Application for Tomographic Emission) simulation by comparing the results of GATE simulation and experiment in real SPECT system. Futhermore, we want to prove that it is possible that the quantitative research of gamma camera/SPECT imaging for therapeutic radio isotope by using GATE simulation. In this study, the SPECT system on simulation referred to the parameters of Stream-R Forte version 1.2 (Philips Medical System, Best and Heerlen, Netherlands). To understand the I-131 image of gamma camera/SPECT system, we acquired the energy spectrum and measured the full width at half maximum (FWHM) which comes from line spread function (LSF) with and without scatter material in real SPECT system. And to compare with experiment, we also measured the FWHM and acquired the energy spectrum without scatter material in GATE simulation. As a result, without scatter material, the energy peak was almost same location, which are located nearby 364 keV, and other spectrum factors are same tendency in both cases. The FWHM was increased by increasing the distance of source to detector, and the error rate was approximately 3.8%. When we used the line source with scatter material, energy spectrum also indicated similar tendency in both cases. As you confirmed earlier, GATE simulation included real instrument and radioisotope characters for therapeutic radioisotope. Therefore this result that it was possible that various quantitative study for therapeutic radioisotope imaging in gamma camera/SPECT using GATE simulation.

• Korean Journal of Digital Imaging in Medicine
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• v.14 no.2
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• pp.39-46
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• 2012

Purpose : The purpose of this study was to reduce Entrance Surface Dose and maintain image quality by changing Source to Image receptor Distance. And we'd like to compare ESD on this study to DRLs in other contries. Materials and Methods : We used indirect DR system(Definium 8000, General Electric, USA)and phantom(ART-200X, Flukebiomedical, USA),glass dosimeters(GD-352M, Asahi Techno Glass, Japan)for this study. The imagies were obtained throuh 80kVp fixed, and different tube currents using AEC mode in $16{\times}16$(inch) field size and changing Source to Image receptor Distance from 100 cm to 130 cm per 10 cm unit. The phantom with attaching 5 glass dosimeters on abdomonal skin was set at supine and erect position as a anterioposterial projection on detector For measuring Entrance Surface Dose. Image analysis was conducted by histograms of Image J(1.46r) which was given from National Institutes of Health(NIH). Results : Due to inverse square law of distance, the tube currents were increasing 42.6 % in supine position and 32.6 % in erect position according to the change of Source to Image receptor Distance. While Entrance Surface Doses were rapidly decreasing 14.2 % in supine position and 29.4 % in erect position according to the change of Source to Image receptor Distance. As the results of histogram using Image J, pixel mean values from 100 cm to 110 cm, 120 cm and 130 cm were decreasing each 1.4%, 2.5%, 2.7%, 4.5%, 2.2 %, 5.8 % in supine, erect position. While standard deviations from 100 cm to 110 cm, 120 cm and 130 cm were increasing each 1.4 %, 2.5 %, 2.5 %, 4.0 %, 2.0 %, 4.9 % Consequently, there are no significant differences in abdomen images taken. Conclusion: As the results described above, we strongly recommend using long Sourceto Image receptor Distance than 100cm that we have been using. So, we should deliver less Entrance Surface Dose to the patients while maintaining image quality in abdomen radiography.

• Progress in Medical Physics
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• v.5 no.2
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• pp.57-68
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• 1994

Purpose : The purposes are to discuss the reason to measure dose distributions of circular small fields for stereotactic radiosurgery based on medical linear accelerator, finding of beam axis, and considering points on dosimetry using home-made small water phantom, and to report dosimetric results of 10MV X-ray of Clinac-18, like as TMR, OAR and field size factor required for treatment planning. Method and material : Dose-response linearity and dose-rate dependence of a p-type silicon (Si) diode, of which size and sensitivity are proper for small field dosimetry, are determined by means of measurement. Two water tanks being same in shape and size, with internal dimension, 30${\times}$30${\times}$30cm$^3$ were home-made with acrylic plates and connected by a hose. One of them a used as a water phantom and the other as a device to control depth of the Si detector in the phantom. Two orthogonal dose profiles at a specified depth were used to determine beam axis. TMR's of 4 circular cones, 10, 20, 30 and 40mm at 100cm SAD were measured, and OAR's of them were measured at 4 depths, d$\sub$max/, 6, 10, 15cm at 100cm SCD. Field size factor (FSF) defined by the ratio of D$\sub$max/ of a given cone at SAD to MU were also measured. Result : The dose-response linearity of the Si detector was almost perfect. Its sensitivity decreased with increasing dose rate but stable for high dose rate like as 100MU/min and higher even though dose out of field could be a little bit overestimated because of low dose rate. Method determining beam axis by two orthogonal profiles was simple and gave 0.05mm accuracy. Adjustment of depth of the detector in a water phantom by insertion and remove of some acryl pates under an auxiliary water tank was also simple and accurate. TMR, OAR and FSF measured by Si detector were sufficiently accurate for application to treatment planning of linac-based stereotactic radiosurgery. OAR in field was nearly independent of depth. Conclusion : The Si detector was appropriate for dosimetry of small circular fields for linac-based stereotactic radiosurgery. The beam axis could be determined by two orthogonal dose profiles. The adjustment of depth of the detector in water was possible by addition or removal of some acryl plates under the auxiliary water tank and simple. TMR, OAR and FSF were accurate enough to apply to stereotactic radiosurgery planning. OAR data at one depth are sufficient for radiosurgery planning.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.2
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• pp.83-91
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• 2017

Objectives: The purpose of this study was to evaluate the error of the leaf position accuracy of the MLC due to the gravity effect according to the gantry angle by using picket fence test using EPID and GafChromic EBT3 film. Materials and Methods: A 5 cm solid phantom was placed on the table and the SAD was set to 100 cm. The EBT3 film was placed exactly over the solid phantom and covered a 1.5 cm solid phantom and the picket fence test was performed. The EPID was measured under the same conditions as the EBT3 film at SID 100 cm. The gantry angles were measured at $0^{\circ}$, $90^{\circ}$, $180^{\circ}$ and $270^{\circ}$ in order to evaluate the position of the MLC according to the gantry angle. For the geometric evaluation of the MLC, the leaf position accuracy of the MLC was analyzed using the analysis program. Results: In case of EPID, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.18 mm, 0.31 mm, 0.20 mm, 0.26 mm on the average and the maximum values of the errors were respectively 0.44 mm, 0.54 mm, 0.34 mm, 0.44 mm. In case of EBT3 film, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.19 mm, 0.21 mm, 0.19 mm, 0.31 mm on the average and the maximum values of the errors were respectively 0.35 mm, 0.45 mm, 0.36 mm, 0.48 mm. Conclusion: In this study, we analyzed the position error of the leaf of the MLC according to the gantry angle, and confirmed the position error of the leaf by gravity effect. As a result of comparing the leaf position accuracy using EPID and EBT3 film according to the variation of gantry angle, a larger error occurred in the error analysis method using EPID than that of EBT3 film. Therefore, in the case of IMRT based on MLC, as well as verification of accurate dosimetry should be conducted, it is considered that the quality control and verification for the precise operation of the MLC will be needed. and it is necessary to compare and verify the method of analysis.