• Progress in Medical Physics
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• v.20 no.2
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• pp.106-111
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• 2009

Total scatter factor ($S_{cp}$), head scatter factor ($S_c$) and phantom scatter factor ($S_p$) are very important for accurate radiation therapy at stereotactic radiosurgery (SRS) with irregular field shape using micro-MLC and intensity modulated radiation therapy (IMRT) including many small field sizes. In this study we measured and compared $S_{cp}$ with reference ion chamber, pinpoint chamber and diode detector and adapted the resuls form diode detector. Head scatter factors for small field sizes were also measured with diode detector covered 1.5 cm-thick solid water build-up cap. Some errors like as electron contamination of 1~3% were included in the values of Sc but trend of total results of $S_c$ was coincided with basic theory. Phantom scatter factors for small field sizes were calculated form $S_{cp}$ and $S_c$. The results of $S_p$ were compared and were well-agreed with those of other authors.

• The Journal of Korean Society for Radiation Therapy
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• v.11 no.1
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• pp.6-10
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• 1999

The field size can be beam output, therefore MonitorUnit can be varied due to field size dependence The purpose of this study is to evaluate and compare the dose variation according to exchange of collimator The measurements were perfomed with Wellhofer dosimetry system(water phantom. ion chamber. electrometer. system controller. build up cap. etc)and two types of linear accerlerator (Mevatron KD, MevatronMX) Scatter can be affected to field size dependence and scatter correction is separated into collimator and phantom components, scatter components can affect by exchanging of collimator Measurements of collimator scatter factor(Sc) was done in air with build up cap. 1)Square field (5cm2 to 40cm2) was measured 2)and then keeping the upper jaw constant at loom and varing lower jaw from 5cm to 40cm, 3)keeping the lower jaw constant at 10cm and varing upper jaw from 5cm to 40cm Measurements of total scatter factor(Scp) was done in water at Dmax as the procedure of collimator scatter factor measurements in water Dmax The total scatter factors were obtained to the following equation(Sp=Scp/Sc) The measured data is normalized to the data of reference field size($10{\times}10$), rectangular field is inverted to equivalent field to compare three field size data As the collimator setting is varied, the output was changed In conclusion, the error was obtained small but it must be eliminated if we intend to reach the common stated goal of $5\%$ overall uncertainty in dose determination

• Radiation Oncology Journal
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• v.10 no.1
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• pp.121-123
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• 1992

New measurement method for $S_{p}$ factors (Phantom Scatter Factors) is presented. The theoretical development of the approach is disscused showing that $S_{p}$ factors can be obtained from three measurements of ionnization in a blocked, reference field and open field. This method has been tested using $^{60}Co$ gamma rays. The results were within 1% deviation between the theory and the experiment for the $S_{p}$ factor. The new method does not need air measurement, and we could could determine the $S_P$ factors with a small piece of block

• Progress in Medical Physics
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• v.32 no.4
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• pp.137-144
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• 2021

Purpose: This study aimed to investigate the accuracy of head scatter factor (S_c) by applying a developed multi-leaf collimator (MLC) scatter source model for an unflattened photon beam. Methods: Sets of S_c values were measured for various jaw-defined square and rectangular fields and MLC-defined square fields for developing dual-source model (DSM) and MLC scatter model. A 6 MV unflattened photon beam has been used. Measurements were performed using a 0.125 cm³ cylindrical ionization chamber and a mini phantom. Then, the parameters of both models have been optimized, and S_c has been calculated. The DSM and MLC scatter models have been verified by comparing the calculated values to the three S_c set measurement values of the jaw-defined field and the two S_c set measurement values of MLC-defined fields used in the existing modeling, respectively. Results: For jaw-defined fields, the calculated S_c using the DSM was consistent with the measured S_c value. This demonstrates that the DSM was properly optimized and modeled for the measured values. For the MLC-defined fields, the accuracy between the calculated and measured S_c values with the addition of the MLC scatter source appeared to be high, but the only use of the DSM resulted in a significantly bigger differences. Conclusions: Both the DSM and MLC models could also be applied to an unflattened beam. When considering scattered radiation from the MLC by adding an MLC scatter source model, it showed a higher degree of agreement with the actual measured S_c value than when using only DSM in the same way as in previous studies.

• Progress in Medical Physics
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• v.26 no.4
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• pp.241-249
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• 2015

As radiation therapy is one of three major cancer treatment methods, many cancer patients get radiation therapy. To exposure as much radiation to cancer while normal tissues near tumor get little radiation, medical physicists make a radiotherapy plan treatment and perform quality assurance before patient treatment. Despite these efforts, unintended medical accidents can occur by some errors. In order to solve the problem, patient internal dose reconstruction methods by measuring transit dose are suggested. As feasibility study for development of patient dose verification system, inverse square law, percentage depth dose and scatter factor are used to calculate dose in the water-equivalent homogeneous phantom. As a calibration results of ionization chamber and glass dosimeter to transit radiation, signals of glass dosimeter are 0.824 times at 6 MV and 0.736 times at 10 MV compared to dose measured by ionization chamber. Average scatter factor is 1.4 and Mayneord F factor was used to apply percentage depth dose data. When we verified the algorithm using the water-equivalent homogeneous phantom, maximum error was 1.65%.

• Progress in Medical Physics
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• v.6 no.1
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• pp.59-64
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• 1995

The aim of presentation is to obtain the beam parameters for tratment planning of steretactic radiosurgery. The dosimerical parameters such as TMR, scatter factor, and OAR was measured using diode, film, micro ion chamber, and thimble chanber for water phantom scanning. The results were compared each other. As a result, we determined OAR from film and scatter factor and TMR from diode as a basic data for treatment planning.

• Journal of radiological science and technology
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• v.47 no.1
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• pp.1-6
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• 2024

In Recent years, there has been a noticeable increase in the global incidence of breast cancer, with approximately 2.3 million cases of female breast cancer reported worldwide in 2020. Numerous studies are currently underway to enhance the accuracy of breast cancer diagnosis through the development of digital mammography detectors. This study aims to create Monte Carlo simulation-based mammographic anti-scatter grids and investigate their utility in evaluating the performance of digital mammography detector. Two types of mammographic anti-scatter grids, MAM-CP and Senographe 600T HF, were created using Monte Carlo simulation software (MCNPX 2.7.0), with grid ratios of 3.7 : 1 and 5 : 1, respectively. The grid physical characteristics (sensitivity, exposure factor, contrast improvement ratio) were calculated based on the KS C IEC60627 in the simulations using two X-ray qualities, RQA-M2 (28 kVp) and MW4 (35 kVp). As the X-ray tube voltage increased from 28 kVp to 35 kVp, sensitivity and exposure factor exhibited a decreasing trend, while contrast improvement ratio demonstrated an increasing trend. With an increase in grid ratio from 3.7 : 1 to 5 : 1, all physical characteristics showed an upward trend. Our results were consistent with a previous study that conducted measurements of physical properties using a real phantom. However, the pattern of change in the contrast improvement ratio with X-ray tube voltage differed from the previous study.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.1
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• pp.63-66
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• 2009

Purpose: ACR (American College of Radiology) offers variable parameters to PET/CT quality control by using ACR Phantom. ACR Phantom was made to evaluate parameters which are uniformity, attenuation, scatter, contrast and resolution. Manual analysis method wasn't good for the use of QC because values of parameter were changed as it may user and it takes long time to analysis. Ki-Chun Lim, a nuclear scientist in AMC, developed program that automatically analysis values of parameter by using ACR Phantom to overcome above problems. In this study, we evaluated automatic analysis program's usability, through the comparing SUV of each method, reproducibility of SUV when repeated analysis and the time required. Materials and Methods: Using Flangeless Esser PET Phantom, the ideal ratio of 4 : 1 hot cylinder and BKG but it actually showed a ratio of 3.89 to 1 hot cylinder and BKG. SIEMENS Biograph True Point 40 was used in this study. We obtained images using ACR phantom at Fusion WB PET Scan condition (2 min/bed) and 120 kV, 100 mAs CT condition. Using True X method, 3 iterations, 14 subsets, Gaussian filter, FWHM 4 mm and Zoom Factor 1.0, $168{\times}168$ image size. We obtained Max. & Min. SUV and SUV Mean values at Cylinder (8, 12, 16, 25 mm, Air, Bone, Water, BKG) by automatic program and obtained SUV by manual method. After that, we compared manual and automatic method. we estimate the time required from opened the image data to final work sheet was completed. Results: Automatic program always showed same result and same the time required. At 8, 12, 16 and 25 m cylinder, manual method showed 6.69, 3.46, 2.59, 1.24 CV values. The larger cylinder size became, the smaller CV became. In manual method, bone, air, water's CV were over 9.9 except BKG (2.32). Obtained CV of Mean SUV showed BKG was low (0.85) and bone was high (7.52). The time required was 45 second, 882 second respectably. Conclusions: As a result of difference automatic method and manual method, automatic method showed always same result, manual method showed that the smaller hot cylinders became, the lager CV became. Hot cylinders mean region size, the smaller hot cylinder size becomes we had some trouble in doing ROI poison setting. And it means increase in variation of SUV. The Study showed the time required of automatic method was shorten then manual method.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.183-188
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• 2012

Purpose: The concern of improving the quality of life and reducing side effects related to cancer treatment has been a subject of interest in recent years with advances in cancer treatment techniques and increasing survival time. This study is an analysis of differing scattered dose to the contralateral breast using common different treatment techniques. Materials and Methods: Eclipse 10.0 (Varian, USA) based $30^{\circ}$ EDW (Enhanced dynamic wedge) plan, $15^{\circ}$ wedge plan, $30^{\circ}$ wedge plan, Open beam plan, FiF (field in field) plan were established using CT image of breast phantom which in our hospital. Each treatment plan were designed to exposure 400 cGy using CL-6EX (VARIAN, USA) and we measured scattered dose at 1 cm, 3 cm, 5 cm, 9 cm away from medial side of the phantom at 1 cm depth using ionization chamber (FC 65G, IBA). We carried out measurement by separating effect of medial tangential field and lateral tangential field and analyze. Results: The evaluation of scattered dose to contralateral breast, $30^{\circ}$ EDW plan, $15^{\circ}$ wedge plan, $30^{\circ}$ wedge plan, Open beam plan, FIF plan showed 6.55%, 4.72%, 2.79%, 2.33%, 1.87% about prescription dose of each treatment plan. The result of scattered dose measurement by separating effect of medial tangential field and lateral tangential field results were 4.94%, 3.33%, 1.55%, 1.17%, 0.77% about prescription dose at medial tangential field and 1.61%, 1.40%, 1.24%, 1.16%, 1.10% at lateral tangential field along with measured distance. Conclusion: In our experiment, FiF treatment technique generates minimum of scattered dose to contralateral breast which come from mainly phantom scatter factor. Whereas $30^{\circ}$ wedge plan generates maximum of scattered doses to contralateral breast and 3.3% of them was scattered from gantry head. The description of treatment planning system showed a loss of precision for a relatively low scatter dose region. Scattered dose out of Treatment radiation field is relatively lower than prescription dose but, in decision of radiation therapy, it cannot be ignored that doses to contralateral breast are related with probability of secondary cancer.

• The Journal of Korean Society for Radiation Therapy
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• v.15 no.1
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• pp.19-27
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• 2003

I. Purpose In special cases of Total Body Irradiation(TBI), Half Body Irradiation(HBI), Non-Hodgkin's lymphoma, E-Wing's sarcoma, lymphosarcoma and neuroblastoma a large field can be used clinically. The dose distribution of a large field can use the measurement result which gets from dose distribution of a small field (standard SSD 100cm, size of field under $40{\times}40cm2$) in the substitution which always measures in practice and it will be able to calibrate. With only the method of simple calculation, it is difficult to know the dose and its uniformity of actual body region by various factor of scatter radiation. II. Method & Materials In this study, using Multidata Water Phantom from standard SSD 100cm according to the size change of field, it measures the basic parameter (PDD,TMR,Output,Sc,Sp) From SSD 180cm (phantom is to the bottom vertically) according to increasing of a field, it measures a basic parameter. From SSD 350cm (phantom is to the surface of a wall, using small water phantom. which includes mylar capable of horizontal beam's measurement) it measured with the same method and compared with each other. III. Results & Conclusion In comparison with the standard dose data, parameter which measures between SSD 180cm and 350cm, it turned out there was little difference. The error range is not up to extent of the experimental error. In order to get the accurate data, it dose measures from anthropomorphous phantom or for this objective the dose measurement which is the possibility of getting the absolute value which uses the unlimited phantom that is devised especially is demanded. Additionally, it needs to consider ionization chamber use of small volume and stem effect of cable by a large field.