• Nuclear Engineering and Technology
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• v.49 no.1
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• pp.189-195
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• 2017

Gel dosimeters have unique advantages in comparison with other dosimeters. Until now, these gels have been used in different radiotherapy techniques as a reliable dosimetric tool. Because dose distribution measurement is an important factor for appropriate treatment planning in different radiotherapy techniques, in this study, we evaluated the ability of the N-isopropylacrylamide (NIPAM) polymer gel to record the dose distribution resulting from the mixed neutron-gamma field of boron neutron capture therapy (BNCT). In this regard, a head phantom containing NIPAM gel was irradiated using the Tehran Research Reactor BNCT beam line, and then by a magnetic resonance scanner. Eventually, the $R_2$ maps were obtained in different slices of the phantom by analyzing T2-weighted images. The results show that NIPAM gel has a suitable potential for recording three-dimensional dose distribution in mixed neutron-gamma field dosimetry.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.3
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• pp.1197-1199
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• 2016

Background: This study aimed to facilitate decision-making in cases of breast cancer radiotherapy shifts by simulating millimetric shifts and analyzing their effects on dose distribution. Methods: The study included 30 patients with left side breast cancer who were treated with three dimensional conformal radiotherapy (3D-CRT) in the Radiation Oncology Department in Hatay Public Hospital, between January 2013 and April 2015. A treatment plan shifting at three axes with six different measures was simulated. Results: The biggest difference in values was (+3mm shift) 476cGy, with a 7.7 % change for heart and 25.6% for spinal cord. The shifts in values respectively for CTV min, mean, max were -4.8%, 2.5%, 4%. The differences for lymphatic min, mean, max were 21.3%, 20.3%, -12.2%. Conclusion: The most important thing is not the treatment plan quality, but its practicality. The treatment plan must be practical and its practice must be controlled rigidly.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.260-262
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• 2002

An accurate measurement of dose distribution is indispensable to perform radiation therapy planning. A measurement technique using a radiographic film, which is called a film dosimetry, is widely used because it is easy to obtain a dose distribution with a good special resolution. In this study, we tried to develop an analyzing system for the film dosimetry using usual office automation equipments such as a personal computer and an image scanner. A film was sandwiched between two solid water phantom blocks (30 ${\times}$ 30 ${\times}$ 15cm). The film was exposed with Cobalt-60 ${\gamma}$-ray whose beam axis was parallel to the film surface. The density distribution on the exposed film was stored in a personal computer through an image scanner (8bits) and the film density was shown as the digital value with NIH-image software. Isodose curves were obtained from the relationship between the digital value and the absorbed dose calculated from percentage depth dose and absorbed dose at the reference point. The isodose curves were also obtained using an Isodose plotter, for reference. The measurements were carried out for 31cGy (exposure time: 120seconds) and 80cGy (exposure time: 300seconds) at the reference point. While the isodose curves obtained with our system were drawn up to 60% dose range for the case of 80cGy, the isodose curves could be drawn up to 80% dose range for the case of 31cGy. Furthermore, the isodose curves almost agreed with that obtained with the isodose plotter in low dose range. However, further improvement of our system is necessary in high dose range.

• Journal of the Korean Society of Radiology
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• v.11 no.6
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• pp.509-515
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• 2017

The purpose of this study is to measure the 3 dimensional dose distribution of Gamma knife $Perfection^{TM}$, make a comparative analysis of the result and establish the measurement method for the procedures using EBT3 film. The dose distributions of the Gamma knife $Perfection^{TM}$ installed in two hospitals were evaluated in accuracy and precision. For accuracy, the difference between the mechanical center axis and the dose center axis was assessed on a 4 mm collimator. The allowed difference in accuracy is within 0.3 mm and it was measured as 0.098 mm, 0.195 mm for A hospital and 0.229 mm, and 0.223 mm for B hospital. For precision the difference between the FWHM(Full Width at Half Maximum) of Gamma Plan and measurement in the 4, 8, and 16 mm collimators was calculated. The allowed difference in precision is less than ${\pm}1mm$. The value of the hospital A was -0.283 ~ 0.583 mm, and the hospital B was -0.857 ~ 0.810 mm. When analyzing the dose distributions using the image-j program, it is necessary to establish a clearer reference point of the measurement point, and it is considered that the comparison of the dose distribution should be performed in actual treatment irradiation dose with a high dose usable film.

• Polymer(Korea)
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• v.33 no.3
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• pp.268-271
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• 2009

In this study, the distribution behaviors of the polystyrene sulfonic acid (PSSA) grafting polymer across the FEP-g-PSSA membranes prepared by a simultaneous irradiation method, were investigated by analyzing the cross-section of the membranes with a SEM-EDX instrument. The effects of irradiation conditions such as the degree of grafting, FEP film thickness, and grafting solvent on the distribution of the grafting polymer were mainly studied in this experiment. The results indicate that to obtain the evenly grafted FEP-g-PSSA membranes, the higher degree of grafting is required as the film thickness increases, and the lower dose rate are more effective than the higher dose rate at the given dose.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.217-224
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• 2014

Purpose : Conventional, IMRT, at CSI treatment with VMAT, this study compare the treatment plan with dose changes measured at Junction field according to the error of Setup. Materials and Methods : This study established Conventional, the IMRT, VMAT treatment planning for CSI therapy using the Eclipse 10.0 (Eclipse10.0, Varian, USA) and chose person in Seoul National University Hospital. Verification plan was also created to apply IMRT QA phantom for each treatment plan to the film measurements. At this time, the error of Setup was applied to the 2, 4, 6mm respectively with the head and foot direction. ("+" direction of the head, "-" means that the foot direction.) Using IMRT QA Phantom and EBT2 film, was investigated by placing the error of Setup for each Junction. We check the consistency of the measured Film and plan dose distribution by gamma index (Gamma index, ${\gamma}$). In addition, we compared the error of Setup by the dose distribution, and analyzing the uniformity of the dose distribution within the target by calculating the Homogeneity Index (HI). Results : It was figured out that 90.49%-gamma index we obtained with film is agreement with film scan score and dose distribution of treatment plan. Also, depend on the dose distribution on distance, if we make the error of Setup 2, 4, 6mm in the head direction, it showed that 3.1, 4.5, 8.1 at $^*Diff$(%) of Conventional, 1.1, 3.5, 6.3 at IMRT, and 1.6, 2.5, 5.7 at VMAT. In the same way, if we make the error of Setup 2, 4, 6mm in the foot direction, it showed that -1.6, -2.8, -4.4 at $^*Diff$(%) of Conventional, -0.9, -1.6, -2.9 at IMRT, and -0.5, -2.2, -2.5 at VMAT. Homogeneity Index(HI)s are 1.216 at Conventional, 1.095 at IMRT and 1.069 at VMAT. Discussion and Conclusion : The dose-change depend on the error of Setup at the CSI RT(radiation therapy) using IMRT and VMAT which have advantages, Dose homogeneity and the gradual dose gradients on the Junction part is lower than that of Conventional CSI RT. This a little change of dose means that there is less danger on patients despite of the error of Setup generated at the CSI RT.

• Progress in Medical Physics
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• v.27 no.4
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• pp.180-188
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• 2016

Acuros XB advanced dose calculation algorithm (AXB, Varian Medical Systems, Palo Alto, CA) has been released recently and provided the advantages of speed and accuracy for dose calculation. For clinical use, it is important to investigate the dosimetric performance of AXB compared to the calculation algorithm of the previous version, Anisotropic Analytical Algorithm (AAA, Varian Medical Systems, Palo Alto, CA). Ten volumetric modulated arc therapy (VMAT) plans for each of the following cases were included: head and neck (H&N), prostate, spine, and lung. The spine and lung cases were treated with stereotactic body radiation therapy (SBRT) technique. For all cases, the dose distributions were calculated using AAA and two dose reporting modes in AXB (dose-to-water, $AXB_w$, and dose-to-medium, $AXB_m$) with same plan parameters. For dosimetric evaluation, the dose-volumetric parameters were calculated for each planning target volume (PTV) and interested normal organs. The differences between AAA and AXB were statistically calculated with paired t-test. As a general trend, $AXB_w$ and $AXB_m$ showed dose underestimation as compared with AAA, which did not exceed within -3.5% and -4.5%, respectively. The maximum dose of PTV calculated by $AXB_w$ and $AXB_m$ was tended to be overestimated with the relative dose difference ranged from 1.6% to 4.6% for all cases. The absolute mean values of the relative dose differences were $1.1{\pm}1.2%$ and $2.0{\pm}1.2%$ when comparing between AAA and $AXB_w$, and AAA and $AXB_m$, respectively. For almost dose-volumetric parameters of PTV, the relative dose differences are statistically significant while there are no statistical significance for normal tissues. Both $AXB_w$ and $AXB_m$ was tended to underestimate dose for PTV and normal tissues compared to AAA. For analyzing two dose reporting modes in AXB, the dose distribution calculated by $AXB_w$ was similar to those of AAA when comparing the dose distributions between AAA and $AXB_m$.

• Radiation Oncology Journal
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• v.33 no.3
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• pp.233-241
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• 2015

Purpose: To compare volumetric modulated arc therapy of RapidArc with robotic stereotactic body radiation therapy (SBRT) of CyberKnife in the planning and delivery of SBRT for hepatocellular carcinoma (HCC) treatment by analyzing dosimetric parameters. Materials and Methods: Two radiation treatment plans were generated for 29 HCC patients, one using Eclipse for the RapidArc plan and the other using Multiplan for the CyberKnife plan. The prescription dose was 60 Gy in 3 fractions. The dosimetric parameters of planning target volume (PTV) coverage and normal tissue sparing in the RapidArc and the CyberKnife plans were analyzed. Results: The conformity index was $1.05{\pm}0.02$ for the CyberKnife plan, and $1.13{\pm}0.10$ for the RapidArc plan. The homogeneity index was $1.23{\pm}0.01$ for the CyberKnife plan, and $1.10{\pm}0.03$ for the RapidArc plan. For the normal liver, there were significant differences between the two plans in the low-dose regions of $V_1$ and $V_3$. The normalized volumes of $V_{60}$ for the normal liver in the RapidArc plan were drastically increased when the mean dose of the PTVs in RapidArc plan is equivalent to the mean dose of the PTVs in the CyberKnife plan. Conclusion: CyberKnife plans show greater dose conformity, especially in small-sized tumors, while RapidArc plans show good dosimetric distribution of low dose sparing in the normal liver and body.

• Progress in Medical Physics
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• v.23 no.1
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• pp.54-61
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• 2012

A polymer gel dosimeter was fabricated. A 3-dimensional dosimetry experiment was performed in the small field of the photon of the cyberknife. The dosimeter was installed in a head and neck phantom. It was manufactured from the acrylic and it was used in dosimetry. By using the head and neck CT protocol of the CyberKnife system, CT images of the head and neck phantom were obtained and delivered to the treatment planning system. The irradiation to the dosimeter in the treatment planning was performed, and then, the image was obtained by using 3.0T magnetic resonance imaging (MRI) after 24 hours. The dose distribution of the phantom was analyzed by using MATLAB. The results of this measurement were compared to the results of calculation in the treatment planning. In the isodose curve on the axial direction, the dose distribution coincided with the high dose area, 0.76mm difference on 80%, rather than the low dose area, 1.29 mm difference on 40%. In this research, the fact that the polymer gel dosimeter and MRI can be applied for analyzing a small field in a 3 dimensional dosimetry was confirmed. Moreover, the feasibility of using these for the therapeutic radiation quality control was also confirmed.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.449-457
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• 2015

In this study, to evaluate the usefulness of the treatment plan of tomotherapy and volumetric modulated arc therapy (VMAT) in the radiotherapy for prostate cancer, the absorbed dose, dose volume histogram (DVH), treatment efficiency, and the results of dose verification accuracy using MapCHECK2 were compared and analyzed. Of the prostate cancer patients who underwent tomotherapy treatment in the Radiologic Oncology of H University Hospital between July 2014 and December 2014, 12 patients were randomly selected. As a result of analyzing the absorbed dose and DVH, both radiologic treatment plans showed slight differences in the treatment of the cancer tissues and the bladder, but the difference was in the error range of -5% to +3%, and did not exceed the side effect guideline or the tolerance dose limit. VMAT showed higher treatment efficiency than tomotherapy with a 2.5 times shorter treatment time and a 10.3 times less monitor unit (MU). Both showed 95% or higher dose accuracy satisfying the standard. VMAT showed 2.3% higher efficiency than tomotherapy. In both tomotherapy and VMAT, appropriate doses were absorbed for cancer tissues, and did not exceed the tolerance dose for normal tissues showing no significant difference in dose distribution. However, considering the shorter treatment time, lower total MU, and better treatment efficiency and dose verification accuracy, VMAT may be more useful than tomotherapy in cancer treatments.