• Journal of Yeungnam Medical Science
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• v.39 no.2
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• pp.108-115
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• 2022

Background: This study was aimed at comparing and analyzing the results of FractionLab (Varian/Mobius Medical System) with those of portal dosimetry that uses an electronic portal imaging device. Portal dosimetry is extensively used for patient-specific quality assurance (QA) in intensity-modulated radiotherapy (IMRT). Methods: The study includes 29 patients who underwent IMRT on a Novalis-Tx linear accelerator (Varian Medical System and Brain-LAB) between June 2019 and March 2021. We analyzed the multileaf collimator DynaLog files generated after portal dosimetry to evaluate the same condition using FractionLab. The results of the recently launched FractionLab at various gamma indices (0.1%/0.1 mm-1%/1 mm) are analyzed and compared with those of portal dosimetry (3%/3 mm). Results: The average gamma passing rates of portal dosimetry (3%/3 mm) and FractionLab are 98.1% (95.5%-100%) and 97.5% (92.3%-99.7%) at 0.6%/0.6 mm, respectively. The results of portal dosimetry (3%/3 mm) are statistically comparable with the QA results of FractionLab (0.6%/0.6 mm-0.9%/0.9 mm). Conclusion: This paper presents the clinical performance of FractionLab by the comparison of the QA results of FractionLab using portal dosimetry with various gamma indexes when performing patient-specific QA in IMRT treatment. Further, the appropriate gamma index when performing patient-specific QA with FractionLab is provided.

• Progress in Medical Physics
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• v.28 no.1
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• pp.33-38
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• 2017

Creating individualized build-up material for superficial photon beam radiation therapy at irregular surface is complex with rice or commonly used flat shape bolus. In this study, we implemented a workflow using 3D printed patient specific bolus and describe our clinical experience. To provide better fitted build-up to irregular surface, the 3D printing technique was used. The PolyLactic Acid (PLA) which processed with nontoxic plant component was used for 3D printer filament material for clinical usage. The 3D printed bolus was designed using virtual bolus structure delineated on patient CT images. Dose distributions were generated from treatment plan for bolus assigned uniform relative electron density and bolus using relative electron density from CT image and compared to evaluate the inhomogeneity effect of bolus material. Pretreatment QA is performed to verify the relative electron density applied to bolus structure by gamma analysis. As an in-vivo dosimetry, Optically Stimulated Luminescent Dosimeters (OSLD) are used to measure the skin dose. The plan comparison result shows that discrepancies between the virtual bolus plan and printed bolus plan are negligible. (0.3% maximum dose difference and 0.2% mean dose difference). The dose distribution is evaluated with gamma method (2%, 2 mm) at the center of GTV and the passing rate was 99.6%. The OSLD measurement shows 0.3% to 2.1% higher than expected dose at patient treatment lesion. In this study, we treated Mycosis fungoides patient with patient specific bolus using 3D printing technique. The accuracy of treatment plan was verified by pretreatment QA and in-vivo dosimetry. The QA results and 4 month follow up result shows the radiation treatment using 3D printing bolus is feasible to treat irregular patient skin.

• Journal of the Korea Safety Management & Science
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• v.17 no.1
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• pp.119-124
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• 2015

According as radiation therapy technique develops, standardization of radiation therapy has been complicated by the plan QA(Quality Assurance). However, plan QA tools are two type, OADT (opposite accumulation dose tool) and 3DADT (3 dimensional accumulation dose tool). OADT is not applied to evaluation of beam path. Therefore tolerance error of beam path will establish measurement value at OADT. Plan is six beam path, five irradiation field at each beam path. And beam path error is 0 degree, 0.2 degree, 0.4 degree, 0.6 degree, 0.6 degree, 0.8 degree. Plan QA accomplishes at OADT, 3DADT. The more path error increases, the more plan QA error increases. Tolerance error of OADT path is 0.357 using tolerance error of conventional plan QA. Henceforth plan QA using OADT will include beam path error. In addition, It will increase reliability through precise and various plan technique.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.9-15
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• 2017

Background: The purpose of this study is to assign an appropriate density to virtual phantom for 2D diode array detector with different dose calculation algorithms to guarantee the accuracy of patient-specific QA. Materials and Methods: Ten VMAT plans with 6 MV photon beam and ten VMAT plans with 15 MV photon beam were selected retrospectively. The computed tomography (CT) images of MapCHECK2 with MapPHAN were acquired to design the virtual phantom images. For all plans, dose distributions were calculated for the virtual phantoms with four different materials by AAA and AXB algorithms. The four materials were polystyrene, 455 HU, Jursinic phantom, and PVC. Passing rates for several gamma criteria were calculated by comparing the measured dose distribution with calculated dose distributions of four materials. Results and Discussion: For validation of AXB modeling in clinic, the mean percentages of agreement in the cases of dose difference criteria of 1.0% and 2.0% for 6 MV were $97.2%{\pm}2.3%$, and $99.4%{\pm}1.1%$, respectively while those for 15 MV were $98.5%{\pm}0.85%$ and $99.8%{\pm}0.2%$, respectively. In the case of 2%/2 mm, all mean passing rates were more than 96.0% and 97.2% for 6 MV and 15 MV, respectively, regardless of the virtual phantoms of different materials and dose calculation algorithms. The passing rates in all criteria slightly increased for AXB as well as AAA when using 455 HU rather than polystyrene. Conclusion: The virtual phantom which had a 455 HU values showed high passing rates for all gamma criteria. To guarantee the accuracy of patent-specific VMAT QA, each institution should fine-tune the mass density or HU values of this device.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.2
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• pp.91-97
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• 2007

Purpose: To evaluate the feasibility of a commercial ion chamber array for intensity modulated radiation therapy (IMRT) quality assurance (QA) was performed IMRT patient-specific QA Materials and Methods: A use of IMRT patient-specific QA was examined for nasopharyngeal patient by using 6MV photon beams. The MatriXX (Wellhofer Dosimetrie, Germany) was used for IMRT QA. The case of nasopharyngeal cancer was performed inverse treatment planning. A hybrid dose distribution made on the CT data of MatriXX and solid phantom all of the same gantry angle (0$^\circ$). The measurement was acquired with geometrical condition that equal to hybrid treatment planning. The $\gamma$-index (dose difference 3%, DTA 3 mm) histogram was used for quantitative analysis of dose discrepancies. An absolute dose was compared at the high dose low gradient region. Results: The dose distribution was shown a good agreement by gamma evaluation. A proportion of acceptance criteria was 95.8%, 97.52%, 96.28%, 98.20%, 97.78%, 96.64% and 92.70% for gantry angles were 0$^\circ$, 55$^\circ$, 110$^\circ$, 140$^\circ$, 220$^\circ$, 250$^\circ$ and 305$^\circ$, respectively. The absolute dose in high dose low gradient region was shown reasonable agreement with the RTP calculation within $\pm$3%. Conclusion: The MatriXX offers the dosimetric characteristics required for performing both relative and absolute measurements. If MatriXX use in the clinic, it could be simplified and reduced the IMRT patient-specific QA workload. Therefore, the MatriXX is evaluated as a reliable and convenient dosimeter for IMRT patient-specific QA.

• Progress in Medical Physics
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• v.21 no.2
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• pp.127-136
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• 2010

Emerging technologies such as four-dimensional computed tomography (4D CT) is expected to allow clinicians to accurately model interfractional motion and to quantitatively estimate internal target volumes (ITVs) for radiation therapy involving moving targets. A need exists for a 4D radiation therapy quality assurance (QA) device that can incorporate and analyze the patient specific intrafractional motion as it relate to dose delivery and respiratory gating. We built a 4D RT prototype device and analyzed the patient-specific 4D radiation therapy QA for 2D dose distributions successfully. With more improvements, the 4D RT QA prototype device could be an integral part of a 4D RT decision process to confirm the dose delivery.

• Progress in Medical Physics
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• v.30 no.1
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• pp.14-21
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• 2019

Purpose: To report the initial experience of patient-specific quality assurance (pQA) for the wobbling and line-scanning proton therapy at Samsung Medical Center. Materials and Methods: The pQA results of 89 wobbling treatments with 227 fields and 44 line-scanning treatments with 118 fields were analyzed from December 2015 to June 2016. For the wobbling method, proton range and spread-out Bragg peak (SOBP) width were verified. For the line-scanning method, output and two-dimensional dose distribution at multiple depths were verified by gamma analysis with 3%/3 mm criterion. Results: The average range difference was -0.44 mm with a standard deviation (SD) of 1.64 mm and 0.1 mm with an SD of 0.53 mm for the small and middle wobbling radii, respectively. For the line-scanning method, the output difference was within ${\pm}3%$. The gamma passing rates were over 95% with 3%/3 mm criterion for all depths. Conclusions: For the wobbling method, proton range and SOBP width were within the tolerance levels. For the line-scanning method, the output and two-dimensional dose distribution showed excellent agreement with the treatment plans.

• Radiation Oncology Journal
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• v.24 no.3
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• pp.185-191
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• 2006

[ $\underline{Purpose}$ ]: Standardization quality assurance (QA) program of CyberKnife for suitable circumstances in Korea has not been established. In this research, we investigated the development of QA program for CyberKnife and evaluation of the feasibility under applications. $\underline{Materials\;and\;Methods}$: Considering the feature of constitution for systems and the therapeutic methodology of CyberKnife, the list of quality control (QC) was established and divided dependent on the each period of operations. And then all these developed QC lists were categorized into three groups such as basic QC, delivery specific QC, and patient specific QC based on the each purpose of QA. In order to verify the validity of the established QA program, this QC lists was applied to two CyberKnife centers. The acceptable tolerance was based on the undertaking inspection list from the CyberKnife manufacturer and the QC results during last three years of two CyberKnife centers in Korea. The acquired measurement results were evaluated for the analysis of the current QA status and the verification of the propriety for the developed QA program. $\underline{Results}$: The current QA status of two CyberKnife centers was evaluated from the accuracy of all measurements in relation with application of the established QA program. Each measurement result was verified having a good agreement within the acceptable tolerance limit of the developed QA program. $\underline{Conclusion}$: It is considered that the developed QA program in this research could be established the standardization of QC methods for CyberKnife and confirmed the accuracy and stability for the image-guided stereotactic radiotherapy.

• Progress in Medical Physics
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• v.28 no.3
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• pp.111-121
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• 2017

Verification of dose distribution is an essential part of ensuring the treatment planning system's (TPS) calculated dose will achieve the desired outcome in radiation therapy. Each measurement have uncertainty associated with it. It is desirable to reduce the measurement uncertainty. A best approach is to reduce the uncertainty associated with each step of the process to keep the total uncertainty under acceptable limits. Point dose patient specific quality assurance (QA) is recommended by American Association of Medical Physicists (AAPM) and European Society for Radiotherapy and Oncology (ESTRO) for all the complex radiation therapy treatment techniques. Relative and absolute point dose measurement methods are used to verify the TPS computed dose. Relative and absolute point dose measurement techniques have a number of steps to measure the point dose which includes chamber cross calibration, electrometer reading, chamber calibration coefficient, beam quality correction factor, reference conditions, influences quantities, machine stability, nominal calibration factor (for relative method) and absolute dose calibration of machine. Keeping these parameters in mind, the estimated relative percentage uncertainty associated with the absolute point dose measurement is 2.1% (k=1). On the other hand, the relative percentage uncertainty associated with the relative point dose verification method is estimated to 1.0% (k=1). To compare both point dose measurement methods, 13 head and neck (H&N) IMRT patients were selected. A point dose for each patient was measured with both methods. The average percentage difference between TPS computed dose and measured absolute relative point dose was 1.4% and 1% respectively. The results of this comparative study show that while choosing the relative or absolute point dose measurement technique, both techniques can produce similar results for H&N IMRT treatment plans. There is no statistically significant difference between both point dose verification methods based upon the t-test for comparing two means.

• Journal of radiological science and technology
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• v.35 no.3
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• pp.255-263
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• 2012

The aim of this study was to evaluate the patient specific quality assurance (QA) results of intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) through the AAPM Task Group Report 119. Using the treatment planning system, both IMRT and VMAT treatment plans were established. The absolute dose and relative dose for the target and OAR were measured by using an ion chamber and the bi-planar diode array, respectively. The plan evaluation was used by the Dose volume histogram (DVH) and the dose verification was implemented by compare the measured value with the calculated value. For the evaluation of plan, in case of prostate, both IMRT and VMAT were closed the goal of target and OARs. In case of H&N and Multi-target, IMRT was not reached the goal of target, but VMAT was reached the goal of target and OARs. In case of C-shape(easy), both were reached the goal of target and OARs. In case of C-shape(hard), both were reached the goal of target but not reached the goal of OARs. For the evaluation of absolute dose, in case of IMRT, the mean of relative error (%) between measured and calculated value was $1.24{\pm}2.06%$ and $1.4{\pm}2.9%$ for target and OAR, respectively. The confidence limits were 3.65% and 4.39% for target and OAR, respectively. In case of VMAT the mean of relative error was $2.06{\pm}0.64%$ and $2.21{\pm}0.74%$ for target and OAR, respectively. The confidence limits were 4.09% and 3.04% for target and OAR, respectively. For the evaluation of relative dose, in case of IMRT, the average percentage of passing gamma criteria (3mm/3%) were $98.3{\pm}1.5%$ and the confidence limits were 3.78%. In case of VMAT, the average percentage were $98.2{\pm}1.1%$ and the confidence limits were 3.95%. We performed IMRT and VMAT patient specific QA using TG-119 based procedure, all analyzed results were satisfied with acceptance criteria based on TG-119. So, the IMRT and VMAT of our institution was confirmed the accuracy.