• The Journal of Korean Society for Radiation Therapy
• /
• v.26 no.2
• /
• pp.273-280
• /
• 2014

Purpose : To verify the skin dose in Tomotherapy-based radiation treatment according to the change in tumor locations, skin dose was measured by using Gafchromic EBT3 film and compared with the planned doses to find out the gap between them. Materials and Methods : In this study, to measure the skin dose, I'm RT Phantom(IBA Dosimetry, Germany) was utilized. After obtaining the 2.5mm CT images, tumor locations and skin dose measuring points were set by using Pinnacle(ver 9.2, Philips Medical System, USA). The tumor location was decided to be 5mm and 10mm away from surface of the phantom and center. Considering the attenuation of a Tomo-couch, we ensured a symmetric placement between the ceiling and floor directions of the phantom. The measuring point of skin doses was set to have 3mm and 5mm thickness from the surface. Measurement was done 3 times. By employing TomoHD(TomoHD treatment system, Tomotherapy Inc., Madison, Wisconsin, USA), we devised Tomotherapy plans, measured 3 times by inserting Gafchromic EBT3 film into the phantom and compared the measurement with the skin dose treatment plans. Results : The skin doses in the upper part of the phantom, when the tumor was located in the center, were found to be 7.53 cGy and 7.25 cGy in 5mm and 3mm respectively. If placed 5mm away from the skin in the ceiling direction, doses were 18.06 cGy and 16.89 cGy; if 10mm away, 20.37 cGy and 18.27 cGy, respectively. The skin doses in the lower part of the phantom, when the tumor was located in the center, recorded 8.82 cGy and 8.29 cGy in 5mm and 3mm, each; if located 5mm away from the lower part skin, 21.69 cGy and 19.78 cGy were respectively recorded; and if 10mm away, 20.48 cGy and 19.57 cGy were recorded. If the tumor was placed in the center, skin doses were found to increase by 3.2~17.1% whereas if the tumor is 5mm away from the ceiling part, the figure decreased to 2.8~9.0%. To the Tomo-couch direction, skin doses showed an average increase of 11% or over, compared to the planned treatment. Conclusion : This study found gaps between planned skin doses and actual doses in the Tomotherapy treatment planning. Especially to the Tomo-cocuh direction, skin doses were found to be larger than the planned doses. Thus, during the treatment of tumors near the Tomo-couch, doses will need to be more accurately calculated and more efforts to verify skin doses will be required as well.

• Progress in Medical Physics
• /
• v.17 no.4
• /
• pp.192-200
• /
• 2006

We evaluated the positional accuracy of the delivered beams to the target in a phantom by simulating the whole process of the radiation treatments Including CT scanning, planning and beam exposures with MLCs. For this purpose, a phantom was made to calibrate the alignment between the CT and the attached laser system. A new, convenient method was also devised to align the setup lasers in the treatment room. Film was used for the Identification of the delivered beam and analyzed with a homemade computer program. The positional differences between the target and the beam centers varied with the couch rotations. The accelerator we used showed a maximum discrepancy of 2.0 mm at the table angle of $295^{\circ}$. The same measurements based on the new isocenter from the Winston-Lutz test resulted in the maximum of 1.35 mm for all rotation angles. The evaluation of the differences between the target and the beam centers is useful for the treatment planning.

• Progress in Medical Physics
• /
• v.19 no.2
• /
• pp.113-119
• /
• 2008

In this study, we have estimated error of calculation results for 5-type RTP systems and investigated a toleration for error of the RTPs referenced from the evaluation items of AAPM Report-62. For this study, we have introduced the concept of 'normal dose rate(NDR)' and compared the results of experiment and calculation from RTPs at the same reference level. The results from all RTPs were satisfied at various field shapes and heterogeneous phantom materials except the surface irregularity.

• Progress in Medical Physics
• /
• v.23 no.2
• /
• pp.106-113
• /
• 2012

The purpose of this study is to evaluate the variation of radiation dose distribution for liver tumor located in liver dome and for the interest organs(normal liver, kidney, stomach) with the pencil beam convolution (PBC) algorithm versus anisotropic Analyticalal algorithm (AAA) of the Varian Eclipse treatment planning system, The target volumes from 20 liver cancer patients were used to create treatment plans. Treatment plans for 10 patients were performed in Stereotactic Body Radiation Therapy (SBRT) plan and others were performed in 3 Dimensional Conformal Radiation Therapy (3DCRT) plan. dose calculation was recalculated by AAA algorithm after dose calculation was performed by PBC algorithm for 20 patients. Plans were optimized to 100% of the PTV by the Prescription Isodose in Dose Calculation with the PBC algorithm. Plans were recalculated with the AAA, retaining identical beam arrangements, monitor units, field weighting and collimator condition. In this study, Total PTV was to be statistically significant (SRS: p=0.018, 3DCRT: p=0.006) between PBC and AAA algorithm. and in the case of PTV, ITV in liver dome, plans for 3DCRT were to be statistically significant respectively (p=0.013, p=0.024). normal liver and kidney were to be statistically significant (p=0.009, p=0.037). For the predictive index of dose variation, CVF ratio was to be statistically significant for PTV in the liver dome versus PTV (SRS r=0.684, 3DCRT r=0.732, p<0.01) and CVF ratio for Tumor size was to be statistically significant (SRS r=-0.193, p=0.017, 3DCRT r=0.237, p=0.023).

• The Journal of Korean Society for Radiation Therapy
• /
• v.26 no.2
• /
• pp.297-303
• /
• 2014

Purpose : The purpose of this study is reproducibility evaluation of deep inspiration breath-hold(DIBH) technique by respiration data and heart position analysis in radiation therapy for Left Breast cancer patients. Materials and Methods : Free breathing(FB) Computed Tomography(CT) images and DIBH CT images of three left breast cancer patients were used to evaluate the heart volume and dose during treatment planing system( Eclipse version 10.0, Varian, USA ). The signal of RPM (Real-time Position Management) Respiratory Gating System (version 1.7.5, Varian, USA) was used to evaluate respiration stability of DIBH during breast radiation therapy. The images for measurement of heart position were acquired by the Electronic portal imaging device(EPID) cine acquisition mode. The distance of heart at the three measuring points(A, B, C) on each image was measured by Offline Review (ARIA 10, Varian, USA). Results : Significant differences were found between the FB and DIBH plans for mean heart dose (6.82 vs. 1.91 Gy), heart $V_{30}$ (68.57 vs. $8.26cm^3$), $V_{20}$ (76.43 vs. $11.34cm^3$). The standard deviation of DIBH signal of each patient was ${\pm}0.07cm$, ${\pm}0.04cm$, ${\pm}0.13cm$, respectively. The Maximum and Minimum heart distance on EPID images were measured as 0.32 cm and 0.00 cm. Conclusion : Consequently, using the DIBH technique with radiation therapy for left breast cancer patients is very useful to establish the treatment plan and to reduce the heart dose. In addition, it is beneficial to using the Cine acquisition mode of EPID for the reproducibility evaluation of DIBH.

• Progress in Medical Physics
• /
• v.25 no.4
• /
• pp.210-217
• /
• 2014

This study investigated the dosimetric effects of different dose calculation algorithm for lung stereotactic ablative radiotherapy (SABR) using flattening filter-free (FFF) beams. A total of 10 patients with lung cancer who were treated with SABR were evaluated. All treatment plans were created using an Acuros XB (AXB) of an Eclipse treatment planning system. An additional plans for comparison of different alagorithm recalcuated with anisotropic analytic algorithm (AAA) algorithm. To address both algorithms, the cumulative dose-volume histogram (DVH) was analyzed for the planning target volume (PTV) and organs at risk (OARs). Technical parameters, such as the computation times and total monitor units (MUs), were also evaluated. A comparison analysis of DVHs from these plans revealed the PTV for AXB estimated a higher maximum dose (5.2%) and lower minimum dose (4.2%) than that of the AAA. The highest dose difference observed 7.06% for the PTV $V_{105%}$. The maximum dose to the lung was also slightly larger in the AXB plans. The percentate volumes of the ipsilateral lung ($V_5$, $V_{10}$, $V_{20}$) receiving 5, 10, and 20 Gy were also larger in AXB plans than for AAA plans. However, these parameters were comparable between both AAA and AXB plans for the contralateral lung. The differences of the maximum dose for the spinal cord and heart were also small. The computation time of AXB plans was 13.7% shorter than that of AAA plans. The average MUs were 3.47% larger for AXB plans than for AAA plans. The results of this study suggest that AXB algorithm can provide advantages such as accurate dose calculations and reduced computation time in lung SABR plan using FFF beams, especially for volumetric modulated arc therapy technique.

• Journal of the Korea Convergence Society
• /
• v.8 no.4
• /
• pp.131-137
• /
• 2017

In the present study, we developed the 4D CT data generation program from CAD-based models. To evaluate the developed program, a CAD-based respiratory motion phantom was designed using CAD software, and converted into 4D CT dataset, which include 10 phases of 3D CTs. The generated 4D CT dataset was evaluated its effectiveness and accuracy through the implementation in radiation therapy planning system (RTPS). Consequently, the results show that the generated 4D CT dataset can be successfully implemented in RTPS, and targets in all phases of 4D CT dataset were moved well according to the user parameters (10 mm) with its stationarily volume (8.8 cc). The developed program, unlike real 4D CT scanner, due to the its ability to make a gold-standard dataset without any artifacts constructed by modality's movements, we believe that this program will be used when the motion effect is important, such as 4D radiation treatment planning and 4D radiation imaging.

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

• Progress in Medical Physics
• /
• v.25 no.4
• /
• pp.233-241
• /
• 2014

The aim of this study is to develop a new software tool for 3D dose verification using $PRESAGE^{REU}$ Gel dosimeter. The tool included following functions: importing 3D doses from treatment planning systems (TPS), importing 3D optical density (OD), converting ODs to doses, 3D registration between two volumetric data by translational and rotational transformations, and evaluation with 3D gamma index. To acquire correlation between ODs and doses, CT images of a $PRESAGE^{REU}$ Gel with cylindrical shape was acquired, and a volumetric modulated arc therapy (VMAT) plan was designed to give radiation doses from 1 Gy to 6 Gy to six disk-shaped virtual targets along z-axis. After the VMAT plan was delivered to the targets, 3D OD data were reconstructed from 512 projection data from $Vista^{TM}$ optical CT scanner (Modus Medical Devices Inc, Canada) per every 2 hours after irradiation. A curve for converting ODs to doses was derived by comparing TPS dose profile to OD profile along z-axis, and the 3D OD data were converted to the absorbed doses using the curve. Supra-linearity was observed between doses and ODs, and the ODs were decayed about 60% per 24 hours depending on their magnitudes. Measured doses from the $PRESAGE^{REU}$ Gel were well agreed with the TPS doses at central region, but large under-doses were observed at peripheral region at the cylindrical geometry. Gamma passing rate for 3D doses was 70.36% under the gamma criteria of 3% of dose difference and 3 mm of distance to agreement. The low passing rate was resulted from the mismatching of the refractive index between the PRESAGE gel and oil bath in the optical CT scanner. In conclusion, the developed software was useful for 3D dose verification from PRESAGE gel dosimetry, but further improvement of the Gel dosimetry system were required.

• Progress in Medical Physics
• /
• v.22 no.2
• /
• pp.99-105
• /
• 2011

The purpose of this study is to evaluate the accuracy of IMRT in our clinic from based on TG119 procedure and establish action level. Five IMRT test cases were described in TG119: multi-target, head&neck, prostate, and two C-shapes (easy&hard). There were used and delivered to water-equivalent solid phantom for IMRT. Absolute dose for points in target and OAR was measured by using an ion chamber (CC13, IBA). EBT2 film was utilized to compare the measured two-dimensional dose distribution with the calculated one by treatment planning system. All collected data were analyzed using the TG119 specifications to determine the confidence limit. The mean of relative error (%) between measured and calculated value was $1.2{\pm}1.1%$ and $1.2{\pm}0.7%$ for target and OAR, respectively. The resulting confidence limits were 3.4% and 2.6%. In EBT2 film dosimetry, the average percentage of points passing the gamma criteria (3%/3 mm) was $97.7{\pm}0.8%$. Confidence limit values determined by EBT2 film analysis was 3.9%. This study has focused on IMRT commissioning and quality assurance based on TG119 guideline. It is concluded that action level were ${\pm}4%$ and ${\pm}3%$ for target and OAR and 97% for film measurement, respectively. It is expected that TG119-based procedure can be used as reference to evaluate the accuracy of IMRT for each institution.