Browsing by Author "วิภา บุญกิตติเจริญ"

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    PublicationOpen Access
    Comparison of Second Cancer Risk in Patients with Liver Cancer Treated By Stereo-tactic Body Radiotherapy and Three-Dimensional Conformal Radiotherapy
    (2012) Nattiya Yodtongde; Vipa Boonkitticharoen; Mantana Dhanachai; Putipan Puataweepong; ณัฐิยา ยอดทองดี; วิภา บุญกิตติเจริญ; มัณฑนา ธนะไชย; พุฒิพรรณ พัวทวีพงศ์; Mahidol University. Faculty of Medicine Ramathibodi Hospital. Medical Physics School; Mahidol University. Faculty of Medicine Ramathibodi Hospital. Department of Diagnostic and Therapeutic Radiology
    Background: Stereotactic body radiotherapy (SBRT) is suggested to pose higher second cancer risk than conventional three-dimensional conformal radiotherapy (3D-CRT) for generating greater scatter/ leakage dose to distant organs. Epidemiological reports indicate the need to include primary beam effect in risk assessment because of its great contribution to total cancer risk. Objective: To determine the second cancer dosimetric index, organ equivalent dose (OED), for organ in treatment field (planning target volume, PTV), beam border (uninvolved liver), and distant area (stomach and pancreas) in patients with liver cancer treated either by Cyberknife SBRT (Cyber-SBRT) or 3D-CRT. Methods: Treatment plans for seven patients were optimized and prescription dose of 45 Gy were delivered in 15 Gy x3 fractions for Cyber-SBRT and 1.8 Gy x25 fractions for 3D-CRT. OED for primary beam was calculated from differential dose volume histogram. Image-guided dose and scatter/ leakage dose from each treatment were measured in Rando phantom using thermoluminescence dosimeters. Results: For primary beam component, OEDs of PTV were comparable for both treatments (p = 0.00003). In organs outside the treatment field, Cyber-SBRT generated much lower OEDs than 3D-CRT (p £ 0.059). OEDs for scatter/ leakage component were smaller for 3D-CRT but their contributions to total OEDs were < 1%. OED from image-guided procedure in Cyberknife SBRT was relatively small. In overall, total OEDs were comparable between Cyber-SBRT and 3D-CRT. Conclusion: Total OEDs of normal tissues from both treatments were comparable or apparently lower for SBRT than 3D-CRT (p ³ 0.20) while total OED of PTV from Cyber-SBRT is slightly higher than that of 3D-CRT (p < 0.05).
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    PublicationOpen Access
    Monte Carlo Multiple-source Model for 6 mV Photon Beams from Varian Clinac iX Linear Accelerator
    (2015) Thorfun Tapanya; Vipa Boonkiticharoen; Nakorn Phaisangittisakul; ทอฝัน ทาปัญญา; วิภา บุญกิตติเจริญ; นคร ไพศาลกิตติสกุล; Mahidol University. Faculty of Medicine Ramathibodi Hospital. Medical Physics School; Chulalongkorn University. Faculty of Science. Department of Physics
    Objective: The aim of this study was to build a multiple source model for a 6 MV Photon beam from the Varian Clinac iX linear accelerator (at the Department of Radiology, Ramathibodi Hospital). Methods: Beam Data Processer (BEAMDP) was used to analyze the phase space dara from the EGSnrc (Electron-Gamma Shower National Research Council of Canada)/BEAMnrc code and obtain the parameters for beam representation. A DOSXYZn code was used to calculate dose distribution in a 3D rectangular voxel. The simulation compose of two unknown parameters, energy and full width at half maximum (FWHM). These parameters were determined by using an iterative process and a comparison with the percentage depth dose and the beam profile form the measurement. The five source model were comprised of a point sub-source for target, circular planar sub-source for primary collimator and flattening filter, rectangular planar sub source for election, and positron. The characteristics of beams such as relative intensity, field planar influence distribution and energy distribution from original phase space were derived by using the BEAMDP code. Result: The initial parameter found an energy of 6.5 MeV and radial intensity distribution with a width of 0.6 mm FWHM. Most of the depth dose and beam profile between our source model and the measurement showed good agreement within +2% for field size of 5 x 5, 10 x 10, 15 x 15 and 20 x 20 cm2 except of the 30 x 30 cm2 field size at 100 cm SSD. The relative point dose of the source model in homogenous phantom deviated with +1% and +2% between the original phase space and the measurement respectively. The source model was shown to reduce disk space requirement and CPU time, while the statistical uncertainty of dose calculation was the same as the full Monte Carlo simulation. Conclusion: Our source model accurately simulates the dosimetric characteristics of a photon beam for all field size, except for 30 x 30 cm2.