• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.291-293
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• 2002

Accurate dose calculation in radiation treatment planning is most important for successful treatment. Since human body is composed of various materials and not an ideal shape, it is not easy to calculate the accurate effective dose in the patients. Many methods have been proposed to solve the inhomogeneity and surface contour problems. Monte Carlo simulations are regarded as the most accurate method, but it is not appropriate for routine planning because it takes so much time. Pencil beam kernel based convolution/superposition methods were also proposed to correct those effects. Nowadays, many commercial treatment planning systems, including Pinnacle and Helax-TMS, have adopted this algorithm as a dose calculation engine. The purpose of this study is to verify the accuracy of the dose calculated from pencil beam kernel based treatment planning system Helax-TMS comparing to Monte Carlo simulations and measurements especially in inhomogeneous region. Home-made inhomogeneous phantom, Helax-TMS ver. 6.0 and Monte Carlo code BEAMnrc and DOSXYZnrc were used in this study. Dose calculation results from TPS and Monte Carlo simulation were verified by measurements. In homogeneous media, the accuracy was acceptable but in inhomogeneous media, the errors were more significant.

• The Journal of Korean Society for Radiation Therapy
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• v.11 no.1
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• pp.53-59
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• 1999

The aim of this study is to improve the accuracy of field placement and junction between adjacent fields and block shielding through the use of a computed tomography(CT) simulator and virtual simulation. The information was acquired by assessment of Alderson Rando phantom image using CT simulator (I.Q. Xtra - Picker), determination of each field by virtual fluoroscopy of voxel IQ workstation AcQsim and colored critical structures that were obtained by contouring in virtual simulation. And also using a coronal, sagittal and axial view can determine the field and adjacent field gap correctly without calculation during the procedure. With the treatment planning by using the Helax TMS 4.0, the dose in the junction among the adjacent fields and the spinal cord and cribriform plate of the critical structure was evaluated by the dose volume histogram. The pilot image of coronal and sagittal view took about 2minutes and 26minutes to get 100 images. Image translation to the virtual simulation workstation took about 6minutes. Contouring a critical structure such as cribriform plate, spinal cord using a virtual fluoroscopy were eligible to determine a correct field and shielding. The process took about 20 minutes. As the result of the Helax planning, the dose distribution in adjacent field junction was ideal, and the dose level shows almost 100 percentage in the dose volume histogram of the spinal cord and cribriform plate CT simulation can get a correct therapy area due to enhancement of critical structures such as spinal cord and cribriform plate. In addition, using a Spiral CT scanner can be saved a lot of time to plan a simulation therefore this function can reduce difficulties to keep the patient position without any movements to the patient, physician and radiotherapy technician.