Commissioning and evaluation of electron beam dose calculation in a computerized treatment planning system using generalized gaussian pencil beam and macro monte carlo model

การจัดเก็บและการประเมินการคำนวณปริมาณรังสีอิเล็กตรอนด้วยแบบคำนวณปริมาณรังสี generalized gaussian pencil beam และ macro monte carlo model ในเครื่องวางแผนการรักษาคอมพิวเตอร์

Name: Piyanan Liammookda

LCSH: Electron beams -- Data processing

LCSH: Monte Carlo method

LCSH: Radiation dosimetry

Abstract: The purpose of this study was to perform the commissioning and evaluation of the Generalized Gaussian Pencil Beam (GGPB) and the macro Monte Carlo based dose calculation algorithm (eMC) for electron beam treatment planning. The electron beam energies, which range from 6 to 22 MeV, of a Clinac 23EX linear accelerator were measured and configured to the Eclipse treatment planning system (Version 8.0) for both algorithms. For the eMC algorithm, I studied the calculation accuracy in the verification data set by performing over the range of each of the following algorithm parameters: statistical precision, grid size and smoothing methods. The performance of the treatment planning system in dose distribution calculations was evaluated in comparison with sets of measured data in homogeneous phantoms at different source to surface distances (SSDs) of 100, 105, 110 and 120 cm and shaped fields that included triangle-shaped, L-shaped, and house-shaped fields. Irregular surface measurements were comprised of 30º incidence, stepped surface and nose surface. For heterogeneous phantoms, the measurements were made for air cavity in solid water phantom. An in vivo dosimetry was performed for bone inhomogeneity in Anderson Rando phantoms. The accuracy of the monitor unit (MU) calculations for both electron algorithms was also tested in homogeneous phantoms for standard applicators including 6 × 6, 10 × 10, 15 × 15, 20 × 20 and 25 × 25 cm2 applicators, small and shaped fields at standard SSD. For 10 × 10 cm2 applicator, the investigations of the MU calculations were made at extended SSD. All tests were carried out with electron beam energies of 6, 12, and 18 MeV and with various detectors such as diode, ionization chamber, film and TLDs. For homogeneous phantoms, the agreement between measured and calculated dose distributions of both algorithms was very good as well as in irregular surface phantoms. For heterogeneity phantoms, I found a limitation of GGPB that underestimated the dose distribution near the heterogeneity interface. The eMC calculated distribution results generally agreed much better with the measurements. The relative output factor agreed with measurements within 3%, with the exception of very small and very large field sizes for both electron algorithms. From the results, the eMC is shown to be more accurate to predict dose distribution calculation in heterogeneity and complex geometries under the tested conditions.

Mahidol University. Mahidol University Library and Knowledge Center

Address: NAKHONPATHOM

Email: liwww@mahidol.ac.th

Name: Chumpot Kakanaporn

Role: Thesis Advisors

Created: 2009

Modified: 2553-07-15

Issued: 2010-07-14

วิทยานิพนธ์/Thesis

application/pdf

CallNumber: TH P694c 2009

eng

DegreeName: Master of Science

Level: Master's Degree

Descipline: Medical Physics

Grantor: Mahidol University

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