DocumentCode :
1741140
Title :
Dynamic wedge versus physical wedge: a Monte Carlo study
Author :
Shih, Rompin ; Li, X. Allen ; Chu, James C H
Author_Institution :
Dept. of Med. Phys., Rush Univ., Chicago, IL, USA
Volume :
3
fYear :
2000
fDate :
2000
Firstpage :
1676
Abstract :
The purposes of this study are (1) to analyze the characteristics of dynamic wedge (DW) and (2) to compare DW with physical wedge (PW) in terms of their differences in spectrum, energy fluence, angular distribution, electron contamination, and dose distributions in inhomogeneous phantom. The EGS4/BEAM Monte Carlo codes were used to simulate the exact geometry of a 6 MV beam generated by a Varian 2100C linac and the DOSXYZ code was employed to calculate 3-D dose distribution in phantom. The DW was simulated according to the segmented treatment tables supplied with the Varian linac. The phase-space data files, which contain all particle information, were obtained at various scoring planes for DW, PW and open fields. These phase-space files are then used for beam characterizations and also used as the input data for the dose calculation in homogeneous and heterogeneous phantoms. The percentage depth dose curves and beam profiles for PW, DW, and open fields were measured and used to verify the Monte Carlo simulations. The simulated results were found to agree with the measurements within 1%. The Monte Carlo calculation shows that, for PW, beam-hardening effect is significant and the beam quality changes across the field in wedged direction, while no such phenomena were observed for DW. The spectrum for contaminated electrons for DW was different from that for PW and the open fried. This results in up to 5% difference on the dose in the build-up region. The different spectra between DW and PW results in noticeable changes on dose distribution near a heterogeneity. This is demonstrated by a calculation with an air slab in place for both DW and PW
Keywords :
Monte Carlo methods; dosimetry; medical computing; photon transport theory; radiation therapy; BEAM code; DOSXYZ code; EGS4 code; Monte Carlo codes; air slab; angular distribution; beam characterizations; beam profiles; beam quality changes; beam-hardening effect; dose distributions; dynamic wedge; electron contamination; energy fluence; heterogeneous phantom; homogeneous phantom; inhomogeneous phantom; open fields; percentage depth dose curves; phase-space data files; photon beam radiotherapy; physical wedge; segmented treatment tables; spectrum differences; Contamination; Electron beams; Geometry; Imaging phantoms; Linear particle accelerator; Monte Carlo methods; Particle beam measurements; Pollution measurement; Slabs; Solid modeling;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Engineering in Medicine and Biology Society, 2000. Proceedings of the 22nd Annual International Conference of the IEEE
Conference_Location :
Chicago, IL
ISSN :
1094-687X
Print_ISBN :
0-7803-6465-1
Type :
conf
DOI :
10.1109/IEMBS.2000.900401
Filename :
900401
Link To Document :
بازگشت