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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 Radiol+Oncol
2015 ; 49
(3
): 299-306
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Rounded leaf end effect of multileaf collimator on penumbra width and radiation
field offset: an analytical and numerical study
#MMPMID26401137
Zhou D
; Zhang H
; Ye P
Radiol Oncol
2015[Sep]; 49
(3
): 299-306
PMID26401137
show ga
BACKGROUND: Penumbra characteristics play a significant role in dose delivery
accuracy for radiation therapy. For treatment planning, penumbra width and
radiation field offset strongly influence target dose conformity and organ at
risk sparing. METHODS: In this study, we present an analytical and numerical
approach for evaluation of the rounded leaf end effect on penumbra
characteristics. Based on the rule of half-value layer, algorithms for leaf
position calculation and radiation field offset correction were developed, which
were advantageous particularly in dealing with large radius leaf end. Computer
simulation was performed based on the Monte Carlo codes of EGSnrc/BEAMnrc, with
groups of leaf end radii and source sizes. Data processing technique of curve
fitting was employed for deriving penumbra width and radiation field offset.
RESULTS: Results showed that penumbra width increased with source size. Penumbra
width curves for large radius leaf end were U-shaped. This observation was
probably related to the fact that radiation beams penetrated through the proximal
and distal leaf sides. In contrast, source size had negligible impact on
radiation field offset. Radiation field offsets were found to be constant both
for analytical method and numerical simulation. However, the overall resulting
values of radiation field offset obtained by analytical method were slightly
smaller compared with Monte Carlo simulation. CONCLUSIONS: The method we proposed
could provide insight into the investigation of rounded leaf end effects on
penumbra characteristics. Penumbra width and radiation field offset calibration
should be carefully performed to commission multileaf collimator for intensity
modulated radiotherapy.