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J Korean Soc Ther Radiol > Volume 14(4); 1996 > Article
Journal of the Korean Society for Therapeutic Radiology 1996;14(4): 333-338.
The Sosimetric Effects on Scallop Penumbra from Multi-leaf Collimator by Daily Patient Setup Error in Radiation Therapy with Photon
Byong Yong Yi
1Department of Radiation Oncolog, Asan Medical Center, College of Medicine University of Ulsan, Korea.
2Ratiation Oncology, College of Medicine, Inha University, Korea.
ABSTRACT
PURPOSE:
To evaluate the clinical implications of scallp penumbra width that comes from multileaf collimator(MLC) effect by the daily routine patient setup error.
MATERIALS AND METHODS:
The angles of 0degree, 15degree, 30degree, 45degree, 60degree and 75degree inclined-radiation blocked fields were generated using the both conventional cerrobend block and the MLC. Film dosimetry in the phantom were performed to measure penumbral widths of differences between the dose distributions from the cerrobend block and those of respect the MLC. The patient setup error effect on scallop penumbra was simulated with respect to the table of setup error distribution. Same Procedures are repeated for the cerrobend block generated field.
RESULTS:
There are penumbral widths of to 3mm difference between the dose distributions from two kinds of field shaping tools, the conventional block and the MLC with 4mm setup error model and resolution of 1cm leaf at the isocenter.
CONCLUSION:
We need not additive margin for MLC, if planning target bolume is selected according to the recommendation of ICRU 50. For particular cases, we can include the target volume with less than 3mm additive margin.
Key Words: MLC(Multi-leaf Collimator), Penumbra, Setup Error
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