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In phantom determination of collimator scatter factor
1Department of Radiation Oncology, University of Michigan, Ann Arbor 48109-0010, USA.
Medical Physics
|July 1, 1996
Summary
Collimator scatter factor (Sc) was measured in-phantom for 6 and 15 MV photons, yielding results consistent with in-air measurements. This method better reflects patient treatment conditions by measuring scatter within the phantom.
Area of Science:
- Medical Physics
- Radiation Oncology
Background:
- Collimator scatter factor (Sc) is crucial for accurate radiation dose calculations.
- Traditional Sc measurements are performed in air, which may not fully represent in-patient scatter conditions.
Purpose of the Study:
- To measure the collimator scatter factor (Sc) in-phantom at a clinically relevant depth.
- To compare in-phantom Sc measurements with traditional in-air measurements.
- To assess the feasibility of in-phantom Sc measurements for clinical applications.
Main Methods:
- Sc was measured at 10 cm depth in phantom for 6 and 15 MV photons.
- Square collimator settings ranged from 2.5 cm to 40.0 cm.
- Cerrobend blocks were used to define field sizes, with collimator settings varied.
- Corrections for scatter from Cerrobend blocks were applied.
Main Results:
- In-phantom Sc measurements were consistent with in-air measurements (within 0.4%).
- Corrections for Cerrobend scatter were up to 2%.
- The in-phantom method allows measurement of smaller field sizes, limited only by detector size.
Conclusions:
- In-phantom measurement of the collimator scatter factor (Sc) is a viable alternative to in-air measurements.
- This method provides a more realistic representation of scatter conditions during patient treatment.
- The technique facilitates measurements under full scatter conditions, enhancing treatment accuracy.