500-501 / 3107
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11/22/11
Measurement
(Film,EPID)
Calculation
(TPS,PDIP)
Gamma Value Calculation
Gamma Value
Image
x =
MLC Outline Mask or
10% of MAX threshold
(PTV oriented)
Passing rate
Percentage of pixels having
gamma value <1 in open MLC area
Compression of a gamma value image into one single quality value for IMRT delivery
Region of interest
Example: Passing rate
-Passing rate is always related to its Region of interest.
-Information about the distributions of erroneous pixels is lost
-Very sensitive parameter
Error detection and acceptance criteria