1
Q
AAPM report for IMRT
A
TG120 dosimetry tools and techniques for IMRT
2
Q
differences between 3DCRT and IMRT dosimetry- challenges for IMRT
A
IMRT has to focus on cumulated dose not on QA of a single segment
- IMRT: fluence is varied during treatment so requires integrative dosimetric techniques
- IMRT- sometimes independent dose calculation methods are used as QA
- have to consider oblique-incidence response of clyndrical ion chambers for non-coplanar beams
- Volume averaging is an issue for detectors in small fields- dose will be underestimated due to averaging over the entire size of the detector
- if measuring profiles of dose distributions with rapidly spatially varying doses, the shape of the dose distribution will be blurred by volume averaging – use higher spatial resolution detector if accurate measurement of profile shape is needed
- small ion chamber is more sensitive to position errors
