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The intensity modulation makes it particularly difficult to place the dosimeter in the
field. In order to avoid large uncertainties in the measurement
high gradients
should be avoided
(volume averaging, sensitive to positioning of dosimeter).
CAX
placement is in most cases not possible. Other positions are impractical in
clinical routine
Beam intensity
OK
not OK
Classic entrance dose
in vivo
dosimetry and IMRT ?
Open field or mild intensity modulation
Strong intensity modulation
Where to put the diode/MOSFET/TLD in an intensity modulated field?
not OK