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The limitations
•
Homogeneous water medium assumed
•
Full scatter condition assumed
5 cm beyond the last position of interest for low energy seed (15
cm geometry)
20 cm beyond the last position of interest for E > 50 keV (40
cm radius geometry)
•
No electrons (Dose vs Kerma)
Dose may not be related to photon fluence close to the source
(e g
60
Co)
. .
•
Full 3D source geometry not taken into account
Close to the source
Extended line sources, …
Shielded applicators or directional sources