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Charged Particle Equilibrium
•
only a fraction of electron track deposits
energy in voxel
A
→
dose is low
•
in voxel
B
, a new electron starts but there
is also part of electron track which started
upstream in voxel A
→
dose is higher B
A B C
Charged particle equilibrium (CPE)
exists if for each charged particle with energy
E
leaving a volume
V
, there is an identical particle with same energy
E
entering
V
•
kinetic energies leaving voxel C is balanced
by kinetic energies entering in this volume
→
equilibrium is reached at
C
at C
→
Dose ≈ KERMA
kV Xrays
Lecture 24 MP 501 Kissick 2012