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Whole Pelvic nodal RT and prostate IGRT :
unsolvable?
Which target for repositioning? (independent
motion)
Ä
TRADE-OFF
If you want to spare more bowels from a large
volume?
A wider margin around the prostate and a smaller
margin around the nodes are required
If you want to spare more rectum from a high dose?
A smaller margin around the prostate and a wider
margin around the nodes are required
If the target is : Prostate (Mobile)
?
0 cm prostate shift resulted in an underdosage of
pelvic nodes by
14%
±6%
If the target is : Pelvis (Less mobile)
?
1 cm prostate shift resulted in an average decrease
of
14%
in D95%
?
Isoshift bone = 30% prostate missed!
Hwang AB, Med Phys 2012
Ferjani S, IJROBP 2014