Advanced Brachytherapy Physics - Vienna 2016

Multicenter Center study of inter-/intrafraction variations for target and OARs in cervix BT

 D 90 [%] (fixed plan, variable anatomy)

 D 2cm³ between 2 acquisitions [%] (fixed plan, variable anatomy)

bladder

rectum

sigmoid/bowel

CTV HR

Mean median SD

mean median SD mean median SD mean

median

SD

20.3%

22.0%

26.8%

13.1%

4.5 4.1

1.6 -0.9

-1.1

-1.7 -4.3 -0.8

total

2.7 1.5 1.3 1.5 3.9 0.0

Intraaplication interapplication

17.7 22.3

20.5 23.2

23.5 30.2

10.8 15.1

3.8 5.8

2.3 5.2

-2.3

-3.7

-2.5

6.8

3.7

0.4

Random uncertainties (1SD) of physical dose per BT fraction can be

~ 10% for CTV HR

D 90 (contouring uncertainty ( Petric, Hellebust R&O 2013 ))

~

20% f bl dd

t or a er, rec um 2cm³ D

~ 30% for sigmoid D 2cm³ No correlation with time between images was detected!

Conclusion: As long as there is no direct imaging and dose reporting at the time of irradiation (online i i ifi ti ) h t t 20 30% d i t i t i t f D f OAR f h mag ng, ver ca on , we ave o expec - os me r c uncer a n y or 2cm³ or s or eac fraction, between prescribed and delivered dose.