clinical implementation of a dedicated brain treatment planning...
TRANSCRIPT
Clinical implementation of a dedicated brain treatment
planning optimizer for stereotactic treatments:
a new treatment paradigm
Thierry Gevaert, PhD
Coordinator medical physics group
Radiotherapy department
UZ Brussel
UZB approach SRS/FSRT: the Past
forward planning
one isocenter with 5 equally distributed arcs
80 % prescription isodose
frameless approach with CBCT and ExacTrac
20 minutes / one lesion, max. 3 isocenters / day
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UZB approach: Improvement?
Standard of care: multi-isocenter DCA
Points of improvement
planning and treatment efficiency for multiple
(up to 15) metastases
automated treatment planning optimizer
to achieve the best possible plan
user independent
minimize low dose spread
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UZB new approach
Multiple BrainMet Elements (Brainlab AG)
Combining DCA at different table positions
with single-isocenter treatment planning
optimization
Treatment of up to 15 metastases in a single
treatment session of 20-30 min.
Automatic optimization for all metastases
together
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Automatic detection of the contoured lesions
Multiple Brain Met Elements (Brainlab AG)
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Automatic positioning of
the isocenter and treatment arcs
Multiple Brain Met Elements (Brainlab AG)
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Automatic shaping of the MLC
Multiple Brain Met Elements (Brainlab AG)
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This novel software offers the best of both worlds
(i.e., efficient single-isocenter DCA delivery).Gevaert et al. Radiat Oncol 2016;11:13
What about single brain lesions???
4 pi approach
Radiation Oncology 2014, 9:239
4 pi approach
Radiation Oncology 2014, 9:239
Nguyen et al:
The significantly improved dose coverage and high
dose conformity of 4π radiotherapy made it possible to
escalate the GBM prescription doses from 60 Gy to 100 Gy
or to increase the PTV margins while meeting clinical
critical organ dose constraints.
Cranial treatments
Arc trajectory optimization
Relative cost map algorithm
Arc optimization parameters
Importance of penalties
Optimization of table angles from initial value
(quadratic)
Optimization of gantry angles from initial
values (quadratic)
Radiological depth of PTV (linear)
PTV-OAR overlapping beam‘s eye view,
weighted by relative pointdose (linear)
4 pi exotic arcs
Study Aim
Report the first 20 treated patient with the
automated treatment planning solution
Multiple Brain Mets SRS Elements:
Single isocenter and multiple inversely optimized
dynamic conformal arcs (1-15 mets)
Cranial SRS Elements:
Inversely optimized VMAT approach using automated
arc trajectory optimization
Patient specific QA: Evaluation Gafchromic
EBT3 film vs. portal imager
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Population / constraints
1- 12 brain mets (n = 16)
Targeted on MRI and CT
PTV margin of 2 mm
Assessment of adequate margin
on going
1 x 20 Gy at periphery of the
lesion
No hard constraint for Dmax
in the lesion
Single lesion surrounded by
OAR (n = 4)
Dose prescription is lesion
dependent
OAR constraint dependent on
prescribed dose
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Multiple Brain Mets SRS Elements Cranial SRS Elements
Protocol management: MMET
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Protocol management: MMET
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Protocol management: MMET
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Arc setup management: MMET
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Arc setup management: MMET
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Starting up the plan: MMET
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Automatic positioning of
the isocenter and treatment arcs
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Automatic positioning of
the isocenter and treatment arcs
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Results
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Patients Lesions Number of arcs Number of couch angles
1 2 7 5
2 1 6 4
3 1 6 4
4 2 6 4
5 1 6 4
6 2 6 4
7 3 9 7
8 1 6 4
9 2 6 4
10 2 7 4
11 3 8 7
12 3 5 4
13 5 6 6
14 12 10 10
15 1 6 4
16 2 6 4
Average 3 7 5
SD 3 1 2
Protocol management: Cranial SRS
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Protocol management: Cranial SRS
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Arc setup management: Cranial SRS
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Arc setup management: Cranial SRS
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Arc setup management: Cranial SRS
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Arc setup management: Cranial SRS
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Cranial SRS: example
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Cranial SRS: example
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Patient specific QA
Patient specific QA: Evaluation Gafchromic
EBT3 film vs. portal imager
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Gafchromic film
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Gafchromic film
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EPID
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Results
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Patients Lesions Films Epid
1 2 98,1 97,3
2 1 99,2 100
3 1 88,1 98,5
4 2 97,4 96,3
5 1 99,2 99,7
6 2 99,7 99,8
7 3 99,1 100
8 1 98,2 98,7
9 2 98,8 99,1
10 2 98,7 97,9
11 3 99,1 98,3
12 3 97,9 97,7
13 5 99,1 99,4
14 12 98,1 100
15 1 98,7 98
16 2 98,4 97,9
Average 98,1 98,7
SD 2,4 1,0
1 1 98,6 99,1
2 1 98,2 98,9
3 1 98,7 99,2
4 1 98,6 98,7
Cra
nia
lM
ultip
le m
ets
Gamma 2%/2mm Local
Conclusion
The automated dose planning Elements
Revive dynamic conformal arcs as the paradigm for
linac-based stereotactic radiosurgery of multiple brain
metastases
at the same time implements an improved VMAT
approach for single lesions with the use of automated
arc trajectory optimization
This study shows
the clinical implementation in routine environment with an
improved planning and treatment efficiency.
Patient specific QA
Portal imager can be adequate alternative when
treatment technique is well established
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Acknowledgements