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Choreographing couch, collimator
an gan ry mo on n ra a on
deliverCollaboration of the following people at MSKCC:
Pengpeng Zhang
Yingli YangGig Mageras
Margie Hunt
Jian in Xion
Jie Yang
Maria Chan
Josh Yamada
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in VMAT for paraspinal SBRT
2nd
project was Choreographing couch,
VMAT
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Collimator trajectory in VMAT for paraspinal SBRT
Motivation
Improve dosimetric qualityo Increase target coverage
o
Preserve better critical organ sparing
Explore additional mechanical freedom
IJROBP. 2010; 77(2):591-9.
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Collimator trajectory in VMAT for paraspinal SBRT
Optimize collimator trajectory based on
S nchronize collimator rotation with MLC
motion, gantry rotation, and dose rate
modulation
Development and evaluation in paraspinal
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Collimator trajectory in VMAT for paraspinal SBRT
Why collimator matters?
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Determine collimator trajectory via
Collimator trajectory in VMAT for paraspinal SBRT
principle component analysis
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Collimator trajectory in VMAT for paraspinal SBRT
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Collimator trajectory in VMAT for paraspinal SBRT
Paraspinal SBRT study
1.Retrospective study following
MSKCC paraspinal SBRT protocol
2.Prescription dose: 24Gy to tumor,
cord maximum dose
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Collimator trajectory in VMAT for paraspinal SBRT
All protocol constraints are met with all three plans
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Dosimetr Results:
Collimator trajectory in VMAT for paraspinal SBRT
Coll-VMAT vs VMAT vs IMRT
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-
Collimator trajectory in VMAT for paraspinal SBRT
Again, Why collimator angle
ma ers
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Collimator trajectory in VMAT for paraspinal SBRT
e uce w
Technique Average MUs
Coll VMAT 5164
VMAT 4868
IMRT 13283
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Collimator trajectory in VMAT for paraspinal SBRT
ummary
Coll-vmat provides an additional degreeof freedom
Dosimetric quality of VMAT plans is as
good or better as fixed gantry IMRT forparaspinal SBRT
ord dose lower with oll VMAT than
IMRT
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Choreographing couch,
gantry and collimator
We develo ed a software to facilitate the selection and
optimization of non-coplanar VMAT arcs
e eva ua e e ec n que n e rea men o
tumors
IJROBP. 2011; 80(4):1238-47
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Selecting couch/gantry trajectory
PTVEye
based on PTV/OAR areaoverlap
Brainstem
Cord
cLgcL ,,
i OARiPTVi
i
gcAgcA ,,
,
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Target/OAR Overlap Map
CA=-
60;
GA=-60
CA=45;
GA=100for particular patient
CA=0;
GA=-150
CA=85;GA=60
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Optimization of Couch/gantry Trajectory
,those with minimum overlap score.
Algorithm must remove combos in the forbidden zone collisions areas
Link and extend small arcs to create lon er arcs
Smooth arcs to accommodate mechanical constraints and limitations
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Adding optimized Collimator Trajectories
137o
80o
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Non-coplanar VMAT Delivery Using
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NS Radiotherapy Planning & Comparison
Ten CNS cases, fourteen tumors, three with dose painting,
Treatment techniques
IMRT: 4-6 non-coplanar beams
VMAT: 1-4 arc pairs (orthogonal collimator trajectories)
Std-VMAT: static couch and collimator
Tra-VMAT: d namic couch and collimator
Evaluate:
arge coverage
maximum/mean dose to OARs.
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Plan EvaluationTra Vmat
an ar
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TraTra--VMAT vsVMAT vs IMRT vs StdIMRT vs Std--VMATVMAT
Tra-VMAT Std-VMAT IMRT
PTV Dmin 94.1 16.4% 93.1 17% 87.9 18.1%
ra ns em mean . . . . . .
Chiasm Dmax 76.9 35.8% 78.5 36% 78.2 35.9%Chiasm Dmean 61.6 34.1% 64.2 34.1% 65.9 34.1%
Optical nerve Dmax 57.1 33.3% 59.4 32.3% 63.4 30.6%
Cochlea Dmax 50.9
39.7% 52.3
38.9% 59.3
33.7%mean . . . . . .
MU 614 419 622 446 1262 783
ra n cm Brain V70%(cm3) 173 71 200 91 163 72
(medianSTD)
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SummarySummary
Tra-VMAT vs IMRT
Higher PTV minimum dose, lower dose to brainstem,chiasm, optical nerve, and cochlea
improved treatment efficiency (by 50%)
Tra-VMAT vs Std-VMAT Better target conformality (ie lower brain dose)
Lower dose to brainstem, chiasm, and optical nerve
Superior mechanical flexibility of TrueBeam transforms to
better plan quality
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Future endeavors at our intuition
1) Jaw tracking change jaws per control point
A) To reduce leakage between parked leaves in VMAT
delivery.
B) To reduce the need to split IMRT beams
2) Target motion tracking
A) Collimator trajectory to aid MLC target tracking.