Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of...
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![Page 1: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/1.jpg)
Simplified IMRT Plans Can Be Delivered with Conventional Jaws
Ping Xia, Ph.D.
University of California
San Francisco
![Page 2: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/2.jpg)
Premise of IMRT
• IMRT plans are too complicated, not intuitive, requiring a lot of extra resources- software, hardware, and human.
• IMRT plans use too many small segments and small MUs, overly stretching the limitation of Linac stability, and the initial design of MLCs.
![Page 3: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/3.jpg)
Premise of IMRT
• IMRT plans are delivered with a prolonged time, resulting in biological disadvantages for tumor control.
• IMRT plans requires a lot more MUs than the conventional CRT plans, increasing the total body dose and the requirement of room shielding.
![Page 4: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/4.jpg)
Are Complicated IMRT Plans Necessary?
• Complicated IMRT plans are due to the use of two-step optimization.
• It first optimizes ideal beam profiles, without considering delivery constraints.
• Then it converts the optimized profiles into deliverable MLC shapes (segments).
![Page 5: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/5.jpg)
How Simply They Can Be?
• For typical H&N plans, the number of segments can be reduced from 140-120 segment to 50-60 segments.
• For typical prostate + pelvic lymph node plans, the number of segments can be reduced from 80 segments to 40 segments.
![Page 6: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/6.jpg)
One Step Optimization
• Directly optimize the shapes and weightings for a given number of segments,
• This method is often referred to as Direct Aperture Optimization (DAO).
• DAO was first proposed by Cedric Yu’s group• This method has been first implemented in
Prowess Planning System.• A similar method also has been implemented in
ADAC planning system, referred to as DMPO.
Med. Phys. 29 1001-1018 (2002)
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Prostate + Pelvic Lymph Nodes
Average Plan Quality Indices
0.8
0.825
0.85
0.875
0.9
10 levels 5 levels 3 levels DMPO
Trial
Hom
ogen
eity
Ind
ex
1
2
3
4
5
Con
form
alit
y In
dex
H.I.
C.I.
One Step
Average Plan Quality Indices
0.8
0.825
0.85
0.875
0.9
10 levels 5 levels 3 levels DMPO
Trial
Hom
ogen
eity
Ind
ex
1
2
3
4
5
Con
form
alit
y In
dex
H.I.
C.I.
One Step
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Prostate + Pelvic Lymph Nodes
0
30
60
90
120
150
180
10 levels 5 levels 3 levels DMPO
Trial
Seg
men
ts/F
ract
ion
600
700
800
900
1000
Mon
itor
Un
its/
Fra
ctio
n Segments
MU
Average Number of Segments and MU per Fraction
One Step0
30
60
90
120
150
180
10 levels 5 levels 3 levels DMPO
Trial
Seg
men
ts/F
ract
ion
600
700
800
900
1000
Mon
itor
Un
its/
Fra
ctio
n Segments
MU
Average Number of Segments and MU per Fraction
One Step
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3 levels
5 levels10 levels
One Step Opt
58 Gy54 Gy48.6 Gy35 Gy
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10 levels 5 levels
3 levels One Step Opt
58 Gy54 Gy48.6 Gy35 Gy
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Jaws Only Delivery
• The algorithm of using conventional Jaws to deliver IMRT fields was first proposed by Dai and Hu’s group.
• The algorithm attempted to convert intensity profiles obtained by the conventional two-step optimization using jaws only method
• For a typical prostate and a NPC case, they found that the total number of segments was 147, 426 with jaw only vs 40, 69 with MLC delivery, respectively.
Medical Physics, Vol. 26, (1999)
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MLC Plan (21 segs)
Jaw Only Plan (28 segs)3D Plan
78 Gy,72 Gy,65 Gy,50 Gy35 Gy
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78 Gy,72 Gy,65 Gy,50 Gy35 Gy
MLC Plan (21 segments)
Jaw Only Plan (28 Segs)3D Plan
![Page 14: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/14.jpg)
(b) COIN
0.4
0.5
0.6
0.7
0.8
0.9
1.0
MLC-3AJO-4A
CO
IN v
alu
e
3D
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0 10 20 30 40 50 60 70 800
20
40
60
80
100V
olum
e [%
]
Dose [Gy]
3DJO-4AMLC-3A
0 10 20 30 40 50 60 70 800
20
40
60
80
100
0 10 20 30 40 50 60 70 800
20
40
60
80
100V
olum
e [%
]
Dose [Gy]
3DJO-4AMLC-3A
(a) PTV
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0 10 20 30 40 50 60 70 800
20
40
60
80
100
Vol
ume
[%]
Dose [Gy]
3DJO-4AMLC-3A
0 10 20 30 40 50 60 70 800
20
40
60
80
100
0 10 20 30 40 50 60 70 800
20
40
60
80
100
Vol
ume
[%]
Dose [Gy]
3DJO-4AMLC-3A
(b) Rectum
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(c) Bladder
0 10 20 30 40 50 60 70 800
20
40
60
80
100V
olu
me
[%]
Dose [Gy]
3DJO-4AMLC-3A
0 10 20 30 40 50 60 70 800
20
40
60
80
100
0 10 20 30 40 50 60 70 800
20
40
60
80
100V
olu
me
[%]
Dose [Gy]
3DJO-4AMLC-3A
(c) Bladder
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(a) MU
300
400
500
600
700
800
MU
va
lue
pe
r fr
act
ion
MLC-3AJO-4A3D
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MLC-54 segs Jaw only -63 segs
70 Gy, 59.4 Gy, 54 Gy, 45 Gy
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MLC-54 segs Jaw only -63 segs
70 Gy, 59.4 Gy, 54 Gy, 45 Gy
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0
20
40
60
80
100
120
0 20 40 60 80
Dose (cGy)
Vo
leu
me
(%
)
PGTV (Jaw)
pCTV(Jaw)
pGTV(MLC)
pCTV (MLC)
Tumor Target Dose Volume Histograms
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Brain Stem DVHs
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70 80
Dose (cGy)
Vo
leu
me
(%
)
Jaw
MLC
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RT-Parotid DVHs
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70 80
Dose (cGy)
Vo
leu
me
(%
)
Jaw
MLC
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Chiasm Dose Voluem Histograms
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70 80
Dose (cGy)
Vo
leu
me
(%
)
Jaw
MLC
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Conclusion (1)
• For complicated cases, inverse planning is simpler than 3D-CRT planning.
• It is possible to simply IMRT plans while keeping the same plan quality and improving delivery efficiency.
• The key to simply IMRT plans is to use one step optimization method.
![Page 26: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/26.jpg)
Conclusion (2)
• Using one step optimization method, the conventional jaws can be used for IMRT delivery while keeping the delivery time within 15-20 minutes.
• Inverse planned Jaw only IMRT plans are better than 3D CRT plans.
• Jaw only IMRT plans are clinical achievable without significantly increasing hardware resource.
![Page 27: Simplified IMRT Plans Can Be Delivered with Conventional Jaws Ping Xia, Ph.D. University of California San Francisco.](https://reader034.fdocuments.in/reader034/viewer/2022051416/56649e5f5503460f94b5a0da/html5/thumbnails/27.jpg)
Acknowledgement
Yongbok Kim, Ph.D.
Guangwei Mu, Ph.D
Erica Ludlum, M.S.
Prowess Inc.
Siemens Medical Solutions