Onboard imaging modality for IGRT - Login...

1

Tetrahedron Beam Computed Tomography Based On Multi-Pixel X-Ray Source and Its Application in Image Guided Radiotherapy

Tiezhi Zhang PhD

Advanced X-ray imaging Lab Department of Radiation Oncology

Department of Radiation Oncology

Financial disclosure

bull Patent royalty from AccuRay

bull Research grants from NIH and DOD


Onboard imaging modality for IGRT

Convenient to use Stereoscopic realtime imaging Soft tissue contrast and accurate HU

Inconvenient and no 2D realtime imaging No 3D imaging Poor image quality

2


Limitations of CBCT in IGRT

CBCT FBCT

Lack of soft tissue contrast and strong image artifact do not support deformable image registration and auto-segmentation which are mandatory in online and offline adaptive radiotherapy

Manual

Auto

T Zhang et al ldquoAutomatic delineation of online head and neck computed tomography images toward online adaptive radiotherapyrdquo Int J Radiation Oncology Biol Phys 68(2) 522-530


Limitations of CBCT in image guided proton therapy (IGPT)

bull Critical organs are often located at the distal end of proton beams

bull Online dose calculation is necessary during IGPT treatment

bull Accurate HU is very important for proton dose calculation

bull CBCT does not produce accurate CT number for proton dose calculation


kV x-ray beam

MV x-ray beam

Target

EPID

FPI

Drawback of CBCT in real-time imaging

3


Tetrahedron Beam Computed Tomography (TBCT)

Zhang T Schulze D Xu X amp Kim J 2009 Tetrahedron beam computed tomography (TBCT) a new design of volumetric CT

system Phys Med Biol 54 3365-78


Principle of volumetric imaging by TBCT


k = 1 k = 2 k = 3

y(k)

h

s

d

Simulated Radiographic Imaging

Principle of planar imaging by TBCT

4


Advantages of TBCT

1 Scatter rejection

2 Compact geometry

3 Comparable to high quality discrete CT detectors and photon counting detectors

4 Lower x-ray exposure


SART FDK

Existing problem 1 Approximate cone reconstruction artifact

Images show 24degcone angle XVIrsquos maximum cone angle = 114 degree


bull TBCT is limited by gantry rotation speed

bull Reconstructed images show blurring due to inconsistent projection data

bull Respiration-correlated FDK (rc-FDK) contains streak artifacts due to few

projection angles

Solution 4D iterative reconstruction

Blurred FDK

Existing problem 2 motion artifact

rc-FDK

5


4D iterative image reconstruction

Richard Pham et al Joint Image Domain Motion-Estimation and Motion Compensation for 4D Cone Beam Image Reconstruction Thursday 730-930

Other references 1 Jing Wang et al ldquoSimultaneous motion estimation and image reconstruction (SMEIR) for 4D CBCTrdquo Med Phys 40(10) 101912

2 GH Chen et al ldquoPrior image constrained compressed sensing (PICCS) a method to accurately reconstruct dynamic CT images from highly undersampled projection data

setsrdquo Med Phys 2008 35(2) 660-3


Dual-source Dual Detector TBCT Detector arrays x2

Sou

rce

arra

y2

Sou

rce

arra

y

1

StereoscopicFOV

So

urc

e a

rra

ys

x2

Detector array 1

Detector array 2

StereoscopicFOV

Phys Med Biol 2014 Feb 759(3)615-30 Dual source and dual detector arrays tetrahedron beam

computed tomography for image guided radiotherapy Kim J1 Lu W Zhang T


kV x-ray beam

MV x-ray beam

Target

EPID

FPI

Limitation of CBCT in real-time imaging

6


Dual-source TBCT for IGRT

Kim J Lu W Zhang T ldquoDual source dual detector Tetrahedron Beam Computed Tomography for Image guided radiotherapyrdquo Physics in Medicine and Biology 2014 59(3)615-30


Dual-source TBCT on Linac

Convenient to use

Stereoscopic realtime imaging

Soft tissue contrast and accurate HU


Dual-source TBCT stereoscopic imaging


7


TBCT benchtop system with MPFEX source

MPFEX tube

Multi-slot collimator

Rotation stage

5 row CT detector


Collimator design

~1

5 c

m

So

urc

e a

rra

y to

tal ~

50

-75

pix

els

4m

m

Multi-row CT

detector array

Focus

plane 1

Focus

plane 2

Multi-slot

collimator

Source to detector distance ~150 cm

Rotation

axis


Image quality comparison Philips Fan beam CT TBCT benchtop Elekta CBCT

Rooms to improve for TBCT benchtop

1 Higher tube power

2 Small detector pixel size (current 254mm)

3 Small focal spot size (current 1x2 mm2)

8


Thermionic cathodes

Oxide cathode in small pulse ~1s

Micro-rectangular dispenser cathode

Co

nti

nu

ou

s


Focal spot size measurement

Focal spot size ~05-1 mm 90 kVp ~40 mA


TBCT tube power requirement

Assuming the same source distance detector width and source filtration as helical CT The tube power would be lt10 kW or anode current less than 100 mA With noise suppression algorithms tube power may be relaxed under 5kW

119879119861119862119879 119875119900119908119890119903

119865119861119862119879 119875119900119908119890119903=

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119865119861119862119879

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119879119861119862119879asymp02

FBCT ~10 second to scan 15 cm TBCT ~60 second gantry rotation

9


Thermal management for MPTEX source

bull Focal spot power density is the major power limiting factor

Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)


Energy deposition in W target

MC simulation of 100 keV electrons penetration in tungsten using Geant4

Energy deposition of electrons in tungsten

Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]

Backscattered electrons

0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV


10 pulses Peak Temp = 2152degC

Focal spot temperature for short pulses

1 pulse Peak Temp = 2000degC

Maximum Temperature on Target

10


Maximum Power vs Pulse Width

bull Maximum temperature spikes is limited to 2000degC

0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]

Pulse Width [micros]

FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros

150 micros 280 micros

670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905

Target temperature rise is also given by Oosterkamp et al

W J Oosterkamp ldquoThe heat dissipation in the anode of an X-ray tuberdquo Philiips Res vol3 pp 49-59 1985


Composite x-ray target material


Summary

bull Tetrahedron Beam CT is a new VCT geometry based on linear x-ray source array

bull TBCT immune to the problems of CBCT

bull TBCT can produce diagnostic grade CT images with good soft tissue contrast for adaptive radiotherapy

bull TBCT can be used for online proton dose calculation

bull TBCT can generate fast planar images for realtime imaging

bull Multi-pixel x-ray source power is limited by the focal spot power density

bull MPTEX source is able to produce sufficient power for slow gantry TBCT especially with noise suppression algorithms

11


Acknowledgement

bull Joshua Kim Henry Ford Hospitals

bull Xiaochao Xu Toshiba Medical Research Institute

bull Rock Mackie University of Wisconsin Madison

bull Weiguo Lu UT Southwestern

bull Colleagues students and postdocs at Wash U

Research are supported by DOD LCRP W81XWH-16-LCRP-CA NIH 1R21CA130330-01A1 NIH contract HHSN261201100045C


THANK YOU

2


Limitations of CBCT in IGRT

CBCT FBCT

Lack of soft tissue contrast and strong image artifact do not support deformable image registration and auto-segmentation which are mandatory in online and offline adaptive radiotherapy

Manual

Auto

T Zhang et al ldquoAutomatic delineation of online head and neck computed tomography images toward online adaptive radiotherapyrdquo Int J Radiation Oncology Biol Phys 68(2) 522-530


Limitations of CBCT in image guided proton therapy (IGPT)

bull Critical organs are often located at the distal end of proton beams

bull Online dose calculation is necessary during IGPT treatment

bull Accurate HU is very important for proton dose calculation

bull CBCT does not produce accurate CT number for proton dose calculation


kV x-ray beam

MV x-ray beam

Target

EPID

FPI

Drawback of CBCT in real-time imaging

3








k = 1 k = 2 k = 3

y(k)

h

s

d



4


Advantages of TBCT

1 Scatter rejection

2 Compact geometry




SART FDK







projection angles


Blurred FDK


rc-FDK

5









Sou

rce

arra

y2

Sou

rce

arra

y

1

StereoscopicFOV

So

urc

e a

rra

ys

x2

Detector array 1

Detector array 2

StereoscopicFOV




kV x-ray beam

MV x-ray beam

Target

EPID

FPI


6






Convenient to use






7



MPFEX tube


Rotation stage

5 row CT detector


Collimator design

~1

5 c

m

So

urc

e a

rra

y to

tal ~

50

-75

pix

els

4m

m

Multi-row CT

detector array

Focus

plane 1

Focus

plane 2

Multi-slot

collimator


Rotation

axis




1 Higher tube power



8


Thermionic cathodes



Co

nti

nu

ou

s







119879119861119862119879 119875119900119908119890119903

119865119861119862119879 119875119900119908119890119903=

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119865119861119862119879

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119879119861119862119879asymp02


9




Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)





Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]


0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV






10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

3








k = 1 k = 2 k = 3

y(k)

h

s

d



4


Advantages of TBCT

1 Scatter rejection

2 Compact geometry




SART FDK







projection angles


Blurred FDK


rc-FDK

5









Sou

rce

arra

y2

Sou

rce

arra

y

1

StereoscopicFOV

So

urc

e a

rra

ys

x2

Detector array 1

Detector array 2

StereoscopicFOV




kV x-ray beam

MV x-ray beam

Target

EPID

FPI


6






Convenient to use






7



MPFEX tube


Rotation stage

5 row CT detector


Collimator design

~1

5 c

m

So

urc

e a

rra

y to

tal ~

50

-75

pix

els

4m

m

Multi-row CT

detector array

Focus

plane 1

Focus

plane 2

Multi-slot

collimator


Rotation

axis




1 Higher tube power



8


Thermionic cathodes



Co

nti

nu

ou

s







119879119861119862119879 119875119900119908119890119903

119865119861119862119879 119875119900119908119890119903=

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119865119861119862119879

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119879119861119862119879asymp02


9




Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)





Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]


0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV






10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

4


Advantages of TBCT

1 Scatter rejection

2 Compact geometry




SART FDK







projection angles


Blurred FDK


rc-FDK

5









Sou

rce

arra

y2

Sou

rce

arra

y

1

StereoscopicFOV

So

urc

e a

rra

ys

x2

Detector array 1

Detector array 2

StereoscopicFOV




kV x-ray beam

MV x-ray beam

Target

EPID

FPI


6






Convenient to use






7



MPFEX tube


Rotation stage

5 row CT detector


Collimator design

~1

5 c

m

So

urc

e a

rra

y to

tal ~

50

-75

pix

els

4m

m

Multi-row CT

detector array

Focus

plane 1

Focus

plane 2

Multi-slot

collimator


Rotation

axis




1 Higher tube power



8


Thermionic cathodes



Co

nti

nu

ou

s







119879119861119862119879 119875119900119908119890119903

119865119861119862119879 119875119900119908119890119903=

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119865119861119862119879

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119879119861119862119879asymp02


9




Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)





Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]


0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV






10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

5









Sou

rce

arra

y2

Sou

rce

arra

y

1

StereoscopicFOV

So

urc

e a

rra

ys

x2

Detector array 1

Detector array 2

StereoscopicFOV




kV x-ray beam

MV x-ray beam

Target

EPID

FPI


6






Convenient to use






7



MPFEX tube


Rotation stage

5 row CT detector


Collimator design

~1

5 c

m

So

urc

e a

rra

y to

tal ~

50

-75

pix

els

4m

m

Multi-row CT

detector array

Focus

plane 1

Focus

plane 2

Multi-slot

collimator


Rotation

axis




1 Higher tube power



8


Thermionic cathodes



Co

nti

nu

ou

s







119879119861119862119879 119875119900119908119890119903

119865119861119862119879 119875119900119908119890119903=

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119865119861119862119879

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119879119861119862119879asymp02


9




Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)





Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]


0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV






10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

6






Convenient to use






7



MPFEX tube


Rotation stage

5 row CT detector


Collimator design

~1

5 c

m

So

urc

e a

rra

y to

tal ~

50

-75

pix

els

4m

m

Multi-row CT

detector array

Focus

plane 1

Focus

plane 2

Multi-slot

collimator


Rotation

axis




1 Higher tube power



8


Thermionic cathodes



Co

nti

nu

ou

s







119879119861119862119879 119875119900119908119890119903

119865119861119862119879 119875119900119908119890119903=

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119865119861119862119879

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119879119861119862119879asymp02


9




Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)





Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]


0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV






10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

7



MPFEX tube


Rotation stage

5 row CT detector


Collimator design

~1

5 c

m

So

urc

e a

rra

y to

tal ~

50

-75

pix

els

4m

m

Multi-row CT

detector array

Focus

plane 1

Focus

plane 2

Multi-slot

collimator


Rotation

axis




1 Higher tube power



8


Thermionic cathodes



Co

nti

nu

ou

s







119879119861119862119879 119875119900119908119890119903

119865119861119862119879 119875119900119908119890119903=

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119865119861119862119879

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119879119861119862119879asymp02


9




Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)





Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]


0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV






10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

8


Thermionic cathodes



Co

nti

nu

ou

s







119879119861119862119879 119875119900119908119890119903

119865119861119862119879 119875119900119908119890119903=

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119865119861119862119879

119878119888119886119899119899119894119899119892 119879119894119898119890 119900119891 119879119861119862119879asymp02


9




Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)





Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]


0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV






10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

9




Anodebody

Focal spot(target)

Tube housing

conduction

Radiation

(rotating anode)

Atmosphere

convection

Conduction

(fixed anode)





Tungsten

100 keV e- beam

0 1 2 3 4 5 6 7 8 9 10 [microm]


0

02

04

06

08

1

12

0 2 4 6 8 10 12 14Norm

aliz

ed E

nerg

y D

epositio

n

Depth [microm]

80 keV

100 keV

120 keV






10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

10




0

2

4

6

8

10

12

14

16

0 100 200 300 400 500 600 700 800

Pow

er

[kW

]


FEA Model

Theoretical

19 micros

23 micros 30 micros

40 micros

50 micros

80 micros


670 micros

Δ119879 = 2119875

119860

119905

120587λ120588119888

or

119875 = Δ119879119860

2

120587λ120588119888

119905






Summary








11


Acknowledgement








THANK YOU

11


Acknowledgement








THANK YOU

Onboard imaging modality for IGRT - Login...

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Transcript of Onboard imaging modality for IGRT - Login...