adaptiveradiationtherapywithtomotherapy-100327113046-phpapp02.pdf

8/14/2019 adaptiveradiationtherapywithtomotherapy-100327113046-phpapp02.pdf

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TomoTherapys Implementation of

Image-guided Adaptive Radiation

Therapy

Katja Langen, PhD

M D Anderson

Cancer CenterOrlando

Research supported by TomoTherapy Inc.


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Todays Lecture

Introduction to helical tomotherapy

Image guidance with TomoTherapy

Adaptive radiation therapy with TomoTherapy


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Introduction to helicalTomotherapy


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TomoTherapy

Helical tomotherapy process to deliver IMRT

Same hardware can be used to image (MVCT)

patient (IGRT)


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TomoTherapy

Patient

Tumor

Healthy Organ

Fan beam,

continuouslyrotates


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TomoTherapy

each beamlet can be on/off

Divides beam into 64 beamlets


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TomoTherapy

Patient

Tumor

Healthy Organ

Fan beam,

continuouslyrotates


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TomoTherapy

Patient

Tumor

Fan beam,

continuouslyrotates


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TomoTherapy

Patient

Tumor

Healthy Organ

Fan beam,

continuouslyrotates


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Fan Beam

400 mm

lateral10, 25, or 50 mm

longitudinal

lateral

longitudinal


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Helical Tomotherapy ?

from: W. Kalender, Computed Tomography: Fundamentals,

System Technology, Image Quality, Applications


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Delivery

- 51 projections per

rotation: 360 /51=7

-Temporal modulation

leaf opening time

during projection


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Delivery Instructions

(Sinograms)

Prostate

Head + Neck

64 Leafs

P

r

oj

e

c

t

i

o

ns

-Typical gantry rotation:

15-20 seconds

-Typical treatment time:

Prostate: 5 Min

H+N: 7 Min


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The TomoTherapy unit at M D Anderson Orlando


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The TomoTherapy unit at M D Anderson Orlando


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Binary MLC(all leafs open during MVCT)

40cm

CTFO

V

85cm

Approximately 50cm

6 MV Accelerator(tuned to 3.5 MV for MVCT)

Primary Collimator( 4 mm Slice Width)

Megavoltage CT images

Courtesy of:

TomoTherapy, Inc.

User can adjust:

-Scan range

-Pitch


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Patient Images: Prostate

Diagnostic (kV) CT Tomotherapy (MV) CT


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Patient Images: Head and Neck

Diagnostic (kV) CT Tomotherapy (MV) CT


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Terminology

Image-guided Radiation Therapy (IGRT):

Use images to position patient

-Portal images, Ultrasound, CT-based

Image-guided Radiation Therapy (IGRT) with

TomoTherapy:

Megavoltage CT (MVCT) based


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Image (MVCT) Quality ?

H li l T th


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AAPM CT Phantom [Cardinal Health, Hicksville, NY].

Noise Uniformity

Spatial Resolution Dosimetry Multiple Scan Average Dose (MSAD) in 20 cm

diameter acrylic phantom

Helical Tomotherapy:

MVCT Imaging Performance Characterization

Meeks et al., Med Phys, 32, pp 2673


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Uniformity


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UniformityMaximum Peripheral to Central Deviation


1005100699.60.551.0AcQSim

512

1027101999.60.892.4

1026101999.60.801.6

1027101999.50.941.0768

1031102199.51.042.4

1028101999.60.901.6

1029102099.51.001.0512

1022101399.51.032.4

1027101999.60.971.6

1025101599.50.991.0256

Mean

Peripheral

"CT"

Mean

Center

"CT"

Uniformity

Index

Maximum

Peripheral

Variation (%)

PitchMatrix

Independ

entofpitc

h/reconmatrix

valuesc

omparabl

etodiagnostic

CTscann

ers


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Spatial Resolution: Qualitative Determination

256x256 matrix 512x512 matrix

768x768 matrix

No holes resolved Visible resolution ~1.5 mm

Visible resolution > 1.75 mm

Visible resolution ~1.25 mm

Meeks et al.,Med Phys, 32, pp 2673


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P ti t I


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Patient Images


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Summary


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Uniformity is comparable to diagnostic CT scanners while noise isworse

Spatial resolution using 512x512 matrix is ~1.5 mm

Dose: ~1 cGy for fine setting (pitch of 1) ; dose decreases withlooser pitch

Image Quality is acceptable for patient alignment, and is alsoacceptable for delineation of many soft tissue structures.

Summary



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Average In-Room Times

5 minutes for setup 3-5 minutes MVCT scan

5 minutes reconstruction and registering MVCTto KVCT and shift patient

5-10 minutes beam on time

5 minutes assist patient out

IGRT


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Prostate IGRT: Helical

Transverse, aligned


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Tomotherapy

g

Prostate IGRT: Helical Sagittal, aligned


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Tomotherapy


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Prostate alignment study


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RT: Marker, Anatomy, Contour

MD: Marker, Anatomy, Contour

112 image pairs

3 patients

Prostate alignment study

Langen et al., IJROBP, 62, pp 1517


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RT vs MD registration

Marker Anatomy Contour

A/P: 1 %

S/I: 2 %Lat.: 1 %

A/P: 5 %

S/I: 10 %Lat.: 0 %

A/P: 17 %

S/I: 31 %Lat.: 3 %

Difference 5 mm



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RT vs MD registration

Marker Anatomy Contour

A/P: 2 %

S/I: 12 %Lat.: 2 %

A/P: 15 %

S/I: 32 %Lat.: 3 %

A/P: 48 %

S/I: 52 %Lat.: 24 %

Difference 3 mm



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Conclusions of alignment study


Implanted marker based alignment have

least inter-user variability

Anatomy-based alignments outperform

contour-based alignments

Head and Neck alignment: bony anatomy


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MVCT

Base of skull

aligned

Spinal Cordnot aligned

Head and Neck alignment: bony anatomy


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IGRT and ART,do we need both ?

Daily-IGRT, why ART ?


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Deformation in the Pelvis

Same patient, different days

Dosimetric consequence ?

Daily IGRT, why ART ?

Progressive deformation


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Barker (2004): 14 H+N patients, 13-20 repeat CT, in-room CT

Barker et al. , IJROBP, 59, pp 960, 2004

Observation of tumor regression



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Barker (2004): 14 H+N patients, 13-20 repeat CT, in-room CT

Barker et al. , IJROBP, 59, pp 960, 2004

Observation of parotid shrinkage and migration

kVCT vs end-of-treatment MVCT


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kVCT vs. end of treatment MVCT

kVCT:

PTVSC



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Adaptive Radiation Therapywith the TomoTherapy

system

Terminology


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Terminology

Adaptive Radiation Therapy (ART):

Use information from images to change subsequent

treatments

-Change margin based on observed setup/organ

motion

-Use images to evaluate dosimetry (dose-guided, dose

compensation)

Adaptive Radiation Therapy (ART) with TomoTherapy:

Using MVCT images to evaluate dosimetry on dailybasis

Adaptive Radiation Therapy:


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Acquire MVCT

Recalculate dose distribution on MVCT

Add dose distribution to calculate cumulative dose

Compare with plan

Adapt plan

need accurate HU

numbers

need deformable

image registration


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Accuracy of MVCT numbers

N d MVCT t l t d it lib ti


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Need MVCT to electron density calibration

kVCT MVCT

RMI, Model 467, CT to electron densityphantom

MVCT t l t d it lib ti


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MVCT to electron density calibration curves

kVCT MVCT

MVCT I t it ?


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MVCT Integrity ?

Does the calibration change with time ?

Does calibration change with phantom arrangement ?

Does the calibration change with MVCT pitch ?

MVCT Integrity ?

?


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Does the calibration change with time ?

MVCT Integrity ?


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Does the calibration change with phantom arrangement ?

MVCT Integrity ?


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Does the calibration change with phantom arrangement ?

MVCT Integrity ?

D th lib ti h ith MVCT it h ?


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Does the calibration change with MVCT pitch ?

Dose re-computation end-to-end tests


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Rigid phantom

Fictitious targetGenerate treatment plan

MVCT scan phantomRe-calculate dose in MVCT

Compare plan DVH with recalculated DVH

Expect agreement !!!

kVCT scan



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all target D95are within 0.5



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Deformed anatomy ?

Plan 2 Plan 2,Deformation 1

Plan 2,Deformation 2

Point of ion chamber measurement



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-10.8-11.5Plan 1, Def 2

+3.2+3.3Plan 2, Def 1

-9.3-10.5Plan 1, Def 2

+2.9+ 2.7Plan 1, Def 1

Re-calc. Diff (%)Meas. Diff (%)

Conclusions


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- MVCT numbers are reproducible

MVCT to electron density calibration is reliable

MVCT images can be used for

reliable dose computations

- Phantom end-to-end test results aretypically

within 1 % of plan results

Langen et al.: Use of mega voltage CT (MVCT) images fordose computations. PMB, 50, pp 4259

Daily-IGRT, why ART ?


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Deformation in the PelvisSame patient, different days


Evaluate dosimetric consequence:


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Dose Re-calculation

Use pre-treatment MVCT

Recalculate plan based on planned MLC pattern

Recalculate Dose on MVCT image



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Evaluate dosimetric consequence

Obtain MVCTDose recalculation

MVCT contours



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Plan DVH

39 true DVHs



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Plan DVH

39 true DVHs

1) Requires manual contouring2) Need deformable image registration to

calculated the cumulative DVH

Deformable image registration


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Relate voxel location x to its location in the second

image (at a later time t) using a displacement

vector u(x,t)

x(x,t)=x+u(x,t)

Algorithm minimizes u and differences in HU units

Lu et al. , Phys Med Biol, 49, pp 3067, 2004

MVCT to kVCT


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deformable image registrationAlgorithm requires same HU for same voxel

in MVCT and kVCT

MVCT are noisier

=> apply edge-preserving smoothing

=> MVCT numbers kVCT numbers

intensity histogram calibration

Lu et al. , Phys Med Biol, submitted, 2006

MVCT to kVCT


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deformable image registrationAlgorithm maps each MVCT voxel to kVCT


Algorithm can map each kVCT voxel to MVCT

can be used for automatic

contouring of MVCT

automatically generated MVCT contours can be

used to visualize deformation map

MVCT to kVCT


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deformable image registration


MVCT to kVCT


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deformable image registrationkVCT:

PTVSC

MVCT:

PTV

SC


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Accuracy of automatic H+N MVCT


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contours ?

kVCT contours:

MVCT contours:

Parotids: Visual inspection of automatic

contours

Accuracy of automatic H+N MVCT


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contours ?Parotids: Visual inspection of automaticcontours

- 6 patients, 150 MVCT scans, 2 physician

Conclusion: The parotid contours generatedby the deformable algorithm correlate with the

location of these structures on the dailyMVCT images.

Submitted toASTRO 06, Manon et al.

Automatic MVCT contouring


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Tx 1 Tx 7 Tx 15kVCT

kVCT contours:

MVCT contours:

Automatic MVCT contouring


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Tx 1 Tx 7 Tx 15kVCT


Dosimetric consequence


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Tx 7

1.4 Gy

DVH


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Clinical example73 year old Head and Neck patient:


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PTV prescription: 70 Gy in 35 fractions

Clinical example


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First 17 fractions:

Plan vs. deformable registration DVH


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after 17 fractions

15 Gy17 Gy

Rt.

Parotid

Lt.

Parotid

Generate adaptive plan


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-Obtain new kVCT scan of patient

-How to transfer dosimetry

information to new kVCT ?

Generate adaptive plan


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-Use kVCT-kVCT deformable

registration to transfer original structures

to second kVCT

-Physician reviewed structures

-Generate new plan Limit dose toover-dosed parotid region

Rt. Parotid DVH (after 17 Txs)


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Low dose0-10 Gy

Medium dose

10-20 Gy High dose> 20 Gy

Dose difference mostly in

10-20 Gy region

Parotid DVH


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Generate contour

that corresponds to

10-20 Gy region

Generate second plan


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First Plan

Second Plan

PAROTID

TARGET

P i l


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Patient completes treatment

Daily scans

Daily deformable registration

FULL COURSE

WHAT IF SCENARIOS.compare


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-Original Plan P1(35)

-Plan 1 delivered for 17 fx + Plan 2 for 18 fx

Planned to deliver with adaptive RT

D1(17)+P2(18)-Actual delivery (Plan 1-17 fx and Plan 2-18 fx)

D1(17)+D2(18)

-without adaptive RT, Plan 1 only D1(35)

What if .. (Rt. Parotid DVH)

100


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0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70

Dose (Gy)

P1(35)


100


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0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70

Dose (Gy)

P1(35)

D1(17)+P2(18)


100


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0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70

Dose (Gy)

P1(35)

D1(17)+P2(18)

D1(17)+D2(18)


100


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0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70

Dose (Gy)

P1(35)

D1(17)+P2(18)

D1(17)+D2(18)

D1(35)

Conclusion


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Opportunities

- Assess consequenceof deformation

- Correct differencesbetween delivered and

planned dose in adaptive

Plan

- When to adapt plan ?

Challenges

- How often ?

- Verify accuracy of

deformable registration

- Shrinking volumes ?

Thanks !MD Anderson: TomoTherapy:

Sanford Meeks Gustavo Olivera


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Sanford Meeks Gustavo Olivera

Tom Wagner Jason Haimerl

Twyla Willoughby Ken Ruchala

Omar Zeidan Weigu Lu

Amish Shah Sam Jeswani

Arati Limaye Quan Chen

Patrick Kupelian Eric Schnarr

Rafael Maon

Daniel Buchholz

Alan Forbes

Wayne Jenkins

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