DosimetriccomparisonofSBRTforDosimetric …chapter.aapm.org/swaapm/Past/Fall2009/2009_Fall_Papers/Z...DosimetriccomparisonofSBRTforDosimetric comparison of SBRT for lung cancer: Cyberknife

Dosimetric comparison of SBRT forDosimetric comparison of SBRT forDosimetric comparison of SBRT for Dosimetric comparison of SBRT for lung cancer: Cyberknife vs. Linaclung cancer: Cyberknife vs. Linac

Chuxiong Ding Ph D Cheng Hui Chang Ph D Joshua HaslamChuxiong Ding, Ph.D., Cheng-Hui Chang, Ph.D., Joshua Haslam, Ph.D., Robert Timmerman, M.D., Timothy Solberg, Ph.D.

Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX

DEPT OF RADIATION ONCOLOGYDEPT OF RADIATION ONCOLOGY

History of Stereotactic RadiosurgeryHistory of Stereotactic RadiosurgeryHistory of Stereotactic RadiosurgeryHistory of Stereotactic Radiosurgery

Single large radiation dose.

Multiple non-coplanar beams

Leksell L, A stereotaxic apparatus for intracerebral surgery Acta Chir Scand

Multiple non-coplanar beams.

Accurate targeting.


intracerebral surgery, Acta Chir Scand. 99:231, 1949

E l ti f T h l i l I tiE l ti f T h l i l I tiEvolution of Technological InnovationEvolution of Technological Innovation

DEPT OF RADIATION ONCOLOGYDEPT OF RADIATION ONCOLOGYLung, Liver, Pancreas, Prostate, Spine

Stereotactic Body Radiation Stereotactic Body Radiation Th (SBRT)Th (SBRT)Therapy (SBRT)Therapy (SBRT)

•• Radiation delivery to a demarcated tumor target Radiation delivery to a demarcated tumor target iiusing:using:optimal immobilizationoptimal immobilizationmotion accountingmotion accountingmotion accountingmotion accountingmany small fieldsmany small fieldsaccurate targetingaccurate targetingg gg gheterogeneous target doseheterogeneous target dosesteep dose gradients outside targetssteep dose gradients outside targetsablative intentablative intentfew large dose treatmentsfew large dose treatments


Conformal high doseConformal high doseConformal high doseConformal high dose

Prescription Dose: 60Gy in 3 fractionsPrescription Dose: 60Gy in 3 fractionsPrescription Dose: 60Gy in 3 fractionsPrescription Dose: 60Gy in 3 fractions

TargetTarget 60Gy60Gy 30Gy30Gy 7.5Gy7.5Gy


Challenges for lung tumor SBRT Challenges for lung tumor SBRT t t tt t ttreatmenttreatment

•• LocalizationLocalizationLocalizationLocalization

•• Respiratory MotionRespiratory Motion

InhalationInhalation ExhalationExhalation MIPMIP


Tumor excursion Diaphragm excursion

Purpose of StudyPurpose of StudyPurpose of StudyPurpose of Study

IGRT technique IGRT technique

Immobilization

Linac used

Collimator

Respiration CompensationCompensation

Treatment planning system

etc.


Dosimetric Difference

Linac Based Lung Cancer SBRTLinac Based Lung Cancer SBRT--T L li tiT L li tiTumor LocalizationTumor Localization

•• SBRT Frame: immobilization, localization.SBRT Frame: immobilization, localization.,,

•• Cone Beam CTCone Beam CT


Linac Based Lung Cancer SBRTLinac Based Lung Cancer SBRT--R i t M ti C t lR i t M ti C t lRespiratory Motion ControlRespiratory Motion Control

•• Large margin to GTV, Gating, ABC, AbdominalLarge margin to GTV, Gating, ABC, AbdominalLarge margin to GTV, Gating, ABC, Abdominal Large margin to GTV, Gating, ABC, Abdominal Compression, etc.Compression, etc.

Playba

Upper Threshold

Playback

Indicator

Breathing Signal

Lower ThresholdBeam On /

Off Indicator

GTV PTVGTV PTV


Cyberknife Lung Cancer SBRTCyberknife Lung Cancer SBRT--T L li tiT L li tiTumor LocalizationTumor Localization

• Sophisticated image guidance tumor LocalizationSophisticated image guidance tumor Localization


Cyberknife Lung Cancer SBRTCyberknife Lung Cancer SBRT--R i t M ti C t lR i t M ti C t lRespiratory Motion ControlRespiratory Motion Control

Internal Fiducial Markers External Optical Markers


Clinical SBRT Procedure in UTSWClinical SBRT Procedure in UTSWClinical SBRT Procedure in UTSWClinical SBRT Procedure in UTSW

0%

50%

4DCT4DCT MIP for contourMIP for contour Tx PlanningTx Planning

90%

QAQA


Patient SetupPatient SetupCBCT AlignmentCBCT AlignmentDose DeliveryDose Delivery

SBRT Dose prescription in UTSWSBRT Dose prescription in UTSWSBRT Dose prescription in UTSWSBRT Dose prescription in UTSWRTOG 0236RTOG 0236A Phase II Trial of Stereotactic Body Radiation Therapy (SBRT) in the y py ( )Treatment of Patients with Medically Inoperable Stage I/II Non-Small Cell Lung Cancer

Prescription: 60Gy in 3 fractions.Prescription: 60Gy in 3 fractions.

6060--90% isodose line cover at least 95% of PTV.90% isodose line cover at least 95% of PTV.6060 90% isodose line cover at least 95% of PTV.90% isodose line cover at least 95% of PTV.

99% of PTV should receive a minimum of 90% of 99% of PTV should receive a minimum of 90% of prescript doseprescript dose

Parallel Tissue Critical Volume (cc) Critical Volume Dose Max (Gy)

Endpoint (≥Grade 3)

prescript dose.prescript dose.


Lung (Right & Left) 1000 cc 13.5 Gy Pneumonitis

Target DefinitionTarget DefinitionTarget DefinitionTarget Definition

InhalationInhalation ExhalationExhalation MIPMIP

Tumor excursion Diaphragm excursion

PTV3D GTV


PTV4DITV

Study ProtocolStudy Protocol GTVStudy ProtocolStudy ProtocolRadiation

Start TimingRespiratoryCycle

PTV3D

PTV4D

g Cycle

4D CT StudyITV

… …0% 50% 90%

ITV, PTV3D, MIP, and AVG images

Synchrony

4D calculation

50% 90%0%

GTV, PTV4D, 50% phase CT

……

% %%

Deformable Registration


50% phase

GTVPTV4D

Result (1): Dose to TumorResult (1): Dose to TumorPatient 1

Result (1): Dose to TumorResult (1): Dose to Tumor

0.8

1

GTV C b

a

0.4

0.6

Volu

me

GTV_CyberPTV4D_CyberGTV SBRTPTV4D SBRT

b

0

0.2

c0

0 20 40 60 80

Dose (Gy)


•• Tumor coverageTumor coverage•• Tumor dose homogeneousTumor dose homogeneous•• Maximum DoseMaximum Dose

Result (1): Dose to TumorResult (1): Dose to TumorResult (1): Dose to TumorResult (1): Dose to TumorDHI for GTV

(D D )/DMaximum point dose to

GTV (Gy)(D20-D80)/Dprespcription GTV (Gy)

Cyberknife Linac Cyberknife Linac

10.09 2.31 78.2 70.3Patient 1

1

10.09 2.31

9.01 3.51 72.4 72.2

5.93 2.38 74.3 66.9

75 2 71 30.4

0.6

0.8

Volu

me


LinacLinac

11.28 5.43 75.2 71.3

6.24 5.84 73.3 73.2

8.36 2.17 77.1 68.10

0.2

0 20 40 60 80

(G )

CyberCyber

8.62 2.61 73.3 73.2

10.13 2.53 76.2 70.2

75 0±2 0 70 7±2 3

Dose (Gy)


8.71±1.87 3.35±1.47 75.0±2.0 70.7±2.3

Result (1): Dose to TumorResult (1): Dose to TumorResult (1): Dose to TumorResult (1): Dose to Tumor

7~10 beams7~10 beams More Than More Than 100 Beams100 Beams

Patient 11

100 Beams100 Beams

0.4

0.6

0.8

1

Volu

me



0

0.2

0 20 40 60 80

Dose (Gy)

Result (2): Dose to LungResult (2): Dose to LungResult (2): Dose to LungResult (2): Dose to LungInstitutional Dose Limit for Lung Institutional Dose Limit for Lung SBRT: 1000cc lung get less thanSBRT: 1000cc lung get less thanSBRT: 1000cc lung get less than SBRT: 1000cc lung get less than 13.5Gy13.5Gy

V20

Dose to


1000cc Lung

Result (2): Dose to LungResult (2): Dose to LungResult (2): Dose to LungResult (2): Dose to LungMinimum Dose to 1000cc Lung

6 00

7.00

8.00

9.00

10.00y)

Anterior Middle Posterior

2.00

3.00

4.00

5.00

6.00

Dose

(Gy

CyberknifeLinac SBRT

0.00

1.00

1 2 3 4 5 6 7 8

Patients

vs.vs.


Result (2): Dose to LungResult (2): Dose to LungResult (2): Dose to LungResult (2): Dose to LungPatient VPTV4D V20

Cyberknife Linac1 0.34% 1.34% 3.27%2 1.19% 3.67% 3.11%3 0.91% 4.31% 4.90%

V20

3 0.91% 4.31% 4.90%4 4.75% 16.32% 13.37%5 1.49% 2.16% 2.59%6 1 74% 9 11% 6 95%6 1.74% 9.11% 6.95%7 0.53% 2.21% 2.74%8 1.02% 4.83% 5.67%

mean±std 1.5%±1% 5.5%±5% 5.3%±3.6%

bVmV DPTV +×= 420 r2= 0.88 r2= 0.84


bVmV DPTV +× 420 r 0.88 r 0.84

Result (3): Whole body doseResult (3): Whole body doseResult (3): Whole body doseResult (3): Whole body dose•• Cyberknife: Total MU 25,000 ~ 50,000Cyberknife: Total MU 25,000 ~ 50,000y , ,y , ,•• Linac: Total MU 10,000 ~ 15,000Linac: Total MU 10,000 ~ 15,000

Cover PTVCover PTV Cover 60~80% PTV dimensionCover 60~80% PTV dimension


Result (3): Whole body doseResult (3): Whole body doseResult (3): Whole body doseResult (3): Whole body dose•• The absolute risk of both modalities are minimal.The absolute risk of both modalities are minimal.The absolute risk of both modalities are minimal.The absolute risk of both modalities are minimal.•• CyberKnife risk was higher due to the greater CyberKnife risk was higher due to the greater

number of MU’s.number of MU’s.

CK risk / IMRT risk CK risk / Hypo IMRT risk


Bellon M, Followill D, Ibbott G, et al. Risk of Secondary Fatal Malignancies From Cyberknife Radiosurgery. Med Phys 2008:35:2983–2983. (A joint Study by oint Study by UTSW and RPC, MD AndersonUTSW and RPC, MD Anderson))

CK risk / IMRT risk CK risk / Hypo IMRT risk

Some Practical ConsiderationSome Practical ConsiderationSome Practical ConsiderationSome Practical ConsiderationCyberknife Linac

Treatment Planning • Inverse Planning.• No beam come through

posterior of patient

• Beam can come through posterior of patient

• Beam angle limited by table and gantry collision

Tumor Localization • Few X-Ray images • CBCT Required

Respiratory Control • Need Fiducial (Synchrony)• Non Fiducial tracking (X-

sight Lung tracking)

• Larger target area• Abdominal compression

sight Lung tracking).

Dose Delivery • Robert moving time• More MU

• Less MU• Adjust treatment couch angle


o e U djust t eat e t couc a g e

ConclusionConclusionConclusionConclusion•• No difference in dose coverage.No difference in dose coverage.No difference in dose coverage.No difference in dose coverage.•• Cyberknife is heterogeneous dose to GTV.Cyberknife is heterogeneous dose to GTV.•• All lung dose within constrainsAll lung dose within constrainsAll lung dose within constrains.All lung dose within constrains.•• No difference to lung in high dose region.No difference to lung in high dose region.•• Lung dose depends on tumor location in low doseLung dose depends on tumor location in low dose•• Lung dose depends on tumor location in low dose Lung dose depends on tumor location in low dose

region.region.


Thank you!Thank you!Thank you!Thank you!


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DosimetriccomparisonofSBRTforDosimetric …chapter.aapm.org/swaapm/Past/Fall2009/2009_Fall_Papers/Z...DosimetriccomparisonofSBRTforDosimetric comparison of SBRT for lung cancer: Cyberknife