Departments of Mechanical Engineering and Radiation Oncology 1 - - PowerPoint PPT Presentation

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Departments of Mechanical Engineering and Radiation Oncology

Schools of Engineering and Medicine, Bio-X Program, Stanford University

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Imaging During Beam Delivery

• Existing solutions are limited:

Radiographic x-ray Electromagnetic Real-time marker-less soft-tissue image guidance during beam delivery is an unmet challenge

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How about ultrasound?

• Previous investigations use imaging prior to delivery,
• r imaging in phantoms

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• A. Hsu, N. R. Miller, P. M. Evans et al., "Feasibility of using ultrasound for real-time tracking

during radiotherapy," Medical physics 32 (6), 1500-1512 (2005). –

• Q. Xu and R. J. Hamilton, "A novel respiratory detection method based on automated

analysis of ultrasound diaphragm video," Medical physics 33 (4), 916-921 (2006). –

• E. J. Harris, N. R. Miller, J. C. Bamber et al., "Performance of ultrasound based

measurement of 3D displacement using a curvilinear probe for organ motion tracking," Physics in medicine and biology 52 (18), 5683-5703 (2007). –

• A. Sawada, K. Yoda, M. Kokubo et al., "A technique for noninvasive respiratory gated

radiation treatment system based on a real time 3D ultrasound image correlation: a phantom study," Medical physics 31 (2), 245-250 (2004). –

• F. Jacso, A. Kouznetsov, and W. L. Smith, "Development and evaluation of an ultrasound-

guided tracking and gating system for hepatic radiotherapy," Med Phys 36 (12), 5633-5640 (2009).

Unresolved Question: How can we control the US imaging process during beam delivery from outside the treatment room?

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3D US image stream Haptic Interface US-guidance workstation computer Linear Accelerator Patient 4D US probe US Robot US imaging system Robot Control

Novel Image Guidance Solution

Accelerator control console Treatment Intervention Probe position data (6 DOF) Optical tracker

Telerobotic system enables remote probe control

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Key Issues

• Design of customized robotic manipulator

– Range of motion – Radiotherapy environment constraints – Human safety

• Robustness of telerobotic human imaging
• Treatment plan compatibility
• Performance during radiation exposure

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Robot Design Specs

• Range of motion

– Optical tracking – Probe pitch critical: 0-45°

• Radiotherapy environment

constraints

– 360 degree gantry rotation – Limited mounting areas on treatment couch – Limited clearance between patient and LINAC head

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Manipulator Design

R4 R5 P1 y z R2 R3 y x R4 RCM

R2 R4 P1 R5

x y z Load Cell

P1 R2 R3

Blue = Locking Joint Red = Actuated Joint Blue = Locking Joint Red = Actuated Joint

R4 R5

x y z

Critical motions are actively controlled during treatment

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Telerobotic Imaging

Remote Haptic Interface Robot

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Telerobotic Imaging

Volunteer #1 Volunteer #2 Volunteer #3

Pitch Force

Image quality remotely maintained over 10 minutes

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Impact on Treatment Plan

Plans are nearly identical. Potential margin reduction from real-time guidance is beneficial.

Clinical prostate IMRT plan Re-optimized IMRT plan with restricted beam angles to avoid US probe and robot links Re-optimized plan with 2mm margin reduction as potentially enabled by real-time image guidance

Rectum Bladder PTV GTV Rectum Bladder PTV GTV

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Performance During Delivery

Beam Off Beam On

Probe 0mm Probe 16mm

p-Value Servo cycle interval 0.99 Force control 0.46 Pitch tracking error 0.47 US tracking error 0.68

LINAC interference inconsequential for robot and US

p-Value 0.99 0.46 0.47 0.68

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Conclusion

+ =

Could provide non-invasive guidance that truly reflects soft tissue anatomy Telerobotic ultrasound imaging is feasible during beam delivery

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Questions?

• Email: jschlosser@stanford.edu

Departments of Mechanical Engineering and Radiation Oncology

Schools of Engineering and Medicine, Bio-X Program, Stanford University