Dynamic TargetingTM Image-Guided Radiation Therapy

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Dynamic TargetingTMImage-Guided Radiation Therapy
Varian _

• Scott Johnson, PhD
• Varian Medical Systems
• Palo Alto, California

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Varian IGRT Statistics

• As of the end of Dec, Varian had booked 80 orders
  for the On-Board Imager (OBI)
• As to today, 35 installations have been completed
• And another dozen installations currently are in
  progress
• As of today, cone-beam CT software has been
  installed at 7 sites
• Aarau, Switzerland
• Karolinska, Sweden
• MSKCC, New York
• Emory, Atlanta
• Stanford, Palo Alto
• Duke, Durham
• Henry Ford, Detroit
• With an additional installations scheduled in the
  very near future
• MD Anderson, Houston

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What is IGRT?

• IGRT means several things
• Use of images for online setup correction, before
  treatment begins
• Position patient on table. Align the patient to
  lasers.
• Acquire images
• Images usually are kV
• Images may be an orthogonal pair of radiographs
  or a volumetric image (e.g., cone-beam CT)
• Compare the acquire images to reference images
• Analysis may be automated and/or manual
• Analysis may rely on radiopaque markers, bony
  anatomy or soft-tissue anatomy
• Result of the analysis is data on how to correct
  the patient position
• Move the treatment couch remotely to
  automatically correct the patient position
• Optional Acquire and analyze another set of
  images to verify the correction
• Begin treatment delivery

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Movie of the clinical process
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What is IGRT?

• Use of images for online setup correction, before
  treatment begins
• Whats new here
• Use of kV imaging in the treatment room
• New image analysis tools for the therapist
• Fast, easy to use, integrated into the existing
  workflow
• Remote couch control, to speed the process
• The result is
• Significant improvement in target localization
• Reduced likelihood of missing the target
• An opportunity to reduce CTV-to-PTV margins and
  thus the volume of normal tissue irradiated to
  high dose
• May reduce the toxicity of RT

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What is IGRT?

• IGRT also may mean adaptive radiation therapy
• Tumors, hopefully, respond to treatment and
  shrink over the course of therapy
• As the surrounding tissues are pulled inward, the
  result may increase the dose to critical
  structures
• With adaptive RT, goal is to use images to
• Perform online setup correction of patient
  position
• Acquire a volumetric image (cone beam CT scan)
• Automatically detect any changes in the target
  shape
• Automatically adapt the treatment plan to reflect
  the new target shape
• Provide the therapist with important information
  on how the plan has changed
• Deliver the new plan
• (Its kind of like a boost plan, but done online
  with the patient on the table)
• Above process should occur within 15-20 minutes,
  or less

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What is IGRT?

• With adaptive radiation therapy, images of the
  tumor size, shape and location are used to adapt
  the treatment plan before it is delivered

Critical structure
Target
Prescription isodose
Critical structure
Original treatment plan and anatomy
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What is IGRT?

• With adaptive radiation therapy, images of the
  tumor size, shape and location are used to adapt
  the treatment plan before it is delivered

Critical structure
Target
Prescription isodose
Critical structure
Original treatment plan and new anatomy with
tumor shrinkage due to radiation
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What is IGRT?

• With adaptive radiation therapy, images of the
  tumor size, shape and location are used to adapt
  the treatment plan before it is delivered

Critical structure
Target
Prescription isodose
Critical structure
Adapted treatment plan
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What is IGRT?

• With adaptive radiation therapy, images of the
  tumor size, shape and location are used to adapt
  the treatment plan before it is delivered
• No one is doing this yet!
• Before it can be done, the following are needed
• Ability to acquire CT scans on the treatment
  table. DONE!
• Automated image segmentation tools that
  automatically contour the patient anatomy
• New treatment plan analysis tools for the
  therapist
• Including tools that clear show what treatment
  plan adaptations are needed and what the effect
  of those changes is
• Fast, easy to use software that is well
  integrated into the existing treatment delivery
  process
• Guidelines on when adapted treatment plans should
  be reviewed by a physicist or physician
• Guidelines on how to QA the adaptive radiation
  therapy process
• Etc

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What is IGRT?

• IGRT also can be considered to include dose
  guided radiation therapy
• Acquire a CT scan of the patient on the treatment
  table in the treatment position
• Deliver the treatment plan
• Use an EPID to capture transit dose images or
  capture linac and MLC log files
• Use transit dose to back project delivered dose
  onto CT or use log files to forward project
  delivered dose onto CT
• The result is a realistic calculation of the dose
  delivered that day including the impact of
  bladder and rectal filling, bowel gas, etc

Dose actually emitted by the linac overlayed onto
CT scan of patient on treatment table
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What is IGRT?

• IGRT also can be considered to include dose
  guided radiation therapy
• Now, imagine repeating the above process at each
  treatment session and having the ability to morph
  the results onto each other
• Summing the results allows you to visualize the
  dose actually delivered to the target and
  critical structures over a series of treatment
  sessions
• With advanced treatment planning tools, you then
  may choose to adapt the treatment plan mid-stream
  so that the final, cumulative dose satisfies the
  physicians prescription

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What is IGRT?

• IGRT also can be considered to include dose
  guided radiation therapy
• Again, no one is doing this yet, but we are
  getting close
• Before it can be done, the following are needed
• Ability to acquire CT scans on the treatment
  table. DONE!
• Ability to capture linac and MLC log files or
  transit dose. DONE!
• Ability to project beams recorded in log files
  into CT scans. DONE!
• Image and dose morphing tools that allow you to
  sum the dose to a volume over several sessions,
  given that the volume is changing size, shape and
  location
• Fast, easy to use software that is well
  integrated into the existing treatment delivery
  process
• Guidelines on when to adapt a plan and when that
  adapted plan should be reviewed by a physicist or
  physician
• Guidelines on how to QA the dose guided radiation
  therapy process
• Etc

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Will IGRT replace IMRT?

• No, the two are complementary.
• IMRT allows the dose to conform tightly to the
  PTV.
• IGRT allows the PTV to shrink to the CTV.
• IG-IMRT then allows simultaneously
  margin-reduction and dose conformation.

Conventional RT
PTV
Organ at risk
CTV
High dose isodose
IMRT
IG-IMRT
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• Varian IGRT Technology
• On-Board Imager accessory
• Available as an upgrade to any Clinac installed
  in 1997 and after

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On-Board Imager

• Hardware
• Two robotic arms
• kV Xray source
• Amorphous silicon imaging panel
• OBI workstation
• Three modes of operation
• Radiographic
• Online setup correction
• Bony anatomy or markers
• CBCT
• Online setup correction
• Bony or soft tissue anatomy
• Visualization of delivered dose
• Adaptive radiation therapy
• Fluoroscopic
• Verification of gated radiation therapy
• Fluoro-based tumor tracking (Future option)

Trilogy and the On-Board Imager
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Command Center
Clinac console, 4D Console, OBI workstation, RPM
Gating workstation
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Robotic arm motion
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Robotic arm motion
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Robotic arm motion
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Robotic arm motion
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• Varian IGRT Technology
• Orthogonal radiographs for online patient setup
  correction

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Acquisition of a lateral radiograph
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Acquisition of an AP radiograph
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Sample radiographs
Images courtesy of Karolinska Medial Center
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Sample radiographs
Images courtesy of Karolinska Medial Center
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On-Board Imager workstation
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On-Board Imager workstation
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Marker matching using the On-Board Imager
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Marker matching using the On-Board Imager
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• Varian IGRT Technology
• Cone beam CT for online patient setup correction
• (and adaptive radiation therapy and dose guided
  radiation therapy)

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Acquisition of a cone beam CT scan
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Acquisition of a cone beam CT scan
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Acquisition of a cone beam CT scan
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Acquisition of a cone beam CT scan
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Acquisition of a cone beam CT scan
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Acquisition of a cone beam CT scan
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Acquisition of a cone beam CT scan
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CBCT field of view and slice thickness

• With a single 360 degree rotation of the gantry,
  CBCT scans can be reconstructed with the
  following specifications

OR
Field of view 27cm Scan length 17cm Slice
thickness, down to 0.5mm
Field of view 48cm Scan length 15cm Slice
thickness, down to 0.5mm
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Sample CBCT image
Images courtesy of Duke University Hospital
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• Varian IGRT Technology
• Controlling for respiratory motion

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Respiratory gating

• RPM Gating System
• Infrared camera
• External marker block
• Gating workstation
• Process
• Place block on patients abdomen
• Camera monitors block motion
• Respiratory waveform shows how the block moves up
  and down in time
• User sets upper and lower thresholds on block
  motion
• Whenever the block comes between the thresholds,
  the beam is on
• Whenever the block moves outside the thresholds,
  the beam is off
• Free-breathing and breath hold protocols are
  supported, as are gating at inhalation or
  exhalation or at any other point in the
  respiratory cycle

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Fluoro-based verification of gating

• With the On-Board Imager, gated kV radiographs
  are used to verify patient setup and kV
  fluoroscopy is used to verify the gated treatment
  port.

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• Varian IGRT Technology
• Whats next?

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Where we are headed

• New software tools for online adaptive radiation
  therapy and dose guided radiation therapy
• Automated segmentation of acquired CBCT scans
• Treatment planning and plan review tools at the
  Command Center
• Fast, automated plan modification tools
• New software tools for fluoro-based gating, in
  which the gating signal is based on the motion of
  internal anatomy (rather than an external marker
  block)

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Where we are headed

• New MLC control system to enable real-time tumor
  tracking

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• Varian IGRT Technology
• Why we think it is superior

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Varians IGRT technology

• Compared to Tomotherapy
• We use kV photons rather than MV for superior
  image quality
• We use cone-beam CT rather than helical
  slice-based CT because cone-beam CT images are
  superior and CBCT is the future
• Radiology, in general, is moving toward CBCT
• 1 slice scanner gt 2 slice gt 4 slice gt 8 slice gt
  16 slice gt
• Because of the exquisite detail, CBCT already has
  been adopted by Cardiology
• We can develop fluoro-based tools to monitor and
  control for respiratory motion
• Tomotherapy will have a difficult time dealing
  effectively with respiratory motion

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Varians IGRT technology

• Compared to Novalis and CyberKnife
• We use a gantry-based system, rather than a
  room-based system, to have the option of
  acquiring CBCT scans
• Volumetic imaging is not possible with Novalis or
  CyberKnife

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Varians IGRT technology

• Compared to Synergy
• We use robotic arms to position the kV source and
  kV imager to allow remote control and superior
  flexibility in imaging geometry
• We use high-quality Varian imagers, which have a
  much higher image acquisition rate
• Up to 30 frames per second, compared to 3-5
  frames per second for Elekta
• Most clinicians feel that a frame rate of at
  least 12-15 images/second is required for
  fluoro-based gating

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Conclusion

• Varian offers the most integrated and
  comprehensive solution available
• kV radiographs
• kV/MV radiographs
• Gated radiographs
• Marker-based setup corrections, 2D-2D and 2D-3D
• CBCT acquisition and analysis
• Pretreatment verification of gated treatment
  ports
• Robotic couch motion
• IGRT software integrated with the VARiS Vision
  Eclipse database
• Varian is well-positioned to quickly deliver the
  next generation of IGRT technology

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• Thank you