Surface Guidance Advancement Novel Usage of SGRT for CBCT-based Adaptive Radiation Therapy

SGRT US 2024
David Parsons,
PhD Associate Director of Medical Physics Residency Program
University of Texas Southwestern

1. 2024 Annual US SGRT • Phoenix, AZ1

2. Simulation Omitted Radiation Therapy with SGRT
David Parsons
June 6, 2024

3. 2024 Annual US SGRT • Phoenix, AZ
Outline
§The beginning pieces – deflated vaclock bags
§Simulation omit with conventional radiation therapy
§Simulation omit with adaptive radiation therapy
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The beginning pieces –
deflated vaclock bags

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Deflated vaclock bags…

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What are the options?
§Re-sim the patient?
§This was our default answer for the past decade
§Delays the patient until the new plan is ready (2-4 days)
§Utilizes extra resources
§CT – takes a slot for another patient
§Physician – new contours
§Dosimetry – new plan
§Physics – initial chart check, IMRT QA
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Re-simulation is unnecessary (for most) in the era of SGRT
25-year-old male with B-cell lymphoma in the axilla

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SGRT to the rescue

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SGRT to the rescue
•30 mins in-vault
time
•Daily average
~22 mins
•2 set of kV-MV
images taken
•1 mm SI
•2 mm RL
•1 mm AP

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Simulation omit with
conventional radiation therapy

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Sim-Omit RT
§Can you treat a patient on their first visit to the
department?
§Can you skip/omit CT simulation?
§Can you do it in less than an hour?
§Standard sim-plan-treat workflow is ~5.9 hours in the
department
§INPATIENT
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12. 2024 Annual US SGRT • Phoenix, AZ
Sim-Omit RT with conventional plans
§All utilize AP-PA or Lateral fields only (at the
moment)
§Whole brain (SO-Whole)
§Palliative spine (SO-Pal)
§Heterotopic ossification (SO-HO)
§Diagnostic imaging for planning
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David Sher, MD and Andrew Godley, PhD

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SO Timeline
Case ID
MD checks for CT
image of relevant site
Import
Import diagnostic image
Plan
•Dosi presents field to MD
•MD confirms and dosi calcs the plan
•Plan exported to R&V system
•Physics checks
Verify and Treat
•Setup patient with SGRT
•Make immobilization
•Image (kV-kV, CBCT, MV BEV)
•Final dose difference <5% Slide courtesy of Eric Chambers, MBA

14. 2024 Annual US SGRT • Phoenix, AZ
SO-Whole
§72-year-old male
§Metastatic lung cancer to
the brain
§20 Gy in 5 Fx
§Dosimetry planned off a
diagnostic CT angiogram
§Missing posterior portion of the
skull
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SO-Whole Setup
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§Transfer to the Tx couch, SGRT Setup + Mask 15 mins

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SO-Whole Setup
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§Transfer to the Tx couch, SGRT Setup + Mask 15 mins
§Imaging + Treatment 21 mins
§In-vault time 36 mins

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SO Duration
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Average Time
Vault:
37 ± 10 mins
Total in Dept:
66 ± 26 mins
Slide courtesy of Eric Chambers, MBA

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Simulation omit with
adaptive radiation therapy

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CBCT-based ART
§Varian Ethos
§Uses the CBCT of the day to
deform the planning CT for dose
calculation
§Optimization priority decided
beforehand
§ART team would decide between
§Original plan with today’s contours
§Adapted plan with today’s contours
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~5800 ART fractions treated
June 2021 – May 2024

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SGRT with AlignRT InBore
AlignRT
AlignRT
InBore

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Hippocampal Sparing Whole Brain Radiation Therapy
Slide courtesy of Liyuan Chen PhD, Zohaib Iqbal PhD and Mu-Han Lin PhD

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Sim-Omit Hippocampal Sparing Whole Brain
§31-year-old with leptomeningeal disease
§30 Gy in 10 Fxs with hippocampal sparing
§Contoured and planned using a T1 MRI + sCT
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SGRT for Setup and Mask fabrication

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SGRT for Setup and Mask fabrication

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Resultant ART
ART reduced the
max left and right
hippocampal dose
by ~3 Gy
OriginalAdapted

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Time in the vault
ActivityTime [min]
SGRT Setup and Mask Fabrication9.7
ART Workflow13.6
Plan Review + QA4.4
Treatment6.5
Transport Out3.7
Time in Vault38
Time in Department71

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SO Pelvis
§72-year-old male with bladder wall
cancer
§Started to bleed requiring
continuous irrigation
§Planned on diagnostic CT
§CT couch removed and avoiding
entrance dose through areas of
high deformation
§36 Gy in 6 Fx to the PTV once a
week
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SGRT for Setup and Vaclock fabrication

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Resulting PlanCBCT
sCT
Δ
PTV decreased by 210 cc over the course of ART

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ActivityTime [min]
Ambulance Door to Vault7.0
Transport to Tx couch2.6
Make immobilization with SGRT9.0
ART Workflow19.4
Plan Review + IMRT QA4.3
Treatment5.0
Patient out of Vault4.0
Vault to Ambulance7.0
Total time in Vault44
Total time in building58

31. 2024 Annual US SGRT • Phoenix, AZ
Summary
§SGRT has become an essential part of our sim-omit
workflow
§Thereby greatly decreasing inpatient time in our
department
§Decreased from 5.9 hours to an ~hour
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Traditional [hours]SO [hours]SO-ART [hours]
In-vault̶0.6 ± 0.20.7 ± 0.1
In-dept5.9 ± 1.51.1 ± 0.41.0 ± 0.1

32. 2024 Annual US SGRT • Phoenix, AZ
Acknowledgments
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§Andrew Godley
§David Sher
§Eric Chambers
§Kara James
§Jennifer Cleaton
§Jeff Dubas
§Khoi Nguyen
§EROC TPOD Team
§Ethos Adaptive Team
§Mu-Han Lin
§Zohaib Iqbal
§Liyuan Chen
§Thomas Banks
§Tu Dan
§Neil Desai
§Tingliang Zhuang
§All our radiation therapists
§Physics Residents

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SO Pelvis
§Bleeding bladder tumor needing
continuous irrigation
§Planned on diagnostic CT