SGRT in Planning Our Clinical Experience in Surface Guided Clearance Mapping

SGRT US 2024
Siqiu Wang
PhD
Medical Physics Resident
University of Texas Southwestern

1. SGRT 2024 • Scottsdale, AZ1

2. Virtual Clearance Mapping for Non-
Coplanar Treatment Planning
Siqiu Wang, David Parsons
June 6th, 2024
SGRT 2024

3. SGRT 2024 • Scottsdale, AZ
Outline
§Why non-coplanar treatments?
§Why not non-coplanar treatments?
§MapRT for non-coplanar planning
oLung SBRT
oBreast sPBI
3

4. SGRT 2024 • Scottsdale, AZ
Why Non-Coplanar?
§Goal of radiotherapy planning:
Respect target coverage and reduce OAR doses (especially
important in stereotactic treatments)
§Evolution of treatment techniques:
o3D → IMRT → VMAT
More degrees of freedom -> More capability for dose shaping
oCoplanar (CP) → Non-coplanar (NCP)
4

5. SGRT 2024 • Scottsdale, AZ
Why Non-Coplanar?
5
Steven Montalvo, M.D.
§Systematic
literature review
in progress

6. SGRT 2024 • Scottsdale, AZ
Why NOT Non-Coplanar?
§Treatment time
§Intra-fractional patient motion
§Delivery accuracy
§Patient safety/collision risk
6

7. SGRT 2024 • Scottsdale, AZ7
Manual Angle Checks
X 10
•~15 min machine/therapist time per case
•Mean turnaround time 6.2 hours (n=60)

8. SGRT 2024 • Scottsdale, AZ
MapRT
9
§2 units at UTSW (one
in each CT vault)
§Each consists of 2
Horizon cameras
MapRTSimRT
MapRT
MapRTSimRT

9. SGRT 2024 • Scottsdale, AZ
MapRT
10
§A patient-specific SGRT-based virtual clearance mapping
system

10. SGRT 2024 • Scottsdale, AZ11
MapRT
Imported Dicom
parameters
Clearance
Map
with arc
locations
Collision
Zones
Interactive
Window

11. SGRT 2024 • Scottsdale, AZ12
System QA and Validation
•Comparison with physical angle check
MethodClearance AgreedClearance DisagreedSuccess Ratio
Physical Angle Check55 5 91.7%
MapRT60 0 100%
•Physical Phantom MeasurementAccurate within 1°

12. SGRT 2024 • Scottsdale, AZ13
Going Live with MapRT
§An estimated in-vault time savings of
– 15.0 hours per month
EROC MapRT go-liveAROC MapRT go-live

13. MapRT for Lung SBRT Planning

14. SGRT 2024 • Scottsdale, AZ15
Planning with MapRT for Lung SBRT
§74-year-old female
§17.6 cm3 right lung lesion
§SBRT candidate with 60Gy in 5Fx

15. SGRT 2024 • Scottsdale, AZ16
CP Planning with MapRT
7cm

16. SGRT 2024 • Scottsdale, AZ17
Leveraging MapRT for NCP Planning
•Spread out the entrance and exit doses

17. SGRT 2024 • Scottsdale, AZ18
Result comparison
CP
CIPaddick = 0.89
GI50% = 4.54
GI25% = 28.5
5688 MU
NCP
CIPaddick = 0.91
GI50% = 4.30
GI25% = 15.1
4061 MU

18. SGRT 2024 • Scottsdale, AZ19
Over 20 lung SBRT patients
•NCP plans are more conformal
•Significantly lower V25%
•Less low dose spillage over a large
distance from PTV range

19. MapRT for Stereotactic Partial
Breast Irradiation (sPBI) Planning

20. SGRT 2024 • Scottsdale, AZ
Breast sPBI: Why is heart dose critical?
§Long life expectancy for breast cancer patients
§Every 1 Gy increase in mean heart dose results in
an excessive 7.4% increased risk of major
coronary events in their lifetime
§Potentially no threshold dose
21
Darby SC et al. N Engl J Med 2013;368:987-998.van Nimwegen et al. J Clin Oncol 2015;34(3).

21. SGRT 2024 • Scottsdale, AZ22
Planning with MapRT for Breast sPBI
§Case #1
§64-year-old female
§70 cm3 left breast CTV
§Medial and partially coplanar
with the heart
§sPBI with 30 Gy in 5 Fx

22. SGRT 2024 • Scottsdale, AZ23
CP Planning with MapRT
•Avoid contralateral breast
•Maximize arc angles
•Check clearance with MapRT

23. SGRT 2024 • Scottsdale, AZ24
Leveraging MapRT for Breast NCP planning
What if we can steer the beams away from the heart using NCP arrangement?

24. SGRT 2024 • Scottsdale, AZ25
CP vs. NCP Plans
CP
Heart Dmean = 130.95 cGy
Heart V150cGy = 18.73%
Heart V700cGy = 4.64
LAD Dmean = 111.72 cGy
NCP
Heart Dmean = 67.61 cGy
Heart V150cGy = 9.08%
Heart V700cGy = 0.99%
LAD Dmean = 94.11 cGy
CPNCP

25. SGRT 2024 • Scottsdale, AZ26
Planning with MapRT for Lung SBRT
§Case #2
§59-year-old female
§84 cm3 left breast CTV
§Very close and coplanar to heart
§sPBI with 30 Gy in 5 Fx

26. SGRT 2024 • Scottsdale, AZ28
Leveraging MapRT for Breast NCP planning
Adding a vertex field

27. SGRT 2024 • Scottsdale, AZ29
Leveraging MapRT for Breast NCP planning

28. SGRT 2024 • Scottsdale, AZ30
CP
Heart Dmean = 113.67 cGy
Heart V150cGy = 19.97%
LAD Dmean = 101.15 cGy
Lungipsi V900cGy = 6.89%
NCP
Heart Dmean = 59.43 cGy
Heart V150cGy = 6.53%
LAD Dmean = 54.63 cGy
Lungipsi V900cGy = 5.04%
CP vs. NCP Plans
CPNCP

29. SGRT 2024 • Scottsdale, AZ31
18 breast sPBI patients
•Lower heart and LAD doses
•Similar plan quality otherwise
Heart
LAD
Plan Quality Indice

30. SGRT 2024 • Scottsdale, AZ
Outline
§Why non-coplanar treatments?
§Why not non-coplanar treatments?
§MapRT for non-coplanar planning
oLung SBRT
oBreast sPBI
§REVISIT: Why not non-coplanar treatments?
32

31. SGRT 2024 • Scottsdale, AZ
Why NOT Non-Coplanar?
§Treatment time
§Breast: 1 min 57 sec vs. 2 min 29 sec (couch rotation in-vault)
§Intra-fractional patient motion
§SGRT motion monitoring
§Delivery accuracy
§Sub-millimeter couch rotation walkout
§Patient safety/collision risk
§SGRT-based virtual clearance mapping
33

32. SGRT 2024 • Scottsdale, AZ
Summary
§MapRT is a novel SGRT clearance mapping system
§More accurate than manual clearance checks
§Greatly reduces the planning time
§Enables efficient and effective beam selection for NCP
planning
34

33. SGRT 2024 • Scottsdale, AZ
Acknowledgments
35
§Andrew Godley
§David Sher
§Eric Chambers
§Zohaib Iqbal
§Xinran Zhong
§Yesenia Gonzalez
§Kara James
§Jennifer Cleaton
§Johanna Garza
§Wendy Garcia-Ramirez
§Lindsi Seaux
§Phu Ho
§Rashad Campbell
§Gannon Arnold
§Jordan Getchell
§Weihan Lee
§Jeff Dubas
§Romona Frame
§Hung Ho