Patient Positioning for SRS Treatments Method to Compare SGRT Deltas vs IGRT Shifts

Karen McGoldrick,
BAppSc (RT)
Clinical Lead Radiation Therapist Peter MacCallum Cancer Centre – Moorabbin Campus

2. Method to compare AlignRT deltas versus
IGRT shifts for determining correct patient
positioning in SRS treatments
Karen McGoldrick - Clinical Lead Radiation Therapist

3. 3
Disclosure
Peter MacCallum Cancer Centre has a collaboration
agreement with Vision RT
Vision RT sponsored my travel to attend and present

4. 4
Peter Mac Moorabbin

5. 5
Commenced Brain SRS program
in October 2020

6. BRAINLABtm ELEMENTS

7. ECLIPSE HYPERARCTM Planning
Dedicated SRT module in Eclipse :
•Pre-set couch angles – no clearance
issues
•Optimised collimator angles
•Automatic Lower dose objective
•Automatic SRS NTO

8. IGRT – Intrafraction Imaging
•Orthogonal imaging could be achievable TrueBeam™ with 2D-
3D MV-kV pair for couch 315/45
•Non-paired imaging solution 2 x 2D MV for Couch 270/90 when
collison risk occurs
CBCT for initial setup +Margin not accounting for other uncertainties
No intra-fraction Imaging1.4mm isotropic
2D planar MV at all other couch positions 0.7mm laterally and longitudinally and 1.1mm vertically
Orthogonal pairs where possible + 2D planar imaging where restricted0.7mm isotropic

9. IGRT - Intra-fraction imaging
MV-kV Pair not always possible due
to collision of panel & patient
Solution: 2 x Single Plane
MV Images
Couch 90/270
MV Imaging Vrt: 80
MV Energy: 6x
MV Exposure: Low Dose
G180
2D/3D Match to Bones
Auto Matching
G135/225
2D/3D Match to Bones
Auto Matching

10. IGRT -Intra-fraction imaging Workflow

11. 2021 SGRT Begins @ PeterMac

12. •CDR Open Face mask
•Initial patient positioning closer to planned
position
•Post CBCT Reference capture for patient
monitoring throughout treament
SRS with SGRT

13. Comparison of Intrafraction Imaging
Matches for CLOSED vs OPEN Face
Masks
Courtesy: J Hughes PMCC 2022

14. Comparison of Frequency of
Intrafraction Shifts for CLOSED vs OPEN
Face Masks
Courtesy: J Hughes PMCC 2022

15. Compare Intrafraction Imaging shifts Vs AlignRT RTD values

Review IGRT Requirements

16. 16
Multi Vendor Challenges
Reference: Varian TrueBeam 2.7 and Elekta MOSAIQ Guide
MOSAIQ

17. 17
Multi Vendor Challenges
TrueBeam IGRT SHIFTS
Combined logs – can be coded to extract auto match results, positioning match and
couch movements but not without some issues:
•a manual match is performed, and no shifts are applied – the record of the final
match is not saved
•Frame of Reference Corrections - Reversing sign for some values to permit
comparison with IGRT shifts displayed on OBI

18. 18
ALIGNRT
So many time points in data!!!!!!!
•Some time points not relevant such as camera blocking due to OBI imaging
panels
•Difficult to determine which time point most relevant to compare to IGRT
Courtesy: J Hughes PMCC 2024
Multi Vendor Challenges

19. 19
3 Different Isocentres
TRUEBEAM MV ISOCENTRE
OBI ISOCENTRE
ALIGNRT ISOCENTRE

20. 20
Isocentre Head Phantom Test 1
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
Couch 45Couch 315Couch 270Couch 90
(Degrees)
SGRT to MV iso
rtnpitchroll
-0.04
-0.02
0
0.02
0.04
0.06
Couch 45Couch 315Couch 270Couch 90
(cm)
SGRT to MV iso
vrtlnglat

21. 21
Isocentre Head Phantom Test 1
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
vrtlnglatrtnpitchroll
Difference to MV Iso Couch
Rotation 1
MV/MVMV/KVAlignRT
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
vrtlnglatrtnpitchroll
Difference to MV Iso Couch Rotation
2
MV/MVMV/KVAlignRT

22. 22
Print Screens
•A simple solution to compare IGRT Shifts with AlignRT deltas!!!!
COUCH ROTATION 1COUCH ROTATION 2

23. 23
Print Screens

24. 24
Preliminary Results
(cm)
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
Difference AlignRTto MV/kV @ Couch
Rtn1
vrtlnglat
(degrees)
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
Difference AlignRT to MV/kV @ Couch
Rtn 1
rtnpitchroll
N = 21 fractions from 8 patients (1 patient/2 fractions excluded due to incorrect protocol)

25. 25
Which surface?

26. 26
Preliminary Results
(cm)
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
Difference AlignRTto MV/kV @ Couch
Rtn2
vrtlnglat
(degrees)
-2
-1.5
-1
-0.5
0
0.5
1
Difference AlignRTto MV/kV @ Couch
Rtn2
rtnpitchroll
N = 21 fractions from 8 patients (1 patient/2 fractions excluded due to incorrect protocol)

27. 27
Conclusion
ResourceProsCons
MOSAIQ? •Not able to support On-Demand
images
•6DoF match results do not account
for rotations applied prior to IGRT
•Precision accuracy - only reports to
nearest mm
TrueBeam Combined Logs•All time points and steps easily
identified
•Does not save manual match result
if the shift is not applied
AlignRT RTD Reports•All time points recorded•Difficult to identify specific time
points for data collection
Print Screen•Targeted at specific time points
for easy data collection
•Relies on user to capture at correct
time point
•Manual data entry at this stage

28. Acknowledgements:
Jeremy Hughes – Medical Physicist PMCC
Moorabbin Campus
Kenton Thompson – Research Radiation Therapist
PMCC
All the treating Radiation Therapists at PMCC
Moorabbin for the many screen captures they are
taking

29. Thank you.