Clinical Experience with SGRT Applications for Bore-based Systems

George (Guang) Li,
PhD, DABR Attending Physicist, Memorial Sloan Kettering Cancer Center

2. Clinical Experience with SGRT for
Bore-based Systems (Halcyon/Ethos)
SGRT Community Meeting, June 6, 2024
Guang (George) Li*, Xiaoning Liu, Michelle Savacool,
Michalis Aristophanous, and Laura Cervino

3. 3Scottsdale, AZ, SGRT Community Meeting 2024
MSK Commitment to SGRT
AlignRT inBore Systems for 4 Ethos/Halcyon Systems at MSK
1. Two AlignRT inBore systems are used and two more are budgeted
2. Developing new procedures to meet Ethos/Halcyon challenges
3. Treatment sites: pelvis, breast, lung, and head-and-neck (NH)
MSK Linac are 100% SGRT machines except for the MR-Linac
1. MSK is the largest AlignRT user group (30+) for clinical applications
a. Uniform clinical procedures and SGRT teams across 8 MSK clinical centers
b. One-weekend system upgrade is achieved, more feature requests are made
2. MSK is committed to SGRT applications based on SGRT research
a. A VRT-MSK research agreement has been signed to facilitate clinical research
b. Weekly SGRT meetings on clinical and clinical research issues alternatively

4. 4
OUTLINE
Background: AlignRT inBore with a bore-based ring camera set
• AlignRT inBore ≈ AlignRT Adv (@sim ISO) + inBore camera (@txt ISO)
Clinical SGRT applications using inBore system
1. Commissioning the AlignRT inBore system for Ethos Liancs
• Challenges in daily Ethos collision check and inBore daily QA
2. Achieve a pseudo-6DOF couch using inBore to correct body rotation
• The first SGRT site: pelvis (post-op prostate with nodes)
3. Head-and-neck (NH) SGRT setup has just started
• ROI definitions for HN with 2 areas to reproduce neck curvature
Research opportunities and future directions using inBore
• Daily SGRT data and daily IGRT (CBCT) data for many disease sites.
Scottsdale, AZ, SGRT Community Meeting 2024

5. 5
Background: AlignRT inBore Due-ISO System
Scottsdale, AZ, SGRT Community Meeting 2024
@Setup ISO
@Treatment ISO
(motion tracking)

6. 6
Background: AlignRT inBore = Advance + inBore Ring
SGRT patient setup @setup ISO (= sim ISO = user origin)
1. Use the ceiling-mounted AlignRT Advance for SGRT setup
• Apply 6DOF in SGRT to correct body rotation, achieving a pseudo-6DOF couch
2. The setup ISO is defined at the Ethos’ laser ISO point
• The fixed shift from the Setup-ISO to Treatment-ISO is calibrated.
3. The delta couch shift (DCS) must be applied to IGRT plans
• Setup consistency among SGRT, conventional, and IGRT setups
SGRT patient monitoring at treatment ISO
1. Use the bore-based ring camera set for patient motion monitoring
• Capture a new on-site reference for real-time delta (RTD) monitoring
2. No MMI: manual AlignRT patient loading, and manual beam control
Scottsdale, AZ, SGRT Community Meeting 2024

7. 7
AlignRT inBore Setup and Motion Monitoring
Scottsdale, AZ, SGRT Community Meeting 2024
RGB
BW

8. 8
Commissioning (1): inBore Ring was in the Beam
CBCT showed the InBore camera image
• Moved the ring to the front by 2.0cm
Scottsdale, AZ, SGRT Community Meeting 2024

9. 9
Commissioning (2): Daily Collision Check and QA
New York State regulation: Ethos daily collision check is required
1. Daily collision check moves the bore cover → the camera ring
a. AlignRT inBore camera is mounted on the bore cover
2. How to make AlignRT inBore daily QA passing after collision check?
a. Working VisionRT support team to fix the inBore ring cameras rigidly
b. Developing a “gentle” collision check procedure to minimize bore movement
c. It took 4-month to develop, test, and validate the new daily QA procedure
Understanding inBore camera QA tolerances
1. Relative camera shift < 1mm between the two cameras on the ring
2. Ring position shift < 2mm between calibration and daily QA position
3. Daily QA data over three months, illustrating its stability.
Scottsdale, AZ, SGRT Community Meeting 2024

10. Worked with VisionRT engineers
1. Fixed the inBore cameras to pass the relative
camera tolerance < 1mm
2. Developed a gentle collision check method to
minimize ring position shift < 2mm
3. No need for daily calibration anymore…
10
Daily QA Troubles from Daily Collision Check
Scottsdale, AZ, SGRT Community Meeting 2024
- Nguyen et al, Physica Medica, 2020, 80; 159-166.

11. 11
A New “Gentle” Collision Check Procedure
Scottsdale, AZ, SGRT Community Meeting 2024
•Where: At the back of the Ethos
•(A) Before: Mark the abutting line between two covers.
•(B) During: Use thumbs to push upward to trigger a collision.
•(C) After: Use index fingers to pull down to the abutting line.

12. 12
DailyQA History Examples (3/2024)
Scottsdale, AZ, SGRT Community Meeting 2024
ISO

13. 13
DailyQA History Examples (4/2024)
Scottsdale, AZ, SGRT Community Meeting 2024
ISO

14. 14
Commissioning (3) - Other AlignRT InBore Tests
InBore camera stability
InBore and CBCT setup consistency in the IEC60217 system
Scottsdale, AZ, SGRT Community Meeting 2024
TestConditionAlignRT (cm)CBCT (cm)Couch (cm)
VRTLNGLATVRTLNGLATVRTLNGLAT
SetupSetup ISO0.01-0.010.00-23.445.61.4
Treat ISO0.04-0.05-0.020.07-0.06-0.10-9.392.90.2
CBCT Setup-0.020.010.070.020.000.00-9.292.80.1
CouchIntroducing Couch Shifts (-0.4, 0.39, 0.41) (cm)
Initial0.36-0.37-0.350.40-0.39-0.41-9.693.20.5
CBCT Correct-0.040.010.07 -9.292.8

15. 15
Patient Preparation for IGRT Planning from Eclipse
AlignRT inBore IGRT patient preparation:
1. In Eclipse: turn on delta couch shift (DCS) before DICOM exporting
a. Treatment unapproving & reapproving a plan do not change UID
2. In AlignRT inBore system, two coordinate systems must be displayed
a. One @Setup ISO (BW) and one @Treatment ISO (RGB)
No MMI communication between AlignRT and Ethos systems
1. No beam control for reference surfaces
2. No send to couch function for auto-shift correction
Consistency between AlignRT, marker-based, and CBCT setups
1. If AlignRT is down, simply switch to marker-based setup
Scottsdale, AZ, SGRT Community Meeting 2024

16. 16
SGRT 6DOF Setup: Achieving a pseudo 6DOF couch
New disease sites (Pelvis and HN)
1. Region of interest (ROI) for different anatomical sites
a. Prostate site (post-op with nodal involvement)
b. Head and neck (HN) and PBI just started.
2. The pelvis ROI is the same as VRT recommends.
Pelvis rotation correction and benefits:
1. Ten prostate patients participated this clinical studies
2. Two cohorts: marker-based setups vs. SGRT setups
3. End point 1: CBCT setup shifts >1cm (marker) vs. <1cm (SGRT)
4. End point 2: CBCT rotation correction differences
Scottsdale, AZ, SGRT Community Meeting 2024

17. 17
SGRT 6DOF Pelvis Setup Results and Benefits
CBCT apparent shifts and corrections
1. Body rotation correction can reduce the CBCT setup shifts.
a. Usually, reduced from >1cm to <1cm CBCT shifts.
b. Besides rotational correction, body deformation can be minimized.
Rotational correction @Setup ISO reduces CBCT rotation shifts
Scottsdale, AZ, SGRT Community Meeting 2024

18. 18
ROI Definition for HN Patients (two Areas)
Scottsdale, AZ, SGRT Community Meeting 2024

19. 19
A Correlation Study of Anterior Surface and Spinal Canal
Scottsdale, AZ, SGRT Community Meeting 2024

20. 20TWA, SGRT Community Meeting 2023
Summary
We have developed SGRT QA procedures for Ethos systems
1. Moved the inBore camera ring to the front by 2cm
2. Had the inBore camera sets fixed by VisionRT (∆<1.0mm)
3. Developed the gentle collision check to reproduce the ring (∆<2.0mm)
4. Passing dailyQA without re-calibrating the inBore system.
We have implemented SGRT setup procedures for Ethos treatments
1. Pelvis (prostate) patient setup to create a pseudo 6DOF couch.
2. HN SGRT setups to battle with deformation, reproducing neck curvature.
3. PBI and lung SGRT patient setups are coming...
4. SGRT is applied for IGRT, and will be applied for adaptive planning…

21. Thank You!
Any Questions?

22. 22TWA, SGRT Community Meeting 2023
Quiz:
1. Does AlignRT inBore use different ISO for setup and treatment?
1. True. (√)
2. False.
2. Is delta couch shift (DCS) required for bore-based SGRT setup?
1. Yes. DCS must be applied in Ethos/Halcyon plans. (√)
2. Maybe. DCS may or may not be used, it does not matter.
3. Maybe. It is a choice of user at your hospital.
4. No. DCS is not required for AlignRT inBore SGRT setup.
3. AlignRT inBore daily QA often false due to daily collision check?
1. True.
2. False. (√)

23. 23TWA, SGRT Community Meeting 2023
Quiz:
4. AlignRT inBore commissioning needs to check the followings?
1. InBore camera ring position and stability.
2. SGRT setup consistency with conventional and IGRT setups.
3. Establish setup ISO and treatment ISO consistency via calibration.
4. All of the above. (√)
5. What are the facts of the AlignRT inBore system?
1. It views the ROI better when patients are inside at treatment position.
2. The field of view of inBore cameras is smaller than ceiling-mounted ones.
3. The inBore system uses different servers from the Advance system.
4. All of the above. (√)
5. None of the above.