Overcoming the Challenges of Mark-Free Prone Setups with SGRT

Andrew Leek, RT(T)(ARRT), BSHA
Radiation Therapist, New Mexico Cancer Center

2. Overcoming Challenges of
Prone Setups with SGRT
An overview of the successes and failures while
going mark-less.

3. Andrew Leek RT(T) BHA
RT(T) for 2 years
2 years at New Mexico Cancer Center
During the summer of 2023 NMCC became the 1st mark-less
center in New Mexico.
We currently use Vision RTs’ Align RT with postural alignment
subscription.
We use a Varian Trubeam with Aria and the Eclipse planning
software

4. Objectives for Today's Lecture
How to perform a CT simulation to prepare for a mark-less treatment course.
How dosimetry can give us additional tools to prepare for first day.
Workflow of first day and challenges that may present.
Daily treatment workflow and efficiency increases we have seen.
This talk serves as a knowledge builder for any center seeking to go mark-less.

5. Where we started
First setups we used SGRT for included supine
breasts and thorax.
We expanded to supine pelvis and extremities and
lastly was the prone setups.
The greatest hurdle we faced was patient position
on the device for prone rectal patients and ROIs for
prone breast.
Prone breast presents a couple of unique
challenges primarily in lateral positioning and ROI.

6. Prone Rectum CT Sim
Accomplishing mark-less treatment starts in the CT sim.
We use a Civco Simmed prone belly board.
Your center will create standard processes that work best
for your workflows both on the planning side and the
treatment side.
This mostly entails patient position on the device and wire
usage as dosimetry deems necessary.

7. We have determined that permanent wire
placement on the board at the 30cm ruler
position is a position that generally works as an
isocenter placement.
With the laser zeroed at 30 we position the
patient so the superior border of the intergluteal
cleft and the 30cm wire coincide.
The beauty here is you will rarely have to even pre
scan the treatment device for treatment prep
coordinates.
Prone Rectal CT Sim

8. The top of the inter-
gluteal cleft should
be aligned with the
30cm point on the
board ruler.
(This is definitely not me)

9. 30 cm on the
prone belly board
corresponds with
the inferior board
hole.

10. For Prone Breast we utilize a Qfix Access Prone G2 board.
We place the patient on the device and ensure there is a
finger width of space (1-2cm) medially between the breast
tissue and the medial aspect of the board.
Superiorly, we position the patient so that the breast
tissue falls naturally without any distortion caused by the
superior border of the board.
We place a BB on the nipple and on the corresponding
mark of the ruler.
Prone Breast CT Sim

11. Prone Breast CT SIM
For breast simulations it is imperative to measure
religiously, especially for the first few mark free patients
you do.
This will give you some back up data to fall back on if and
when setup issues arise.
Taking measurements of that medial position is key to
reproducible tissue displacement until you have mastered.
An important BB to place is on the nipple and record the
corresponding ruler mark.

14. First Day Prone Pelvis
If Iso was set on the same plane as CT origin then
no shift or pre-treatment device scan is needed.
If an Iso shift is required
Pre-scan the board during QA and match the
images to input the coordinates into treatment
prep. (Allows auto-enter on first day.)
Keep longitudinal and lateral present values
under 1.5mm to keep bowel drop reproducible.
Do not use the send to couch function except for
pitch and roll.

15. Here we see a CBCT that
occurred mistakenly
without
pre-scanning the device.
This is the same patient
on the device after we
matched the device on
the first.
See the pubic symphysis
difference.

16. Drive to the table coordinates and lock the table down.
Move the patient sup/inf and correct the roll as necessary on Align RT.
Move the patient laterally without moving the table.
This is a common mistake.
Lastly you can send to couch but only send pitch and roll. (Rotation
should be corrected manually on the patient to ensure spine position)
Daily Treatment Prone Pelvis

17. We currently only use prone breast for partial breast
and tangents so we have never had a shift off of the CT
zero.
However, determining initial lateral position of the table
and board requires a device pre-scan.
Pre-scanned device coordinates allow the therapist to
drive to exact device coordinates on first day will be
found to be a great efficiency gain.
NMCC first day imaging protocol for prone breast
includes CBCT and portal images.
First Day Considerations Prone Breast

18. For daily treatment of breast, we initially start with postural alignment
and then look at the deformation (for a standard couch) feature to
ensure that pitch and roll are correct.
Send to couch is a must use feature for prone breast!
This is useful when your present value for pitch or roll reads 1-2
degrees and there’s nothing you can do to manually take that pitch
away.
Only send to couch after long, lat and vert values have been satisfied.
Only send pitch and roll. (Rotation should be corrected manually on
the patient to ensure correct spine position)
Adding 2 degrees of pitch can dramatically shift a pendulous breast
so applying necessary pitch beforehand is a sure way to minimize off
portal images.
Daily Treatment Prone Breast

19. How to monitor your patients with
effective ROIs
Prone rectal patients on the prone belly board should ideally use an arch shape over the
intergluteal cleft.
Exception to this is when a patient has bolus in the intergluteal cleft.
The ROI should be kept away from the cleft to avoid irregularities or flickering.
Prone breast patients should use an ROI utilizing an oval just over each breast with a
bridge on mid or lower back.
Patients with larger body habitus should lose the bridge and just use the ROIs over each
breast.

20. ROIs that do work!

22. ROIs that did not work.
Don’t make our mistakes!

27. In Summary
Prone setups using Align RT do not have to be hard
The primary takeaway for the talk today is first day
device positioning.
Our experience shows pre-scanning devices to be
most useful and most efficient.
Your patients are going to love the lack of tattoo needles.
Thank you all for attending my talk on
“Overcoming the Challenges of Prone Setups with SGRT”

28. References
AlignRT®. Vision RT. (2024, May 1). https://www.visionrt.com/align_rt/
American Association of Physicists in Medicine (AAPM) -wiley online ... (n.d.).
https://aapm.onlinelibrary.wiley.com/doi/full/10.1002/acm2.12313
Saltofosiris. (2014, October 18). The end?. Teach Like You Meme It.
https://teachlikeyoumemeit.wordpress.com/2014/10/18/the-end/