Implementing an End-to-End SGRT Workflow for Breath-Hold SABR

// Month Year
Implementing an end-to-end SGRT
workflow for breath-hold SABR
Presenters: Chelsea Carnall
Senior Regional Therapeutic Radiographer (Central)
Ellen Dear
Senior Regional Therapeutic Radiographer (East)
©GenesisCare 2022

Objective
©GenesisCare 2022 2
Discuss the implementation, benefits and challenges for SGRT to plan and
treat breath-hold SABR.

Introduction to GenesisCare
● Global provider of cancer care - in
Australia, UK, Spain and USA
● We have 14 sites across the UK

SGRT at GenesisCare
● At GenesisCare, we have
incorporated SGRT since January
2018, using VisionRT
● Rolled out throughout all our 14 sites
across the UK March - April 2018
● We are completely tattooless, using
SGRT for all treatment sites

Case Study Outline
● 77yr old gentleman with castration-
resistant prostate cancer (diagnosed
2004), manubrial bony met since 2015,
decision to treat due to progression
● Internal specialist SABR MDT approved
for treatment plan of 30Gy/3#
● Treated on Varian Edge Linac with
6DoF couch (treated similar cases on
our Elekta VersaHD’s)
● Patient treated in breath-hold

VisionRT - SimRT & Breath-hold Coaching
Overview
• SimRT used at planning
CT, which is used routinely
for DIBH and 4DCT
• Ceiling mounted camera
with a stable tracking point
on the patient’s anatomy
• Able to assess patient’s
ability to hold their breath,
can then offer coaching if
needed
Breath-hold coaching
• Coaching the patient into a
suitable breath-hold level
is vital
• We can assess the
patient’s suitability before
delivering any radiation
• In room coaching
○ Guide into breath–
hold
○ Check for back
arching and chest
breaths
Using SimRT for coaching
• SimRT allows us to accurately
assess the breath-hold level
• Asked the patient to hold for 25-
30 seconds (average treatment
beam delivery time)
• We can visualise any air ‘leakage’

• 1x free-breathing 3DCT & 1x breath-hold 3DCT as per our
standard protocol for DIBH patients
• Free-breathing 3DCT to use for on initial set-up on treatment
• Breath-hold 3DCT for accurate assessment of breath-hold
level and treatment
• Can use SimRT to see depth of breath-hold
○ We were able to confidently complete scanning
and treatment without the need for a 4DCT
(ALARP)
○ SimRT gives us confidence that planning datasets
are accurate and will be reproducible on treatment
VisionRT - SimRT for this case

Dosimetric comparison: Free breathing vs Breath hold
● Compared the body surface between the free-
breathing and breath-hold scans
● Showed a difference between 1-2mm
● The planned (BH) CTV was expanded by 2mm to
derive a theoretical and conservative free-
breathing CTV volume
● The PTV was then expanded by a further 3mm
as per SABR protocol
Planned volume on
BH (cc)
Volume on FB (cc)* % Difference
CTV 66.5 85.9 29.20%
PTV (3mm margin) 110.2 134.7 22.25%
* Estimated by expanding BH margins by 2 mm Ant-Post, equivalent to FB surface shifts
Green = FB
Red = BH

This case
Treatment Set Up - AlignRT
● Wingboard & indexed knee rest
● Used postural mode to aid with arm
position
In-room set up
• Two surface structures - FB and BH, created
from the two 3DCT scans
• Initial set-up in free-breathing using AlignRT to
get patient to the isocentre position and correct
for rotations (after #1 can also use saved bed
position)
• Patient holds breath and use BH surface
structure to adjust lateral and longitudinal
position - vertical controlled by level of breath-
hold
• Patient can use real-time-coach (RTC) as a
visual aid.
(SimRT-
VisionRT)

This case
Treatment Delivery - AlignRT
• CBCT used to confirm internal position -
performed in breath-hold
• Treatment delivery is gated, AlignRT
gates 0.2cm movement either side of CT
breath-hold level
(SimRT-
VisionRT)
Overview
• 2 x 6MV FFF VMAT beams
• Patient in control at all times and able to
comfortably hold breath throughout
• When not in correct position, AlignRT
gates the beam
Daily CBCT
workflow by
SABR Technique
Simple Complex Spine
Pre-CBCT Y Y Y
Mid-CBCT At
operator
discretion
At operator
discretion
Y
Post-CBCT Y Y Y

Case Study #1 - AlignRT & CBCT workflow
Initial CBCT showed a max
translational shift of 1.8mm
and rotation of 1.2 degrees.
Translations and rotations
applied using the 6DOF
couch.
During treatment AlignRT
picked up 3mm longitudinal
difference.
Treatment was paused and
a CBCT taken.
CBCT confirmed 3mm
longitudinal shift, applied
and treatment resumed.
Post CBCT showed
intrafractional
motion/discrepancy of
<1mm.

Reflection
Case Study #2&3 - AlignRT & CBCT workflow
● AlignRT allowed for precise set-up,
reducing need for additional CBCTs and
minimising intrafractional motion.
● AlignRT allowed for positional monitoring
during treatment and accurate tracking of
a consistent breath hold.
● AlignRT detected movement of the
patient. Radiographers were able to
pause treatment, re-image and assess
this before any further treatment was
delivered inaccurately. The shift was
corroborated with CBCT, was applied,
and treatment continued to be delivered
with complete accuracy.
#2 & #3 imaging
● #2 and #3 patient stability improved -
● Able to accurately set up and monitor
patient’s breath-hold with AlignRT
● All CBCTs, including the initial set up
CBCT, showed <1mm shifts and <1
degree rotations.
Daily CBCT tolerances for simple SABR
Translations ≤0.5cm
Shift & treat
>0.5cm and ≤1cm
Shift & re-image
>1cm re-
set up
Rotations 3 degrees

Limitations and troubleshooting with SGRT
Tracking point location in
SimRT
Tracking point can be lost as CT bed
moves through the scanner.
Troubleshooted by choosing tracking
point at end of topogram when patient
inside the scanner.
Patients with small breath-hold
With a smaller breath-hold, it is harder
to determine if a patients is in breath-
hold or free breathing.
Troubleshooted by coaching patients,
assessing suitability for breath hold, or
sometimes sending away to practice.
Initial struggle with skin tones
Initially we found AlignRT would
“flicker” or “reflect” and lose the skin
surface. Spoke to VisionRT who
advised to use the skin tone setting to
choose appropriately which has helped.
CBCT not gated - relies on
radiographer observation to
interrupt
Radiographers always watching when
patient in breath-hold to interrupt if
patient releases breath.

To Conclude
● Treating in breath-hold allowed us to limit dose to the patient as we didn’t have to perform a
4DCT (ALARP)
● Treating in breath-hold allowed for reduced irradiated volumes due to minimal target-motion.
● At CT, SimRT allows us to assess level and consistency of breath-hold.
● AlignRT allows patient to be in control of breath-hold during gated treatment
● AlignRT detected patient movement during treatment - able to re-CBCT and apply moves to
ensure accurate treatment
● SGRT allows us to deliver treatment confidently and accurately without need for permanent
tattoo marks.

Studies
● Hamming, V.C., Visser, C., Batin, E., McDermott, L.N., Busz, D.M., Both, S., Langendijk,
J.A. and Sijtsema, N.M. (2019). Evaluation of a 3D surface imaging system for deep
inspiration breath-hold patient positioning and intra-fraction monitoring. Radiation Oncology,
14(1). doi:10.1186/s13014-019-1329-6.
● Heinzerling, J.H., Biester, E.C., Robinson, M., Moeller, B.J., Prabhu, R.S., Ward, M.C.,
Corso, C.D., Gregory, J., Hampton, C.J., Burri, S.H. and Foster, R.D. (2021). Prospective
Study of Surface Guided Radiation Therapy (SGRT) for Breath Hold SBRT Treatments of
the Lung: Analysis of Reliability of Surface Guidance Alone for Internal Tumor Position
During Breath Hold. International Journal of Radiation Oncology*Biology*Physics, 111(3),
p.e539. doi:10.1016/j.ijrobp.2021.07.1468.
● Nankali, S., Hansen, R., Worm, E., Yates, E.S., Thomsen, M.S., Offersen, B. and Poulsen,
P.R. (2022). Accuracy and potential improvements of surface-guided breast cancer
radiotherapy in deep inspiration breath-hold with daily image-guidance. Physics in Medicine
and Biology, [online] 67(19). doi:10.1088/1361-6560/ac9109.

References
● Carnall, C. (2022). Varian Edge Linac. [Photo].
● Dear, E. (2022). PTV outline. [Photo].
● Dear, E. (2022). VisionRT SimRT. [Photo].
● Vision RT. (n.d.). Breast And Deep Inspiration Breath Hold (DIBH). [online] Available at:
https://www.visionrt.com/applications/dibh/ [Accessed 7 Nov. 2022].
● Vision RT. (n.d.). SimRT. [online] Available at: https://www.visionrt.com/simrt/ [Accessed 7 Nov.
2022].
● Vision RT. (n.d.). Virtual Learning. [online] Available at: https://www.visionrt.com/virtual/
[Accessed 7 Nov. 2022].
● www.genesiscare.com. (n.d.). UK Cancer Treatment Centres & Diagnostic Clinics |
GenesisCare UK. [online] Available at: https://www.genesiscare.com/uk/our-centres [Accessed
7 Nov. 2022].
● Vision RT. (n.d) Real Time Coach Display. [online] Available at:
https://www.visionrt.com/products/the-real-time-coach-display/ [Accessed 9 Nov. 2022]

Further questions?
If you have any further questions about our experience please feel free to email us:
chelsea.carnall@genesiscare.co.uk
ellen.dear@genesiscare.co.uk

Implementing an End-to-End SGRT Workflow for Breath-Hold SABR

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