ABC system Radiotherapy Free Breath 4DCT Radiotherapy Symmetry 4DCBCT Radiotherapy Motion Management

1. ABC system, Free Breath 4DCT &
Symmetry
Dr Sanjeet Mandal
Assistant Professor, Radiation Oncology
Kidwai Memorial Institute of Oncology, Bengaluru

2. Introduction
 The advancements in Radiation Oncology is always to aim
higher dose to tumour and less dose to normal tissues.
 ICRU 62 defines Internal Target
Volume (ITV) as CTV with internal
margin
 Planning Risk Volume (PRV) as OAR
with internal margin

3. Organ Motion
Intra – fraction motion
- Swallowing
- Coughing
- Eye movement
- Heartbeat
Inter – fraction motion
- Tumour change
- Weight gain/loss
- Positioning changes
- Respiration
- Bowel and Rectal filling
- Bladder filling

4.  Respiration is most relevant source of motion for lung, breast,
liver and pancreatic cancers.
 Respiratory motion is patient specific
 It may vary between fractions and even within a fraction
 Lung tumours, typically 5-10mm, but in lower lobe ≥5cm
Breast tumours, typically 5-10mm, more in pendulous type
Abdominal tumours (Liver, Pancreas), typically > 10mm

5. Problems from respiration
 Inter and Intraobserver variation in GTV & CTV delineation
 Motion artefacts in CT simulation – target delineation errors
 Daily variation of respiratory motion
 Treatment related anatomic changes, reduction in bronchiole
obstructions and changes in atelectasis
 RT planning & delivery limitations

6. Motion artefact due to respiration
RT planning limitations due to respiration
Free Breath versus Respiratory Gated scan

7. Tumour motion is complex
Some tumour move in AP predominantly
Some tumour move in SI predominantly
Sometimes hysterical
Ref: AAPM TG 76

8. Methods to account for Respiratory motion
 Motion encompassing methods – Slow CT, Inhalation & Exhalation
Breath Hold CT, 4DCT (Symmetry, Bellows belt)
 Respiratory gating methods
External fiducials– RPM system, ExacTrac gating, Anzai belt
Internal fiducials – Hokkaido university & Mitsubishi
Gated IMRT
 Breath hold methods
DIBH – VMAX Spectra 20C, SpiroDyn’RX
mDIBH - Active Breathing Control (ABC) system
 Forced shallow breathing with abdominal compression
 Real time tumour tracking methods

9. Recommended clinical process for respiratory motion management by AAPM TG 76

10. Free Breath 4DCT
Patient Selection
- Tumour motion ≥ 5mm or OAR sparing can be increased
Preparation
- Inform regarding the Immobilisation steps & CT simulation
process (120s slow CT)
- No coaching required
- Patient must be not move during image acquisition (due to
pain or any other discomfort)

11. 4DCT Image Acquisition - Prospective
Images are acquired & sorted during a portion of respiratory
cycle

12. 4DCT Image Acquisition - Retrospective
Images are acquired during entire phase of respiratory cycle &
sorted later

13. Free Breath 4DCT – Bellows belt
 Pulmonary tool kit by Phillips
 It consists of a deformable belt with pneumatic sensors
(placed on patient) with a cable connected to CT gantry
 Image during CT simulation
 It generates breathing signals corresponding to respiration
during all phases (retrospective 4DCT)
 Entire image sets (usually 10) are created – used to create ITV,
average or MIP

14. Free Breathing 4D CT – Bellows belt
during CT simulation

15. Free Breath 4D CBCT – Symmetry
 4D CBCT feature within linac by Elekta (VersaHD)
 No external belt or IR marker required
 Image during treatment
 It generates breathing signals corresponding to respiration
during all phases (retrospective 4DCT)
 Entire image sets (usually 10) are created – used to create ITV,
average or MIP

16. Free Breathing 4D CBCT – Symmetry
during Radiation Therapy

17. Active Breathing Control (ABC) system

18. mDIBH by ABC system
Patient Selection
- Tumour motion ≥ 5mm or OAR sparing can be increased
- Good cardiopulmonary function
- No dental issues
- No facial muscle / upper limb weakness
- No hearing problems
- Able to follow commands

19. mDIBH by ABC system
Preparation
- Inform regarding the Immobilisation steps, mDIBH by ABC
system training, CT simulation & Radiation Therapy process
- Coaching required (Usually 5-7days)
- Patient must be not move during image acquisition (due to
pain or any other discomfort)
- Spirometer exercise

20. mDIBH by ABC system
- A reproducible breath hold method developed at William
Beaumount Hospital and commercialized by Elekta
- It consists of digital spirometer connected to balloon valve
- The valve is inflated to pre-defined tidal volume & duration
- Moderate DIBH, usually 75% of deep inspiratory capacity
(reproducible & comfort)
- Deep Expiration Breath Hold can also be done

21. Free Breathing 4D CT – ABC SYSTEM
during CT simulation

22. DIBH decreases radiation dose to heart & LAD better than FB

23. ITV by various motion management methods

24. Take home message
 Tumour motion ≥ 5mm or OAR sparing may be increased
 Proper patient selection criteria
 Patient should comply throughout radiation treatment
 Choose motion management method appropriately (ABC
system has less ITV volume BUT Free breath 4DCT has better
patient comfort)

25. THANK YOU