Overview of the solutions for motion management during Radiation delivery.

1. Motion Management strategies in Radiation Therapy
Teekendra Singh Faujdar,
Sr. Radiation Therapist
Medanta The Medicity, Gurgaon

2. Aim of Radiotherapy
• To deliver a prescribed dose of
radiation to the Target while
sparing surrounding Healthy
tissues to the largest extent
possible.
How to achieve:
 Correct tumor delineation
 Accurate planning
 Proper Delivery

3. • We want tightly confirming dose distribution
• Pushing backward and forward always not the point of interest
• Because everything moves
 Tumor (lung, liver, breast, mediastinal
lymphoma, prostate…)
 Patient (set-up and weight variation)
 Couch (e.g. CT and TomoTherapy)
 Gantry and MLC
(IMRT/VMAT/TomoTherapy)

4. Motion in Radiotherapy
• Motion: Anything that may lead to mismatch between the
intended and actual location of delivered radiation dose.
• Intra-fraction motion
– during the fraction
 Heartbeat
 Swallowing
 Coughing
 Eye movement
• Inter-fraction motion
- in between the fractions
 Tumor change
 Weight gain/loss
 Positioning deviation
 Breathing
 Bowel and rectal filling
 Bladder filling
 Muscle relaxation/tension

5. Motion in Radiotherapy
• Respiratory motion affects all tumor sites in
the thorax, abdomen and pelvis area.
• Tumors in the lung, liver, pancreas,
esophagus, breast, kidneys, prostate, and
other neighboring sites as known to move
due to respiration.
• Although tumor displacement varies
depending on the site and organ location, it is
most prevalent and prominent in lung
cancers.
• Studies have shown that lung tumors can
move several centimeters in any direction
during irradiation.

6. AAPM/TG-76

7. • Measured 3D projectory for 21 patients
• Used 2mm gold fiducials inserted into or near
tumors and tracked their motion using a real-time
tracking system, imaging three-dimensional co-
ordinates at 30 images per second.
• They concluded that tumor motion was greatest in the superior-inferior direction for unfixed tumors and for lesions close to the
diaphragm. Tumor motion due to breathing was greatest in the cranial-caudal direction for lower-lobe unfixed tumors.
• The amount of motion ranges from a 1-mm displacement to more than a 2-cm displacement. Furthermore, it can be seen that the
motion is nonlinear for about half of the Fiducial markers.

8. Tumor motion during Respiration

9. Problems associated with respiratory motion during RT

10. Image Acquisition Limitations
• Motion artifacts result if respiratory motion not accounted for
• This can result in target/normal tissue delineation errors

11. Treatment Planning Limitations
• Larger margins have to be used when creating PTV from CTV
• Increased margins means, greater volumes of healthy tissue treated

12. Radiation Delivery Limitations
• Intra-fraction motion produces averaging/blurring of dose distribution over
path of motion, Inter-fraction motion produces shift of dose distribution
• Overall effect is blurring of the dose distribution near the beam edges

14. What’s the solution ???

15. • Traditionally, According to International Commission on Radiation Units and
Measurements (ICRU-62) recommendations, tumor motion is taken into account by
adding a specific security margin (internal margin) around the clinical target volume
(CTV), in order to create the internal target volume (ITV).
• Positioning uncertainties are then added to create the planning target volume (PTV).
Motion Management in Radiotherapy

17. • AJ COLE/CLINICAL ONCOLOGY/2014
• AAPM TG-76
 Motion encompassing methods
 Breath hold methods
 Abdominal compression Methods
 Tracking methods
 Respiratory gating methods
Modern Motion Management Strategies

18. 1. Motion encompassing methods
• The three techniques possible for CT imaging that can include the entire
range of tumor motion for respiration (at the time of CT acquisition) are:
Slow CT
Inhale or Exhale Breath Hold CT
Four dimensional (4-D) or respiration-correlated CT

19. Slow CT Scanning
• CT scanner is operated very slowly, and/or multiple CT scans are averaged such
that multiple respiration phases are recorded per slice.
• Acquire CT images at single couch position during a respiratory cycle
• -Record amplitude and phase for each slice
• Move the couch the distance of the detector width and obtain CT images for
respiratory cycle.
• Generate 4D images
• Disadvantage
• – Loss of resolution due to motion blurring
•(larger errors in tumor and normal tissue delineation)

20. Inhale or Exhale Breath Hold CT
• Acquire both inhalation and exhalation gated or breath-hold CT scans
• Relies on the patient’s ability to hold his or her breath reproducibly.
• Require image fusion and extra contouring.
• For lung tumors, Maximum Intensity Projection (MIP) tool can be
used to obtain the tumor-motion encompassing volume, provided
there is no mediastinal tumor involvement.
• Advantage over slow scanning method
• Blurring caused by the motion present during Free Breathing is significantly reduced

21. 4D-CT/Respiration-correlated CT
• Determines the mean tumor position, tumor range of motion for treatment planning and the
relation of tumor trajectory to other organs.
• Can be used to reconstruct inhalation, exhalation, and slow CT Scans.
• The MIP tool can be used for obtaining the tumor-motion encompassing target volume
• A 4D CT scan can be obtained in approximately 1 minute of scanning time with a 16-slice CT
scanner, where generally 8 to 25 complete CT datasets are reconstructed.
• A 4D-CT scan is acquired with the beam ON, during the duration of a number of respirations and
subsequent reconstruction of CT slices at defined points of the breathing cycle.
• The breathing cycle is measured via a surrogate device (e.g. infrared markers, abdominal belt,
reflective marker block placed on the anterior chest wall).
• These slices are then grouped into ‘bins’ with each bin representing a specific part of that patient’s
breathing cycle
• 4D-CT data acquisition mode: -Prospective
-Retrospective

24. 2. Respiratory Gating method
• Involves the administration of radiation during both imaging and treatment
delivery within a particular portion of the patient’s breathing cycle, commonly
referred to as the “gate”
• Displacement Gating (Amplitude)
• the system calculates a running estimate of the breathing cycle and the clinician specifies
delivery, based on a specific phase of respiration.
• the radiation beam is activated whenever the respiration signal is within a pre-set window
of relative positions.
• Phase Gating
• the user defines minimum and maximum limits between which the CT acquisition or
radiation is delivered, dependent on the absolute position of the marker regardless of the
phase of breathing
• the radiation beam is activated when the phase of the respiration signal is within a pre-
set phase window.

25. Varian(RPM) system: Gating method
• RPM Respiratory Gating technology enables correlation of the tumor
position with the patient’s respiratory cycle. Using an infrared tracking
camera and a reflective marker placed on the patient’s chest, the
system measures the patient’s respiratory pattern and range of motion
and displays them as a waveform.
• Once it is determined how the tumor moves in relation to the
waveform, gating thresholds can be set along the waveform to mark
when the tumor is in the desired portion of the respiratory cycle.
• These thresholds determine when the automatic gating system turns
the treatment beam on and off.
• Gating the beam allows for patient-specific treatment margins, rather
than population-based margins, and may permit an increased
prescription dose to the tumor, while reducing dose to the surrounding
tissues.
• Patient friendly system eliminates the need for breath holding.

26. An example of amplitude gating is Deep Inspiration
Breath Hold technique for left sided breast to minimize
dose received to heart.
•An example of phase gating is treatment of Ca lung .

27. 3. Breath-Hold Method
• Active Breathing Co-ordinator™ (ABC) system
– Immobilizes target anatomy during planning, imaging and delivery
– Enables dose escalation for SBRT techniques
– Reduces dose to OARs
– Supports automated gating for workflow efficiencies
Dawson LA,. Int J Radiat Oncol Biol Phys 2005;62: 1247–1252.
Eccles C,. Int J Radiat Oncol Biol Phys 2006;64:751–759
Wong JW,. Int J Radiat Oncol Biol Phys 1999;44:911–919.
Training:
• Patient coached with audio-visual
feedback
• Freeze breathing for about 15-20
seconds, using a valve
• Patient can release valve anytime
• Radiation delivered only when
valve is closed

28. Deep Inspiration Breath Hold (DIBH)
• Deep inspiration breath hold is a radiation
therapy technique where patient take a deep
breath in, during treatment, and hold the breath
while the radiation is delivered.
• By taking a deep breath in, the lungs fill with air
and your heart will move away from your
anterior chest wall.
• Deep inspiration breath hold can be useful in
situations where radiation therapy is needed in
the chest region to avoid radiation dose to the
heart eg. Ca Lt Breast.
• ABC system adds precision and repeatability to
the well-conceived concept of DIBH.
• ABC provides all features required to implement
a breath hold technique within the clinical
environment.

29. • Originally developed for stereotactic irradiation of small lung and
liver lesions.
• The technique employs a stereotactic body frame with an attached
plate that is pressed against the abdomen.
• The applied pressure to the abdomen reduces diaphragmatic
excursions, while still permitting limited normal respiration.
• May be unsuitable for obese patients or those with poor
respiratory function. Can lead to more erratic breathing in some
instances.
• Requires regular imaging due to difficulties associated with plate
position reproducibility.
4. Abdominal Compression method

30. 5. Tracking Method
• Tracking the tumors and simultaneously delivering radiotherapy is an
attractive, but challenging, option.
• Tumor tracking relies on the interpretation of either internal or external
surrogates with real time delivery of radiation.
• Can significantly reduce margins required, therefore subsequent decrease
in dose to OAR, decreased time to deliver treatment compared to Gating.
• The most commonly used tracking system:
• Cyberknife (Accuray Inc., Sunnyvale, California, USA)

31. Cyberknife: Robotic Radiosurgery System
• Consists of a compact LINAC mounted on an industrial
robotic manipulator arm which directs the radiation
beams to the desired target based on inputs from two
orthogonal X-ray imaging systems mounted on the room
ceiling with flat panel floor detectors on either side of
couch, integrated to provide image guidance for the
treatment process.
• The major strength of the system is that it can move and orient the X-ray beam with six degrees of freedom,
so that it can adapt to the full 3D motion of the tumor.
• For real-time monitoring, Images are acquired throughout the treatment duration at periodic intervals
ranging from 5 to 90 seconds, and the couch and robotic head movements are guided through an automatic
process.
• For tumors, those are prone to move with respiration, an additional component of the Cyberknife system
called the Synchrony Respiratory Tracking System is used to compensate for target motion.

32. Synchrony Respiratory Tracking System
• Tracks the target in real time
• Adjusts beam targeting, based on breathing
pattern of patient.
• Synchronizes treatment delivery to the motion
of tumor throughout the treatment

33. SYNCHRONY- HOW DOES IT WORKS?
33

34. Synchrony Tracking with Radixact (TomoTherapy)
• Mounted kV flat-panel imaging hardware (kV tube
and detector) onto a gantry at 90 degrees offset
from the MV treatment beam-line.
• In addition, an optical camera was installed above
the foot of the couch, looking into the bore.
• System acquires periodic kV images to track the
gold fiducials, then correlates the fiducial positions
with breathing amplitudes continuously monitored
by the optical camera following the external LED
markers.
• Jaw positions and MLC leaf patterns are updated
continuously in real-time, re-shaping (effectively re-
pointing) the treatment beam to follow the target
motion.
ESTRO 38 (Italy)

35. Other Commercially available Tracking Systems
• AlignRT – Vision RT (Surface Guided)
• RTRT System
• VERO System
• Exac-Trac System
• Calypso system

36. Which Motion Management system is better??

39. Answer: What Management Acquires

40. RMM Techniques : In Simple Words
 GATING AND SHOOTING
 COMPRESSING AND CRESHING
 HOLDING AND SCOLDING
 TRACKING AND CRACKING

41. Summary
• The management of respiratory motion in radiation oncology is an evolving
field.
• Delivering higher dose to tumor and less dose to normal tissue.
• With proper patient selection, adequate training & minor increase in
treatment time – treatment of moving tumors with respiration is possible.
• IGRT provides a solution for combating organ motion in radiotherapy.
• Use of the IGRT process has improved our awareness and understanding of
daily inter- and intra-fractional setup variations and motion.
• The experience and appropriate trainings of the team is likely more
important than the actual device/treatment technique used.

42. We can not stop the Motion, Technology can help us to manage it
•Thanks…!!!