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Motion Management in Radiation Therapy
Motion management strategies in radiation therapy aim to account for tumor movement during treatment. Key strategies include gating methods that deliver radiation only during specific respiratory phases, breath hold methods that immobilize tumors during deep inhalation or exhalation, tracking methods that follow tumor motion in real-time and adjust beam targeting accordingly, and encompassing methods that define larger target volumes to cover full respiratory excursion. No single approach is clearly superior, as appropriate management depends on tumor location, motion extent, and available technology. The goal of all motion management is to safely escalate dose to tumors while reducing dose to surrounding healthy tissues.
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Motion Management in Radiation Therapy
- 1. Motion Management strategiesin 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 wanttightly 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.
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- 7. • Measured 3Dprojectory 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 duringRespiration
- 9. Problems associated withrespiratory 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
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- 15. • Traditionally, Accordingto 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/CLINICALONCOLOGY/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 encompassingmethods • 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 ExhaleBreath 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 • Determinesthe 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 Gatingmethod • 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: Gatingmethod • 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 ofamplitude 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 BreathHold (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 developedfor 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 RadiosurgerySystem • 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 TrackingSystem • 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 DOESIT WORKS? 33
- 34. Synchrony Tracking withRadixact (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 availableTracking Systems • AlignRT – Vision RT (Surface Guided) • RTRT System • VERO System • Exac-Trac System • Calypso system
- 36. Which Motion Managementsystem is better??
- 39. Answer: What ManagementAcquires
- 40. RMM Techniques :In Simple Words GATING AND SHOOTING COMPRESSING AND CRESHING HOLDING AND SCOLDING TRACKING AND CRACKING
- 41. Summary • The managementof 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 notstop the Motion, Technology can help us to manage it •Thanks…!!!