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IMAGE GUDIED RADIOTHERAPY IN OUR COUNTRY INDIA
- 1. Image Guided Radiotherapy Dr.G. K. Rath Professor and Head of Radiotherapy & Chief, Dr. BRA IRCH, All India Institute of Medical Sciences, New Delhi
- 2. Normal Tissue Complication Probability (NTCP) DOSE Tumor Control Probability (TCP) ConventionalTechnique Dose Escalation Conformal Avoidance Treatment Planning - Goals Deliver maximum dose to the tumor (Increase cure rate) Reduce dose to the surrounding normal structures (reduce complications)
- 3. 3 •Ca Prostate •The rateof positive biopsies decreased linearly as dose escalated (3DCRT) 81 Gy -7% pos biopsy rate, 75.6 Gy -48%, 70.2 Gy -45%, 64.8 Gy -57% Dose Escalation Improved Results Zelefsky et al. Int. J. Radiation Oncology Biol. Phys. 1998;41;491- 500
- 4. 4 MDACC 4 YRPSA free survival rates: <67 Gy-(n=500)-54% 67-77 Gy-(n=495)-71% >77 Gy-(n=132)-77% Pollack et al. Int. J. Radiation Oncology Biol. Phys 1997;39;1011-18 Dose Escalation Improved Results
- 5. 5 IMRT Gives ImprovedConformity • Improved clinical outcomes • Less complications and side effects • More effective treatment • Reduced need for invasive procedures Rectum IMRT Rectum Conventional RT Prostat e Prostate
- 6. Organ Motion isthe CONCERN Interfraction motion occurs between fractions and primarily is related to changes in patient localization Intrafraction - motion occurs during fractions and primarily related to respiration • Interfraction Deformation
- 7. Tumor Cross-sectional View of Patient’sChest Tumor Some motion is mostly Anterior / Posterior Some motion is mostly Superior / Inferior All tumor motion is Complex Tumor Motion During Respiration • All tumor motion is complex
- 8. Tumor Motion: HowOften? Van Herk M. Semin Radiat Oncol 2007; 17: 258-267
- 9. Factors influencing targetlocalization and positioning A. Patient motion B. Weight loss C. Absence or presence of fluid D. Bone mineral losses 9
- 10. Factors influencing targetlocalization and positioning E. Periodic physiologic movements Peristalsis Blood flow Breathing Cardiac motion F. Random physiologic movement Swallowing Coughing Hiccups Sneezing 10
- 11. Factors influencing targetlocalization and positioning G. Transfer errors H. Transpositional errors I. Setup errors (either initial or repeat) 11
- 12. 12 Efficient Treatment AlsoRequires Accuracy !!! The right target Radiation shaped to target but missing target
- 13. CAUTION With tight marginsbeing taken in highly conformal radiotherapy techniques there is a risk of precisely missing the target with organ motion. 13
- 14. To Combat TheseUncertainties volume = 4/3 ¶ r 3 a small reduction in margin (5mm) yields a reduction by half in volume Verellen D, Nature Reviews cancer 2007;7:949-61 2. Use IGRT Or
- 15. IGRT Dawson LA etal. JCO 2007;25:938-46 IGRT is defined as frequent imaging in the treatment room that allows treatment decisions to be made on the basis of these images.
- 16. Four- Dimensional Radiotherapy(4DRT) IGRT in which the localization accuracy– not only in space but also in time – is improved In comparison to that in 3DRT tumor position is monitored during the delivery of the therapeutic beam. Shirato H, et al. Int J Clin Oncol 2007; 12:8–16
- 17. History IGRT Technology 1958-Holloway et.al reported portable x-ray machine mounted on the counter weight to TheratronCo-60 machine
- 18. Clinical Indication forIGRT Tumors adjacent to critical structures Tumors prone to inter fractional motion Tumors prone to intra fractional motion Tumors prone to deformation IMRT, SRS/SRT/SBRT Hypofractionation schemes
- 19. 19 IGRT Tumor Sites Calung Ca Prostate Head and Neck Ca Rectum Ca Cervix
- 20. 20 IGRT : AvailableOptions IGRT encompasses the following present day Technology • Volumetric CT on rails Tomotherapy MV cone beam CT KV cone beam CT • Planar X ray based EPID Cyber knife • Video based Real Time video guided IMRT • Ultrasound based BAT
- 21. Current IGRT inMarket Ultrasound Video-Based Planar: X-Ray Volumetric BAT SonArray I-Beam Restitu Video Subtraction Photogrammetry AlignRT Real-Time Video EPID CyberKnife Novalis RTRT Gantry-Mounted Prototype Tohoku IRIS Commercial Varian OBI Elekta Synergy In-Room CT FOCAL, MSKCC CT-on-Rails Primation Varian ExaCT Tomotherapy MV Cone Beam CT Siemens kV Cone Beam CT Mobile C-arm Varian OBI Elekta Synergy Siemens In-Line Related Technologies RPM gating/4DCT Optical-guided Approaches
- 22. 22 Techniques of TumorTracking • Skin Markers Not adequate for IGRT as margins required for uncertainty will be 1.5 –2cm • Internal markers A. CT based Bony Anatomy tracking B. CT based Soft Tissue Tracking C. Implanted fiducials (Deformation is a problem, Less inter user variation, Good stability) D. Implanted radiofrequency transponders for electromagnetic tracking (miniature Global Positioning Systems) E. Endo-rectal balloon (can reduce rectal radiation dose, Renders rectal dosimetry more predictable by making rectal anatomy more reproducible)
- 23. CT in thetreatment room
- 24. 24 IGRT at AIIMS Megavoltage radiationsource Kilovoltage radiation source Kilovoltage imager Megavoltage imager
- 25. Electronic portal imaging(EPID) 25 Uses 6 MV beam to acquire image. require one AP and one LAT field for setup verification The position error is determined using the rigid body registration between a daily treatment radiographic image and a reference radiographic image digital reconstructed radiographic (DRR) image created in treatment planning Uses bony anatomy or implanted radio-markers position as a surrogate to verify patient setup position DRR Image Portal Image
- 26. Electronic portal imaging(EPID) Pros Mount on the linear accelerator Treatment beam to acquire image Real time imaging Beams eye view verification Low dose (2cGy-3cGy) Setup accuracy < 2mm Cons Very low contrast due to the high energy of the photons matching can only be two-dimensional Tissue information is lacking Patient Rotational error correction not possible 26
- 27. 3D Volumetric Imaging 3-Dvolumetric imaging inside a treatment room true 3-D information can be acquired with a CT scanner in the same room just before the start of treatment allows for more accurate guidance to setup the patient's position relative to the treatment beams In-room CT images used to reconstruct dose distributions allows image-guided adaptive radiotherapy
- 28. Dedicated IGRT/IMRT treatmentuni MVCT imaging Translational correction only Pros MV CT devices offer an advantage when scanning patients with hip prostheses or dental fillings because the high Z material does not produce an artifact at megavoltage energies Large field of view (FOV) of 40 cm Cons Use of MV treatment beam for imaging may force compromises between the dose delivered and the image quality Patient throughput is less Tomotherapy : Helical MVCT
- 29. Flat-panel detectors basedEPID mounted on a linac gantry and the therapy MV x-ray Possible to acquire multiple, low-dose 2-D projection images Advantage it does not require the extensive modification of a Linac CBCT imaging system uses a large detector and a single rotation Disadvantage lack of discrimination of soft tissue and bony objects by the physics of high-energy x-rays Megavoltage cone-beam CT (MV-CBCT)
- 30. • Radiography, fluoroscopy,and CBCT • Large flat-panel imager • kV x-ray tube mounted on a retractable arm at 90 degrees to the treatment beam line • Cone-beam CT reconstruction acquiring multiple kV radiographs as the gantry rotates through at least 180 degrees Advantages • real-time information is available • No surrogates required Disadvantages • Mechanically less stable • Requires careful calibration kV-CB CT On-board imager
- 31. How to Correctfor Displacements Couch corrections Gantry and collimator angle adjustments Modification of multi-leaf collimator leaf positions 31
- 32. Couch Corrections 32 Correction bylateral couch shift (Tomotherapy) Boswell et al. Med Phys. 2005; 32:1630-9.
- 33. Hexapod Couch atAIIMS
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- 35. Advantages • No surrogaterequired (soft tissue visualization) • Remaining random error same magnitude as with initial set-up Disadvantages • CT-contour ≠US-structure • Important inter-user variability Non-Radiographic techniques: Ultrasound • Noninvasive • No radiographic • Relatively easy imaging
- 36. Electromagnetic fields toinduce and detect signals from implanted wireless devices System consists of a console optical tracking system and a tracking station The magnetic array is lightweight and contains the source coils which generate signals to excite the transponders, and the sensor coils which detect the unique response signals returned by each transponder Can actively detect the position of transponder without using the radiographic method The Calypso 4-D Localization system can update target position ten times per second, fast enough to track breathing motion of the tumor Sub millimeter tracking accuracy Electromagnetic Field Tracking: Calypso system
- 37. Methods to accountfor Respiratory motion Motion encompassing methods Respiratory Gating methods Breath-hold methods Forced shallow breathing with abdominal compression Respiratory tracking methods
- 38. Motion encompassing methods (i)Slow CT scanning (ii) Gated/breath hold CT Prospective respiratory correlation (iii) 4DCT Retrospective respiratory correlation
- 39. Principle of 4Dscanning
- 40. Process/Setup 3D 4D Scan– light breathing Acquire ~ 100 slices 1 volumetric study Acquire 1500+slices – multiple volumetric studies Dose ~ 1 cGy 3-5 Time greater dose Reconstruction Conventional Conventional followed by resorting/multiple sets OR projection sorting followed by conventional reconstruction Contouring VOIs Performed on single study Performed on multiple studies; computer assistance needed Aperture design Standard 3D Extract shape and trajectory; create composite ITV Choose beam directions BEV Multiple shape and trajectory; create composite ITV Generate DDRs Conventional At specific phase of pseudo fluoroscopic DRR movie loop Image guided patient set up Standard guidance by bony anatomy of clips Guidance by gated of multiple image acquisitions (compare DRRs) Different between 3D and 4D CT
- 41. Respiratory Gating Radiation deliverysynchronized with the respiratory signal A reflective marker block is placed on the patient to detect respiration motion (or internal fiducial markers) Marker blocks are illuminated by infrared emitting diodes Software tracks the position of the marker
- 42. Respiration Gating withRPM RPM is a external gating system System consists of an infra-red camera that is mounted to the foot of the CT Markers block containing 2 reflectors. The marker block was placed on the patient’s skin in the abdominal region Surrogate signal = abdominal surface motion correlation to tumor motion The x-ray on signal from the CT scanner was recorded synchronously with the respiration signal Real-time position Management system (RPM) Video Camera
- 43. Active Breathing Control(ABC) • Temporarily immobilizes patient’s breathing • The inspiration and expiration paths of airflow are closed at a predetermined flow direction
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- 46. A Survey ofIGRT Use in the United States Of 1089 evaluable respondents, 393 responses (36.1%). Radiation oncologists using IGRT : 93.5%. The percentages using ultrasound, video, MV-planar, KV-planar, and volumetric technologies were 22.3%, 3.2%, 62.7%, 57.7%, and 58.8%, respectively. Among IGRT users, the most common disease sites treated were genitourinary (91.1%), head and neck (74.2%), central nervous system (71.9%), and lung (66.9%). Overall, 59.1% of IGRT users planned to increase use, and 71.4% of nonusers planned to adopt IGRT in the future 46 Simpson DR. Cancer 2010;116:3953–60.
- 47. Academic vs. private-practiceusing IGRT technologies (asterisks, P < .05) 47 Simpson DR. Cancer 2010;116:3953–60.
- 48. Cumulative adoption of IGRTtechnologies Over Years 48 Simpson DR. Cancer 2010;116:3953–60.
- 49. IGRT Modalities byDisease Site 49 Simpson DR. Cancer 2010;116:3953–60.
- 50. TRUS Probe Image GuidedBrachytherapy: Cervix
- 51. Dose reduction tonormal structures Rectal dose (of Pt A) Bladder dose (of Pt A) ICRT 60-70% 70-80% Interstitial 20-25% 20-25%
- 52.
- 53. Image Guided Brachytherapy:Prostate
- 55. Conclusion Ultimate objective ofradiotherapy treatment is Increase tumor control probability Decrease normal tissue complications Has been difficult so far due to Target geometry uncertainty Intra-fraction and inter-fraction motion
- 56. Conclusion The goal ispossible ….. Advances in imaging and modern RT facilities IGRT provides a solution for combating organ motion in radiotherapy Delivering higher dose to tumor and less dose to normal tissue. IGRT provides a natural quality-assurance step for conformal radiotherapy Image is better than imagination, but an image is always different from the real. Limited clinical studies, needs to be studied further