Imrt Head and neck

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A simple tool to make a non radiation oncologist understand the concept of IMRT. If you wish to download the slides pls contact the up loader at drbalunair@gmail.com

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Imrt Head and neck

  1. 1. Intensity Modulated RadioTherapy in Head & Neck cancer Balukrishna S Dept. of Radiation Oncology
  2. 2. <ul><li>GTV : Gross Tumour Volume </li></ul><ul><li>CTV : Clinical Target Volume </li></ul><ul><li>PTV : Planning Target Volume </li></ul><ul><li>OR : Organ at risk </li></ul>ICRU 62
  3. 3. The GTV <ul><li>GTV is the clinical or radiological gross demonstrable extent and location of the malignant growth. </li></ul><ul><li>The GTV consists of </li></ul><ul><li>“ GTV Primary ” </li></ul><ul><li>“ GTV Nodal ” </li></ul><ul><li>“ GTV Metastasis ” </li></ul>back
  4. 4.
  5. 5. GTV
  6. 6. CLINICAL TARGET VOLUME <ul><li>The CTV is a tissue volume that contains a demonstrable GTV and / or sub clinical malignant disease that must be eliminated </li></ul><ul><li>Macroscopic + Microscopic disease. </li></ul><ul><li>(sub clinical extensions around the GTV) </li></ul><ul><li>Eg. The area around the GTV , the draining lymph nodes </li></ul>back
  7. 7. CTV GTV
  8. 8. CTV GTV
  9. 9. PLANNING TARGET VOLUME <ul><li>Variations : INTRAFRACTIONAL </li></ul><ul><li> INTERFRACTIONAL </li></ul><ul><li>PTV encompasses the whole of CTV with a margin around it. </li></ul>back
  10. 10. CTV PTV GTV
  11. 11. ORGANS AT RISK (OR) <ul><li>OR (critical normal structures) are normal tissues whose radiation sensitivity may significantly influence treatment planning and/or prescribed dose </li></ul><ul><li>Tissues or organs at risk can be classified as </li></ul><ul><li>Serial </li></ul><ul><li>Parallel </li></ul><ul><li>Serial-parallel </li></ul>back
  12. 12. CTV PTV GTV
  13. 13. CTV PTV GTV
  14. 14. FOR RADICAL TREATMENT CTV PTV GTV 70Gy to GTV 60Gy to CTV 50Gy Parotids <26Gy Spine <45Gy
  15. 15. + GTV CTV PTV
  16. 16. + GTV CTV PTV GTV CTV PTV
  17. 17. GTV CTV PTV
  18. 18. GTV CTV PTV
  19. 19. GTV CTV
  20. 20. <ul><li>To improve precision </li></ul><ul><li>To decrease normal tissue dose </li></ul><ul><li>To escalate tumour dose </li></ul>?
  21. 21. <ul><li>Blocks and wedges </li></ul><ul><li>Blocks are changed by hand for each beam angle </li></ul><ul><li>Labor intensive </li></ul><ul><li>4 beam angles </li></ul><ul><li>Dose still relatively low </li></ul>Roughly shaped treatment field
  22. 22. 3DCRT
  23. 23. 3-D Conformal Radiation Therapy – late 1980s <ul><li>Custom-molded block(s) match beam shape to tumor profile </li></ul><ul><li>Shaping from multiple angles </li></ul><ul><li>4-6 beam angles </li></ul><ul><li>Dose still relatively low </li></ul><ul><li>Blocks still changed by hand </li></ul><ul><li>Still slow and labor intensive </li></ul>
  24. 24. Shaped fields <ul><li>Multi Leaf Collimator </li></ul>1970’s 1990’s MLC
  25. 25. Let’s take a closer look at a “ Multi-leaf collimator (MLC)”
  26. 26.
  27. 27.
  28. 28. Automated 3-D Conformal Radiation Therapy <ul><li>Beam shaping automated with MLC </li></ul><ul><li>Less labor intensive </li></ul><ul><li>Use CT scans to see tumors in 3-D </li></ul><ul><li>more precise treatment planning </li></ul><ul><li>4-6 beam angles </li></ul>
  29. 29. Computer-controlled Multileaf Collimator Shaping of Radiation fields with a MLC have been the primary use of MLC for many years.
  30. 30. MLCs can be used to modulate radiation beam intensity in addition to the classical use of MLCs as radiation field shaping devices.
  31. 31. <ul><li>To improve precision </li></ul><ul><li>To decrease normal tissue dose </li></ul><ul><li>To escalate tumour dose </li></ul>?
  32. 32. <ul><li>I - Intensity </li></ul><ul><li>M - Modulated </li></ul><ul><li>R - Radiation </li></ul><ul><li>T - Therapy </li></ul><ul><li>Modulation and manipulation of radiation given to certain part of tumor and normal tissue to maximize tumor kill and minimize normal tissue damage. </li></ul>
  33. 33. <ul><li>There are two basic methods of using MLC to modulate radiation beam intensity: </li></ul><ul><ul><li>1 . Sliding Windows technique </li></ul></ul><ul><ul><ul><li>(move leaves while radiation is on) </li></ul></ul></ul><ul><ul><li>2 . Step and Shoot technique </li></ul></ul><ul><ul><ul><li>(move leaves then radiate - no radiation when leaves are moving) </li></ul></ul></ul><ul><ul><li>3. Some combination of the above </li></ul></ul>
  34. 34. SLIDING WINDOW TECHNIQUE
  35. 35. + + + + + + STEP AND SHOOT TECHNIQUE
  36. 36. Conventional RT 3DCRT FORWARD PLANNING Plan Draw contour / CT Digitize / Segment Fix Beam and Dose See distribution Accept
  37. 37. <ul><li>Immobilization </li></ul><ul><li>CT imaging </li></ul><ul><li>Images transferred to the planning system </li></ul>Inverse planning
  38. 38. Segmentation 3 D reconstruction
  39. 39. <ul><li>Decide on number of beams </li></ul><ul><li>Decide on beam directions </li></ul>
  40. 40. Set target dose and assign constraints 70Gy 60Gy 50Gy 45Gy <26Gy to 50% volume
  41. 41. <ul><li>Assign normal tissue constraints </li></ul><ul><li>Assign tumour dose </li></ul>Ask the computer to plan OBJECTIVE BASED RT PLANNING
  42. 42. <ul><ul><li>With DVH </li></ul></ul>Evaluate plan
  43. 43. Checking distribution and dose coverage Evaluate plan
  44. 44. <ul><li>Check whether beam positions are acceptable </li></ul><ul><li>Accept the most optimal plan </li></ul>
  45. 45. <ul><li>Accepted plan data is transferred to the Linac </li></ul><ul><li>Quality assurance </li></ul><ul><li>Treatment is started with the reproducible immobilization </li></ul>
  46. 46. Advantages of IMRT <ul><li>Superior dose distribution </li></ul><ul><li>Better normal tissue sparing </li></ul><ul><li>Increased conformality </li></ul><ul><li>Dose escalation possibilities </li></ul><ul><li>Objective based RT planning </li></ul><ul><li>More target-tailored plans </li></ul>
  47. 47. Rationale for the Use of IMRT in Head & Neck Cancers <ul><li>To increase the conformality of the RT dose to the targets in the Head & Neck. </li></ul><ul><li>Decrease the Toxicity( NTCP) </li></ul><ul><li>Potentially increase the Tumour Control Probability </li></ul>
  48. 48.
  49. 49. hank you all…

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