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Proton therapy seminar

tretment of cancer using proton beam

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Proton therapy seminar

  1. 1. PROTON THERAPY Ankita Pandey
  2. 2. WHAT IS THE PROTON THERAPY • Proton therapy is a type of external beam radiation therapy — a treatment that uses high-energy proton beams to treat tumors
  3. 3. Rationale behind radiotherapy • High tumor dose • Lower dose to normal organs
  4. 4. PROBLEMS WITH PHOTON THERAPY TREATMENT
  5. 5. MORE EXIT DOSE EXPONENTIAL DOSE FALL OF MORE TISSUE IRRADIATION LOW LET
  6. 6. EXIT DOSE INCREASES Dmax increases
  7. 7. DOES PROTON THERAPY HAS SOLUTION ?
  8. 8. Dose rises slowly with depth Rapid dose fall off No tissue irradiated Tissue recieves low dose
  9. 9. PROTON RADIOBIOLOGY
  10. 10. LET and RBE
  11. 11. • The relative biologic effectiveness (RBE) of protons is generally considered to be about 1.1 that of X-rays, similar enough to make tumor and normal-tissue effects with protons predictable based on X-ray experience.
  12. 12. WHAT IS “SOBP” ?
  13. 13. A ‘‘spread-out Bragg peak’’ (SOBP) can be created by using a range of proton energies Whereas most of the radiation dose in a patient with external-beam photons is deposited outside the target, most of the radiation dose with a proton beam can be placed inside the target, affording a significant opportunity to decrease normal-tissue damage
  14. 14. • For clinical use, the beams are spread longitudinally and laterally and then shaped appropriately to conform the high dose regions to the target volume.
  15. 15. HOW IS PROTON GENERATED
  16. 16. CYCLOTRON
  17. 17. passed through an energy selection system, which makes the beam's energy variable for use in each of the treatment rooms served by this beam Electromagnets are positioned along the line to route the proton beams around corners and into each treatment room
  18. 18. SYNCHROTRON
  19. 19. accelerate batches (pulses) of protons to the desired energy Once a batch has reached the required energy, it is extracted and transmitted via the “beam to the treatment room line Each cycle can produce protons of a different energy
  20. 20. • Protons are accelerated with cyclotrons or synchrotrons • An accelerated proton beam entering the treatment delivery head is very thin and it is not suitable for treating three dimensional, arbitrarily-shaped tumor targets. • It is broadened longitudinally and laterally and sculpted to conform to the target shape • There are two main approaches 1. passively-scattered proton therapy (PSPT) 2. magnetic scanning of narrow “beamlets” of protons
  21. 21. PASSIVE SCATTERING proton therapy is delivered through a double-scattered mode in which the narrow beam of protons is scattered twice and flattened to produce a clinically useful beam size and intensity Field sizes of up to 25 cm in diameter are achievable with current double scattering delivery modes.
  22. 22. A set of focusing magnets is used to reduce the diameter of the proton pencil beam. Scanning magnets scan the beam in the lateral directions Range-shifter plates are inserted into the beam path after delivery of the distal- most layer of proton doses for treating the second-most distal and subsequently increasingly more-superficial layers.
  23. 23. The dose delivered at each spot or layer is adjustable, resulting in a modulated dose distribution at each spot or layer as well as between layers, which is known as intensity-modulated proton therapy (IMPT).
  24. 24. • Potential disadvantages of scanning delivery modes include 1. a greater demand for accuracy in target localization 2. reduced speed in treatment delivery increasing the risk of errors related to intra-fraction organ motion 3. increased complexity of the dose-delivery control system and subsequent quality assurance needs
  25. 25. BEAM SHAPING • Range Modulator • Aperture • Range compensator
  26. 26. Range modulation
  27. 27. Beam aperture Range compensator •conform the dose distribution laterally •made from blocks of brass •thickness (2 cm to 8 cm) •Conforms dose distribution to the distal shape of the target •made of a nearly water- equivalent material such as Lucite
  28. 28. • The aperture and compensator for each beam are designed by the planning system, and the design information is used to fabricate these devices using computer-controlled milling machines.
  29. 29. Gantry • Protons may be delivered from the beam line to the treatment area via a gantry or a fixed beam
  30. 30. advantages of the gantry system over a fixed beam • increase in possible beam angles • Simpler strategies for patient immobilization and internal organ motion tracking
  31. 31. disadvantage of the gantry system over a fixed beam • increase in equipment cost, shielding material, and space required
  32. 32. CLINICAL IMPLICATIONS
  33. 33. Choroidal Melanomas and Other Eye Lesions • One of the first sites treated with proton therapy was the eye. Eye treatments could be provided with relatively low-energy protons delivered through a fixed beam. Large numbers of patients have been treated across the world for choroidal melanomas
  34. 34. MEDULLOBLASTOMA
  35. 35. Retroperitoneal sarcoma
  36. 36. Craniopharyngioma
  37. 37. Ependymoma
  38. 38. Maxillary sinus carcinomas
  39. 39. Lymphomas
  40. 40. Prostate cancer
  41. 41. • Barriers for the development and proliferation of proton therapy facilities include 1. the significant cost and complexity of delivery systems 2. the requirement for more intense physics, dosimetry, and engineering support in treatment planning 3. quality assurance 4. equipment operation and maintenance

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  • ammuarpu

    Mar. 1, 2020
  • SamcyArora1

    Apr. 30, 2021

tretment of cancer using proton beam

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