Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Introduction to radiation therapy

24,273 views

Published on

Introduction to radiation therapy

  1. 1. Introduction to Medical Technology: Radiotherapy
  2. 2. Contents <ul><li>Why radiotherapy? </li></ul><ul><li>Some basic principles </li></ul><ul><li>Approaches to radiotherapy </li></ul><ul><ul><li>external beam: x-rays, electrons, p, n, heavy ions </li></ul></ul><ul><ul><li>brachytherapy </li></ul></ul><ul><li>Stages in the radiotherapy process </li></ul><ul><ul><li>QA, imaging, planning, simulation, treatment, verification, modelling outcome </li></ul></ul>
  3. 3. Why Radiotherapy? <ul><li>Radiotherapy used to treat cancers </li></ul><ul><ul><li>In conjunction with surgery and chemotherapy </li></ul></ul><ul><li>Proven benefit </li></ul><ul><li>Cells display strong dose-effect relationship </li></ul><ul><li>Physics, engineering, imaging, technology based </li></ul>
  4. 4. Benefits of Radiotherapy <ul><li>Breast Cancer </li></ul><ul><li>Mastectomy </li></ul><ul><li>Compare surgery and chemotherapy (CMF) with and without radiotherapy </li></ul><ul><li>10 year survival improvement at 10 years </li></ul>
  5. 5. Contents <ul><li>Why radiotherapy? </li></ul><ul><li>Some basic principles </li></ul><ul><li>Approaches to radiotherapy </li></ul><ul><ul><li>external beam: x-rays, electrons, p, n, heavy ions </li></ul></ul><ul><ul><li>brachytherapy </li></ul></ul><ul><li>Stages in the radiotherapy process </li></ul><ul><ul><li>QA, imaging, planning, simulation, treatment, verification, modelling outcome </li></ul></ul>
  6. 6. Radiobiology: Linear-quadratic model <ul><li>Effects of radiation on cell survival described by: </li></ul><ul><li>linear-quadratic model </li></ul><ul><li>Linear </li></ul><ul><ul><li>single hit sufficient </li></ul></ul><ul><li>Quadratic </li></ul><ul><ul><li>multiple events </li></ul></ul>
  7. 7. Radiobiology: Tumour and normal tissue <ul><li>Different responses to radiation </li></ul><ul><ul><li> /  different </li></ul></ul><ul><li>Deliver one large dose </li></ul><ul><ul><li>effects similar </li></ul></ul><ul><li>Deliver many smaller doses </li></ul><ul><ul><li>effects very different </li></ul></ul><ul><li>Fractionation </li></ul><ul><ul><li>e.g. 60 Gy in 2 Gy fractions </li></ul></ul>
  8. 8. Radiobiology: Tumour and normal tissue <ul><li>Radiation effect vs. dose </li></ul><ul><ul><li>sigmoid behaviour </li></ul></ul><ul><ul><li>stochastic process </li></ul></ul><ul><li>Tumour control lower dose than normal tissue damage </li></ul><ul><ul><li>Makes radiotherapy possible! </li></ul></ul><ul><li>Radiotherapy goals and research </li></ul><ul><ul><li>separate two curves </li></ul></ul>
  9. 9. Some Nomenclature <ul><li>Dose response curve </li></ul><ul><ul><li>plot of radiation effect vs. dose </li></ul></ul><ul><li>Radical treatment </li></ul><ul><ul><li>treatment with curative intent (cf. palliation) </li></ul></ul><ul><li>RBE (relative biological effect)=quality factor </li></ul><ul><li>Tumour staging: Tumour, Nodal, Metastasis </li></ul><ul><li>Necrosis and hypoxia </li></ul><ul><ul><li>regions of tumour dead or dormant due to low oxygen level </li></ul></ul>
  10. 10. Contents <ul><li>Why radiotherapy? </li></ul><ul><li>Some basic principles </li></ul><ul><li>Approaches to radiotherapy </li></ul><ul><ul><li>external beam: x-rays, electrons, p, n, heavy ions </li></ul></ul><ul><ul><li>brachytherapy </li></ul></ul><ul><li>Stages in the radiotherapy process </li></ul><ul><ul><li>QA, imaging, planning, simulation, treatment, verification, modelling outcome </li></ul></ul>
  11. 11. Approaches to Radiotherapy <ul><li>External beam </li></ul><ul><ul><li>Fire radiation beam into patient </li></ul></ul><ul><ul><ul><li>Usually several beams from various directions </li></ul></ul></ul><ul><ul><ul><li>Cross-fire effect </li></ul></ul></ul><ul><li>Brachytherapy </li></ul><ul><ul><li>Place set of sealed radioactive sources or seeds into patient </li></ul></ul><ul><ul><ul><li>Often contained in applicator tube </li></ul></ul></ul>
  12. 12. External Beam Treatment <ul><li>Most commonly Cobalt 60  rays (1.25 MeV), x-rays, electrons </li></ul><ul><ul><li>Co 60 radioactive source </li></ul></ul><ul><ul><li>x-rays and e - , electron linac </li></ul></ul><ul><li>Sometimes orthovoltage (up to 300 kV) </li></ul><ul><ul><li>Superficial tumours </li></ul></ul><ul><li>More rarely hadrons (many MeV) </li></ul><ul><ul><li>protons, neutrons, heavy ions </li></ul></ul>
  13. 13. Electron Linac for X-ray and Electron Radiotherapy <ul><li>X-rays (4-50 MV), electrons (4-50 MeV) </li></ul><ul><li>X-rays polychromatic </li></ul><ul><ul><li>Bremsstrahlung </li></ul></ul><ul><li>Electrons scatter in air </li></ul><ul><ul><li>Need for collimation </li></ul></ul><ul><li>Cross-fire effect </li></ul><ul><ul><li>Several beams aimed at tumour/target </li></ul></ul><ul><ul><li>High dose to tumour/small dose to surrounding tissue </li></ul></ul>
  14. 14. Radiotherapy Linacs
  15. 33. X-Ray Beam Characteristics
  16. 40. Beam Shaping Devices <ul><li>Main Rectangular Collimators </li></ul><ul><li>Wedge </li></ul><ul><li>Multileaf Collimator </li></ul><ul><ul><li>Field edge shaping </li></ul></ul><ul><li>Block </li></ul><ul><li>Compensator </li></ul><ul><li>Multileaf Collimator </li></ul><ul><ul><li>IMRT (intensity modulated radiotherapy) </li></ul></ul>
  17. 46. Lead Compensator <ul><li>Sheets of lead </li></ul><ul><ul><li>0.5 mm thick </li></ul></ul><ul><li>Used in conjunction with wedge </li></ul><ul><li>Shapes to breast and shields lung </li></ul>
  18. 47. Granulate Compensator <ul><li>Stainless steel granulate </li></ul><ul><li>Used in conjunction with wedge </li></ul><ul><li>Shapes to breast and shields lung </li></ul>
  19. 48. Intensity Modulated Radiotherapy <ul><li>Most common delivery method MLC (multileaf collimator) </li></ul><ul><ul><li>Dynamic </li></ul></ul><ul><ul><ul><li>Scan MLC leaves across field with radiation on </li></ul></ul></ul><ul><ul><li>Multiple segment </li></ul></ul><ul><ul><ul><li>Delivery set of irradiations at same position with different field shapes </li></ul></ul></ul><ul><li>Compensators </li></ul>
  20. 50. Patient Image Cumulative Intensity Field 1 Field 4 Field 3 Field 2
  21. 52. Electron Beam Characteristics
  22. 59. Brachytherapy <ul><li>Sources placed in patient using metal tubes or applicators </li></ul><ul><ul><ul><li>e.g. Ir 192 </li></ul></ul></ul><ul><li>Afterloading </li></ul><ul><li>High dose rate (HDR) and low dose rate (LDR), pulsed dose rate (PDR) </li></ul><ul><li>Fractionated </li></ul><ul><li>Prescription schemes for location of sources </li></ul>
  23. 70. Hadron Radiotherapy <ul><li>Large accelerators </li></ul><ul><ul><li>High energies needed </li></ul></ul><ul><ul><li>Large magnetic rigidity </li></ul></ul><ul><li>Protons most common </li></ul><ul><ul><li>Over 20 in the world </li></ul></ul><ul><li>Neutrons </li></ul><ul><li>Heavy ions </li></ul>

×