Introduction to radiation therapy

15,115 views
14,843 views

Published on

0 Comments
16 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
15,115
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
1,178
Comments
0
Likes
16
Embeds 0
No embeds

No notes for slide

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>

×