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RADIATION PROTECTION IN RADIOTHERAPY

RADIATION PROTECTION IN RADIOTHERAPY. IAEA Training Material on Radiation Protection in Radiotherapy. Part 5: External Beam Radiotherapy PRACTICAL EXERCISE. IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources. Objectives.

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RADIATION PROTECTION IN RADIOTHERAPY

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  1. RADIATION PROTECTION IN RADIOTHERAPY IAEA Training Material on Radiation Protection in Radiotherapy Part 5: External Beam Radiotherapy PRACTICAL EXERCISE IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

  2. Objectives • To become familiar with different radiation types used for external beam radiotherapy • To understand the function of different equipment used for EBT delivery • To appreciate the implications of different treatment units and their design • To be familiar with auxiliary equipment required and used for EBT • To understand the measures used in this equipment to ensure radiation safety Part 5, Practical 1

  3. Part 5: External Beam Radiotherapy IAEA Training Material on Radiation Protection in Radiotherapy Practical 1: Isocentric Patient Set-up IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

  4. Isocentric treatment unit Part 5, Practical 1

  5. Contents + Objective • Learn about the the differences between isocentric and non-isocentric set-ups • Discuss advantages and disadvantages Part 5, Practical 1

  6. Question • Please discuss the advantages and disadvantages of isocentric patient set-up in the context of your radiotherapy practice Part 5, Practical 1

  7. What Minimum Equipment is Needed? • White board • Paper • A model of a treatment unit would be useful Part 5, Practical 1

  8. Isocentric set-up • Places the tumour in the centre - multiple radiation beams are easily set-up and deliver radiation from many directions to the target without moving the patient! Part 5, Practical 1

  9. Advantages • No patient or couch movement between the delivery of different fields necessary • faster treatment • more stable set-up • More efficient use of couch rotation - everything rotates around the target. • Arc treatment are necessarily isocentric Part 5, Practical 1

  10. Potential problems • Clearance between collimator and patient may be too small - collision danger • Penetration may be less because shorter distance to the patient’s skin • Dose calculation different Part 5, Practical 1

  11. source PDD and TMR Strong ISL dependence beam • Percentage depth dose (PDD) changes with distance of the patient to the source due to variations in the inverse square law (ISL), TAR, TMR and TPR do not. Reference point Weak ISL dependence phantom Part 5, Practical 1

  12. Dose calculation in isocentric treatments • Based on TMRs or TPRs rather than percentage depth dose (PDD) data • Often less familiar to physicists who have performed beam data acquisition using PDD not TMR measurements • May require new planning data Part 5, Practical 1

  13. Now it is over to you... • Please discuss the advantages and disadvantages of isocentric patient set-up in the context of your radiotherapy practice • This could be done in form a table • And a bullet list of issues Part 5, Practical 1

  14. Issues • have only %DD data • isocentric could be faster for pelvic treatment if we commence treating with four fields • 80cm FAD unit does not have enough clearance Examples • To do list • check with oncologist about preference • does our planning system support isocentric set-up? Part 5, Practical 1

  15. Considerations: • what set-ups are currently in place for which patients • what is your case load like • what data is available for planning • what is your calibration set-up Part 5, Practical 1

  16. Questions? Let’s get started... Part 5, Practical 1

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