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RADIATION PROTECTION IN RADIOTHERAPY

RADIATION PROTECTION IN RADIOTHERAPY

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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 12: Quality Assurance PRACTICAL EXERCISE IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

  2. Objectives • To be familiar with the concepts of Quality Assurance as a multidisciplinary activity and its interrelation with radiation protection in radiotherapy. • To be familiar with Quality Assurance procedures as a tool for reviewing and assessing the overall effectiveness of a radiation protection program. • To be able to understand the need for and role of specific tests in the context of quality control and be able to identify appropriate national and international protocols for this task • To be aware of the need for involvement of professionals in a quality assurance program and for radiation protection Part 12, Practical 2

  3. Part 12: Quality Assurance IAEA Training Material on Radiation Protection in Radiotherapy Practical 2: Check X Ray light field coincidence for a megavoltage treatment unit IAEA Post Graduate Educational Course Radiation Protection and Safe Use of Radiation Sources

  4. Geometry Must work for • all collimators • different field sizes • different SSDs • gantry and collimator angles • blocks Part 12, Practical 2

  5. X Ray light field co-incidence • Also applicable to 60-Co gamma rays • Also applicable to some diagnostic equipment • If treatment set-ups are mostly fixed distance and aligned to marks on the skin, this is one of the most important factors for successful treatment. Part 12, Practical 2

  6. Contents + Objective • Appreciate the importance of X Ray/ /light field coincidence checks • Use a simple test based on film to check coincidence Part 12, Practical 2

  7. What Minimum Equipment is Needed? • Radiographic film • Pen, ruler Part 12, Practical 2

  8. Set-up • Place slab phantom at desired distance • Place pre-packaged film on top and secure with tape • Mark the light field outline using • pressure and a pen • radio-opaque objects • Use appropriate build up to remove electron contamination Part 12, Practical 2

  9. Film with marks Tape to secure the film Mark beam geometry Marks for light field Package labeled Slab phantom Part 12, Practical 2

  10. Comments • If no pre-packaged film is available, one can use a film cassette from the X Ray department • Suitable radio opaque objects are screws, washers, …. Part 12, Practical 2

  11. Typical film • Marked with pen - shows thin white lines where emulsion has been squeezed • Test two fields at the same time • Arrow marks Gun/Target direction • Can verify field collimator readouts • Important to label film directly after developing it Part 12, Practical 2

  12. Technique using pin pricks Part 12, Practical 2

  13. Repeat as necessary for • Different SSDs • Different field sizes • Different gantry angles • Blocks • MLC Courtesy Elekta Part 12, Practical 2

  14. Questions? Let’s get started... Part 12, Practical 2