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Questions and Answers
What are the two methods used to move the teletherapy source from the BEAM-OFF to the BEAM-ON position?
What function does the primary timer serve in the teletherapy machine?
What happens to the beam in the event of a power failure?
What is the average permissible leakage radiation from a teletherapy machine head as per international regulations?
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What additional time should be included in the treatment setting for the teletherapy machine?
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What material is the source head of the teletherapy machine primarily made from for shielding?
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What is the typical amount of head leakage radiation at a distance of 1 meter from the source?
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Which of the following is a feature that appears when the source is in the BEAM-OFF position?
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What does the secondary timer act as in the teletherapy machine?
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What component of the teletherapy machine is responsible for creating the clinical gamma ray beam?
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Which safety feature is incorporated into both methods for moving the teletherapy source?
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What applies to leakage radiation from the teletherapy machine when the source is in the BEAM-OFF position?
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What is the primary purpose of the secondary timer in the teletherapy machine?
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During treatment with teletherapy machines, what is included in the set treatment time?
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Which of the following describes the head of a cobalt-60 teletherapy machine?
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What characteristic is true about the source moving mechanisms in cobalt-60 teletherapy machines?
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How does optical visualization of the radiation field occur in a cobalt-60 teletherapy machine?
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Which of these statements about the motion of the teletherapy source is most accurate?
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Which of the following is a key function of the primary timer in the teletherapy machine?
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What should be the average leakage radiation from a teletherapy machine head according to regulations?
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Study Notes
Cobalt-60 Teletherapy Machine
- The source head is constructed with a steel shell incorporating lead for effective radiation shielding.
- Mechanism utilized to position the radiation source in front of the collimator to generate the gamma ray beam.
Source Movement Methods
- Two primary methods for transitioning the teletherapy source from BEAM-OFF to BEAM-ON:
- Sliding drawer mechanism.
- Rotating cylinder mechanism.
Safety Features
- Both source movement methods include an automatic beam termination feature during power failures or emergencies.
- Optical visualization is provided when the source is in the BEAM-ON position, indicated by a light source above the collimator opening.
Leakage Radiation
- Leakage radiation can occur even when the source is in the BEAM-OFF position.
- Head leakage typically measures less than 1 mR/h (0.01 mSv/h) at a distance of 1 meter from the source.
- International safety standards mandate that average leakage from a teletherapy machine head remains below 2 mR/h (0.02 mSv/h).
Dose Delivery Mechanism
- Treatment dose delivery is regulated by two timers: primary and secondary.
- The primary timer controls the beam time and switches it off after the prescribed duration.
- The secondary timer functions as a backup to ensure the beam is turned off if the primary timer fails.
- Treatment time must factor in shutter correction time, accounting for the source's travel time between BEAM-OFF and BEAM-ON positions.
Cobalt-60 Teletherapy Machine
- The source head is constructed with a steel shell incorporating lead for effective radiation shielding.
- Mechanism utilized to position the radiation source in front of the collimator to generate the gamma ray beam.
Source Movement Methods
- Two primary methods for transitioning the teletherapy source from BEAM-OFF to BEAM-ON:
- Sliding drawer mechanism.
- Rotating cylinder mechanism.
Safety Features
- Both source movement methods include an automatic beam termination feature during power failures or emergencies.
- Optical visualization is provided when the source is in the BEAM-ON position, indicated by a light source above the collimator opening.
Leakage Radiation
- Leakage radiation can occur even when the source is in the BEAM-OFF position.
- Head leakage typically measures less than 1 mR/h (0.01 mSv/h) at a distance of 1 meter from the source.
- International safety standards mandate that average leakage from a teletherapy machine head remains below 2 mR/h (0.02 mSv/h).
Dose Delivery Mechanism
- Treatment dose delivery is regulated by two timers: primary and secondary.
- The primary timer controls the beam time and switches it off after the prescribed duration.
- The secondary timer functions as a backup to ensure the beam is turned off if the primary timer fails.
- Treatment time must factor in shutter correction time, accounting for the source's travel time between BEAM-OFF and BEAM-ON positions.
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Description
This quiz explores the components and mechanisms of the Cobalt-60 teletherapy machine used in cancer treatment. It covers the structure of the source head, including shielding and the methods for moving the source between BEAM-OFF and BEAM-ON positions. Perfect for students in Medical Physics.
