Mosby’s Radiation Therapy Equipment and Quality Assurance – Flashcards
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Grenz ray x-ray tubes operates in the range of ____ to ___ kV.
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5 to 15 kV
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Superficial therapy machines operates in the range of ____ to ____ kV.
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50 to 100 kV
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Superficial therapy machines have an SSD of what?
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15-20 cm
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Orthovoltage therapy machines operates in the range of _____ to ____ kV.
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100-200 kV
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Orthovoltage therapy machines have an SSD of what?
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50 cm
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Filters could be used to do what to the beam?
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harden it!
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Supervoltage units operated in the range of ______ to ____ kV.
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500+ kV.
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Supervoltage units have an SSD of what?
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80 to 100 SSD
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What did William Hansen invent?
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linear accelerator
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What are the 5 main components of the accelerator?
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drive stand, gantry, patient support assembly, electronic cabinet, and console
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What are the major components of the gantry?
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waveguides, electron gun, accelerator structure, and collimator head.
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Electrons get accelerated with the use of what?
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microwaves
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Microwave power to provide the energy in the waveguide is provided by the _______ or ______.
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magnetron or klystron
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The magnetron is usually used for what?
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for low energy linacs and generates high frequency power
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the klystron is usually used for what?
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for higher energy units and generates high frequency power.
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What are the different bending magnets?
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90 and 270 bending magnets.
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The raw electron beam is also referred to a ?
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pencil beam
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The scattering foil is for what?
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for electron beams to spread out the electrons and make it more uniform
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What do the attachable cones do?
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The cones help to control the free scattering of electrons in the air.
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The flattening filter is for what?
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It evenly distributes the energy of the photon beam.
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What does the monitoring ion chamber do?
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keeps track of the dose rate and field symmetry.
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The collimator area opening is typically limited to?
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40 x 40 cm
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The field size setting is defined where?
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SSD setup - on the skin SAD setup - at isocenter
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What is the tolerance for X-ray output constancy?
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3%
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What is the tolerance for Distance Indicator?
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2 mm
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What is the tolerance for laser localization? nonIMRT, IMRT, SBRT
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2 mm 1.5mm 1 mm
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what is the average energy that the cobalt machine produces?
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1.25 MV
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What is the rate of decay for cobalt a month?
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about 1 % decay in a month
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Housing for the cobalt unit should only emit how much transmission?
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0.1% transmission
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What is the formula for penumbra?
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p = s (SSD +d - SDD) / SDD
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what are the trimmer bars?
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the tertiary collimators used to help minimize penumbra reaching the patient
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Half life of cobalt-60 is?
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5.26 years
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Half life of Cesium 137 ?
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30 years
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Half life of Iridium 192 ?
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73.8 days
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Half life of Iodine 125 ?
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60 days
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Half life of Palladium 103 ?
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17 days
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Half life of Gold 198 ?
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2.7 days
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Half life of Strontium 90 ?
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28.9 years
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half life of Strontium 89 ?
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51 days
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Half life of Iodine 131 ?
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8.06 days
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What is tomotherapy?
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Has the similar design as a CT machine, it can deliver radiation from all angles around the patient using IMRT.
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What is Brachytherapy?
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Using radioactive seeds, the sources can be placed permanently or temporarily into or on the patient.
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Radiation detectors brachytherapy units should be calibrated how often?
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monthly
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How often should wipe testing be done for radioactive sources?
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6 months for long half lives
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If the patient stays in the hospital with radioactive sources inside, what is the limit of radiation that should be leaving that room?
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0.2 mSv /hr
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If the patient is allowed to leave with a a permanent source inside, what is the limit of radiation allowed to be emitting from the patient?
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less than 0.5 mSv/hr at one meter.
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Conventional Simulators are?
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They are used to localize the target volume using fluoroscopy and or x-ray imaging. It provides a 2 dimensional field of the patient. It looks like a treatment gantry machine
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CT simulators are?
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Have a large bore that the patient goes through to create a 3 dimensional view of the patient.
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What does OBI stand for?
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Onboard Imaging
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What does CBCT stand for?
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Cone beam CT
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What does IMRT stand for?
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Intensity Modulated radiation therapy
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How many monitor units are used for MV images?
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3 MU or less
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What does IGRT stand for?
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Image guided radiation therapy
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what is the purpose for IGRT?
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To localize the tumor on a day to day basis because the margins of the tumor are small
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When is respiratory gating used?
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when breathing can effect the location of the target.
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What does BAT stand for?
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B-mode acquisition and targeting
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What is BAT used for?
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to visualize the location of the target before treatment. It uses ultrasound
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What is BrainLab system?
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Similar to BAT, it uses reflective markers on the patient body and an infrared tracking system. It is attached to an ultrasound probe.
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What does SRT stand for?
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Stereotactic Radiation therapy can be termed SRS for single dose use.
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What does SRS stand for?
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Stereotactic radiosurgery
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What is SRT and SRS used for?
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Uses very small and highly conformal beams to treat small target volumes while sparing tissues. It can be used in a single fraction or multiple fractions.
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Single dose fraction for SRS has a dose range of?
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12 to 25 Gy
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Multiple dose fractions for SRT has dose sizes of ? and a total dose ofof?
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4-7 Gy for a total of 41Gy
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What does MLC stand for?
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Multileaf collimator
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What is the gamma knife unit?
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is an SRS system that allows the positioning of up to 200 sources in a helmet like frame.
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what is cyberknife ?
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another approach to SRS. it uses a miniature 6 MV robotic arm.
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What are examples of beam directional devices?
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front/back pointers breast bridges lasers and cross hairs BB trays, the field light and mirror assembly Digital readouts for G and C electron cones and collimators
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What are examples of beam modifiers?
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standard wedges, dynamic wedges, custom tissue compensators, bolus materials, cerrobend blocks, MLC.
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What is the R and V system?
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Record and Verify system
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How does the R and V system help?
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Records the parameters of the patient's treatment position. Interlocks are placed in the system to help minimize errors.
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How much does the cerrobend block have to attenuate the beam in order for it be acceptable?
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to less than 5%
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What is the tolerance error for the computer to make on daily and cumulative dose information?
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2%
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How often should input and output devices for the R and V system be checked?
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Daily
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How often should algorithms and transfer data from the CT be checked?
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monthly
