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Radiation Therapy QA

Quality Assurance information for Radiation Therapy

QuestionAnswer
1. What is the energy range for superficial (Crookes tube) therapy machines? 50 to 100 kV
2. What machines had "hot cathode" tubes and generated medium energy ranges? Orthovoltage or deep therapy machines
3. What is the energy range for orthovoltage machines? 150 - 500 kV
4. What are the five main components of a typical linear accelerator? drive stand, gantry, patient support assembly (PSA), electronic cabinet, and console
5. What are the 4 major components of the drive stand? Klystron or magnetron, waveguide, circulator, and water cooling system
6. What is a klystron? it is an amplifier of microwaves that are produced by a radio-frequency drive ; used for 10MV and above
7. What is a magnetron? it is a source of microwaves; used for 6MV and below
8. What is a waveguide? a series of tubes/pipes that transport microwaves to the accelerator guide
9. What are major components of the gantry? electron gun, accelerator guide, treatment head
10. What are the components of the treatment head? bending magnet, x-ray target, flattening filter, scattering foil, monitor chambers, optical distance indicator, primary and secondary collimators
11. In a linear accelerator, what components helps create a uniform electron beam? scattering foil
12. In a linear accelerator, microwave amplification occurs in the: klystron
13. On a conventional simulator what can be used to reduce unwanted scatter radiation? beam-restricting diaphragms
14. The conventional simulator design was meant to mimic what other piece of equipment? It was meant to simulate the mechanical, geometric, and optical conditions of a variety of treatment units
15. Gantry, x-ray head and collimator, x-ray tube and generator, imaging device, and couch are all components of what simulator? Conventional or fluoroscopic-based simulator
16. On a conventional simulator, what defines the edge of the treatment field? field-defining wires
17. Every image taken in conventional simulation should show evidence of what? collimation by displaying a 1 to 2 cm clear border of unexposed film
18. A typical image intensifier contains what four major components? film holder, image intensifier, television camera, and video monitor
19. True or False: A conventional simulator could potentially produce CT images. True if the machine has a CT mode.
20. What are the two major methods of CT data acquisition? slice by slice and volumetric (spiral) CT
21. In CT simulation, what does aperture size refer to? The diameter of the hole into which the patient is positioned
22. Each small square on a CT image is called what? pixel
23. Window selection determines what in CT simulation? It determines what anatomy will be seen.
24. What are the two window selections that can be made? window level & window width
25. _______________ represents the range of grey scale on a CT image? Window width
26. What does window level represent? It represents the center of the window width
27. A pixel is a two-dimensional representation of what? a corresponding tissue volume or voxel
28. On a conventional simulator, localizing lasers and ODI checks should be performed when and within what tolerance? daily and 2mm
29. On a conventional simulator, rotation isocenter checks should be performed how often and be within what tolerance? annually and 2mm
30. Radiographic checks should be performed ______________ on a conventional simulator. annually
31. Orientation of gantry lasers on a CT simulator should be performed when? monthly or after laser adjustments
32. On a CT simulator what should have a QA procedure run annually? Table indexing and position, gantry tilt accuracy, gantry tilt position accuracy, scan localization, radiation profile width
33. The table vertical and longitudinal motion on a CT simulator should be checked when and be within what tolerance? monthly and within 1mm over the range of table motion
34. For CT simulator image quality, image noise should be checked when and be within what tolerance? daily and be within the manufacturer's specifications
35. What are the three major categories of a quality assurance procedure on treatment machine? Dosimetry, mechanical, and safety
36. The emergency off switches should be checked how often? monthly
37. The audiovisual monitor should be checked ___________ for _____________. daily for functionality
38. X-ray output constancy and electron output constancy should be checked __________ and the tolerance is _________. monthly and within 2%
39. Acceptance testing requires _________________. a comparison of output and performances values as measured against what the manufacturer promised.
40. Light field and radiation field congruence should be checked: monthly
41. For a linear accelerator the tolerance for variation in collimator rotation around the point of isocenter is: 2mm
42. The door interlock should be checked: daily
43. Leak tests of sealed radioactive sources should be conducted at what interval? 6 month intervals or twice a year
44. When performing a leakage test on a Cobalt 60 machine housing, what radioactivity level should NOT be exceeded? 0.005 mCi
45. What should be checked weekly on a Cobalt 60 unit? the source positioning
46. Radiation detectors used with brachytherapy should be calibrated when? once a month or after repairs
47. When ionization chambers are properly calibrated their accuracy approaches _________. 2%
48. Due to a properly calibrated ionization chamber's accuracy, it makes them suitable for measurement of ____________________. the radiation output of therapy equipment
49. Calibration equipment, scanning equipment, dosimetry accessories, and devices are all types of what? quality control check instrumentation
50. In brachytherapy, source strength should be checked and verified when? Upon receipt and at an agreed upon interval depending on the half-life
51. What is the tolerance for the daily check of linac output constancy? 3%
52. How often should field size indicators be checked? monthly
53. What professional organization for medical physicists is a forerunner in developing minimum QA standards? AAPM
54. For dynamic MLC QA, why should ion chamber measurements be taken in a solid phantom for patient fields? to provide a direct independent check of MU calculations
55. Film dosimetry with sufficient spatial resolution for intensity-modulated patterns should be checked because ___________________. It is a good way to compare the delivered dose distributions to the planned ones
56. To ensure a constant dynamic MLC output and to track long-term stability what should be measured monthly? Ion chamber and diode array measurements should be taken at different gantry and collimator angles.
57. To provide a visual assessment of dynamic MLC function what should be checked biweekly? Predesigned fields using film image patterns
58. A periodic dosimetric verification of intensity-modulated fields is performed for dynamic MLC QA to ensure ______________________. Accuracy of dose patterns and fluence
59. True or False: Specific QA tests should not be performed on each field of a patient's IMRT plan. False- tests SHOULD be completed on each field to ensure accuracy
60. ____________ through MLCs contributes to increased patient exposure. Leakage
61. What are 6 disadvantages of an orthovoltage unit? lack of penetrating ability, high skin dose, low output, large penumbra, doses not homogenous over treatment field, not isocentrically mounted
62. What is D max? D max is the depth at which electronic equilibrium is reached
63. Is the relationship between D max and energy direct or indirect? direct
64. What is the SAD of a linear accelerator and Cobalt 60 unit? linear accelerator SAD is 100cm; Cobalt 60 SAD is 80 cm
65. When using photons what is required to be present in the path of the beam to create a uniform dose distribution? flattening filter
66. When electrons are produced what must be removed out of the path of the beam, and what must be added to spread the beam? the target must be removed and a scattering foil must be added
67. What is the average energy of a Cobalt 60 unit? 1.25 MV; it is comprised of two gamma rays with energies of 1.17 MV & 1.33MV
68. What is a half-value layer (HVL)? the amount of material needed to reduce radiation transmission by 50%
69. What is the HVL of Co-60? 1.2 cm of lead
70. How much lead is required to reduce the transmission of a Cobalt 60 beam to approximately 6%? 4.8 cm of lead
71. What is the D max for a Cobalt 60 unit? 0.5 cm
72. Approximately, what percentage of Cobalt 60 decays each month? 1.1% each month
73. When discussing Cobalt 60 units what is timer error? it is an adjustment made to treatment time to account for the time it takes to move the source in and out of position
74. What are the leakage parameters of a Cobalt 60 machine in the OFF position? Average not to exceed 2mR/hour at 1 meter; Maximum at any point must not exceed 10mR/hour at 1 meter
75. What are the leakage parameters of a Cobalt 60 machine in the ON position? must not exceed 0.1% of the useful beam at 1 meter
76. What is the "useful beam" referring to in regards to a Cobalt 60 unit? It refers to the output and is changed on a monthly basis to account for decay
77. What is geometric penumbra? the area of unsharpness at the edge of the field
78. What is the relationship (direct/indirect) of geometric penumbra to SSD, source size, and SDD/SCD (source diaphragm distance or source collimator distance)? SSD-direct, Source size- direct, SDD-indirect
79. What is transmission penumbra? a) It occurs when straight edge blocks are used for shielding because they do not follow the beam path. Custom blocks do diverge with the beam.
80. How far should Cobalt 60 trimmers or blocks be away from the patient? at least 15 cm in order to avoid increased skin dose from scatter
Created by: cj2218
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