Term
| list and define primary technial factors (KVP) |
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Definition
-Penetrability
-Quality of the beam
-Energy of the beam (high quality beam=high kvp=high energy) |
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Term
| list and define primary technical factors (MAS) |
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Definition
mA x seconds (time)
-Quantity of the beam
-Reps the amound of exposure |
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Term
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Definition
Occurs when an x-ray photons chanes direction
-occurs primarily in the patient
-it impairs the image quality by producing an unwanted density on the image |
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Term
| Identify ways to minimize/reduce scatter |
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Definition
1) Restrict the beam (COLLIMATE) = reduce the amount of scatter produced, reduce patient dose, increase image quality (improve contrast)
2) Use a grid = "cleans up" scatter before it hits IR, improves image contrast |
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Term
| Describe the different between 1) preventing scatter from occuring in the first place, and 2) preventing scatter from reaching the IR after it has already occured... |
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Definition
| Collimaters (before it occurs), grids (after it occurs) |
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Term
| Discuss different beam restrictors; importance, function, etc. |
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Definition
1) Aperture diaphragms
2) Cones/cylinders
3) Collimators |
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Term
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Definition
| (Positive beam limiting): auntomatically collimates the beam to the size of the cassette, sensing switch that limits the field size to the IR size |
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Term
| Attenuation, and what affects different rates of attenuation |
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Definition
| Reduction in the total # of x-ray photons remaining in the beam after passing through a given thickness of material. (Atoms w/ higher atomic # will affect different rates of attenuation) |
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Term
| Describe the relationship between pathology and technical factor (kVp, mAs) selection |
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Definition
-Diseases will either increase or decrease technical factors
-Additive = increase tech. factors
-Destructive = decrease tech. factors |
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Term
| List 3 things that happen when x-rays interact with matter |
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Definition
1) Pass through
2) Absorb
3) Change direction |
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Term
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Definition
| Grid lines & interspace material |
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Term
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Definition
| lead is material of choice, inexpensive, easy to shape, and moisture resistant |
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Term
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Definition
Made of Aluminum or plastic and shouldnt absorb radiation
Aluminum = easy, durable |
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Term
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Definition
INfluence on the abilty of the grid to increase (improve) contrast. Ratio of the height of the lead strips to the distance between them
H = height of lead strips / D = distance between them |
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Term
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Definition
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Term
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Definition
| (Type of linear); lines go in on eidrection, lead lines are angled to match the divergent x-rays must be used at specific SID. (Thicker on sides because of leaning) |
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Term
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Definition
| Lines go in one direction (most common) |
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Term
| Identify and explain grid errors |
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Definition
| Off level, off center, off focus, up-side down |
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Term
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Definition
| Tube is angled across long axis of the grid lines or film/ IR is tilted |
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Term
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Definition
| Tube isnt entered to the grid (left or right) |
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Term
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Definition
| SID not within specifi distance range for focused grid (grid cut off at periphery) |
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Term
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Definition
| Placing grid up-side down while making the exposure with a focused grid |
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Term
| Scattered photons will not impair image quality |
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Definition
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Term
| The radiographer must try to minimize the amount of scatter radiation reaching the IR |
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Definition
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Term
| The only way to prevent scatter from reaching the IR is to restrict the beam |
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Definition
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Term
| Two principle factors that affect scatter are mAs and soure to image distance |
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Definition
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Term
| kVp affects the quantity of protons in te beam |
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Definition
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Term
| By decreasing kVp you can decrease scatter |
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Definition
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Term
| kVp is the primary controller of the quantity of photons produced |
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Definition
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Term
| Scattered photons add quality to the IR |
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Definition
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Term
| The smaller the tissue size, the greater the amount of scatter that's produced |
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Definition
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Term
| A large field size will increase the amount of scatter produced |
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Definition
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Term
| Low atomic number materials will absorb more radiation |
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Definition
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Term
| In attempting to reduce the production of scatter, the only thing the radiographer can do is use a grid |
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Definition
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Term
| A field size of 14x17 will produce less scatter than a field size of 8x10 |
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Definition
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Term
| Cylinders, collimators and diaphragms are different types of beam restricting devices |
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Definition
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Term
| The term cylinder is just another word for collimator |
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Definition
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Term
| Penumbra is geometric unsharpness in the center of the image |
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Definition
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Term
| Off focus radiation originates in the patient |
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Definition
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Term
| The most common type of beam restrictor used today is the aperture diaphragm |
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Definition
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Term
| The mirror within a collimator adds to the overall filtration of the beam |
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Definition
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Term
| a PBL device makes sure you dont colliate smaller than the IR size |
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Definition
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Term
| The collimator shutters help to reduce penumbra and off focus radiation because they are set at two different levels |
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Definition
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Term
| Another way to reduce scatter from reaching the IR on lateral lumbar spine, is to open up the collimators all the way |
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Definition
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Term
| The thicker the body part being radiographed, the greater the attenuation |
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Definition
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Term
| The higher the atomic number the less radiation is absorbed |
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Definition
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Term
| Air absorbs more radiation than bone |
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Definition
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