Quality Assurance Flashcards
What is image detail?
the degree of sharpness
What is FFD?
Focal-film distance
What happens if the tube head is too close to the structure being radiographs?
Theres magnification and loss of distinction of the margins of the structure
What should the FFD be set to?
36-48 inches
The _____ the focal spot, the _____ detail present on the film
greater; less
How do you minimize focal spot?
Place the structure as close to the film as possible
What does the density of the image refer to?
degree of blackness of the image
______ tissue absorbs _____ radiation than ______ tissue
Thicker; more; thinner
What is the major factor that affects density?
mAs
What does the mAs setting determine?
The quantity of x-rays produced
The higher the mAs, the greater the ______/_____ of the film
darkness/density
Besides mAs, what else can affect film density?
peak kilovoltage (kVp)
What happens if you increase kVp?
increase in energy level of x-rays produced
results in darker/denser image
If you move the tube head closer to the structure being radiographed, what happens?
the image is denser/darker
What is the inverse square law?
the intensity of the x-ray beam at a given location is inversely proportional to the square of the distance from the x-ray source
FFD doubled –> intensity is 1/4 original strength
What is contrast?
Its the opacity/density difference between two areas or structures on the radiograph
What are the two types of contrast?
high contrast/low contrast
What are high contrast images?
These images are primarily black/white
What is low contrast?
These images have multiple shades of gray w/in the image
What is high contrast used for?
Bone structures
What is low contrast used for?
Soft tissue, thoracic, abdominal images
What has the greatest effect on contrast?
kVp
The _________ the kVp, the ________ the scale of contrast
higher; lower
What happens w/ kVp in terms of contrast?
with a higher kVp, the x-rays are more uniformly absorbed amongst body tissues, resulting in lower contrast
inversely proportional
_____ kVp is preferred for thoracic images and _______ kVp is selected for skeletal images
higher; lower
What should you do if the anatomical structures are not visible due to being too dark/over-penetrated?
Decrease kVp by 10-15%
What should you do if the anatomical structures are too light/under penetrates with no anatomical structures visible?
Increase kVp by 10-15%
What should you do if the anatomical structures are visible but the image is too dark?
Decrease in mAs of 30-50%
What should you do if the anatomical structures are visible by the image is too light (has little density)?
Increase mAs by 30-50%
What are the three things that must be evaluated for image quality?
Contrast, density, the anatomical structure is centered on the film w/ proper positioning
How do you ensure that the anatomical structure requested is centered on the film w/ proper positioning?
Adequate collimation, appropriate R or L marker, and film is properly identified
How is a technique chart established?
Using trial and error
What factors should be kept constant when creating a technique chart?
film age, screen speed, cassette type, FFD, and developer & fixer age
What is a technique chart?
Its a chart developed to use as a guide for the settings on the specific machine that will obtain the best possible diagnostic image
