Lecture 6 Flashcards
What is the degree of blackness on a radiograph dependent on
The amount of x-rays reaching the film
If there’s no patient between the film and the x-ray beam what color will the film be
Black
What is the emulsion layer of the film
Contains silver hollered crystals suspended and disbursed evenly throughout the layer. On both sides to increase film sensitivity, speed, density, contrast
When the film is developed in developer solution the sensitized silver will be converted to what on the x-ray film after processing
Dark black dots
If there is an object between the x-ray beam and the film, exposing the film to radiation will create a what image because not all x-rays will reach the film
Latent
After producing the film the latent image will be converted to what
2-D image
What is MA used for
To control the quality of x-rays produced by the x-ray beam. When MA is increased a higher number of x-rays are generated
What is the length of exposure time
The period of time during which the x-rays are permitted to leave the x-ray tube.
What is the general exposure time for dogs at Vanier
1/24
What is the general exposure time for cats at vanier
1/30
What does the MAS describes
The total quantity of x-rays produced by the x-ray tube at a given time.
What is the KV P
Amount of electrical energy being applied to the anode and cathode to accelerate the radiation from the cathode toward the target
What happens when KV P is increased
The penetrating power of x-ray through tissue is increased
What are the three things that radiographic quality is dependent on
Radiographic density, radiographic contrast, radiographic detail
What is radiographic density
The degree of blackness on a radiograph.
What can the radiographic density be increased by
Increasing the MAS, increasing the KV P
What is radiographic density also influenced by
Thickness and type of tissue
Tissues. That have higher density absorb more x-rays and result in what color
White or light image
What can you say about bones and x-rays in terms of density and contrast
They have a high density. But decrease the radiographic density. They are high contrast
What is radiographic contrast
The difference in density between two adjacent areas on a radiographic image
What is low contrast
Long scale of contrast. Many shades of gray
What is a high contrast
Short scale of contrast. Few shades of gray. Ex: bones
What is radiographic contrast affected by
Subject density, KV P level, scatter radiation, film fogging
What is the definition of subject density in relation with radiographic contrast
The ability of the different tissue density us to absorb x-rays. Xers penetrate the various tissues depending on differences in atomic number and thickness
What happens when you increase subject density
Will increase radiographic contrast.
What can High KVP produce
A low curling trust radiograph. The higher the KV P, the longer the scale of contrast.
What happens with low KVP
Produces a high contrast radiograph with a short scale of contrast.
What anatomical regions require a high KVP setting
Thorax and abdomen
What anatomical regions require low KVP setting
Bones
What is scatter radiation
Radiation produced when x-rays from primary beam collide with objects in its path, I merge in all different directions.
Why is scatter radiation undesirable
Fogs the film, contrast is decreased, you are exposed to radiation
Why does high KV P produce more scatter radiation
Controls penetrating power of x-rays so more x-rays get through patient and through the film
What is an important beam limiting device
Collimators or grids
What are the causes of film fogging
Leaks in darkroom, scatter radiation, heat, improper processing
What is a grid
Device placed between patient and film to absorb scatter radiation and improve image quality
What is a Bucky
Device placed under the x-ray table that moves the grid back-and-forth. Placed in the cabinet beneath x-ray table with a trade to hold cassette. Decreases or eliminates white gridlines on radiograph
What is Geo metric unsharpness due to
Patient motion, long exposure time
How do you prevent geometric unsharpness
Have shortest possible exposure time
What is foreshortening
When image seems smaller than really is not parallel to recording surface. Subject must be parallel to photo graphic plate
