Introduction to Radiology and Radiation Safety

x-rays use short wavelengths, high energy, and high frequency. The image is created from the shadow of the object

Understand the unique properties of x-rays and how they can be used to create a radiograph

the energy is high enough to knock electrons out of orbit

Know how x-rays cause biologic damage

ionization and destruction of DNA

What is direct effect x-ray biological damage?

production of free radicals that can then diffuse far enough to reach and damage the critical target.

What is indirect effect x-ray biological damage?

Stem cells are more radiosensitive than mature cells

Young tissue is more radiosensitive than old tissue

Tissue with high metabolic activity is more radiosensitive than tissue with low metabolic activity

Describe the radiosensitivity of various tissues

distance: maximize from the radiation source

time: minimize duration of exposure

protection: wear gloves, apron, and thyroid shield

What are the basic principles of radiation protection and describe how to apply them

mA selector: number of x-rays in beam

Focal Spot Selector: trade-off between resolution and quantity of radiation

Timer: number of x-rays in beam

mAs Selector (mA x Time): number of x-rays in beam quantity

kVp Selector: energy of beam (quality) and number of x-rays (quantity)

Describe the controls on an x-ray machine console that are used to modify the x-ray beam parameters

when the x-rays pass through an object causing diffusion and reducing image contrast

How is scatter radiation caused and how does it degrade an image?

collimator: limits the beam to just the area of interest

grid: devices used to prevent scatter from reaching the film

How is scatter controlled?

Immediately after exposure a numbered grid is created differentiating between the various levels of x-ray absorption. Each number in the grid is assigned to a shade of gray or color.

How is a radiographic image formed?

Metal: white

Bone: less vibrant white

Soft tissue: gray

Fat: dark gray

Air: black

Be able to identify the 5 basic radiographic opacities

when two objects are superimposed over each other the overlapping portions of the object will appear more opaque.

What is summation effect?

when two objects of the same subject density are in contact, they will appear to blend together radiographically

What is silhouetting effect?

refers to enlargement of the image relative to the actual size of the object being imaged

What is imagine distortion and magnification?

summation

What effect is shown?

silhouetting

What effect is shown?

distortion/magnification

What effect is shown?

named based on "where the x-rays enter" - "where the x-rays exist"

V/D - L marker is on the R D/V - R marker is on the left

Know the proper orientation of radiographs

opaque on x-ray

Define radiopaque

translucent on x-ray

Define radiolucent

number of x-rays in beam (exposure)

mA selector

low output = high resolution

high output = high exposure

Focal Spot Selector

exposure time

mAs Selector

determines contrast of an image

higher kVp = higher contr\ast

kVp Selector