Radiographs Flashcards
Which views should be used
What are x-ray grids & when should they be used
Consist of alternating strips of plastic & lead which filter out x-ray photons that are not traveling in forward direction
Reduces scatter radiation reaching x-ray cassette & thus improves radiographic contrast
Grid absorbs portion of primary beam so higher exposure (increase mAs) is required
When part being radiographed is over 10cm thick
What is contrast media
Substances that are administered to patient which are either more radiopaque or more radiolucent than surrounding tissue
Provide detail of organ size, shape, position, internal detail & sometimes function
Useful for hollow organs
Describe negative contrast media
Negative contrast media have low radiographic opacity
Radiolucent appearance on radiographs
e.g. air, gases
Advantages: cheap, quick, convenient & safe
Disadvantages: poor mucosal detail if used alone, air slowly eliminated from body (may confuse later studies)
Mainly used in bladder & GI tract
Describe positive contrast media
Positive contrast media have high radiographic opacity
Radiopaque appearance on radiographs
e.g. barium, meglumine diatrozoate, iohexol
Used for GI contrast studies
Advantages: low toxicity, excellent mucosal detail
Disadvantages: care with aspiration, irritant if inters body cavities
What are the ideal properties of contrast media
Different radiopacity from tissue under examination
Not toxic or irritant
Persist for duration of study
Totally eliminated after study
Easily administered
What artefact is this
Electrical noise artefacts
Small to medium sized non-uniform echoes on image
Caused by electrical equipment
Enhanced by gain being too high
To resolve/prevent:
Turn off electrical equipment
Reduce time gain compensation
What artefact is this
Acoustic shadowing:
Anechoic shadowing deep to structure being imaged
Caused by total reflection of sound waves at tissue interfaces with impedance differences
What artefact is this
Acoustic enhancement
Structures displayed more clearly deep to fluid-filled organs
Can be useful to improve imaging
What artefact is this
Reverberation artefacts:
2 common appearances:
Numerous parallel lines present of decreasing intensity as go deeper – caused by poor transducer contact
Comet tail or ring-down artefact – caused by reverberation between 2 highly reflective interfaces
To resolve use plenty of coupling gel & ensure good contact with patient
What artefact is this
Faint reversed image of structure adjacent to original
To resolve alter transducer angle & change gain
