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What makes something whiter on a radiograph? What is the basis of radiology?

thicker means whiter, higher density means whiter

differential absorption of x-rays passing through tissues is the basis of all radiology


What is the definition of radiographic opacity? What is radioopaque? What is radiolucent?

the relative ability of a material to
block passage of (absorb) x-rays

Radiopaque: white (or relatively white) areas on

Radiolucent: black (or relatively blacker) areas
on radiographs


What is the opacity interface? What can be used to enhance opacity interfaces and what are the two types?

Boundary between opacities

Contrast media can be used to create or
enhance opacity interfaces
Positive contrast is radiopaque (barium, iodine)
Negative contrast is radiolucent (air, CO2)


What is contrast? What is an example of high contrast? low contrast?

Definition: the degree of opacity difference
between adjacent areas on a radiograph
» High contrast: lung with liver
» Low contrast: fat with liver


What happens in magnification? What happens to something the further it gets from the image detector?

Things that are further from the image detector appear larger

Gets larger - but also more blurry


What happens in the summation sign?

Occurs when parts of objects in different planes
are superimposed
 Overlapping portions appear to have an opacity equal
to the sum of the individual tissues


What is the silhouette sign?

Materials of the same radiographic opacity
in contact results in the loss of the opacity
interface (no contrast)


What is distortion?

Image misrepresents true shape or position of
» Caused by unequal magnification of the part
being radiographed
 Portion of object is farther from the image detector
 Keep object parallel to image detector


Why are oblique views (vs. en face) helpful when looking at abnormalities?

» Generally, abnormalities (fractures, bony
reactions, etc) are easier to see if the x-ray
beam strikes them tangentially
» Abnormalities are much more difficult to
see if the x-ray beam strikes them head-on
(en face)
» Nearly obligatory for complex structures
(equine carpus and tarsus, skull)


How are images of the trunk usually hung?

cranial at top, caudal at bottom, patients right on your left


How are markers placed?

By convention, the positioning markers should be
placed at the lateral aspect or the cranial/dorsal
aspect of an extremity


What are the 5 radiographic opacities?

 Air (gas) opacity – black
 Fat opacity – dark gray
 Fluid/Soft tissue opacity – light gray
 Fluid: water, blood, urine, etc
 Soft tissue: muscle, organ
 Bone opacity – gray white
 Metal opacity – white


What are the Roentgen signs?

 Size
 Shape
 Number
 Location/position/alignment
 Margination (shape)
 Function


How do you hang Lateromedial (lateral)/mediolateral (lateral)
view of extremities?

 Proximal portion of image at top of viewing
 Cranial (or dorsal) portion of image positioned
on viewer’s left


study this - the leg part mostly