radiographic quality

image quality

visible sharpness of the image

image quality components (7)

• definition

• resolution

• detail

• sharpness

• visibility of detail

• edge gradient

• umbra

opposite of detail (2)

penumbra and blur

resolution

ability to image two separate objects and visually distinguish one from the other

types of resolution (2)

spatial and contrast resolution

spatial resolution

ability to distinguish between two separate objects of high subject contrast

spatial resolution example

bone and soft tissue

contrast resolution

ability to distinguish anatomical structures if similar subject (low) contrast

what would we see if there was increased contrast resolution?

more shades of gray

what would we see if there was decreased contrast resolution?

less shades of gray

factors affecting image quality (6)

• noise

• screen and film speed

• magnification

• shape distortion

• focal-spot blur

• subject factors

noise

random fluctuation in the density with a grainy appearance on a radiograph

film mottle

irregular clumping of silver halide crystals

structure mottle

physical imperfections of intensifying screens

quantum mottle

uneven shower of light photons from the device

what causes quantum mottle?

x-ray beam being uneven

quantum mottle: _______ exposure times and ______ screens

short, fast

as speed increases, noise _________ and radiographic quality ________

increases, decreases