Radiographic Imaging - Chapters 3 & 4

Front 1

Image Receptor

Back 1

a device that receives the radiation leaving the patient

Front 2

Differential Absorption

Back 2

process whereby some of the x-ray beam is absorbed and some passes through

Front 3

Beam Attenuation

Back 3

as the primary beam passes through anatomic tissue it loses energy

Front 4

Absorption

Back 4

beam energy deposited in the atoms of the tissue and not transmitted

Front 5

Photoelectron

Back 5

electron ejected from the inner shell

Front 6

Ionization

Back 6

x-ray beam causing ejection of orbital electrons

Front 7

Photoelectric Effect

Back 7

x-ray interaction with matter in which an inner-shell electron is ejected; results in complete absorption of the x-ray photon

Front 8

Scattering

Back 8

photons not absorbed but instead lose energy with the tissues

Front 9

Compton Effect

Back 9

loss of x-ray beam energy for ejection of outer shell electrons - called Compton electrons or secondary electrons

Front 10

Coherent Scattering

Back 10

interaction with low energy x-rays causing a change in direction of the x-ray

Front 11

Properties of Scattered Photons

Back 11

no useful diagnostic information
adds to patient radiation exposure
adds to room radiation exposure

Front 12

Factors Affecting Beam Attenuation

Back 12

thickness of anatomic part
atomic number
tissue density

Front 13

Effect of Tissue Thickness

Back 13

increasing thickness increase beam attenuation
50% reduction for each 4-5 cm of tissue

Front 14

Effect of Tissue Type

Back 14

higher atomic number tissues, such as bone, attenuate beam more than lower atomic number tissues

Front 15

Tissues that Account for Beam Attenuation

Back 15

bone, muscle, fat and air

Front 16

Effect of X-Ray Beam Quality

Back 16

high-penetrating beam transmitted through tissue
low-penetrating beam likely to be attenuated

Front 17

Transmission

Back 17

x-ray photon passing through the anatomic part without any interaction

Front 18

Exit Radiation

Back 18

same as remnant radiation

Front 19

Three Processes of X-Ray Beam Tissue Interactions

Back 19

absorption, transmission, scattering

Front 20

Manifest Image

Back 20

the visible image that is made after processing of the latent image

Front 21

Spatial Resolution

Back 21

smallest object that can be detected in an image

Front 22

Brightness

Back 22

amount of luminance of the display monitor

Front 23

Density

Back 23

amount of overall blackness on the processed image

Front 24

Primary factor affecting brightness or density

Back 24

quantity of radiation reaching the image receptor

Front 25

Grayscale

Back 25

number of different shades of gray

Front 26

Scale of Contrast

Back 26

range of densities (film images)

Front 27

High Contrast

Back 27

few densities, but great differences in densities

Front 28

Short-Scale Contrast

Back 28

same as high contrast

Front 29

Low Contrast

Back 29

large number of densities, but few differences between them

Front 30

Long-Scale Contrast

Back 30

same as low contrast

Front 31

Contrast Resolution

Back 31

ability of an IR to distinguish between objects having similar contrast

Front 32

Distortion

Back 32

misrepresentation of size or shape of anatomic part

Front 33

SID

Back 33

source to image receptor

Front 34

OID

Back 34

object to image receptor

Front 35

Foreshortening

Back 35

images that appear shorter than the true objects

Front 36

Elongation

Back 36

images that appear longer than the true objects

Front 37

Quantum Noise or Quantum Mottle

Back 37

visible brightness or density fluctuation on the image
occurs when fewer photons reach the IR

Front 38

Artifact

Back 38

any unwanted image on the radiograph

Front 39

Dynamic Range

Back 39

range of exposure intensities on an IR

Front 40

Matrix

Back 40

combination of rows and columns of pixels

Front 41

Pixel

Back 41

picture elements
recorded as a single value of brightness; low values are brighter

Front 42

Pixel Bit Depth

Back 42

number of bits controlling the pixel
greater pixel depth means greater contrast resolution

Front 43

Pixel Density

Back 43

number of pixels per unit area

Front 44

Pixel Pitch

Back 44

distance measured from the center of a pixel to an adjacent pixel

Front 45

Active Layer or Emulsion

Back 45

active layer of radiographic film

Front 46

Intensifying Screen

Back 46

convert exit radiation into visible light

Front 47

Light Transmittance

Back 47

density of the film image
compares the light transmitted through the film to the original amount of light - called transmittance
I(t) / I(0) -> 0 = all light transmitted

Front 48

Densitometer

Back 48

device used to measure the density (blackness) of a radiograph

Front 49

Optical Density

Back 49

Log (I(0) / I(t)
Range between 0 - 4
0 = very bright
4 = very black