Chapter 3- Image Formation and Radiographic Quality

Question 1

Anatomic tissues absorb and transmit x-rays differently based on their composition (atomic number and tissue density)

Answer 1

Differential Absorption

Question 2

______ absorbs more x-rays than muscle?

Answer 2

Bone

Question 3

The primary x-ray beam loses some of its energy (number of photons) as its interacts with anatomic tissue.

Answer 3

Attenuation

Question 4

What are the two types of attenuation?

Answer 4

Absorption and scattering

Question 5

Complete absorption of the incoming photon

Answer 5

Photoelectric effect

Question 6

During absorption, the energy of the _______ beam is deposited within the atoms comprising the tissue

Answer 6

Primary

Question 7

What are effects of photoelectric

Answer 7

X-ray ionizes atom
low energy secondary x-ray photon created
probability of photoelectric effect dependent on the energy of the incoming x-ray photon and tissue atomic number

Question 8

Occurs when an incoming photon loses some but not all of its energy, then changes its direction

Answer 8

The Compton effect (Scattering)
* It can occur within all diagnostic x-ray energies and is dependent only on the energy of the incoming photon, not the atomic number of tissue

• Higher KVP reduces the number of interactions, but the the Compton interactions increases in comparison to the number of photoelectric interactions

Question 9

Factors affecting beam attenuation: (att)

Answer 9

Tissue thickness- reduce by 50% for each 4 to 5cm
Type of tissue- higher atomic # will increase beam att.
Tissue density- increase compactness of atomic particles will increase beam att.
X-ray beam quality- higher KVP increases the energy of the x-ray beam will decrease beam att

Question 10

Scatter radiation reaching the image receptor creates _______ exposure called ______

Answer 10

Unwanted

Fog

Question 11

______ or exit radiation is composed and transmitted and ________ radiation

Answer 11

Remnant

Scattered

Question 12

What radiation creates an image that structurally represents that anatomic area of interest?

Answer 12

Transmitted and Absorbed (Exit Radiation)

Question 13

X-ray beam passes through matter there is a gradual reduction in the number of photons, what is this called?

Answer 13

Absorption or Attenuation

Question 14

What does an x-ray beam produce on a image receptor?

Answer 14

Latent Image

Question 15

What is an excellent demonstration of the different absorption characteristics

Answer 15

CT

Question 16

Dense structures and those of high atomic number appear _______ areas on the image

Answer 16

lighter

Question 17

_____ and _______ appear as dark areas on the image

Answer 17

Air (low density)

Fat (low atomic #)

Question 18

Dense and high atomic numbers appear _______ shadow on the film and are usually ________?

Answer 18

Light

Bone

Question 19

What are technical factors radiation therapist use for differential absorption on the film?

Answer 19

KVP or MA

Question 20

_______ structures represent areas of _______ atomic numbers

Answer 20

Dark

Low

Question 21

_______ structures represent tissue that is dense with ______ atomic numbers

Answer 21

Light

High

Question 22

Density = __________

Answer 22

Darkness

Question 23

_______ radiation reacts with an image receptor such as film screen system to create latent image until processed to produce the manifest or the _______ image.

Answer 23

Exit

visible

Question 24

Low Density = ____________

Answer 24

Brightness

Question 25

______ radiation creates higher brightness or low density on the displayed image

Answer 25

Absorbed

Question 26

________ radiation creates lower brightness or high density on the displayed image

Answer 26

Transmitted

Question 27

The various shades of gray recorded in the image make atomic tissue _________.

Answer 27

Visible

Question 28

Visibility of anatomic structures

Answer 28

Density | Contrast

Question 29

Accuracy of structural lines (sharpness)

Answer 29

Resolution or recorded detail | Distortion

Question 30

True of False- A quality radiographic image accurately represents the anatomic area of interest, and its information is well visualized for diagnosis.

Answer 30

True

Question 31

A film image is evaluated by the amount of ________ or overall blackness after processing

Answer 31

Density

Question 32

A digital image is evaluated by the amount of _______ or ______ (Light emission)

Answer 32

Brightness | Luminescence

Question 33

The range of brightness levels are a result of the tissues _______ _______ of the x-ray photons

Answer 33

Differential Absorption | Ex: Barium (contrast material)

Question 34

True or False- The ability to distinguish among types of tissues is determined by the difference in brightness levels or densities in the image or contrast

Answer 34

True

Question 35

Gray scale is?

Answer 35

The number of different shades of gray that can be stored and displayed in a digital image

Question 36

Scale of contrast is?

Answer 36

The range of densities visible on film

Question 37

_______ resolution describes and imaging receptors ability to distinguish between objects similar in subject contrast?

Answer 37

Contrast

Question 38

True or False- Anatomic details do not have to be recorded accurately?

Answer 38

False- They must be, with the greatest amount of sharpness

Question 39

_______ resolution refers to the smallest object that can be detected in a digital image?

Answer 39

Spatial

Question 40

_______ detailed refers to the distinctness or sharpness of the structural lines that make up the recorded film image?

Answer 40

Recorded

Question 41

True of False- All radiographic images have some degree of unsharpness

Answer 41

True

Question 42

Size distortion or magnification is an _______ in the objects image _____ compared to its true or actual _______.

Answer 42

Increase Size Size

Question 43

True or False- Shape distortion is a representation of an object's image shape

Answer 43

False- Its a misrepresentation * Elongation and foreshortening * Central ray (CR) alignment of the x-ray tube, part and image receptor affect distortion

Question 44

Does scatter and fog decrease image contrast?

Answer 44

YES

Question 45

True or False: Digital image receptors can detect lower levels of radiation intensity and therefore are less sensitive to scatter?

Answer 45

False- They are MORE sensitive to scatter

Question 46

Visible as brightness or density fluctuations and is photon dependent

Answer 46

Quantum Noise * Provides no useful information * More visible in digital imaging * Too few x-ray photons result in increase

Question 47

Classified as plus density and minus density

Answer 47

Image Artifact

Question 48

In digital imaging what is the column and the rows called

Answer 48

Matrix

Question 49

What are the small boxes in a digital image called

Answer 49

Pixel- picture element or smallest component of matrix

Question 50

Recorded a single numerical value representing a brightness level on a display monitor

Answer 50

Matrix

Question 51

True or False: Location of pixel in the matrix corresponds to an area within the patient or volume of tissue

Answer 51

True

Question 52

True or False: If the Matrix size is smaller the greater number of smaller pixels?

Answer 52

False: the quality is improved with a larger matrix. This will increase digital storage, processing time and network transmission time.

Question 53

Numerical value assigned to a _______ is determined by the relative attenuation of x-rays passing through the volume of the tissue

Answer 53

Pixel

Question 54

What determines the shade of gray in image

Answer 54

pixel bit depth or number of bits (2") determines the number of gray that can be displayed

Question 55

Active layer of film that contains the crystals that serve as latent imaging centers?

Answer 55

Film Emulsion

Question 56

Used to convert exit radiation intensities to visible light and expose the emulsion crystals

Answer 56

Intensifying Screens

Question 57

Is chemically processed to display the range of densities created as a result of the x-ray attenuation characteristics of anatomic structures

Answer 57

Film

Question 58

_______ _________ image receptors have a limited dynamic range that vary greatly in x-ray attenuation

Answer 58

Film Screen

Question 59

Receptors have a wide dynamic range, and therefore anatomic areas of widely different attenuation properties can be more easily visualized on a digital image.

Answer 59

Digital Image

Question 60

The range of exposure intensities an image receptor can accurately detect

Answer 60

Dynamic Range