Image Analysis Radiographic Contrast 1.3

Question 1

Visibility of detail factor that describes the difference between adjacent densities on an image

Answer 1

contrast

Question 2

What must be present on an image for anatomic structures to be visualized?

Answer 2

entity it must exhibit contrasting shades of black, white, and gray compared to the structures that surround it

Question 3

Define short scale contrast

Answer 3

images the display just a few gray shades and appear mostly black and white

Question 4

define long scale contrast

Answer 4

images that display many shades of gray and few blacks and whites

Question 5

Contrast caused by the anatomic density, atomic number, and thickness differences of the patients body parts, and how differently each tissue composition will absorb x-ray photons

Answer 5

subject contrast

Question 6

what the kVp factor determines

Answer 6

the energy of x-ray photons produced and the differential absorption that occurs in the patinets tissues as the x-ray pass thru the patients body

Question 7

what is the penetrating power of the beam?

Answer 7

kVp

Question 8

What type of images does using high kVp produce?

Answer 8

low contrast images

Question 9

Using high kVp causes more what?

Answer 9

scatter

Question 10

How does an image appear when using high kVp?

Answer 10

long-scale contrast (few blacks and whites and many grays)

Question 11

What type of image does low kVp produce?

Answer 11

high contrast images–produces low energy photons that are easily absorbed

Question 12

What images will exhibit when using low kVp

Answer 12

short scale contrast (mostly black and white with few grays)

Question 13

How images will appear when using low KVP?

Answer 13

appear mostly black and white

Question 14

What must be evaluated to obtain desired level of contrast and gray scale

Answer 14

each patients body part being imaged and select the appropriate kVp for that specific patient

Question 15

Define optimum kVp

Answer 15

the kVp that will provide adequate part penetration and sufficient image contrast

Question 16

what to do to the technique when you need higher contrast and will have to alter the technical factors always from optimum kVp

Answer 16

decrease original kVp by 15%, and increase mAs by 100% alter factors away from optimum kVp

Question 17

What to do the technique when you need lower contrast and must deviate from optimum kVp?

Answer 17

increase original kVp used by 15%, decrease mAs by 50%

Question 18

what is the general rule with adjusting the contrast with kVp?

Answer 18

you should stay relatively close to optimum kVp level for the specific structure being imaged to maintain sufficient penetration

Question 19

how scatter radiation affects radiographic contrast

Answer 19

scatter radiation decreases contrast by putting a blanket of density (fog) over the image

Question 20

what happens to the radiographic contrast as the amount of scatter increases

Answer 20

the greater the decrease in contrast and decrease in visibility

Question 21

how to control the amount of scatter reaching the IR and improve contrast

Answer 21

by reducing the amount of tissue irradiated, collimate, decreasing the field size, and using a grid

Question 22

what higher grid ratios does to an image

Answer 22

the greater the scatter cleanup and the higher the radiographic contrast

Question 23

how to improve the visibility of recorded detail on an area of interest that will have an increased thickness

Answer 23

place a large, flat contact shield or straight edge of a lead apron along appropriate border

Question 24

define artifact

Answer 24

any undesirable structure or substance recorded on an image

Question 25

Groups that artifacts can be categorized into

Answer 25

- anatomic structure that obscure area of interest or have no purpose for being there and can be removed from an image - externally removable objects (possessions) - internal objects (prostheses or monitoring lines) - appearances that result from improper equipment use (grid cutoff)

Question 26

define anatomic artifact

Answer 26

any anatomic structure that is within the image that could have been removed

Question 27

best way to avoid anatomic artifacts

Answer 27

explaining to the patient the importance of remaining in that position; visually check

Question 28

define external artifacts

Answer 28

artifacts found outside the patients body

Question 29

what are some common external artifacts

Answer 29

earrings, rings, necklaces, bra hooks, dental structures, hair pins, monitoring lines, gown snaps

Question 30

define internal artifacts

Answer 30

artifacts found within the patient

Question 31

examples of internal artifacts

Answer 31

prosthesis and pacemaker and port a caths

Question 32

define grid alignment artifacts

Answer 32

grid lines that result from the use of stationary grids and the improper use of all grid type

Question 33

when do grid lines occur and what do they look like

Answer 33

because the lead strips absorb primary radiation and are visible as small white lines on an image

Question 34

what are the causes of grid lines

Answer 34

1.Parallel grid was tilted or CR was angled toward the lead strips, image will demonstrate grid lines on the side toward which the CR is angled 2. if parallel or focused grid was off focus (taken at an SID outside focusing range) image will demonstrate grid lines on the entire image 3. if focused grid was tilted or CR was angled entire image will demonstrate grid lines 4/ if focused grid was upside down, image demonstrates grid lines on both sides 5. if focused grid was off centered (CR not centered on the center of grid) image demonstrated grid lines on entire image

Question 35

what are film handling and processing artifacts

Answer 35

improper film handling and processing can cause artifacts such as film creases, static, fog, stains, scratches, and hesitation marks

Question 36

when must an image be repeated in regards to artifacts

Answer 36

if an artifact can be eliminated obscures any portion of area of interest the image needs to be repeated

Question 37

when does it not need to be repeated in regard to artifacts

Answer 37

if the artifact is located outside the area of interest the image does not need to be repeated

Question 38

define what an optimal image is

Answer 38

when an image meets all necessary requirements and does not need to be repeated

Question 39

factors to consider when deciding if an image is acceptable or not

Answer 39

- your facilities standards - age and condition of patient - conditions under which the patient was imaged - whether obvious pathology is evident - whether the indications for the exam were met

Question 40

who decides if an image is acceptable

Answer 40

each facility has its own standards that will determine whether an image should be repeated, has to be acceptable in the yes of the radiologist and the technologist to a point

Question 41

why would less than optimal images be accepted

Answer 41

because repeating the image may be impossible, as in a surgery cases or in other cases where patient cannot cooperate

Question 42

what must you do when a less than optimal image is accepted

Answer 42

record on requisition or in the computer any information about the patients condition or situation that resulted in the acceptance of that image