Image Analysis Radiographic Contrast 1.3 Flashcards Preview

Radiography Spring 2016 > Image Analysis Radiographic Contrast 1.3 > Flashcards

Flashcards in Image Analysis Radiographic Contrast 1.3 Deck (42):

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



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

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


Define short scale contrast

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


define long scale contrast

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


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

subject contrast


what the kVp factor determines

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


what is the penetrating power of the beam?



What type of images does using high kVp produce?

low contrast images


Using high kVp causes more what?



How does an image appear when using high kVp?

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


What type of image does low kVp produce?

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


What images will exhibit when using low kVp

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


How images will appear when using low KVP?

appear mostly black and white


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

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


Define optimum kVp

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


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

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


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

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


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

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


how scatter radiation affects radiographic contrast

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


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

the greater the decrease in contrast and decrease in visibility


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

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


what higher grid ratios does to an image

the greater the scatter cleanup and the higher the radiographic contrast


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

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


define artifact

any undesirable structure or substance recorded on an image


Groups that artifacts can be categorized into

-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)


define anatomic artifact

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


best way to avoid anatomic artifacts

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


define external artifacts

artifacts found outside the patients body


what are some common external artifacts

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


define internal artifacts

artifacts found within the patient


examples of internal artifacts

prosthesis and pacemaker and port a caths


define grid alignment artifacts

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


when do grid lines occur and what do they look like

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


what are the causes of grid lines

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


what are film handling and processing artifacts

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


when must an image be repeated in regards to artifacts

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


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

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


define what an optimal image is

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


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

-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


who decides if an image is acceptable

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


why would less than optimal images be accepted

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


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

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