Image Critique

What's the reference plane for a patient in a 68 degree angle

halfway between 45 and 90 degrees

if the ratio or percentage difference is greater between 2 details then the contrast is _______

high

the _______ the SNR the more desired to undesired signals that were used

higher

the ______ the contrast resolution, the _______ the gray shade difference

higher, higher/greater

If the image histogram was narrower than the LUT histogram, which the remnant beam demonstrated ______ subject contrast than desired, the algorithm applied to the data would widen the histogram, ________ the # of gray scales, which ________ the degree of difference between each gray scale, ________ the contrast between details

higher, increasing, decreases, decreasing

Patients who are in good shape, strong muscles, low fat content, and dense bones, usually display the _______ subject contrast

highest

lateral foot, ankle, lower leg, knee, and femur display as if they were hanging from the _____

hip

determining the technical adjustment for underexposure: Step 1. determine if a ________ ________ error has occurred. If no error, move to step 2

histogram analysis

when imaging pediatrics, the _____ used may not be high enough to obscure creases or folds in unlaundered material or flame-resistant clothing

kV

determining the technical adjustment for underexposure: Step 3. determine how much the _____ or ______ need to be adjusted to move the EI number to the ideal value and eliminate quantum noise

kV, mAs

mobile and trauma imaging: set an optimal ______ and _____ or AEC

kV, mAs

if the cortical structures aren't seen then an increase in _____ is required

kVp

technical factor that determines the energy and penetrating ability of the photons produced and is the controlling factor for differential absorption

kVp

Lateral projection: align the _______ foot surface with the IR. Align the CR ________ to the IR and lateral foot surface

lateral, perpendicular

Crosstable projections: a ________ projection is performed

lateromedial

lateral projection gonad shielding

lay a flat contact shield along an imaginary plane that connects the coccyx and a point 1 inch posterior to ASIS

name an anatomic artifact

lead marker

the markers are constructed of ______ so they are radio_______

lead, radiopaque

metallic objects and contrast mediums are recorded on the ______ in the graph

left

Gray shade values between white to black are positioned on the histogram from ______ to ______

left to right

adjusting the window width changes the _______ of the dynamic range used for the projection

length

if 2 structures are closer together, the amount of separation between the structures when an angled CR is used would be _____, and if the 2 structures were farther apart, the separation between the structures on the resulting projection would be _____

less, greater

images of bony structures that have lost minerals are ______ dense because of disease, appear darker gray than lighter and demonstrate _____ subject contrast

less, low

the bones of infants and children are ______ dense and more porous than adult bones, resulting in _____ subject contrast

less, low

displayed projections with histogram analysis errors ale demonstrate EI errors, and can be too ______ or too ______, or have excessive ______ or gray scale

light, dark, contrast

CR: During digitization, each pixel is assigned a digital value that represents the amount of _______ that was _________ from that surface of the IP.

light, emitted

spatial frequency is expressed as

line pairs per millimeter (lp/mm)

During DR, the tech must choose the correct exam from the workstation before the exposure is made to ensure the correct _______ is applied to the displayed image

lookup table (LUT)

during CR, when selecting the correct exam or body part, it ensures that the correct ______ ______ is applied when the image is rescaled

lookup table (LUT)

if the ratio or percentage difference is less between 2 details then the contrast is _______

low

more than adults, children are more susceptible to ______ levels of radiation because they possess many rapidly dividing cells and have a longer life expectancy

low

patients who have retained fluid because of disease or injury display _____ subject contrast

low

patients whose bodies have deteriorated because of disease or age and obese patients display ______ subject contrast

low

______ blur indicates that the spread is minimal, involving fewer ______ and indicating high detail _______

low, pixels, sharpness

Pediatric imaging requires _______ kVp and mAs

lower

intensity at the anode end of the tube is _____ because fewer photons emerge from that end of the tube than at the cathode side

lower

if the histogram is wider than the LUT, which the remnant beam demonstrated ______ subject contrast than desired, the algorithm applied to the data would narrow the histogram, _______ the # of gray scales, which ________ the degree of difference between each gray scale and _______ the contrast between details

lower, decreasing, increases, increases

the _______ the contrast resolution, the _______ the gray shade differences

lower, lower

if contrast resolution is adequate, _______ should be adjusted to offset quantum noise

mAs

no amount of adjustment in ______ will ever compensate for insufficient kV

mAs

when a grid is added or changed from one grid ratio to another, IR exposure will be inadequate unless the _____ is adjusted

mAs

the controlling factor for intensity and IR exposure is _______ with what 5 factors?

mAs 1. kV 2. SID 3. OID 4. collimation 5. grids affecting it in smaller degrees

when an OID increase causes significant scatter radiation to be diverted from the IR, the ______ should be increased by about ____% for every cm of OID to compensate and to keep the EI number at the ideal

mAs, 10%

inverse square law

mAs1/mAs2 = D2^2/D1^1

exposure maintenance formula

mAs1/mAs2=D1^2/D2^2

if contrast masking is done unevenly, the perceived location of the CR is changed on the _______ projection

masked

contrast _____ doesn't replace good collimation and shouldn't be used to present a perceived radiation dose savings to the patient by moving one or more of the sides into the _______ region.

masking, exposed

intensity refers to the total ______ of photons that expose the patient and IR

quantity

this is demonstrated when the amount of exposure reaching the IR is too low, causing the number of photons hitting the IR to be low and the random distribution of photons to be soon on the projection as graininess or a random pattern superimposed on the projection

quantum noise

CR: All the digital numbers (gray shade values) together make up what is referred to as the ______ ______

raw data

always use the ______ plane to determine the amount of obliquity. Don't assume a sponge of a set angle will always position the patient at the same angle.

reference

refers to the ability of an imaging system to record sharp detail edges and distinguish small adjacent details from each other in a projection

spatial resolution

the projection is evaluated for how recognizable the details are as defined by what 3 factors?

spatial resolution, magnification, shape distortion

a ____% mAs adjustment is needed for a field size change from 14x17 to a 10x12, and a ____% mAs change is needed for a 14x17 to an 8x10

35%, 50%

this allows mAs to be automatically determined by controlling the exposure time

Automatic Exposure Control (AEC)

Projection: AP and Lateral humerus Where should the anode and cathode be placed?

Anode = elbow Cathode = shoulder

Projection: AP and Lateral femur Where should the anode and cathode be placed?

Anode = knee Cathode = hip

Projection: AP and Lateral forearm Where should the anode and cathode be placed?

Anode = wrist cathode = elbow

How many degrees of rotation does it take to affect the appearance of the lungs?

2-3 degrees

when the structure being imaged is smaller than the IR, collimation is brought within _____ inch of the closest _____ line

0.5 inch, skin

tightly collimate to within _____-____ inches of the VOI

0.5-1

2. Central ray centering: each projection requires a specific CR centering and collimation within ____ to ____ inch of the VOI.

0.5-1 inch,

shields are to be made of a minimum of ____ mm of ______

1 mm of lead

5 common causes of histogram errors

1. Part selection from workstation menu 2. Central ray centering 3. external and internal artifacts 4. scatter radiation control 5. Computed rad. only

4 common factors that cause noise

1. artifacts 2. scatter radiation 3. quantum mottle 4. electronic noise

overexposure is identified when what 3 different things can occur?

1. brightness has been rescaled to the LUT 2. VOI demonstrates a loss of subject contrast 3. SNR is low

4 good collimation practices

1. clearly delineate VOI 2. decrease radiation dosage by limiting the amount of patient tissue exposed 3. improve the visibility of recorded details by reducing the amount of scatter radiation that's produced 4. reduce histogram analysis errors

12 topics to analyze in projections

1. demographics 2. projection is accurately displayed on monitor 3. correct marker placement 4. appropriate collimation 5. relationships between anatomic structures are accurate 6. max. spatial resolution 7. radiation protection 8. image histogram was accurately produced 9. adequate exposure reached IR 10. contrast resolution is optimal for demonstrating VOI 11. no preventable artifacts are present 12. ordered procedure and the indication for the exam have been fulfilled

6 steps for repositioning the CR for repeat projections

1. identify the 2 structures that are mispositioned 2. determine which of the identified structures is positioned farthest from the IR 3. determine the direction in which the structure situated farthest from the IR must move to be positioned accurately with respect to the other structure 4. determine the number of inches or cm that the 2 mispositioned structures are off on the projection 5. estimate how much the structure situated farthest from the IR will move per 5 degrees of angle adjustment placed on the CR 6. place the needed angle on the CR and direct the CR in the direction indicated

6 steps for repositioning the patient for repeat projections

1. identify the 2 structures that are mispositioned 2. determine the number of inches that the 2 mispositioned structures are "off" 3. determine if the 2 structures will move toward or away from each other when the main structure is adjusted 4. begin the repositioning process by first positioning the patient as they were positioned for the poorly projection. From this, move the patient as needed for proper positioning 5. if the structures move in opposite directions from each other when the patient is repositioned, adjust the patient half of the distance that the structures are off 6. if only one structure moves when the patient is repositioned, adjust the patient so that the structure that moves is adjusted the full amount

The alignment of the CR with the part must be accurate to what 3 things?

1. obtain open joint spaces 2. clearly see fracture lines 3. obtain specific anatomic relationships

10 characteristics of the optimal projection

1. projection is accurately displayed 2. demographic info. 3. correct marker placement 4. desired anatomic structures are in the exposure field and are in accurate alignment w/ each other 5. maximum spatial resolution 6. radiation protection 7. image histogram was accurately produced w/o errors 8. adequate exposure reached the IR based on ideal EI 9. contrast resolution identifies the subject contrast 10. noise is minimal

the degree of contrast resolution presented on images is determined by what 3 things?

1. quality of the subject contrast in the remnant beam 2. dynamic range available 3. processing algorithm applied to the image data before it's displayed

the desired signals in SNR represent remnant beams of the VOI on the projection and the noise includes what 3 things?

1. scattered radiation 2. quantum mottle 3. electronic static on the image

3 AEC factors to consider when imaging an obese patient

1. select a high mA 2. avoid long exposure times 3. adjust the backup timer to 150% to 200% of the expected manual exposure time

the greatest edge sharpness is obtained by what 4 things

1. small focal spot size 2. longest possible SID 3. shortest possible OID 4. controlling motion

The degree of contrast resolution present is determined by what 3 things?

1. the quality of the subject contrast represented in the remnant beam 2. the dynamic range available 3. the processing algorithms applied to the data before they're displayed

imaging professionals have a responsibility to adhere to effective radiation protection practices for what reasons

1. to prevent the occurrence of radiation-induced nonstochastic effects by adhering to dose-equivalent limits that are below the threshold dose-equivalent levels 2. to limit the risk of stochastic effects to a reasonable level compared with nonradiation risks and in relation to society's needs, benefits gained, and economic factors

6 factors to consider when making a decision to send your images

1. your facility's standards 2. age and condition of patient 3. conditions under which patient was imaged 4. whether obvious pathology is evident 5. whether indications for exam have been fulfilled 6. whether windowing/modifying the projection by processing it with a different procedural algorithm will display the needed info

to keep the EI at the ideal, any change in SID of greater than _____% should be compensated for by adjusting the mAs by the exposure maintenance formula

10%

maintain an SSD of at least ____ inches (____ cm) to prevent an unacceptable entrance skin dose

12 inches (30 cm)

the anode heel effect is considered when a ____inch (____ cm) or longer field length is used to accommodate the structure, as with long bones and the vertebral column

17inch (43 cm)

radiosensitive cells: shield the eyes, thyroid, breasts, and gonads whenever they lie within _____ inches of the primary beam

2 inches (5cm)

at a 40 inch SID, the divergence of x-rays is ____ degrees per inch the anatomy is off-centered in any direction from the CR; at a 72 inch, it's _____ degree per inch

2, 1

the normal heart shadow on a chest projection will occupy slightly less than _____% of the transverse dimension of the thorax

50%

as one is adjusting kVp from optimum because of increased thickness or an additive disease process, it should be noted that if the kVp is set above _____ kVp, absorption of the photons will no longer take place in soft tissue and if set above _____ kVp will no longer happen in bone

80, 120

Projection: AP lumbar vertebrae Where should the anode and cathode be placed?

Anode = 1st lumbar vertebrae Cathode = 5th lumbar vertebrae

Projection: AP thoracic vertebrae Where should the anode and cathode be placed?

Anode = 1st thoracic vertebrae Cathode = 12th thoracic vertebrae

Projection: AP and Lateral lower leg Where should the anode and cathode be placed?

Anode = ankle Cathode = knee

ALARA stands for

As Low As Reasonably Achievable

mobile and trauma imaging: use the smallest possible ______

OID

to keep size distortion at a minimum, use the shortest possible _____ and the longest feasible ______

OID, SID

After the image histogram has been created and analyzed, the EI is read by the computer at the midpoint ______ of the defined VOI

S-ave

the shade value for the average pixel value (usually soft tissue) identifies as ______ and is located halfway between S-min and S-max

S-ave

the shade value that is identified on the left is labeled _____ and represents the minimum useful gray shade value (brightest shade), and the shade value identified on the right is labeled ______ and represents the maximum useful gray shade value (least brightness)

S-min, S-max

Spatial Resolution: to offset magnification when the part can't be placed at an acceptable OID, the ______ can be increased the ratio between the OID and SID must remain the same for equal ________ results, and because this requires unacceptable SIDs, equal magnification is seldom obtained

SID magnification

Magnification factor formula

SID/SOD

After the exposure, the ______ acts as a switching gate, sending the stored signals to the computer in an orderly manner for processing and manipulation where each DEL signal is given a digital number that represents the ______ shade value

TFT, gray

collimation determines how the ______ will fill the workstation screen

VOI

What's the reference plane for a patient in a 23 degree angle

halfway between 0 and 45 degrees

CR: the number and distribution of the trapped electrons in each area of the IP represent the differential _________ and latent image of the body part being imaged

absorption

_________ and _________ patient conditions that result in change to the normal bony structures, soft tissues, or air or fluid content of the patient, require technical adjustments to compensate for the exposure change that the condition causes

additive, destructive

________ diseases cause tissues to increase in mass density or thickness, resulting in them being more ________, whereas _________ diseases cause tissues to break down, resulting in them being more _________

additive, radiopaque, destructive, radiolucent

For trauma oblique projections: Align the CR with the plane, line, or ________ structure that's used for an AP. Adjust the CR in the direction needed to set up the correct ___________ between the CR and structure

anatomic, alignment

When evaluating the contrast in a projection it's important to compare the contrast of ________ structures in the ______ with each other

anatomical, VOI

position the thinner side of the structure at the ______ end of the tube and the thicker side at the ______ end of the tube

anode, cathode

any undesirable structure or substance recorded on an image

artifacts

general types of histogram analysis: type 3

associated with a procedure when a large radiopaque area is present in the exposure field, such a positive contrast medium or non-removable metallic object

general types of histogram analysis: Type 1

associated with procedures that have raw exposure area between the anatomical structure and the collimation border

general types of histogram analysis: type 2

associated with procedures that won't have raw exposure tail on the far right of the image histogram

when an angled CR or diverged x-rays are used, the anatomy will move in the direction that the ______ travel

beams

the maximum range of pixel values that a digital system can store is expressed as

bit depth of the pixels

a high contrast projections appears more ______

black

as a general collimation guideline each projection should have a small collimated ________ around the entire VOI, unless the entire IR is used to prevent clipping of needed anatomy

border

with decreased window width it appears _______ and with increased window width it appears _______

brighter, less bright

digital radiography allows for post processing manipulation of the images _______ and contrast to demonstrate the VOI more accurately

brightness

to rescale for ________ the histogram will move the obtained values to the right or left to match the LUT histogram

brightness

The projection is evaluated for how visible the details are as defined by what 3 factors?

brightness, contrast, noise

bone and soft tissues are recorded near the ______ in the graph

center

as a general guideline the anatomical VOI is in the ______ of the projection or the CR is _______ in the VOI, and narrow the radiation beam on all sides to include only the required VOI and _____-_____ inch of surrounding anatomy

center, centered, 0.5-1 inch

Spatial resolution CR

choose the smallest possible IR

To produce optimally exposed projections, the techs goal is to obtain EI readings that are as ______ to the _____ EI as possible

close, ideal

When the joints can't be positioned in the true projection simultaneously because of a fracture: The joint _________ to the fracture should be positioned in the true projection

closest

When imaging obese patients, remember to ________ tighter

collimate

Collimation: a decrease in the area exposed on the patient, as determined by _______, changes the amount of scatter radiation produced and hence the amount of scatter reaching the IR and overall IR exposure

collimation

contrast masking is to only extend to the exposed areas, matching the _______ borders

collimation

LUTs provide the standard for S-min, S-max, and S-ave that the image histogram is ________ and _______ to

compared, rescaled

What are the 2 types of digital imaging systems used to acquire and process the radiographic image?

computed radiography (CR) and digital radiography (DR)

mobile and trauma imaging: never leave a ______ patient/trauma patient unattended in the room

confused

the ratio or percentage of difference between 2 adjacent brightness levels

contrast

the ability of an imaging system to distinguish between details by displaying them with different gray shades

contrast resolution

the peaks and valleys in the histogram represent the subject _____ in the remnant radiation and are determined by the total ________ that's used and the resulting differential absorption that creates the latent image

contrast, exposure

3 things that indicate accurately displayed projection

correct procedure algorithm was selected, the correct structures are at the top of the image, and the marker is correctly displayed

Pediatric cartilaginous spaces and epiphyseal plates appear as _______ shaded spaces and lines. They may look similar to an irregular _________ or joint space

darker, fracture

the displayed projection demonstrates quality issues that are similar to projections seen with technical factors being incorrectly set, BUT they are due to the computer's inability to correctly decipher and modify the _______ to the LUT

data

increasing the OID may result in a noticeable __________ in IR exposure because of the reduction in the amount of scatter radiation detected by the IR when a portion of the scattered x-rays generated in the patient are scattered _______ from the IR.

decrease, away

increasing the SID will ________ IR exposure and decreasing the SID will ________ IR exposure by the inverse square law

decrease, increase

determining the technical adjustment for underexposure: Step 4. scatter noise on thicker patients is reduced by ______ the field site and by adding a grid or by using a grid with a ______ grid ratio

decreasing, higher

spatial frequency is defined in terms of the number of _______ than can clearly be visualized in a set amount of space

details

the quality of the displayed projection is defined by how well the ______ in the VOI have been resolved

details

DR: The IR contains a matrix of pixel-size radiation absorption areas called _______ _______, which includes a ______-______ _______ that captures the electrons which are freed through _________ in the DEL when the remnant radiation strikes it, and the storage capacitor that stores the electrons

detector elements (DELs), thin-film transistor (TFT), ionization

What's the purpose of image analysis

explore how to evaluate projections for acceptability, determine how to improve positioning and technical skills before repeating a projection, and continually improve skills

mobile and trauma imaging: ________ all equipment and devices during procedures

disinfect

image analysis DR

displayed on the workstation in a manner they were obtained or after a preprocessing algorithm has been applied

When radiation causes DNA mutations in a rapidly dividing cell, the cell can't repair the damaged DNA sufficiently and continues to _______; therefor the DNA remains in _______

divide, disrepair

CR demographic

each CR cassette has a barcode label that's used to match image data with patient's ID barcode and exam request

image analysis CR

each IR has a "top" and "right" or "left" side orientation. These indicators align the image orientation with the computer algorithm of the patient

radiation protection factors that should be evaluated to provide projections that can be obtained by following ALARA include:

effective communication, immobilization devices, SSD, pregnancy, and gonadal shielding

Saturation is caused by overwhelming the digital system with ______ _______ due to using extreme exposure

electronic signals

________ occurs when one of the structures axes appears disproportionally longer on the projection than the opposite axis

elongation

the most common shape distortion is

elongation

If the CR isn't positioned perpendicular to the IR then the resulting image will demonstrate _________ in the direction toward which the CR was angle. & the more accurate the CR and IR angle, the greater the _________

elongation, elongation

EI stands for

exposure index

S-ave is used to calculate the _______ ______ readings and can be used to determine the _______ of the IR exposure if there's no exposure field recognition error

exposure index (EI), accuracy

5. computed radiography only: using an IR size where the VOI will cover the entire IR eliminates any _______ values from being recored on the IR that aren't of interest. You should also have a minimum coverage of ____% so the smallest possible IR should be chosen

exposure, 30%

anatomy positioned ______ from the IR move at greater distances than those positioned _______ to the IR

farthest, closer

The amount of exposure loss will depend on the degree of OID increase and the amount of scatter that would typically reach the IR, which is determined by what 3 things?

field size, patient thickness, and kVp

finger, wrist, forearm are displayed as if the patient were hanging from the ______

fingertips

2 geometric factors that affect blur

focal spot size and distances

4. Scatter radiation control: light scatter _______ can be compensated for by the digital rad. _________, but extreme amounts can't be totally corrected

fogging, processing

________ occurs when one of the structures axes appears disproportionately shorter on the projection than the opposite axis

foreshortening

name an external artifact

gown snaps, bra hooks, jewelry

a low contrast projection appears more ______

gray

to rescale for _______ scale, it will adjust the values up or down to align them with the gray scale in the LUT which means it will widen or narrow the histogram

gray

the ideal EI represents a medium ______ value, which usually indicates ______ _______

gray, soft tissue

CR: Pixels that received _______ IR exposure are assigned values that represent darker gray shades, whereas pixels receiving ________ exposure are assigned values that represent lighter gray shades

greater, less

mobile and trauma imaging: use a ______ if the patient thickness is more than _____ inches (____cm) and more than _____ kV is used

grid, 4 inches (10 cm), 60 kV

insufficient IR exposure will also result when the ______ and _____ are misaligned

grid, CR

an intermediate contrast range is ________

ideal

an increase in mAs will cause a direct ________ in IR exposure and a _________ in quantum noise

increase, decrease

as CR angulation or x-ray divergence ________, the degree of anatomy movement _______

increases, increases

quantum noise is decreased by _______ the IR exposure by _______ the kV or mAs

increasing, increasing

mobile and trauma imaging: Assess the site of interest for physical signs of ________

injury

Exposure indicators (EIs) are readings that denote the amount of radiation ________ (quantity of photons) that struck the IR

intensity

why is the exposure maintenance formula used?

it's used to adjust the mAs needed to maintain the required exposure to the IR and prevent quantum noise

when ______ are of interest, oblique projections may be added to visualize obscured areas better

joints

What 2 conditions can't be evaluated properly on a rotated PA chest projection?

mediastinal widening and cardiac size

Routine tabletop lateral foot: a __________ projection is performed

mediolateral

mobile and trauma imaging: determine the degree of patient ________, _________, and ________ to follow requests

mobility, alertness, ability

the farther away a part is situated from the IR, the _______ magnified the structure will be

more

can a projection that's been masked and sent to PACS be unmasked?

no

this is defined as any non useful input to the projection that will interfere with the visibility of the VOI

noise

this refers to using a high enough mA at a given focal spot size to minimize motion, but not so high that the exposure times are shorter than the AEC minimum response time

optimum mA

means that the photon intensity reaching the IR is higher than that required to produce an acceptable projection and an excessive dose was delivered to the patient

overexposure

for an open joint space or fracture to be demonstrated, the CR or diverged rays recording the joint or fracture line must be aligned _______ with it. Failure to accomplish this alignment will result in a _______ joint or poor fracture visualization

parallel, closed

Routine lateral foot projection: The foots lateral surface is aligned ________ to the IR. The CR is aligned _______ to the part and IR

parallel, perpendicular

mobile and trauma imaging: _______ patient to the ER

patient

Collimation: the amount of exposure change will depend on the field size and the amount of scatter that would typically reach the IR, which is determined by what 2 things?

patient thickness and kVp

demographic requirements

patient's name, age/birth date, ID number, facility name, and exam time and date

determining the technical adjustment for underexposure: Step 2. determine if the densest and thickest details in the VOI have been _______. If there are cortical outlines that haven't been, then a ______ adjustment is required. If all the cortical outlines have been, then kVp can be adjusted up to _____% from optimal and the reminder made with ______

penetrated, kVp, 15%, mAs

adequate _________ is demonstrated when the cortical outlines of the densest and thickest bony structures of interest are seen

penetration

Oblique projections: If the patient is unable to rotate the arm then position the CR _________ to the line connecting the epicondyles. adjust the angle _____ degrees medially, positioning the medial epicondyle farther from the tube than the lateral. The IR would then be aligned as close to _______ to the CR as possible

perpendicular, 45, perpendicular

To demonstrate long bones with the least amount of distortion and obtain optimal anatomical alignment: The CR is aligned _______ and the IR is ______ with the bone's long axis

perpendicular, parallel

CR: The emitted light is directed through the light channeling guide to the _________ _______, where it's amplified and converted to an ________ _______ and then sent to the analog-to-digital converter (ADC) to be ________

photomultiplier tube (PMT), electrical signal, digitized

EIs aren't measurements of dose to the patient because they don't take into account the energy level of ______ or ________

photons, attenuation

spatial frequency is directly related to ______ size because each pixel can only visualize one gray shade, distinguishing only one detail, and _____ pixels are needed to make up a line pair

pixel, 2

To display projections at full resolution, the display screen must be able to display the same number of ______ as those at which the digital system acquired the projection

pixels

display station resolution refers to the maximum number of ______ that the screen can demonstrate

pixels

the sharpness of the recorded detail on a projection refers to how many ______ the detail's edge will spread across because of _______

pixels, blur

CR: The IP is divided into a matrix with rows and columns of _______, and a laser beam is scanned back and forth across the plate, releasing the trapped ________, resulting in the ionized atoms moving to a ________ state and the extra energy from the photon being released as visible light through a process called _________ ___________

pixels, electrons, neutral, photostimulable luminescence

Histogram analysis errors produce _______ quality projections because the image histograms _______ doesn't match the histogram analysis type used

poor, shape

mobile and trauma imaging: determine whether ________ devices and _______ may be removed

positioning, artifacts

understanding the acquisition and processing steps of each system will help the tech with what 3 things?

prevent errors that cause poor acquisition and processing, understand the indicators used to analyze quality, and improve the image

mobile and trauma imaging: determine the ________ that will be needed

projections

mobile and trauma imaging: obtain the requested _________

projections

name an internal artifact

prosthesis, pacemaker, endotracheal tube

mobile and trauma imaging: use good radiation _______ practices

protection

mobile and trauma imaging: ________ any necessary projections

repeat

1. part selection from workstation menu: if the wrong body part or projection is selected on the workstation, the image will be ______ using the wrong ______. It can be corrected by ________ under the correct LUT as long as it's not sent to PACS yet

rescaled, LUT, reprocessing

any radiation dose, small or large, is expected to produce a ________

response

fat and gaseous air are recorded on the ______ in the graph

right

the tail or high spiked portion on the far ______ of some histograms represents the ______ background value that is sometimes outside the VOI and in the exposure field

right, black

the goal of mobile and trauma imaging is the same as that of _______ imaging

routine

this is demonstrated on a projection as a loss of contrast resolution where some or all of the structures in the VOI demonstrate a black shade

saturation

elbow and humerus display as if they were hanging from the ________

shoulder

this is used to compare one exposure to the next and is defined as the ratio between the desired signals from the undesired signals that are used to create an image

signal to noise ratio (SNR)

________ on neonates may also cause artifacts when they overlie the chest

skinfolds

When imaging an obese patient, using a _______ focal spot size may not work. The mA is typically limited to ______ mA or less, and the long exposure time to achieve the needed IR exposure may result in motion

small, 300

if the digital system's matrix size is ______ than the display station's matrix size, the values of surrounding pixels are rounded up or down as needed to display the whole projection

smaller

the _____ the focal spot size, the better the spatial resolution because less blur will be spread to the adjacent pixel

smaller

Spatial resolution: _______ focal spot sizes produce better res. a detail that's smaller than the fss used to produce the projection will be entirely ______ and blend with the surrounding details

smaller blurred

used to describe the expected quality of the spatial resolution that's obtained by a digital system at a set focal spot size and using a set SID and OID

spatial frequency

the difference in radiation intensity in the remnant beam that demonstrates the degree of differential absorption resulting from the differing absorption characteristics of the body structures, such as what 3 things?

subject contrast 1. atomic density 2. atomic number 3. part thickness

Most positioning routines require AP/PA and lateral projections to be taken to demonstrate what 3 things?

superimposed anatomical structures, localize lesions/foreign bodies, and determine alignment of fractures

mobile and trauma imaging: gather and organize the _______

supplies

What is spatial resolution impacted by?

system matric and pixel sizes, focal spot size, SID and OID, motion, and double exposure

spatial resolution DR:

systems have a set matrix and pixel size, determined by the size of the detector DELs and the spacing between them. Spatial resolution capabilities of approx. 3.7 lp/mm

mobile and trauma imaging: process the projections and evaluate them for positioning and _______ accuracy

technical

What is the LUT

the "ideal" histogram for every projection

DR demographic

the exam and patient are match when the patient's info is pulled up on the work station before the exam is obtained

______ patients attenuate more of the primary photons

thicker

what 2 things can reduce the scatter radiation fog reaching the IR

tight collimation and appropriate grid usage

toe(s) and AP and AP oblique foot display as if they were hanging from the ______

toes

umbra vs penumbra

umbra is the true part you want to image. penumbra is all the unsharpness in an image or the focal spot blur

VOI stands for

values/volume of interest

when should you shield the gonads

when they are within 2 inches (5cm) of the primary beam x-ray and if the patient is of reproductive age and the shield doesn't cover the VOI

3. external and internal artifacts: the add an unexpected bolus of _____ on the _____ side of the image histogram

white, left

this occurs after the image is displayed on the monitor

windowing

After raw data has been acquired for both CR and DR, a histogram graph is generated that has the pixel gray shade values on the ___-axis and the number of pixels with that gray shade on the ___-axis

x-axis, y-axis

if doing a bilateral projection, do you mark both sides?

yes