film eval - guidelines for image analysis

chapter 1

the purpose of image analysis is to teach technologists how to:

1. evaluate projections for acceptability

2. determine how to improve positioning and technical skills

3. continually improving skills

why do we care about optimal images?

to help people

it takes only _____ to ____ degrees of rotation to affect the appearance of lungs, causing differences in brightness values

2 to 3

the normal heart shadow on such a projection will occupy slightly ________ (more/less) than _____ percent of the transverse dimension of the thorax.

less; 50%

4 characteristics of an optimal image:

1. projection is accurately displayed

2. demographic info

3. there is maximum detail

4. correct markers in appropriate position

once a projection is correctly displayed, it’s evaluated for positioning and technical accuracy. this evaluation should follow a __________ approach.

systematic

systematic approach is used because:

1. reduces the chance of missing important details

2. provides a structured pattern to use in a stressful situation

image analysis process:

1. demographic requirements are visualized on the projection

2. projection is accurately displayed on the workstation monitor

3. correct marker

4. appropriate collimation

5. relationships b/w anatomic structures are accurate

6. projection demonstrates maximum spatial resolution

7. radiation protection is present

8. image histogram was accurately produced

9. adequate exposure reached

10. contrast resolution is optimal for demonstrating the VOI

11. no preventable artifacts

12. ordered procedure and indication have been fulfilled

demographic requirements include before sending to PACS:

1. correct pts. name, age/DOB

2. pt. identification number

3. facility name

4. exam time and date

good collimation practices:

1. clearly portrays the anatomy of interest

2. decreases radiation dose

3. improves visibility of recorded details

4. reduces histogram analysis errors

as a general guideline, each projection should demonstrate a _________________ around the anatomy

small collimated border

____________________ should be avoided when using computed radiography because it may affect the exposure field recognition process

rotation of the collimator head

________ occurs because the divergence of the x-ray beam has not been taken into consideration during collimation

clipping

_____________ - use large IR and place diagnolly

long bones

__________________ - can be used to determine the actual IR coverage

collimator guide

____________________ - the thicker the body party being imaged, the smaller the collimator’s light field that appears on the skin surface

collimator light field on the patient

____________ adds a black background around the anatomy

contrast masking

_______________ does not replace good collimation practices

contrast masking

T or F: a projection that has been masked and sent to PACS cannot be unmasked.

true

the anatomical ____ is the center of the projection or ____ is centered to the VOI

VOI; CR

centering the CR to the VOI represents the ____________________

anatomy the truest

at 40 SID, the divergence of the x-rays is __ degrees per inch the anatomy is off center

2

at 72 SID, the divergence of x-rays is __ degree per inch the anatomy is off center

1

when angled CR is used the anatomy will move in the direction the ____________

CR is angled

an angled CR projects the structure situated _______________ (closer to/farther from) the IR than a structure situated _______________  (closer to/farther from) the IR. 

farther from; closer to

as the CR angulation _____________, the degree the anatomy movement also ____________

increases; increases

2 types of distortion:

size and shape

what is size distortion

magnificaition

what is shape distortion?

foreshortening and elongation

all projections demonstrate some degree of __________________

size distortion

to keep size distortion to a minimum, use the _____________ OID and ____________ SID

shortest; longest

the part ____________ (closet/farthest) from the IR will be the most magnified

farthest

________________________ depends on how far each structure is from the IR

amount of magnification

_________ SID will result in the least magnification

longer

____________ elongation occurs when the CR is aligned perpendicular to the part and IR and the part and IR are aligned with each other

least

the __________ CR angle, the __________ elongation

greater; greater

the __________ the IR angle, the __________ elongation

greater; greater

the ________ the “off-centering” the ___________ elongation

greater; greater

______________ occurs when CR and IR are perpendicular to each other, but the part is inclined

foreshortening

the ___________ the incline, the ___________ foreshortening

greater; greater

for open joint space or fractures to be visualized, the CR must be aligned ___________ with the joint

parallel

the greatest sharpness is obtained by using a __________ focal spot, ________ SID, _______ OID, and controlling ____________

small; longest; short; motion

spatial resolution impacted by:

1. system metric and pixel sizes

2. focal spot size

3. SID and OID

4. motion

5. double exposure

_____________ are readings that indicate the amount of radiation intensity struck the IR

exposure indicator

cause tissues to increase in mass density or thickness, more radiopaque

additive disease

cause tissues to break down, more radiolucent

destructive disease

anatomic structure within the image or superimposed

anatomic artifact

found outside the body

external artifact

cannot be removed, must be accepted

internal artifact

artifact with CR only

phantom image artifact

back of cassette toward source during exposure

phosphor platet-handling artifact

The path of the x-ray beam refers to ___________

projection

The patient's position refers to ______________

position

What is display station resolution?

maximum number of pixels in the screen

In AP/PA projections of the torso, vertebrae, and cranium, the marker is placed:

laterally on the correct side of the patient

In lateral projections of the torso, vertebrae, and cranium, the marker should be placed:

on the side closer to the IR (anterior or posterior, but posterior may be obscured by scatter)

For AP/PA oblique projections of the torso, vertebrae and cranium, the marker is placed:

on the side of the patient closer to the IR and on the correct side of the patient (Downside)

True or False: on bilateral extremity images, you only have to mark the one that hurts worse

False: mark both on bilateral projections

What are good collimation practices to have? (list)

1. clearly portrays anatomy of interest
2. decreases radiation dosage
3. improves visibility of recorded details
4. reduces histogram analysis errors

Why should rotation of the collimator head be avoided when using CR?

because it may affect the exposure recognition process

Why does clipping occur (overcollimation)?

because the divergence of the beam has not been taken into consideration during collimation

The thicker the body part being imaged, the _______________ the collimators light field that appears on the skin's surface

smaller

When angled CR is used, the anatomy will move in what direction?

in the direction the CR is angled

True or False: all projections demonstrate some degree of shape distortion

false, size distortion

What degrees are the following extremity flexions?
a. Full extension
b. Two adjoining bones are aligned perpendicular to each other
c. Halfway between full extension and 90 degrees
d. Halfway between 45 degrees and 90 degrees
e. Halfway between full extension and 45 degrees
f. Beyond 90 degrees

a. 0
b. 90
c. 45
d. 68
e. 23
f. 113 and 135

If structures move in opposite directions from each other, adjust the patient _________________________ that the structures are off

half the distance

If only one structure moves, adjust the patient so the structure that moves is ____________________________

adjusted the full amount

When repositioning the CR for repeats, estimate how much of the structure is situated farther from the IR, which will move per ____________________ of angle adjustment placed on CR

5 degrees

What does pixel size determine?

1. minimum size a detail can be and still be resolved
2. how far adjacent details have to be from each other for them both to be resolved

What geometric factors affect blur?

focal spot size and distance

What is the technologist's goal to produce optimal images?

to produce images that result in the EI coming as close to the ideal as possible

There must be a/an ____________________ in mAs of _________% to compensate for a/an _________________disease

decrease, 25-50%, destructive

There must be a/an ____________________ in kVp of _________% to compensate for a/an _________________disease

increase, 5-15%, additive

You must increase kVp by 5-15% in ___________ diseases

additive

You must decrease mAs by 25-50% in _________ diseases

destructive

Is emphysema additive or destructive?

destructive

IS chronic osteomyelitis additive or destructive?

additive

IS cardiomegaly additive or destructive?

additive

Is atrophy additive or destructive?

destructive

is ascites additive or destructive?

additive

Is degenerative arthritis additive or destructive?

destructive

is atelectases additive or destructive?

additive

Is calcification stones additive or destructive?

additive

Is osteoblastic metastases additive or destructive?

destructive

is pneumothorax additive or destructive?

destructive

Is pneumoconiosis additive or destructive?

additive

Is anorexia nervosa additive or destructive?

destructive

Is bowel obstruction additive or destructive?

destructive

Is pulmonary edema additive or destructive?

additive

Is acromegaly additive or destructive?

additive

Is aortic aneurysm additive or destructive?

additive

Is aseptic necrosis additive or destructive?

destructive

Is empyema additive or destructive?

additive

Is an abcess additive or destructive?

additive

Is multiple myeloma additive or destructive?

destructive

Is sclerosis additive or destructive?

additive

Is pneumonectomy additive or destructive?

additive

Is osteoporosis additive or destructive?

destructive

Is hydrocephalus additive or destructive?

additive

Is cirrhosis additive or destructive?

additive

Is edema additive or destructive?

additive