RADT 334 UNIT 5

The invisible image on an unprocessed radiograph

latent image

Using a film emulsion that has the same absorption properties as the color of light emitted by a radiographic intensifying screen

spectral matching

Marks, spurious objects, or unwanted optical density on the image that do not represent the anatomic structure

artifact

A reduction in image contrast resulting from x-ray exposure of unprocessed film by other than the useful beam; usually occurs during storage

radiation fog

The length of time radiographic film can be stored without objectionable increased fog

shelf life

Humidity range for radiographic film storage

40-60%

List the parts in order of a double emulsion film from one side to the other

overcoat, emulsion, adhesive layer, base, adhesive layer, emulsion, overcoat

What determines the proper darkroom safelight filter color selection?

type of film

Green sensitive film would require what color of safelight in the darkroom?

red

What happens if a single emulsion film is placed in double intensifying screen cassette?

Overexposed film

Temperature for radiographic film storage

less than 20 degrees C

A component of the turnaround assembly; a curved metal lip with smooth grooves to guide the film around the bend

guide shoe

Total processing time, from start to finish: normally 90 seconds. Development: 22 seconds; fixing: 22 seconds; washing: 20 seconds; drying: 26 seconds

Dry-to-drop

Steps of automatic processing of a radiograph

developer, fixer, wash, dry

Acidic spH solution of the automatic processor

fixer

basic pH solution of the processor

developer

Fixer's other name?

Clearing agent

Universal wetting agent?

water

If film is damp when it drops in the receiving bin, what is the probable cause?

underreplenished developer

If the film turns brown once stored in the file room, what could be the problem?

Inadequate fixing or inadequate washing

How should film be fed into the feed tray?

short side against guide rail

The undesirable continuing emission of light after exposure of the phosphor to x-rays

afterglow

The ability to image small, high contrast objects

spatial resolution

Appears on a radiograph as a speckled background; occurs most often when fast screens and high KVp techniques are used

image noise

The visible light emitted during fluorescence or phosphorescence

luminescence

Visible light only emitted while x-ray beam is on

fluorescence

Another name for afterglow

phosphorescence

Name the layers of an intensifying screen from cassette to film

Base, reflective layer, phosphor, protective coating

Causes of image fog

Heat, radiation, improper processing

Name a tool for testing for good screen-film contact

wire mesh tool

The splotchy appearance of a radiograph that has been exposed by a limited number of x-ray photons

quantum mottle

Any unwanted optical density on the image that does not represent an anatomic structure

exposure artifact

Found along the leading or trailing edge of the film; they occur when the guide shoes in the turn-around assembly of the processor are sprung or improperly positioned

guide shoe marks

An artifact produced in the processor when a dirty roller or other object peels off flecks of the emulsion

pick-off

A mark (e.g., fingernail marks, pressure smudges) seen on the processed radiograph resulting from excess pressure of the emulsion before processing

pressure mark

A pressure-type mark produced when film is bent sharply before processing

kink mark

Yellow-brown stain on radiograph after long storage time. It indicates that not all the thiosulfide from the fixer was removed during washing

bypo retention

The amber or red light in a darkroom that allows the radiologic technologist to see, but does not expose unprocessed film

safelight

When developer or fixer drains down a vertical film and some is improperly retained, the finished product may appear as though viewed through a curtain.

curtain effect

An artifact appearing at 3.14 inch intervals as a result of dirt or chemical stain on a 1 inch diameter transport roller

Pi line

An image artifact produced during processing

processing artifact

Four stages of a film's life cycle during which artifacts tend to occur

exposure, processing, handling, storage

Three examples of exposure artifact

foreign objects, double exposure, grid cutoff

Three types of processing artifact

guide show marks, pi lines, emulsion pick-off, gelatin buildup, chemical fog, wet-pressure sesitization

What does 3.1416" have to do with pi lines?

the circumference of a 1-inch transport roller

Three ways fog can occur on a radiograph

Chemical fog, radiation fog, safelight fog

Cause of static artifact on processed radiograph

low humidity

Three types of static artifact patterns

crown, smudge, tree

How can we best avoid processor artifacts?

regular processor QC

Concerns people; monitoring of the patient, technologist, radiologist and interpretation of images

quality assurance

Concerns equipment; j. that part of quality assurance that deals with the performance of imaging systems

quality control

Minimum amount of filtration required for general purpose radiographic units

2.5 mm Al

The follow up of patient reports to make sure the diagnosis was correct

outcome analysis

Continuous quality improvement- an ongoing process that involves QA and QC; never ends

CQI

If 50 mAs produces x-ray intensity of 100 mR then an exposure at 100 mAs should produce an x-ray intensity of 200 mR- this is an example of what?

exposure linearity

If 50 mA @ 1 sec produces 50 mAs (100 mR output intensity) then 100 mA @ 0.5 seconds should also yield 50 mAs with a 100 mR intensity

reciprocity

Three steps of quality control for radiographic equipment

acceptance testing; routine maintenance; preventative maintenance

Reason why TJC QA program is used in hospitals?

higher patient care, accreditation, reimbursement

Three people on the diagnostic imaging QC team

supervising radiologist, QC technologist, medical physicist

Why are proper x-ray beam alignment and collimation important?

To ensure that only the anatomy of interest is imaged

What are the limits for radiographic misalignment?

+/-2% of the SID along any edge

Three QC tools to measure focal-spot size?

Pinhole camera, star pattern, slit camera

What is the permitted variation of radiographic reproducibility?

+/-5%

What test is performed to check for screen-film contact?

wire mesh

How often should lead apparel be checked for integrity?

Annually

How do we check kV accuracy?

dedicated kV meter

Unit of luminance on a viewbox

candela per meter squared

How often should an automatic processor be cleaned?

weekly

What is the importance of preventative maintenance on a processor?

Preventative maintenance reduces the probability of nonscheduled maintenance

What is the permitted radiographic collimator misalignment?

2% of the SID

What tools are used for processor monitoring?

Sensitometer, densitometer, and thermometer

Also known as the true negative fraction- ability to be given a negative diagnosis when no diesease is present; How well are we able to rule our or eliminate the possibility of the disease not being there; has a low false positive rate

specificity

Also referred to as the true positive fraction; indicates the likelihood of obtaining a positive diagnosis in a patient with the disease ( ability to detect disease); How well can the exams pick things up; has a low false negative rate

sensitivity

True positive plus the true negative divided by the total number of exams; How accurate are the exams; How many true positive and true negatives do we get when we look at all exams- how many are read correctly?

accuracy

If a radiologist determines something on a film to be a disease and further lab tests confirm it is that disease

true positive

If a radiologist dictates the presence of a disease on an image and further tests determine that a disease (or the disease dictated) is not present

false positive

If a radiologist dictates no disease present and further testing results in demonstrating no disease present

true negative

If a radiologist dictates no disease present and further testing determines that a disease is present

false negative

Dark bands at the interfaces of structures have differing brightness levels (contrast ans surrounding tissue, hardware)

halo artifact

Can result from unerased IR or way over exposed IR that didn't get completely cleared

Phantom image artifact

Poor collimation leads to this error in CR and DR image processing

histogram analysis

Scratches or dust/dirt on the PSP plate will appear on the image

white

Dust in the path of the laser beam in the CR reader may cause this type of artifact

line

When an erasure lamp is not working properly, this artifact may result

phantom image

When grid lines are parallel to the direction of laser beam travel in a CR reader, this artifact can result

Moire or Aliasing

How often should image receptors be cleaned as part of a QC program in digital imaging

weekly

How often should CR cassettes be erased

daily

Who is responsible for acceptance testing of radiologic equipment?

medical physicist

Who is responsible for routine maintenance of radiologic equipment?

technologist

Who is responsible for preventative maintenance/ system adjustments of radiologic equipment?

vendor service personnel

Skin exposure rate that should not be exceeded during fluoroscopy with ABS

10R/min

Skin exposure rate that should not be exceeded during fluoroscopy without ABS

5R/min

minimum SSD for mobile fluoroscopy units

12"

Minimum SSD for fixed fluoroscopy units

15"

Matrix is composed of

pixels

TFT arrays are composed of

DELS

White lines of this tool can be used to check for image distortion on a display screen

SMPTE test pattern

Identify the different methods of silver recovery

metallic replacement, electrolytic, chemical precipitation

Display monitor: has a greater viewing angle

CRT

Display monitor: has better contrast resolution

LCD