Test 4 Chapters 10-11 Flashcards by Hannah Johnson

Ability to image small objects

Spatial Resolution

How well did you know this?

Not at all

Perfectly

Distinguish anatomy with similar subject contrast

Contrast Resolution

How well did you know this?

Not at all

Perfectly

OID refers to

Size, magnification

How well did you know this?

Not at all

Perfectly

You want OID as small or large as possible?

Small

How well did you know this?

Not at all

Perfectly

Most CR/DR systems run between speeds of what?

200-400

How well did you know this?

Not at all

Perfectly

Direct exposure means what in regard to patient exposure and intensifying screens?

No intensifying screens and TONS of patient exposure

How well did you know this?

Not at all

Perfectly

Speed number is directly or indirectly related to patient exposure?

Directly

1-50 is a reduction by 50. 100-200 is a reduction by 100

How well did you know this?

Not at all

Perfectly

Noise looks like what on an image?

Fuzzy, grainy

How well did you know this?

Not at all

Perfectly

Noise is what?

Film graininess-actual piece of film NOT image
Structure Mottle
Quantum Mottle-number of photons controlled by mAs
Scatter

How well did you know this?

Not at all

Perfectly

Image quality speed

How efficiently photons are converted to light. The faster the speed, the faster the conversion, the less mAs needed to convert, thus less exposure to patient

How well did you know this?

Not at all

Perfectly

Spatial resolution improves as…

Screen blur decreases
Motion blur decreases
Geometric blur decreases

How well did you know this?

Not at all

Perfectly

The random fluctuation in the OD (optical density) of the image

Radiographic Noise

How well did you know this?

Not at all

Perfectly

The use of high-mAs, low-kVp and of slower image receptors reduces…

Quantum mottle

How well did you know this?

Not at all

Perfectly

Fast image receptors have…

High noise
Low spatial resolution
Low contrast resolution

How well did you know this?

Not at all

Perfectly

High spatial resolution and high contrast resolution require

Low noise

Slow image receptors

How well did you know this?

Not at all

Perfectly

Low noise accompanies slow image receptors with

High spatial resolution

High contrast resolution

How well did you know this?

Not at all

Perfectly

Exposure to film and the percentage of light transmitted through the processed film is

Sensitometry

How well did you know this?

Not at all

Perfectly

Optical Density is referring to

How much % of light that gets through

-Degree of darkening of the image

How well did you know this?

Not at all

Perfectly

Measurements in film exposure and % of light transmitted through describe what relationship?

Between OD (optical density) and Radiation Exposure

How well did you know this?

Not at all

Perfectly

The relationship between OD and Exposure is called what?

Characteristic Curve

How well did you know this?

Not at all

Perfectly

At low and high radiation exposure levels, what kind of variations in exposure result in only a small change in OD?

Large variations

How well did you know this?

Not at all

Perfectly

At intermediate radiation exposure levels, what kind of changes in exposure result in large changes in OD?

Small variations

How well did you know this?

Not at all

Perfectly

The portions of the characteristic curve that represent the large variations in exposure are called?

Toe and Shoulder

How well did you know this?

Not at all

Perfectly

The region in which properly exposed radiographs appear is the

Straight-line portion

How well did you know this?

Not at all

Perfectly

A densitometer

measures OD

Already on the film, built in density even with no exposure

Base and Fog

A characteristic curve that is more horizontal

Is a slower speed and has long scale contrast-more shades of gray-therefore higher kVp and higher mAs

A characteristic curve that is more vertical

Is a faster speed and has short scale contrast-fewer shades of gray-therefore lower kV and lower mAs

Latitude is referencing

Margin of error

Wide latitude means

Have room to play with, long scale contrast-more shades of gray, slower speed

Narrow latitude means

Less room to play with, short scale contrast-fewer shades of gray, faster speed

Optical density + 0.3 LRE does what to image?

Twice as much density, image will appear twice as dark

Base + Fog =

Base= 0.1 Fog= 0.1 Base + Fog = 0.10-0.30 How much density is already built into the film

Where do useful radiographic densities lie?

0.25-2.5

The HD curve (rise over run) is telling you what?

Numerical number for contrast

When does the reciprocity law fail for screen film?

When the mAs difference is extreme in either faster time or slower time: less than 10 ms or greater than 2 seconds

Reciprocity law ALWAYS works for what kind of exposure of film?

Direct exposure

Inherent system (film/IR) contrast is designed to be what in relation to grey scale?

Shorter scale

Screen film or Digital systems ALWAYS have shorter scale than what?

Direct exposure

Contrast scale gets (blank) the faster the system (goes clear to black fast)

Shorter

Subject contrast is determined by what?

Size Shape Attenuating characteristics of subject

Latitude and contrast are (blank) related

Inversely | Wide latitude means you have long scale contrast

The wider the latitude the wider...

The range of acceptable exposures

Processing includes:

Chemical concentration (strength) Agitation Time Temperature

What happens if the temperature is too hot during processing?

The image is going to convert to dark quicker-temperature will effect density AND contrast

What happens during the fixing stage of processing?

You stop the image from processing-turning dark,and you remove the silver crystals that weren't exposed

If an image measures at the "toe" of an HD curve chart what does your image look like?

Light, way underexposed

If an image measure at the "shoulder" of an HD curve chart what does your image look like?

Dark, way overexposed

Objects will always be (blank) than my image if lined up properly. If object size is (blank) than image size-something is wrong. (especially in math problems)

Smaller | Bigger

Shape distortion is what?

Unequal magnification of object

If you have foreshortening/elongation this means what in relation to the object?

Object was not parallel to the image receptor

How do you minimize distortion?

Keep you anatomy of interest in the center of your IR and keep the CR on the area of interest.

If I decrease SID (get closer with the tube) I will do what with magnification?

Get MORE magnification.

Chose a small focal spot for

Detail ie bone work

Chose a large focal spot for

Heat loading capability concern

If you're using a small focal spot, do you use more or less mAs than with a large focal spot?

Less mAs for a small focal spot

Unsharpness and loss of detail are worse with larger or smaller focal spots, shorter SID and longer OID

Larger think of lateral c-spine: You back tube up to 72 inches to reduce magnification, and because there's an air gap between the neck and the image receptor.

Focal spot blur is worse on Anode or Cathode side?

Cathode | More photons on the cathode side

What is good to reduce magnification, is also good to reduce...

Focal Spot Blur

In relation to focal spot blur you want to Minimize (blank) and Maximize (blank)

Min- OID | Max- SOD

Most important influence on subject contrast is

kVp

Low kVp gives what kind of scale

Short scale (absorption)

High kVp gives what kind of scale

Long scale (scatter)

Iodine gives us...

Differential Absorption

You can enhance subject contrast with...

Contrast Media that has a relatively high atomic number-gives you photoelectric absorption

What would a low atomic number contrast media be and what would it give you image wise?

Air, it's radiolucent so blackness

To help reduce motion blur what can you do?

``` Good instructions Immobilization devices Comfortable positions Short exposure times Long SID Short OID ```

In screen film scenarios, image density is Directly or Indirectly proportional to mAs?

Directly

In order to see a change in screen film density from one set of technical factors to another, what must you do?

Have a 30% change in mAs

Between Direct exposure, Screen film and CR/DR-which has the longest scale of contrast, and then the next etc

Direct has longest scale of contrast, then Screen film, then CR/DR

Which type of imaging has the highest patient dosage and therefore is unacceptable?

Direct exposure

Contrast results from attenuation differences...which is

Differential Absorption

As grid ratio increases, scale of contrast...

Decreases

What happens to patient does when using a grid?

Goes up

Increased collimation is a smaller or larger light field?

Smaller

What makes detail visible?

Contrast

What attributes to image sharpness?

``` Recorded detail: Small focal spot Short OID Long SID Eliminate motion Slowest acceptable imaging system ```

What attributes to image visibility?

Reduce fog and scatter by restricting the beam, use grids

What attributes to Distortion?

Control with tube, image receptor, part alignment and patient positioning

What is scatters relationship with density?

It adds to Density

If you remove scatter you do what to image density?

Decrease the image density

Ways to reduce scatter

Beam restriction Grids kVp

Beam restriction does what?

Remove off direction photons | Better image clarity and shorter scale of contrast

When you use beam restriction you have to do what to mAs?

Increase, need more quantity to maintain image density.

Low kVp gives you more of what kind of reaction?

More Photoelectric

High kVp gives you more of what kind of reaction?

More Compton

PBL stands for and does what?

Positive Beam Limitation | Automatic beam collimation, detects image receptor size and automatically collimates to that size.

In relation to soft tissue, which interaction is most likely at less than 20 keV?

Mostly photoelectric

In relation to soft tissue, which interaction is most likely at more than 20 keV?

Mostly compton

In relation to bone, which interaction is most likely at less than 40 keV?

Mostly photoelectric

In relation to bone, which interaction is most likely at more than 40 keV?

Compton

How does grid use influence patient dose?

It increases it because you have to use more mAs to get the image you need

What are the different grid parts usually made of and why?

Lead strips-to absorb the lower quality photons that produce scatter Interstrip material that is radiolucent to allow photons to pass through to the IR

Grid ratio is

Height divided by distance

The higher the grid ratio...

The more sensative, more grid cut off etc. You must be more precise with positioning.

As you go up in grid ratio the lead strips are packed more tightly giving you what kind of contrast scale? And causing what with patient exposure?

Shorter Scale | Go up

Two most common grid patterns

Parallel and Focused

What kind of a grid is in the wall bucky or table?

Reciprocating grid-moves to blur the lead lines.

Focused-Grid misalignments: | Off Level

Cutoff across image; underexposed, light image

Focused-Grid misalignments: | Off Center

Cutoff across image; underexposed, light image

Focused-Grid misalignments: | Upside down

Severe cutoff toward edge of image

Focused-Grid misalignments: | Off Focus

Cutoff toward edge of image

The need for a grid is reduced with ...

Increased OID

Keep SID and SOD as (blank) as possible and OID as (blank) as possible

Long | Short

Noise, what can you control?

Quantum Mottle | Very small amounts of mAs is when this comes into play

Structure mottle is what?

Screen inherent-the way it's made,nothing you can do about it

Faster imaging systems have (blank) structure mottle

Worse