POI

Improves as screen blur increases

Spatial resolution

Improves as motion blur decreases

Spatial resolution

Improves as geometric blur decreases

spatial resolution

the random fluctuation in the OD of the image

radiographic noise

somewhat under the control of radiologic technologist and is a principal contributor to radiographic noise in many radiographic imaging procedures

quantum mottle

refers to the the random nature by which x-rays interact with the IR

quantum mottle

the use of ________mAs, _________ kVp and of slow image receptors ______ quantum mottle

*High
*Low
*reduces

what are the three radiographic quality rules

1. Fast IR's have high noise and low spatial resolution and low contrast resolution and low contrast resolution
2. High spatial resolution and high contrast resolution require low noise and slow image receptors
3. Low noise accompanies slow IR's with high spatial resolution and high contrast resolution

Fast IR's have ____ noise and ____ spatial resolution and _____contrast resolution and _____ contrast resolution

*high
*low
*low
*low

High spatial resolution and _____ contrast resolution require ____ noise and _____image receptors

*high
*low
*slow

Low noise accompanies _____ IR's with _____ spatial resolution and _____ contrast resolution

*slow
*high
*high

Film factors of radiographic quality

*film factors
*geometric factors
*subjected factors

what are the geometric factors

1. distortion
2.magnification
3. blur

what are the subject factors

*Contrast (thickness, density, atomic #)
*motion

what are the film factors

*Characteristic curve (density, contrast, speed, latitude)
*Processing (time, temperature)

an increase in LRE of ______ results from doubling the radiation exposure

0.3

what is the formula for optical density

0D= log10 (Io/It)

the useful range for OD is approx.

0.25 to 2.5

base density has a value of approx.

0.1

unexposed radiographic film allows more than approx. _____% of incident light photons to be transmitted

80%

The OD of unexposed film are attributable to ______ _____ and _____ _____

*base density
*fog density

Base plus fog OD has a range of approx.

0.1 to 0.3

states that the OD on a radiograph is proportional only to the total energy imparted to the radiographic film and independent of the time of exposure

reciprocity law

the reciprocity law fails for ________ exposures at exposures times less than approx.___ or longer than approx. ____

*screen film
*10ms
*2s

inherent in the screen film combination and is influenced somewhat by processing of the film

image receptor contrast

determined by the size, shape, and x-ray attenuating characteristics of the anatomy being examined and the energy (kVp) of the x-ray beam

subject contrast

Film contrast is related to the slope of the straight line portion of the __________ ___________.

characteristic curve

what is the formula for IR contrast

average gradient= OD2-OD1/LRE2-LRE1

What is the formula for IR speed

speed= 1/exposure in roentgens to produce an OD of 1.0 plus base fog

Accurate representation of the atomic area of interest and its information is well visualized for diagnosis

Radiographic image quality

How many ways are image quality measured

3

What are the three ways that image quality is measured in

*spatial resolution
*contrast resolution
*presence of artifacts

The minimum separation at which two objects can be recognized as two separate objects

Spatial resolution

Improves as screen blur decreases, motion blur decreases and geometric blur decreases

Spatial resolution

The ability to image and distinguish similar tissue

Contrast resolution

Often referred to detail or recorded detail

Contrast resolution

Accurate representation of the atomic area of interest and its information is well visualized for diagnosis

Radiographic image quality

How many ways are image quality measured

3

What are the 4 components of noise

*film graininess
*structure mottle
*quantum mottle
*scatter radiation

Distribution in size and space of silver halide grains in the emulsion

Film graininess

Distribution of the phosphor crystals in the intensifying screen

Structure mottle

Are not controlled by technologist

*film graininess
*structure mottle

Random speckled appearance on the recorded image

Quantum mottle

Principle contributor to radiographic noise

Quantum mottle

Can somewhat be controlled by technologist

Quantum mottle

Is greater when high speed screens and low mAs techniques are used

Quantum mottle

Caused by too few photons reaching IR to form the image

Quantum mottle

Fast IR have _____noise and _____ spatial resolution and ______ low contrast resolution

*high
*low
*low

High spatial resolution and ______ contrast resolution requires ______ noise and _____ receptors

*high
*low
*slow

Low noise accompanies ______IRs with ______ spatial resolution and ______contrast resolution

*slow
*high
*high

What are the principle factors that affect radiographic quality

*film factor
*geometric factors
*subject factors

______film you can see through

*unexposed


(Film factor)

______ film will have a variance of shades of black and white

*exposed

(Film factor)

_______ _______ film will be completely black

*heavily exposed

(Film factor)

The study of the degree of blackness on a film

Sensitometer

A graph of the optical density and relative exposure that is characteristic of a particular type of x-ray film

Characteristic curve

Also known as the H and D curve

Characteristic Curve

What is the equipment needed to construct a characteristic curve

Sensitometer and densitometer

An instrument designed to expose a reproducible,uniform,optical step wedge pattern into a film

Sensitometer

Characteristic curve for the toe

Low exposure level (0.2-0.5)

Characteristic curve for shoulder

High exposure level ( > 2.5)

Characteristic curve for base plus fog level

Added density from
from film due and storage (.05 to .10)

Straight characteristic curve

Line portion/ region of properly exposed radiograph (exposure latitude) (0.5-2.5)

The minimum separation at which two objects can be recognized as two separate objects

Spatial resolution

Random fluctuation in the OD of the image

Radiographic noise

Less noise...

Increase image quality

Improves as screen blur decreases, motion blur decreases and geometric blur decreases

Spatial resolution

The ability to image and distinguish similar tissue

Contrast resolution

Often referred to detail or recorded detail

Contrast resolution

What is another word for density

Receptor exposure

the degree of blackness

OD

Radiographic film contains ODs that range from...

0-4

The OD on a radiograph is proportional only to the total energy imparted to the radiographic film and independent of the tine of exposure

Reciprocity law

Important for special procedures that require very short or very long exposure time

Reciprocity law

Differences int the blacks and whites on an image or OD variations

Radiographic contrast

High contrast

Large differences in OD

Low contrast

Small differences in OD

Product of two separate factors for radiographic contrast

IR contrast and subject contrast

Inherent in the type film-screen combination

IR contrast

Influenced by OD and film processing techniques

IR contrast

Contrast is lost when OD is showing in the toe or the shoulder of the curve

IR contrast

Related to slope of the H and D curve

IR contrast

The sensitivity of x-ray film

IR speed

The _______ _______ can be used to demonstrate different IR speeds

Characteristic curve

A _______ IR will be positioned to the left on the cure closer to the y-axis as compared to a slower speed IR

Fast

is expressed in 100s

IR speed

Range of exposures over which the IR responds with OD in the useful range

Exposure latitude

Margin of error for technical factors use

Exposure latitude

mAs cannot vary

Narrow latitude

Latitude and contrast are

Inversely proportional

What are the 3 principle geometric factors

*magnification
*Distortion
*focal-spot blur

Misrepresentation of the size of an object on the radiograph

Magnification

The object images will appear larger than normal

Magnification

Object size cannot be determined in some cases

Magnification

Misrepresentation of the shape of an object

Distortion

Unequal magnification

Distortion

3 things that contribute to image distortion

1. Object thickness
2.object position
3. Object shape

Are thick object more distorted than thin objects

Yes

What are the three ways that image quality is measured in

*spatial resolution
*contrast resolution
*presence of artifacts

Thick objects are always...

more distorted than thin objects