Rad 102-2 Part 1

The radiographic film consists of three basic components: (5)

base, emulsion, and supercoat

Base (5)

polyester and the film is usually blue-tinted to reduce eye strain

How think and flexible is the base? (5)

approx. 150-300 micrometers

What consists of gelatin and photosensitive agents? (5)

emulsion

Gelatin (5)

acts as a neutral lucent suspension medium for the silver halide crystals

photosensitive agents (5)

collectively reffered as silver halide crystals

What makes us 95% and 98% of the silver halide crystal? (6)

silver bromide

supercoat (6)

protective gelatin designed to prevent the soft emulsion underneath. It may be anti-static

Three of the primary types of films for radiographic imaging? (6)

1. Direct exposure or non-screen film

2. intensifying screen film or screen-film

3. Special application films

Direct exposure or non-screen film (6)

one single layer of emulsion, fine grain

Intensifying screen film or screen-film (6)

combining intensifying screens with radiographic film.

Special application films (6)

its applied for specific modalities and contain specific differences from scree-film.

Types of special application films: (6-7)

1. duplication film

2. fluroscopic spot film

3. mammography film

4. laser film

duplication film (7)

is pre-exposed to maximun optical density by the manufacturer

fluroscopic spot film (7)

conjuction with a fluroscope to record static images during procedures. it is sensitive to the green light from fluoroscope.

mammography film (7)

single-emulsion film that is designed to be exposed with a single radiographic intensifying screen

laser film (7)

digital electronic signal from an image device to create a hard copy film.

radiographic film depens on what factors (7)

1. resolution

2. speed

3. latitude

Resolution (7)

ability to accuretely image an object. it’s determined by the size of silver halide crystals.

speed (7)

is the amount of density (blackening) produced by the given amount of exposure.

latitude (7)

the range of exposures that will produce densities within the diagnostic range.

what is thought as the margin error in technical factors? (8)

Latitude

considerations for proper storage: (8)

1. heat

2. humidity

3. light

4. radiation

What temperatures should film be stored at? (8)

68 degreed F or lower, in a dry, cool place.

What can result of heat increasing on a film (8)

fogging on a radiograph

what percent should huminity be mantained at for film? (8)

30-60

what are the dangers or ow humidity on film (8)

static discharge

what are the dangers of high humidity on film (8)

condensation build up

light considerations (8)

Film must be stored and handled in relative darkness

radiation considerations (8)

rad film is sensitive to xray exposure, therefore it requires more lead protection. ionizing radiation creates an image artifact by increasing film fog.

storage and shel-life considerations (8)

store boxes of film on edge rather than laying them flat. it should be stored so that oldest film is used first

Intensifying screens (10)

amplify the incoming xray beam and reduce patient radiation dose

Producing large amount of photons when struck by xrays permits in a great —— in amount of radiation nexessary to produce diagnostic quality image. (10)

recution

Components layers have four distinct layers: (10)

1. basse

2. reflective layer

3. phospor layer

4. protective coating

What is 1 milimiter thick and serves as a mechanical support for the active layeer (10)?

base

what is between the phospor and the base? 10

reflective layer. When it is added nearly twice as mich light is reflected toward the film.

Phospor layers (10)

contains phosphos or crystals

What does phosphor layer vary in thickness from? 11

50 to 300 um

protective coating (11)

closest to the radiographic film. This layer is made transparent to light so that it does not interfire with luminescence. it prevents eliminate static electricity and it is resistant to abrasions

two types of luminescence 11

1. fluerescence

2. phosphorescence

fluorescence 11

visible light is emitted only when phosphor is stimulates. its considered an instantaneous emission

phosphorescence 11

continues to emit light after stimulation. considered a delayed emission and is referred as lag or afterglow.

what is most desiable during luminescence? (11)

maximun fluorescence and minimal phosphorescence are most desirable

resolution 12

phosphor crystal size and phosphor layer thickness are both inversely related to it.

what is one of the most common resolution problems caused by? 12

poor contact

quantum mottle 12

the principal component of noise. caused by insufficient quantity of photons striking the intensifying screen making the image appear grainy.

A radiographer controls the quantity of photons with the mas seeting… 13

therefore an increase in mas eliminates quantum mottle

A white spot 14

represents an area where an artifact blocked the transmission of light between the screen and film.

what are the common causes of white spot 14

pitted screens, dust on the film, poor film-screen contact

how should intensifying screens be cleaned regularly? 14

with a manufacturer electrostatic cleaning solution

What is a grid 16

a device used to improve contrast of the radiographic image by absorbing scatter radiation before it reaches the IR

What 3 things will occur with the primary photons that originated at the target: 16

1. Pass through the body unaffected

2. be absorbed by the body

3. Interact and change direction

The amount of scatter radiation increases with several factors 17

1. increasing patient thickness

2. larger field sizes

3. decreases in atomic number of the tissue

A grid is employed under what conditions 17

1. body part thickness exceeding 10cm

2. kvp above 60

What is a grid made of? 17

a series of radiopaque strips which alternate with radiolucent interspace strips.

Radiopaque strips 17

absord scatter radiation and must be made of a dense material with a high atomic number, usually lead.

Two interspace material 17

aluminum, plastic fiber

aluminum 17

is the material of choice because of its higher atomic number than the alternative

plastic fiber 17

interspace grids might be used

how, it also attenuates some of the primary photons so it requires high mas when used… 17

this results in a higher patient dose.

Plastic fiber 17

interspace grids may also be used. its preferred to be used when using low kvp

grit ratio 17

the ratio of the height of the lead strips to the distance between strips. G=h/d

An inverse relationship exists between the distance between lead strips and grid rstio when the height of the grid strips… 18

remains the same

What does a 5:1 grid cleans up approx.? 18

85% of scatter radiation

what does a 16:1 grid cleans up to? 18

97% of the scatter radiation

higher grid ratios are more effective at removing scatter. Grid ratios from… 18

5:1 to 16:1

Grid frequency 18

is the number of grid lines per inch or centimeter

grid frequency ranges in …18

60-200 lines per inch

most common grid frequency have… 18

85-103 ines per inch

a higher patient dose results from using higher frequencies because of a higher radiographic technique… 18

is required to compensate for the loss of OD

linear grids 18

grids with lead strips running in only one direction

crisscross or cross-hatched 18

two linear grids on top of one another so the gris lines are running at right angles

grid cut off 19

anguation across the long wxis will result in the primary beam being directed into lead strips, allowing lead to absorb an undesirable amount of primary radiation

parallel grids 19

are made with lead and interspace strips running parallel to one another

focused grids 19

are designed so the central grid strips are parallel and as the strips move away from the central axis they become more and more inclined

what is the purpose ina grid with lead strips? 19

to match the divergence of the xray beam

parallel grids are less commonly employed because the strips do not coincide with the divergence of the… 19

xray beam and some grid cut off will occurs along the lateral edges

grid selectivity 20

absors greater percentage of scatter than primary radiation

selectivity 19

% primary radiation transmitted / % scatter radiation transmitter

the better a grid is at removing scatter… 20

the greater the selectivity of the grid will be

as ratio increases, …. 20

the amount of clean up of scatter also increases

the difference between 12:1 and 16:1 grid 20

are minor

patient dose increases as ratio increases 20

so his must be considered

Grid errors 21

proper tube/grid aligment is essential to prevent undesiable absorption of primary radiation known as grid cut off

off level 21

tube is angled across the long axis of the grid strips

off center 21

the most perpendicular portion of the xray beam will not correspond to the most perpendicular portion of the grid.

off focus 21

grid is used at a distance other than that specified as the focal range of a focused grid

upside-down 21

grid error are caused when the focused grid is placed on top of the cassette upside down

type of grid errors 21:

1. off-level

2. off-center

3. off-focus

4. upside-down

The latent image is the invisible change that is induced in… 23

the silver halide crystal

the silver halide crystal must have an impurity added, 23

usually gold-silver sulfide to form sensitivity specks

photon interaction 23

radiation interacts with film, the reaction of silver and halide atoms forming a latent image

photoelectric 23

xray is totally absorbed

compton 23

if xray is partially absorbed

latent image 23

invisible change

the concentration of electrons at the sensitivitty center produces a region of negative electrification…. 24

positive silver ions are electrostatically attracted to the sensitivity center

after migrating to the center, the silver ions are ———- by the elctrons and are converted to ——- 24

Neutralized, metallic silver

the group of silver atoms is called… 24

latent image center