Pt Care Midterm

1895

x rays were discovered in

high-voltage electricity

xray beam energy is produced using

x rays

pass through matter and strike an image receptor

image receptor

converts the energy of x-rays into an image; cassetes/IP/film; converts information received

x-ray production requirements

vacuum tube
source of electrons
high voltage
target

cathode

source of electrons (negative end of xray tube)

voltage

method to accelerate electrons to great speed across the tube

target

method to stop electrons and cause energy transformation

classes of radiation

Primary radiation
Scatter radiation
Absorbed radiation
Remnant radiation

attenuation

the loss of radiation energy as a result of passing through an absorbing material, such as the human body (absorption/scatter)

density; atomic number

different materials absorb radiation energy differently based primarily upon _____ and _____

differential absorption

different degrees of absorption in different tissues that result in image contrast and formation of the x-ray image; the higher the atomic number the more xray is absorbed

high attenuation

occurs in radiopaque matter (higher atomic number)

low attenuation

occurs in radiolucent matter (lower atomic number)

matter

xrays pass through____

patient

When we talk about matter we are really talking about the?

anode

positive end of xray tube, the target of the electrons being propelled by voltage

primary radiation

xray beam after it leaves the xray tube and before it reaches the object; out of the four, travels with the most force (not speed)

scatter radiation

Radiation that is deflected from its original path as it strikes matter, the body is made of different atoms, when radiation hits they change direction (can be slight or dramatic); not useful information

beam divergence

spread out of xrays

absorbed radiation

when some photons enter, they do not have enough force to fully penetrate the body. Some tissue then can absorb the photons, not allowing the xray beams to reach the image receptor

remnant radiation

any radiation which starts out as primary, passes through the patient and makes it to the image receptor; no scattering

white

totally absorbed xray is going to be what color

black

xray not absorbed will be what color

image receptor

primary radiation from the xray tube travels through matter, some scattering, some scattering, some finally is detected by an _______

latent image

remnant radiation sitting in the image center, it has created chemical changes that are invisible

radiograph

the latent image must be processed to convert it into this visible image

film screen systems

considered an analog type of imaging; obsolete

computed radiography

known as a cassette, PHOTOstimulable phosphor technology, storage phosphor technology

photostimulable

when xray touches this it GLOWS

digital radiography

the processor is built into the image receptor

film screen radiography

uses xrays to create a permanent image on a piece of polyester film with a silver bromide coating kept in a dark room

film screen radiography

consists of xrays directed at a radiographic cassette with an intensifying screen

film screen radiography

intensifying screens convert the xray energy to light, and light energy creates chemical changes in film

intensifying screens

made up of phosphors that lit up when they were hit by xrays

processor

exposed xray film is chemically processed in a wet chemistry automatic ___-

processing

converts invisible latent image into a manifest image

radiograph

is analyzed for quality and submitted to radiologist for interpretation

prime factors

these factors are often referred to as the ____ of exposure technique

mAs

milliamperage (mA) and time (seconds)

kVp

kiloVoltage peak

SID

source to image distance (distance between the tube and image receptor)

chest xray SID

72 in

shoulder SID

40 in

Three Prime Factors

mAs
kVp
SID

radiographic quality

a proper balance between photographic and geometric qualities is required for optimum image quality

radiographic quality

photographic qualities and geometric qualites

radiographic density

the overall darkness or blackness of an image as demonstrated on a polyester-based film media

low exposure

not much information received by image receptor

high exposure

too much information received by image receptor

mAs

quantity of xray

image receptor exposure

primarily affected by
mAs
S (exposure time)
SID
kVp

least dense to most dense

gas/air
fat
muscle
bone
tooth enamel
metal

kVp

when we are selecting the FORCE for an xray

kVp

Selecting the average of all xray force, the PEAK of the bell curve

mAs

representative of quantity

mA x seconds

mAs

proportional

mAs has a ____ relationship with quantity. (double Milliamperage double quantity, double time double quantity, half either of them, half quantity)

Milliamperage

source of our electrons (very low voltage hitting small wire at cathode end)

mAs reciprocity law

Regardless of the mA and time combinations, the same mAs value will yield the same exposure.

mAs

how MUCH xray

kVp

controls xray beam penetration

kVp

direct relationship with exposure but not linear; can influence how much beam we get. If you increase this you do increase amount of xray and exposure. INFLUENCER

kVp

has the 15% rule

15% rule

increase by 15% = double mAs
decrease by 15% = half mAs

digital

higher kVP values recommended with ___ systems

distance

displayed as source to image distance

target

the source is where the beam reaches the ___

xray

production is similar to a point-light source

ex more distance from source, covers more area but power dims
less distance from source, smaller area and brighter

inverse

SID and beam intensity is an ___ relationship

ex SID is small, beam intensity will be stronger
SID is large, beam intensity will be less

inverse square law

I1/I2 = D2^2/D1^2

intensity

does not change when you change distance, its dispersed differently

halved

when intensity is quadrupled, distance is

quadrupled

when intensity is halved, distance is

increase

If i want to keep intensity the same, if I double the distance, I should ____ the mAs

intensity

the same as "exposure"

before and after

the xray beam can be modified ___ it enters the patient

filtration

designed to remove very low energy xrays from reaching the patient

aluminum

most filtrations are made of

alterations

beam ____ can improve image quality and reduce dose

collimation

built into the tube at the bottom with lead shutters and stops the xray beam and focuses on the part of the body needed

scatter control process

modification of remnant radiation

noise

anything on the image that makes it less useful

scatter

radiation that provides little diagnostic information to image

fog

not good collimation

common methods of scatter control

beam restriction
radiographic grids
beam filtration

grids

used to reduce the amount of scatter radiation reaching the image receptor

grids

improves image quality

grids

constructed with lead strips and radiolucent interspace material

grids

intercept a portion of the remnant radiation keep the primary as much as possible but blocking the scatter

grids

between the patient and image receptor

specific characteristics of grids

grid ratio
grid frequency
focal range (angling of strips)
short axis vs long axis
linear vs cross hatch (everything we use is linear)

half value layer HVL

the amount of absorbing material that will reduce the intensity of the primary beam to one-half its original value

HVL

half value layer

image receptor

detect the remnant radiation from the patient and convert it into chemical or electrical changes that make up the latent image

Image receptor types

film/screen
storage phosphor technology
flat panel detectors using thin film

film screen receptors

uses special film that is sensitive to light energy from an intensifying screen

manifest image

visible image

99%

percentage of image on film screen comes from the screen LIGHT

PSP technology

enables an affordable transition from film/screen to digital imaging