RDT 180 EXAM 2 11/9

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scintillator:

converts xrays to light

the laser is made of

helium neon or solid state diode

what is used on screen to release any trapped electrons

high intensity bright light

the light that is released is considered our

image

AMFPI/AMA stands for

Active-Matrix flat panel imagers active matrix array can both be used

flat panel detector

Solid state detector Rigid protective housing Used in both direct and indirect capture

conversion process for indirect capture

X Ray photon absorption-Phosphor based scintillator Conversion from light to electric charge-photodetector (made of = amorphous silicon) (a-Si) Readout layer-TFT ADC conversion

conversion process for direct capture

X Ray photon absorption-photoconductor- amorphous selenium (a-Se) Conversion to electric charge- electric charge Readout layer- TFT ADC conversion

sensing and storage material: photoconductor=

a:SE

as the light is stimulating the color layer

absorbs the stimulating and reflects emitted light forward

AMFPI/AMA MEASURES

absorption NOT AMOUNT OF XRAYS

things that can cause imaging plate to have artifacts

age - areas of radiolucency static from low humidity can cause hair to stick to ip dust dirt scrcthed back scatter-can cause dark lines on image

Absorption and conversion material attached array surface is our:

ama

conversion material for indirect

amorphous silicon

what does the monochromatic red light do

applied to release electrons from f-trap

operating processing artifacts can include

backward cassette incorrect part/position insufficient collimation incorrect sampling BIII

stimulating light is

bad

phosphor/active layer is made of

barium fluoride with small amounts of europium

when the laser passes through the beam what happens

beam shaping and oscillating / rotating mirror narrow the beam keeps size shape speed and intensity constant

what is emitted when the electrons are given energy

blue and violet light

switch=

circuit device that collects electrical signal When TFT is activated/closed signal is sent to ADC computer

solve imaging plate artifcts

clean plate refer to vendors recommondations frequency of cleaning depends on usage

what does the light collecting optics/ guide do?

collects light focuses and narrows light towards optical filter filtering out stimulating light-noise

while the light is stimulating what 2 layers are working

color and reflective layer

photodetector/photodiode/photomultiplier

convert light to electrons (signal;)

digital electronics

convert signals to digital forms

photoconductor:

converts x-ray photons into electrons

how often should the plate be in erase mode

daily or once a week

ADC converts to

digital signal unique values-preprocessing any remaining energy removed with bright white light

phosphor is taking

electrons converting to light

the signal is the

emitted light

as the laser scans it gives what to the trapped electrons

energy to release them

2 things preventing artifact

felt in cassette conductive layer in plate

insufficient erase=

ghost or phantom image

low snr=

grainy image

stationary grids= MOIRE EFFECT

grid lines must run perpendicular to laser scan

ghost/phantom image

if another image was taken on top of cr plate before laser extracted image

the remnant beam (process of acquiring image) -

interacts with the electrons of the barium fluoride crystals they give energy to the electrons in the crystals trapping them in the phosphor center-LATENT IMAGE signal remain for hours-loses intensity till process

what is slow scan

ip is moved slowly along axis-beam constant plate moving up

fast scan is

laser moved across ip in raster pattern left to right horizontal

sensitivity center where electrons are trapped and stored is

latent image in the phosphor active layer

the photodetector takes

light converting it to an electrical signal in adc

the cassette is made of

lightweight plastic material lead back felt

our readers stimulates with what type of laser

monochromatic red light

greater the sampling frequency

more info collected

laser is a

narrow intense beam of light

on the plate reader why would white leans appear

parallel lines caused by dirt dust or scratched on light guide or collection mirror

where is the late image stored

phosphor active layer

absorbing material for indirect

phosphor based scintillator

the emitted light is sent to the

photo detector

photo detector is also the

photo multipler photo diode

absorbing and converting material for direct

photoconductor (amorphous selenium)

computed radiography is comprised of

photostimuable storage phosphor cr reader digital electronics

process stimulating the phosphor and releasing light

photostimulable luminescence PBL

readout of our image

placed in reader immediately plate removed inside

artifacts include

plate reader imaging plater printer image processing PIPI

most is tased during

process when electrons return to low energy state

what will improve signal to noise ratio in the psp plate process

proper filtering

cr imaging plate layers

protective layer phosphor/ active layer reflective layer conductive layer color/light shielding layer support layer backing layer

the felt in the cassette is useful because

protects against static electricity, dust nd mechanical damage

backing layer

protects back

reflective layer

reflects light sends light in forward direction to reduce stimulating light and escape of emitted light loss of detail

measure of the true signal

represents actual anatomy to amount of noise prpesent

grid selection and collimation is

same as screen film more important-sensitive to scatter ratio focus grids

coherent light

same frequency traveling in same direction

the electrical signal is :

sampled and digitized assigned a value to each light photon to represent location in matrix and brightness

how many pixels per mm the laser scans with each line

sampling frequency

rate at which the laser extracts the image data from the plate

sampling frequency

the cr plate is sensitive to

scatter

support layer

semi-rigid strength support layers

as the light is stimulating the reflective layer

sending emitted light in forward directing

storage

should not be stored n temp over 95 no direct sunlight rough handling dropping can cause cracking

readers can be

single or multiloaders

correct cassette is chosen by

size and type standard or high resolution plate

high resolution plates are

small cassette extremityi thinner phosphor small pixel size

the more signal sampled

smaller the pixels

each del contains:

storage capacitor, thin film translator (switch) and pixel detector

capacitor=

stores electrons and measures charge

light emitted is proportional to

the absorbed radiation

the absorbing material depends on:

the conversion direct or indirect

emitted light is

the image good

the more radiation absorbed

the more light emitted

the barcode or id window indicates

the orientation of the plate when taking an xray to display it correctly on the monitor

protective layer=

thin clear plastic protects phosphor

TFT AND FET stand for:

thin film transistor switch field effect transistor switch used interchangeably

to increase spatial resolution we must increase

thinner phosphor layer bigger crystals translation speed smaller diameter laser beam increase sampling frequency pixel size

photostimuable storage phosphor

to acquire xray projection

cr reader

to extract the electronic latent image

slow scan is also

translation subscan

crystals in the phosphor=

turbid

the barcode / id window is a

unique code to match image with patient scanned under correct cord so apr is processed correctly

indirect=

x ray photons -> light -> electrical charge/signal Scintillator-phosphor and photodiode/photodetector

direct=

x ray photons->electric charge/signal Photoconductor-no phosphor/scintillator

sensing and storage material; photodiode=

a:SI

what does dye n the phosphor active layer dp

absorb stimulating light preventing spread

the pixel detector is considered the:

absorbing/converting material

conductive layer

absorbs and reduces static electricity

color/light shielding layer

absorbs stimulating lights and reflects emitted light

pixels in our ama are called

DEL detector elements

amfpi/ama:

Flat panel array with an x ray absorption material array of pixels


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