TEST 2 CLASS REVIEW FLUORO

what is the formula for magnification?

input screen diameter / diameter of input screen used

what is total brightness gain?

measure of the increased image intensity/brightness done by image intensifier tube (II Tube)

minification gain - total brightness gain

compacting the same number of electrons from a large input screen on a small output screen

flux gain - total brightness gain

measurement of the increase in light photons due to the conversion efficiency of the output phosphor

never use fluoro to ….

• positioning guide/preview

• position anatomy

the cones of eyes control what type of visual activity?

PHOTOPIC acuity (daylight)

• image intensifiers amplify the brighter of fluoro images to activate photopic acuity

• increases image brightness 500-8000 times

what lies between the input screen and photocathode? What it’s purpose?

thin protective coating

• prevents any chemical interactions between the two

What is the function of the photocathode?

it absorbs LIGHT PHOTONS and emits ELECTRONS

what does the output screen do? (output phosphor)

converts/absorbs ELECTRONS to LIGHT PHOTONS that exit the tube
- coated with zinc-cadmium sulfide phosphor

a single incident photon can potentially produce how many light photons at the input screen?

over 1,500

what happens when greater voltage is applied to the electrostatic lenses?

increased voltage accelerates the electrons and moves the focal point closer to the input screen

what degree from the patient/primary beam produces the highest energy scatter?

90 degrees

what does photoemissive materials do?

absorb light photons and emit electrons

• photocathode material is photoemissive metals

what is the name of edge distortion in image intensification tubes?

vignetting - dark fuzzy cloudy

TGT technology for fluoro allows for what type of contrast detectability?

low contrast detectability = optimizes fine detail

what is the math formula for minification gain?

input screen diameter² / output screen diameter² 

steps in processing an image in an intensifying tube?

xray to light

light to electrons

electrons to light

what does the final light go through and what it’s changed into?

video camera then converts to electronic signal for viewing on our monitors

define vignetting

edge distortion

• diminished resolution and contrast at the image periphery due to decreased exposure rate and periphery. affects 8-10% of image edge distortion

why is fluoro the domain of the rads?

they’re actively diagnosing - called dynamic imaging

what invention enabled the brightness to be enhanced

the image intensifier

includes II tube, video camera and monitor system

the rad tech responsibilities during fluoro

post fluoro xrays
assist radiologist/PA

static exams

what does flux gain do to image quality

decreases image quality

what does flux gain deal with

gain accomplished by electron to light conversion at the output screen.

what are the mA ranges for fluoro

0.5 - 5 mA

what are the mA ranges for diagnostic?

50-1200 mA

cumulative timers sound after how long in fluoro?

5 min

what is the minimum skin distances for mobile fluoro?

12 inches

what is the minimum skin distances for stationary fluoro equipment?

15 inches

what does CSI (phosphors) stand for?
what % of the incident beam do they absorb?

Cesium Iodide Phosphors
66%

what are the components of the image intensification tube (tube II)?

input screen

photocathode

electrostatic lenses

anode

output screen

the fluoro skirt has ___ mm pb/eq

0.25

how do you reduce patient dose when utilizing the mag factor?

collimation

digital fluoro resolution cannot be as high as radiography because the fluoro pixels are ___ lp/mm

2-3 lp/mm

digital fluoro resolution cannot be as high as radiography because the radiography is ___ lp/mm.

10-12

digital fluoro reduces patient exposures up to __%

90

after the x-ray photon leaves the patient, what does it strike next?

input screen

what is the purpose of electrostatic lens?

• accelerates and focus electrons

• intensifies the image

what is ABC? How does it function?

Automatic Brightness Control
Automatically adjusts the exposure

what is the output screen made of?

zinc cadmium sulfide phosphor (silver activated zinc cadium)

the photocathode is comprised of what material?

photoemissive iodine / CSI

what reduces quantum mottle?

increase mA

list some dynamic studies

BE

UGI

VCUG

Esophogram

Arthrogram

What are the types of c-arm arrangements / fluoro machines

under-table unit
over-table unit

T/F: In fluoro the focal point reverses the image so that output screen is reversed from the input screen?

TRUE, the focal spot DOES reverse image

what is the purpose of the concaved shape of the input screen?

to maintain an equal distance to the output screen

Over-table units operate with a minimum tabletop exposure rate not to exceed ___ R/min.

10 R/min

Most units exposure range operate around __ R/min

1-3

what is the formula of Total Brightness Gain?

minification gain x flux gain

what is the formula of flux gain?

output / input

order of fluoro

tube - patient - light - electron - light

what is image intensifiers

they amplify brightness to activate photopic activity

what are electrostatic lenses order?

reverses
Right to Left - Inferior to Superior on output screen

what do electrostatic lenses do?

accelerate and focus the electron steam

greater voltage causes what in electrostatic lenses?

accelerate more - moves focal point closer to input screen = increase magnification

define ABC

intensity flowing from cathode and anode, and maintains fluoroscopic density and contrast.

SLOW

Varying kvp / mas / pulse time

digital fluoro contrast?

good low contrast resolution

what do CSI phosphors do in TFT flat pannels?

the absorb xray photons and emit light from TFT

what does removing the grid do in dose while in fluoro?

reduces dose from 30-50%

lead apron and gloves

0.5 pb/eq

last image hold does what to exposure?

it reduces additional pt dose

name 4 digital flat panel benefits

ensures best image brightness

best spatial resolution

low contrast

lowest patient dose

benefits in digital flat panel Magnification mode

no vignetting
no increase in patient dose