Test 2 - Fluoroscopy 💕

What is the magnification formula?

Input screen diameter
Diameter of input screen used during magnification

Example:

If I am using a 9” diameter II tube, and once
MAG is turned on, my diameter used is 3”, the
equation would be?

9”/3” = Magnification factor of 3

Describe the total brightness gain and the equation 

Measure of the increased image intensity (increased brightness) achieved by an image intensifier tube (II tube)

Brightness gain= minification gain x flux gain

What does the total brightness gain consider? 

Minification Gain and Flux Gain

Describe minification gain 

Compacting the same number of electrons from a large input screen on a smaller output screen

Describe flux 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 of anatomy

How do the cones of the eyes control PHOTOPIC acuity (daylight)

Image intensifiers amplify the brightness of our fluoro images to activate Photopic acuity

*Capable of increasing image brightness 500 – 8,000 times

*Remember, back in the day, fluoro required dark acuity (scoptic) which took time for the rods of the eyes to adjust and wasn’t fully diagnostically sound

What do the cones of the eye do?

• Daylight (photooptic)

• High visual acuity

What do the rods of the eye do?

• Nightlight (scotopic)

• Low visual acuity (10 x less)

What lies between the input screen and photocathode? What is its
purpose?

Thin protective coating

*Prevents any chemical interactions between the two

Describe the function of the photocathode?

absorbs light photons and emit electrons

*Remember, it’s a cathode so it is going to have something to do with
electrons, just like in our x-ray tubes

What does the output screen do?

converts electrons to light that exits the tube

*Also called the output phosphor

*Coated with zinc-cadmium sulfide phosphor

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

A single x-ray photons can produce over 1,500 light photons

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

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

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

90 degrees

*stand behind doctor/PA

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

TFT technology for fluoroscopy allows for what type of contrast detectability?

Low-contrast detectability

*optimize fine detail

What is the mathematical formula for minification gain?

Minification gain = Input screen diameter 2
                              Output screen diameter 2

Identify the steps in the processing of an image in an intensifying tube?

• x-ray to light

• light to electrons

• electrons to light

What does the final light go through and what is it changed to? (processing an image in an intensifying tube) 

Light goes though video camera and is converted to electronic Signal for viewing on our monitors

Define vinetting?

Edge distortion 

*Diminished resolution and contrast at the image periphery due to decreased exposure rate at the periphery
*Affects 8-10 % of the image edge distortion

Why is fluoro the domain of the radiologists?

Fluoroscopy involves active diagnosis

*diagnosis happening during exam also called Dynamic Imaging

What invention enabled the brightness to be enhanced?

The image intensifier

*Developed in 1948 Included II tube, video camera, & monitor system

Identify the rad tech responsibilities during fluoro?

• Post fluoro x-rays

• Assist radiologist/PA

• Static exams

What does flux gain do to image quality?

Decreases image quality

**Deals with the gain accomplished by the electron to light conversion at the output screen

**Image brightness is intensified but that doesn’t mean image quality doesn’t suffer. Radiographs have better image quality than fluoro images

What are the mAs ranges for fluoro?

0.5 – 5 mA

*Remember that in fluoro we are working with much lower mA than x-ray (radiographs

What are the mAs ranges for diagnostic xray?

50 – 1,200 mA

Cumulative timers sound after ____ minutes of fluoroscopy time?

5 minutes

What is the minimum source to skin distance for mobile fluoro?

12 inches

*Mobile fluoro units = C-ARMS and O-ARMS

The minimum source to skin distance for stationary fluoro equipment is?

15 inches

What does CsI (phosphors) stand for, and what % of the incident beam do they absorb?

Cesium iodide phosphors (CsI)
* absorb 66% of incident beam from patient

**Input screen coated with cesium iodide phosphors (CsI)

List the components of the image intensification tube?

Input screen
Photocathode
Electrostatic Lenses
Anode
Output Screen

The fluoro skirt has ___ mm Pb/eq?

made of 0.25 mm Pb

How thick are lead aprons required to be for fluoro?

0.5 mm Pb/eq

watch your back side

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

Collimate

Digital fluoro resolution cannot be as high as radiography because the fluoro pixels are ___ lp/mm and radiography is ___ lp/mm.

Digital fluoro pixels - 2-3 lp/mm

Radiography pixels - 10-12 lp/mm

Digital fluoro reduces patient exposures up to ___%?

90%, compared to older fluoro units

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 and how does it function?

Automatic Brightness Control (ABC)

**Automatically adjusts the exposure

What similar tool is ABC for x-ray?

AEC

What is the output screen made of?

coated with zinc- cadmium sulfide phosphor
(silver-activated zinc-cadmium)

The photocathode is comprised of what material?

photoemissive metals

What reduces quantum mottle?

Increasing mA

List some dynamic studies

BE, UGI, VCUG, Arthrogram, Esophogram, HSG, etc

List two types of c-arm arrangements (fluoro machines) Which uses II tube and which uses TFT plate?

• Under-Table Unit - TFT plate

• Over-Table Unit - II tube 

True or False: In fluoroscopy, the focal point reverses the image so the output screen is reversed from the input screen

True, the focal spot does reverse the 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 _____? Most units operate around _______?

10 R/min

1-3 R/min