Week #12

Question 1

What type of technology do most fluoroscopy systems use?

Answer 1

Television technology

Question 2

What is fluoroscopy primarily used for?

Answer 2

Dynamic studies that require evaluation of functional anatomy

Question 3

What technical factors are used for fluoroscopy?

Answer 3

Low mA (0.0-5mA) and high kvp

Question 4

What distinguishes fluoroscopy from radiology?

Answer 4

Image intensifier
Several thousand times more sensitive than a standard screen film combination

Question 5

A complex device that receives the image forming xray beam and converts it into visible light image

Answer 5

Image intensifier

Question 6

What potential difference is maintained in the image intensifier?

Answer 6

About 25,000 V is maintained across the tube between photocathode and anode so that electrons will be accelerated to the anode

Question 7

What are the 4 principal components of the image intensifier?

Answer 7

-vacuum enclosure
-input layer
-electronic lenses
-output layer

Question 8

Converts xray signals to electrons

Answer 8

Input layer

Question 9

Focuses the electrons

Answer 9

Electronic lenses

Question 10

Converts the accelerated electrons into visible light

Answer 10

Output layer

Question 11

Absorbs xray photons, converts their energy into visible light

Answer 11

Input layer

Question 12

What is the input later made of?

Answer 12

Cesium iodide (csl)

Question 13

Takes xray photons and converts them to light

Answer 13

Input phosphor

Question 14

Thin metal layer that converts input phosphor light into electrons
(Called photo emission)

Answer 14

Photocathode

Question 15

Consists of electrostatic lenses that “intensify” and focus the stream of e-

Answer 15

Image intensifier

Question 16

Shape the electric field - focusing the electrons onto the output phosphor

Answer 16

Electrostatic focusing lenses

Question 17

Consists of:
Anode
Output phosphor
Output window

Answer 17

Output layer

Question 18

A thin circular aluminum plate with a hole in the middle through which electrons pass to the output phosphor

Answer 18

Anode

Question 19

What material is the output phosphor made of?

Answer 19

Zinc cadmium

Question 20

What is the output phosphor capable of resolving?

Answer 20

Approximately 4-6 lp/mm

Question 21

T/F
Each photoelectron that arrives at the output phosphor produces 50-75 times as many light photons as were necessary to create it

Answer 21

True

Question 22

The last section of the II
Part of the vacuum bottle made to be transparent to light
*this is where light photons come out

Answer 22

Output window

Question 23

Size varies from 10-40cm

Answer 23

Input phosphor

Question 24

Size is fairly standard at 2.5 or 5 cm

Answer 24

Output phosphor

Question 25

What is determined by the physical size of the II?

Answer 25

Field of view

Question 26

What might larger II’s be used for?

Answer 26

Gastrointestinal/genitourinary work

Question 27

What might smaller II’s be used for? (23cm)

Answer 27

Cardiac imaging

Question 28

As magnification is increased:

Answer 28

A smaller area of the II is visualized **Spatial resolution is improved

Question 29

A reduction in brightness at the periphery of the image

Answer 29

Vignetting

Question 30

The collimator adjusts to narrow the xray beam to a smaller field of view when what mode is engaged?

Answer 30

Magnification mode

Question 31

Magnification mode results in:

Answer 31

Better spatial resolution Better contrast resolution Higher patient radiation dose

Question 32

T/F In order to minimize patient dose, the MRT should use as little magnification as possible

Answer 32

True

Question 33

A function of the fluoroscopic unit that maintains overall appearance of the fluoroscopic image by automatically adjusting kvp, mA or both

Answer 33

Automatic brightness control

Question 34

Decreases image noise, increases contrast resolution

Answer 34

Automatic brightness control

Question 35

II tubes serve as the fluoroscopic image receptor II tubes are electronically coupled to a tv monitor for remote viewing

Answer 35

Conventional fluoroscopy

Question 36

Computer has been added, as have multiple monitors and the ability to remotely control the imaging system

Answer 36

Digital fluoroscopy

Question 37

What are the differences between conventional vs digital fluoroscopy?

Answer 37

-addition of a computer -multiple monitors -more complex operating console

Question 38

What are 2 advantages of digital fluoro?

Answer 38

-speed of image acquisition -post processing to enhance image contrast

Question 39

At least how many monitors are used in digital fluoro?

Answer 39

2

Question 40

Done by regulating the cray exposure rate incident on the input phosphor of the II

Answer 40

Automatic brightness control

Question 41

What are some methods to minimize radiation dose during fluoro?

Answer 41

-5 minute alarm timer -use of pulsed/low dose mode -use of last image hold -minimal use of magnification feature

Question 42

Enables the last live image to be shown after the operator removes their foot from the pedal/exposure switch

Answer 42

Last frame (image) hold

Question 43

T/F Fluoroscopic imaging sequences are not typically recorded

Answer 43

True Frames from live imaging are saved as single images

Question 44

What are the 2 monitors used for in digital fluoro?

Answer 44

-one is used to enter/edit patient data and adjust exam parameters -the other monitor displays image acquisition and editing tools

Question 45

-Thin aluminum window -part of vacuum bottle -curved to withstand air pressure -vacuum is necessary to accelerate electrons across open spaces without interaction

Answer 45

Vacuum window

Question 46

What is cesium iodide used for the input phosphor?

Answer 46

-long needle like crystals channel the visible light within them with minimal lateral soreading

Question 47

T/F Electrons released by the photocathode have very little kinetic energy but are accelerated by an electric field between the photocathode and anode

Answer 47

True

Question 48

Why is the output phosphor thin?

Answer 48

In order to preserve high spatial resolution

Question 49

The increase in energy of each electron as it is accelerated across the II

Answer 49

Electronic gain

Question 50

What is the measurement of electronic gain?

Answer 50

Flux gain

Question 51

The ratio of the number of light photons at the output phosphor to the number of X-rays at the input phosphor

Answer 51

Flux gain

Question 52

The reduction in the size of the output phosphor image compared with that of the input phosphor image

Answer 52

Minification gain *the reduction in image diameter leads to concentration of electrons

Question 53

Ability of II to increase the illumination level of the image

Answer 53

Brightness gain *most II have multiplied mode or mag mode

Question 54

T/F As the effective diameter of the input phosphor increases, the brightness gain increases

Answer 54

True

Question 55

T/F Brightness gain decreases with tube age and use, causing an increase in patient dose

Answer 55

True

Question 56

Reflected light within the output window -can reduce image contrast

Answer 56

Veiling glare

Question 57

How is veiling glare reduced?

Answer 57

Increasing the thickness of the output window whereby internally reflected light eventually strikes the side of the window

Question 58

Produced by increasing the voltages applied to the electrostatic focusing lenses in the II *the electron focal spot moves farther from the output phosphor

Answer 58

Mag mode

Question 59

T/F When mag mode is increased, the brightness of the image is decreased

Answer 59

True

Question 60

To maintain the same level of brightness when using mag modes, what is used?

Answer 60

The xray tube mA is increased by ABC *increases patient dose