Fluoro 1 + 2

Question 1

Purpose of input layer

Answer 1

Convert x-rays to e-

Question 2

Purpose of electron lenses

Answer 2

focuses e-

Question 3

Purpose of anode

Answer 3

to accelerate e-

Question 4

Purpose of output layer

Answer 4

e- to visible light

Question 5

How many light photons are given off per x ray in input phospher

Answer 5

2000-3000:1

Question 6

Is the input phospher curved or flat?

Answer 6

curved

Question 7

What is important about the scintillating phospher layers structure?

Answer 7

Thin spaces to channel light (improved spatial resolution)

and thick , dense material to absorb light.

Question 8

What element is contained in the photocathode?

Answer 8

Antimony cesium oxide (Sb-CsO)

Question 9

What is the conversion efficiency of Sb-CsO?

Answer 9

15-20% ( so 15 to 20 electrons are ejected from photocathode for every 100 light photons.)

Question 10

What does the black paint on Output window stop?

Answer 10

veiling glare …. this is when light photons bounce around the output window , off axis and reduce image contrast.

Question 11

Ration of e- to light photons at output window?

Answer 11

1:1000

Question 12

What is an optical distributor?

Answer 12

acts to convert the small image on the output image to a video image.

Question 13

What is CCD and CMOS?

Answer 13

Optical distributors that give a continuous readout of fluoroscopic images at 30 FPS

Question 14

minification gain

Answer 14

: in which a given number of light photons

emanates from a smaller area

Question 15

flux gain

Answer 15

where electrons accelerated by high voltages produce

more light as they strike a fluorescent screen.

Question 16

brightness gain

Answer 16

ratio of brightness between output screen of II and brightness of the standard screen.

Question 17

What is the overall brightness gain range?

Answer 17

2500 - 7000

Question 18

What creaates the gain in brightness

Answer 18

flux x minification

Question 19

The number of light photons created in the output is dependent on?

Answer 19

The energy of the e- .

Question 20

What is a typical flux gain value?

Answer 20

at least 50

Question 21

Minification gain equation

Answer 21

(di/do) squared

Question 22

What should the constant tube potential be when measuring conversion factor?

Answer 22

85 kvp

Question 23

What are the 4 main artefacts in the Image intesifier?

Answer 23

Veiling glare

Pincushioning

vignetting

S distortion

Question 24

What causes pin cushioning?

Answer 24

Curved input screen , curving the image on the output due to bending of electrons

Question 25

What causes vignetting?

Answer 25

Brighter centre and dimmer periphery occurs due to reduced exposure at periphery of input and reduced precision of e- hitting periphery at output.

Question 26

What is S distortion?

Answer 26

SPATIAL WARPING OF IMAGE and caused by STRAY MAGNETIC FIELDS

Question 27

What does a flat panel detecor have over a II?

Answer 27

TFT

Question 28

when is the Ma and the Kv able to be changed by the AERC

Answer 28

Continuous mode

Question 29

What is the purpose of the AERC?

Answer 29

To keep the SNR constant

Question 30

Is it better to have a wider or narrow dynamic range?

Answer 30

Wider such as when using a flat panel detector.

Question 31

What is typical spatial resolution capabilities of the fluoro system is in the range of?

Answer 31

4-6 Lp/mm

Question 32

Why doesnt the rad change exposure settings when in magnification mode?

Answer 32

The AERC does it itself.

Question 33

What is Interrogation time?

Answer 33

is the time required for the tube to be | switched on and reach the required kVp and mA

Question 34

What is the exctinction time?

Answer 34

is the time required for the tube to be switch | off

Question 35

What is. the interrogation and extinction times of digital fluoro

Answer 35

less than 1ms

Question 36

What inch II is used for cardiac imaging?

Answer 36

typically, 9 inch.

Question 37

What adjusts in magnification mode?

Answer 37

collimater to make a smaller FOV on the input ... less divergence. .. more focusing

Question 38

Why is the AERC important for magnifcation mode?

Answer 38

as FOV on input decreases (increased mag) the brightness gain also decreases.. meaning we need to compensate by increasing exposure.

Question 39

Purpose of frame averaging

Answer 39

To lower temporal resolution (fluoro has this in abundance) to decrease noise.... Will create a less noisy image but MORE LAG.

Question 40

Can frame averaging lower dose?

Answer 40

Yes.

Question 41

What will a decrease in temporal resolution cause?

Answer 41

increased lag

Question 42

What is road-mapping?

Answer 42

Software enhanced last frame hold. can be done on dual monitor.. one with the still and one with the live feed. or overlay

Question 43

what is roadmapping good for?

Answer 43

catheter implantations

Question 44

Typical fluoro spatial res?

Answer 44

3-5 cycles/mm ... 4-6 lp/mm

Question 45

what limits spatial res in fluoro?

Answer 45

Video camera matrix sampling size across FOV inability to focus elctrodes res of input and output fluoro screens

Question 46

What lowers spatial res outside the II

Answer 46

Scattered x-rays Patient movement potential fluctuations

Question 47

is contrast better or worse in fluoro when compared to general xray?

Answer 47

worse. It has a LOW SNR

Question 48

how can you increase contrast res in fluoro?

Answer 48

increase Mas

Question 49

What causes blurring in temporal resolution

Answer 49

movement in time domain

Question 50

Why are video cameras the weakest area of fluoro unit

Answer 50

they have high lag. and create the most lag in the entire fluro unit

Question 51

what time does human eye create lag at

Answer 51

0.2 seconds

Question 52

The radiation dose depends on the:

Answer 52

 type of examination,  patient size,  equipment, the technique,

Question 53

 The performance of the fluoroscopy system with respect | to radiation dose is best characterized by:

Answer 53

 Receptor entrance exposure |  Skin entrance exposure rates.

Question 54

The receptor entrance exposure rate is:

Answer 54

 the most important dose performance parameter.  measures the effective "speed" of the imaging system, that is, the amount of radiation used in image formation.  critical because  skin dose is dependent on and increases with increasing receptor entrance exposure  because the level of image noise, and thus the perceptibility of lowcontrast detail, is also dependent on it.  normally specified as the entrance exposure at the surface of the image receptor (with the grid removed) required to produce a single image for a given x-ray spectrum.

Question 55

Skin Dose

Answer 55

This measurement, quantifies the dose at the beam entrance surface to a patient-simulating medium on a fluoroscopy system.

Question 56

TO get a realistic measurement of patient dose that is it importnant to meausre?

Answer 56

average skin entrance exposure

Question 57

What is the DAP

Answer 57

Dose area product meter Indirect and widely used method of monitoring dose.

Question 58

Skin doses may be reduced by using:

Answer 58

``` intermittent exposures,  grid removal,  last image hold,  dose spreading,  beam filtration,  pulsed fluoroscopy, ```

Question 59

Why can a higher quality beam reduce dose in fluoro

Answer 59

more chance of transmission over absorption

Question 60

 There are two basic ways to magnify the image in | fluoroscopy:

Answer 60

 Geometric: Using divering beam by changing FFD or OID... can lead to higher dose if patient is moved closer to tube... closer to tube = more mag bbut more dose.  Electronic:

Question 61

What are dose level settings?

Answer 61

Built in exposures that give differnt doses.. low, med and high. low dose = lower SNR. (more noise) High dose = Increased SNR