dynamic image recording (fluro)

Question 1

what is fluoroscopy?

Answer 1

real time ‘dynamic’ x-ray images

Question 2

who was fluoroscopy invented by?

Answer 2

thomas edison

Question 3

when does luminescence occur?

Answer 3

occurs when materials absorb energy and emit light

Question 4

two categories of luminescence

Answer 4

• fluorescence - light emitted very quickly
• phosphorescence - light emitted more slowly

Question 5

when in radiography is fluoroscopy used?

Answer 5

when images should be sharp

Question 6

what type of imaging does fluoroscopy use?

Answer 6

continuous ‘real time’ imaging
- low continuous x-ray exposures (0.5mA - 2mA)

Question 7

what is fluorography

Answer 7

can select on machine the function to give a still image with HIGH resolution

Question 8

image intensifiers

Answer 8

older way of obtaining fluoroscopy and fluorography

Question 9

pros of image intensifiers

Answer 9

reduces patient dose by amplifying image signal

Question 10

cons of image intensifiers

Answer 10

• image noise
• loss of sharp image
• image distortions

Question 11

what is image noise

Answer 11

• signal that comes from anything apart form anatomy of patient
• noise present in all electronic systems
• appears as irregular granular pattern

Question 12

examples of general fluoro procedures

Answer 12

• gastrointestinal studies
• angiography of vessels
• micturating cystograms
• proctograms
• HSG

Question 13

examples of interventional fluoroscopy procedures

Answer 13

• angioplasty
• stenting
• embolization
• biopsy
• drainage

Question 14

how does an image intensifier work in a fluoroscopic chain

Answer 14

Electronic vacuum
- convents remnant beam —> light
- light —> electrons
- electrons —> back to light
- increases light intensity in the process

Question 15

5 components of fluoroscopic chain

Answer 15

• x-ray tube
• collimators
• filtration
• patient table
• anti-scatter grid

Question 16

what is the patient table made up of and why

Answer 16

carbon fibre
- strong enough to hold patient with minimal radiation absorption

Question 17

where is the image intensifier position

Answer 17

the intensifier usually above table

Question 18

what does an image intensifier include?

Answer 18

• input phosphor and photocathode
• electrostatic focusing lens
• accelerating anode
• output phosphor

Question 19

how much kV to accelerate electrons in image intensifier

Answer 19

25-35 kV

Question 20

what does an input phosphor do?

Answer 20

converts x-ray photons to (blue) light photons

Question 21

what is an input phosphor made of

Answer 21

fine caesium iodide crystals (CsI) - high X-ray absorption rate

Question 22

what does thicker layers help achieve

Answer 22

improved efficiency - 60% of X-ray energy converted to light

Question 23

what does a photocathode do

Answer 23

converts blue light photon energy to energy possessed by released electrons

Question 24

why is the photocathode curved

Answer 24

so that all electrons travel the same distance to output phosphor

Question 25

what is a photocathode made of

Answer 25

made of Sb.Cs (antimony and caesium)

Question 26

what is the purpose of negatively charged focusing electrodes

Answer 26

repel electron stream steering them to output phosphor

Question 27

what is the potential difference across the vacuum in an image intensifier

Answer 27

25-35kV = accelerates electrons as they pick up kinetic energy

Question 28

where is the anode located in the image intensifier

Answer 28

at the neck - +ve charged to provide a stream of electrons at constant velocity

Question 29

what does the output phosphor have a thin layer of and why

Answer 29

- aluminium - prevent light travelling back to input phosphore

Question 30

what is output phosphor made of

Answer 30

- zinc cadmium sulphide - converts electron energy into green light

Question 31

describe the process of flux gain

Answer 31

- converting x-ray photon energy to many light photons - converting light photons to energy gained by electrons - electrons emitted from cathode - accelerate + gain kE - converts electron energy to light photons - gives 100x increase in brightness

Question 32

describe the process of minification gain

Answer 32

- output phosphor is smaller than input phosphor - reduction in actual image size (minification) = same number of electrons concentrated on smaller surface area - results in a 100x brighter image

Question 33

what is the intensifiers ability to increase the brightness of image is called

Answer 33

flux gain x minification gain (brightness gain or conversion factor)

Question 34

what is exposure factors in fluoroscopy controlled by

Answer 34

ABC (automatic brightness control) - automatically adjusts kVp + mA - achieved by monitoring brightness of output phosphor intensity - ensure brightness of image at monitor is constant

Question 35

how to adjust magnification in an image intensifier

Answer 35

- achieved by increasing the voltage to focusing electrodes - focuses down electron beam by electrostatic repulsion - so only electrons from centre portion of photocathode interact with output phosphor

Question 36

what reduces brightness

Answer 36

only central part of photocathode provides electrons to output phosphor

Question 37

how does ABC contribute to compensate in reduce brightness

Answer 37

may automatically increase radiation dose