Physics Chapter 14

Question 1

Know the two ways that image intensifiers improved the image process

Answer 1

• Brightened the image significantly (eliminated the need to dark adapt)
• Allowed for a means of immediately viewing the fluoro image (reduced radiographic dose)

Question 2

Know what the conventional fluoroscopic chain consists of

Answer 2

x-ray tube, an image intensifier, a recording system, and viewing system

Question 3

Know the 5 basic parts that make up an image intensifier

Answer 3

Input phosphor, photo cathode, electrostatic focusing lenses, accelerating anode, and output phosphor

Question 4

Know why the input phosphor is made of cesium iodide

Answer 4

It absorbs remnant x-ray photon energy and emits light in response

Question 5

Know the size correlation between the input and output phosphor

Answer 5

output phosphor is much smaller

Question 6

Know how brightness gain has traditionally been found

Answer 6

Multiplying the flux gain by the minification gain

Question 7

Know the size of the image intensifier tube

Answer 7

50 cm in length and 15-58 cm diameter

Question 8

Know how flux gain is expressed

Answer 8

The ratio of the number of light photons at the output phosphor to the number of light photons emitted in the input phosphor

Question 9

WHat results from the higher the conversion factor or brightness gain factor

Answer 9

image appears brighter because the same number of electrons is being concentrated on a smaller surface area

Question 10

Know what happens as the image intensifier tube ages

Answer 10

The ability of the image intensifier to increase brightness deteriorates with the age of the tube

Question 11

Know what happens in regards to radiation as the image intensifier tube ages

Answer 11

More and more radiation is necessary to produce the same level of output brightness, translating to an increased patient dose

Question 12

Know how ABC commonly operates

Answer 12

By monitoring the current through the image intensifier or the output phosphor intensity and adjusting the exposure factor if the monitored value falls below preset levels

Question 13

Know how to find the degree of magnification

Answer 13

Dividing the full size input diameter by the selected input diameter

Question 14

Know what magnification improves

Answer 14

The fluoroscopist’s ability to see small structures (spatial resolution) but at the expense of increasing patient dose

Question 15

Know how spatial resolution is measured

Answer 15

Line pairs per millimeter

Question 16

Know what distortion is a result of in fluoro

Answer 16

Inaccurate control or focusing of the electrons released at the periphery of the photocathode and the curved shape of the photocathode

Question 17

Define a pincushion appearance

Answer 17

The combined result is an unequal magnification (distortion) of the image

Question 18

Know how a “noisy” or “grainy” image occurs

Answer 18

If too few x-rays exit the patient and expose the input phosphor, then not enough light is produced, which decreases the number of electrons released by the photocathode to interact with the output phosphor

Question 19

Know how to fix a “noisy” image

Answer 19

increasing the mA

Question 20

Know what the 2 devices are that convert the image from the output phosphor to an electrical image

Answer 20

The camera tube and charge-coupled device (CCD)

Question 21

Know what the camera tube most often used is

Answer 21

vidicon tube

Question 22

Know what the deflection coils act to accelerate

Answer 22

the electron beam

Question 23

Know what the CCD is made from

Answer 23

A series of metal oxide semiconductor capacitors

Question 24

Know what is sent from the capacitors

Answer 24

Charge is sent as an electronic signal to the tv monitor

Question 25

Know what the purpose of the television monitor is

Answer 25

Convert the electrical signal from the camera tube to CCD back into visible light

Question 26

Know what typical television monitors are called

Answer 26

525 line systems

Question 27

Know the resolution of HIGH resolution monitors

Answer 27

1024 lines per frame

Question 28

Know what the image intensifier is capable of resolving

Answer 28

Approximately 5 lp/mm whereas the monitor can display only 1-2 lp/mm

Question 29

Know the 3 types of recording systems

Answer 29

Cassette sport film, film cameras, video recorders

Question 30

Know what happens when the spot film exposure button is pressed

Answer 30

The cassette is moved into position between the patient and image intensifier and the machine shifts from fluoroscopic to radiographic mode and exposes the film

Question 31

Know what happens in regards to radiation dose when imaging from fluoro to radiographic mode

Answer 31

fluoro to the radiographic mode uses a much higher radiation dose to the patient

Question 32

Know what film is commonly used in the film cameras

Answer 32

105 mm "chip" film or 70 mm roll film

Question 33

Know what the number of bits that a signal is divided into determines

Answer 33

the contrast resolution (number of gray shades) of the system

Question 34

Know what the charge-coupled device (CCD) eliminated

Answer 34

Some of the problems associated with the camera tube

Question 35

Know the 2 forms of flat panel detectors are used for fluoroscopic applications

Answer 35

* cesium iodide amorphous silicon indirect capture detector | * amorphous selenium direct capture detector

Question 36

Know why the size, bulk, and weight of the fluoroscopic tower in digital fluoro is an advantage

Answer 36

Flat panel reduces all 3 allowing easier manipulation of tower, greater flexibility of movement and greater access to the patient during the exam

Question 37

Know what the flat-panel detectors replaced

Answer 37

the spot0filming and other recording devices

Question 38

Know why additional radiographic images are commonly not needed in digital fluoroscopy

Answer 38

they are capable of operating in radiographic mode

Question 39

Be able to describe some of the other advantages of digital fluoro

Answer 39

* flat panel detectors don't degrade with age * more durable * provide more information * better contrast resolution * higher detective quantum efficiency * wider dynamic range

Question 40

Know the advantage of digital fluoro in regards to artifacts

Answer 40

They do not exhibit most image artifacts such as veiling glare and peripheral distortion seen with image intensifiers

Question 41

Know the advantage of digital fluoro in regards to radiation dose

Answer 41

50% lower radiation dose

Question 42

Know why Quality Control Programs are vitally important for all ionizing radiation producing equipment

Answer 42

to monitor equipment performance and minimize patient dose

Question 43

Know the role of the radiologist in a quality control program

Answer 43

supervision of the whole quality control program and process

Question 44

Know the role of a radiographer in a quality control program

Answer 44

facilitator in the process

Question 45

Know the role of the medical physicist in a quality control program

Answer 45

has primary responsibility for performance testing and interpretation

Question 46

Know some of the responsibilities a radiographer may have in a quality control program

Answer 46

* Operational inspection of the equipment * inspection of suite itself to examine the general physical condition of the room, unit, supporting electrical cables, and control booth, monitoring anywhere or deteriorating condition * performance inspection and testing equipment * Check following items - bucky slot cover - table tilt motion - monitor brightness - exposure switch