test 1: lecture 3

Question 1

Cathode has ___ charge

anode has ___ charge

Answer 1

negative

positive

Question 2

the kinetic energy from electrons striking the anode turn into ___

Answer 2

Bremsstrahlung <1%

Heat production 99%

Question 3

mAs

Answer 3

of electrons that flow from cathode to anode

increasing mAs increases # of electrons but not overall energy created

→ increased # of xrays produced

Question 4

kVP

Answer 4

change in voltage from cathode to anode, the bigger the change the stronger the Xray produced

increasing both the # of photons and the overall energy

increased quality and quantity

Question 5

two types of attenuation

Answer 5

Photoelectric effect = Absorption

photon removed from beam

Compton effect = Scattering

photon changes direction, can fog the detector (decreases contrast) and can expose personnel (=radiation hazard)

Question 6

compton effect

Answer 6

Compton effect = Scattering

photon changes direction, can fog the detector (decreases contrast) and can expose personnel (=radiation hazard)

Question 7

photoelectric effect

Answer 7

= Absorption

photon removed from beam

Question 8

low kVp increases the change of what type of attenutation

Answer 8

photoelectric effect

(absorption)

Question 9

high kVP increases the chance of ___

Answer 9

compton scatter (foggy)

Question 10

photoelectric effect increases with ___ materials and ___ energy Xrays

Answer 10

high atomic number (bone high)

low energy (low kVp)

Question 11

___ gives Xrays contrast

Answer 11

photoelectric effect (absorption- high atomic number and low kVp)

Question 12

compton scatter increases with ___ tissues and ___ energy Xrays

Answer 12

higher density

high

Question 13

how does analog work

Answer 13

film incased in two intensifying screens

screens will convert Xrays to visible light photons

these will interact with the film and provide a picture

Question 14

During analog, energy absorbed from X-ray photons is released as ___ in crystals within screen of cassette. X-ray film is usually most sensitive to green, blue, or UV light.

Answer 14

visible light photons

Question 15

limitations of analog

Answer 15

^{•Narrow exposure latitude,}

^{•Need for chemical processing}

^{•Incompatibility with electronic transmission}

^{•No image enhancement}

^{•Higher costs for film materials and labor}

Question 16

what does narrow exposure latitude mean?

Answer 16

the amount of settings where you get a good xray is limited

too low exposure → underexposed

too high → overexposed

Question 17

___: wide latitude and ability to compensate for underexposures and overexposures with image preprocessing and postprocessing capabilities that are not possible with film.

Answer 17

DIGITAL DETECTORS

Question 18

digital detectors have wide latitude, meaning

Answer 18

there is a wide range in which you can get a good quality xray

Question 19

how are xrays stored online?

Answer 19

Picture Archiving and Communications System (PACS)

Question 20

two types of digital xray

Answer 20

computed

direct digital

Question 21

steps for computed radiography

Answer 21

xray still needs to be processed by a reader

Question 22

steps of direct digital radiography

Answer 22

2 steps, very fast, no need for processing step

Question 23

Computer radiography is on __ plate made of __.

Answer 23

flexible image

photostimulable storage phosphor

Question 24

why do you have to process computer radiography quickly

Answer 24

žPlate needs to be processed by the laser reader quickly after exposure as the latent image is stable for a short period of time

Question 25

how are computed radiography made

Answer 25

X-ray photons strike cassette containing photostimulable storage phosphor: Electrons excited to higher energy level when interacting with photons

Cassette placed inside a laser reader where laser beam stimulates phosphor crystals to release trapped electrons → light energy emitted. The amount of light released is directly related to the intensity of x-rays that struck that portion of the cassette.

The information is spatially encoded and sent to computer for image reconstruction

Question 26

Answer 26

direct radiography

flat panel detector

X-ray photons strike a flat panel detector containing a scintillator that creates visible light photons when struck by x-ray photons.

Light photons stimulate photocathode (light into electrical energy)

Electrical energy is spatially encoded by a thin film transistor and directly transmitted to computer for image reconstruction

Question 27

Answer 27

digital radiography

flat panel detector

X-ray photons strike selenium plate and create charges (photoconductor)

Charges are spatially encoded and directly transmitted to computer for image reconstruction

→ xray directly into electrical charge

Question 28

difference between the two types of digital radiography flat panel detectors

Answer 28

xray directly into readable electrical charge by selenium plate

xrays changed into visible light by scintillator then light into electric charge by photocathode, electrical charge processed by thin film transistor to computer

Question 29

how does charged couple detectors work

Answer 29

xray hit scintillator and turn into visible light

lens minification (reduction)

CCD converts light into electrical charge

electrical charge → computer

Question 30

why is minification needed in charged couple detectors

Answer 30

size of CCD is smaller then the plate. needs to be reduced to fit

Question 31

advantages of digital radiography

Answer 31

Wide dynamic range: e.g. 12 bit system → 2¹² possible gray values (0-4095) → MANY MORE THAN FILM-SCREEN RADIOGRAPHY!!!!!ž

Digital storage and retrieval

Lower radiation dose often possiblež

Distribution and reproduction of multiple exact copiesž

Workflow efficiency gain even for CRž

Post processingž

Telemedicine and Teleradiology

Question 32

CR or DDR

Answer 32

Computed Radiography: cheaper, takes longer- needs post processing

Direct Digital Radiography: faster

Question 33

flat panel

or

charged couple detectors

Answer 33

both are direct digital radiography and do not need post processing

CCD: minification can increase noise, can’t take at an angle, may increase dose of radiation cause less efficient then flat, less expensive

FT: can take at any angle, efficient, expensive, mobile

Question 34

Regarding digital radiography systems, which ONE of the following is FALSE:

Computed radiography systems are cheaper than flat panel systems

Computed radiography, flat panel systems and charged couple detectors systems all allow digital storage and retrieval of radiographs using a PACS system

Computed radiography, flat panel systems and charged couple detectors systems all produce images with thousands gray level values (wide dynamic range)

Radiographs obtained with digital systems can only be viewed on a computer monitor

Flat panel systems usually allow for more workflow improvement than computed radiography systems

Answer 34

Radiographs obtained with digital systems can only be viewed on a computer monitor

Question 35

With radiographic film‐screen systems, what is needed to reveal the latent image?

An intensifying screen

A computer monitor

A processor

A scintillator

A computer plate

Answer 35

A processor

Question 36

In a flat panel detector:

A scintillator is always present

X‐ray photons are always directly converted into electrical charges

A magnification process happens after exposure, in contrast with the minification process seen with CCDs

A charged couple detector spatially encodes and digitizes the informaion after conversion of the X‐ray photons into electrical charges

A thin film transistor spatially encodes and digitizes the information after conversion of the X‐ray photons into electrical charges

Answer 36

A thin film transistor spatially encodes and digitizes the information after conversion of the X‐ray photons into electrical charges