ASRT Digital Imaging Module 1

Question 1

Primary Beam consists of photons of __________ energies. With different abilities to ____________.

Answer 1

1. varying

2. penetrate tissue in a patient

Question 2

The tissues in the human body have varying abilities to _______ or _______ x-ray photons.

Answer 2

attenuate or absorb

Question 3

The beam containing useful and diagnostic information is the _____________.

Answer 3

remnant beam

Question 4

In film imaging, the chemical interactions are between the _____________ and the _____________.

Answer 4

1. processing solutions

2. emulsion/recording layer (of the film)

Question 5

Digital images allow us to see structures that would have required ______________ with film technology.

Answer 5

additional imaging

Question 6

Film screen is always considered __________.

Answer 6

analog

Question 7

Analog IR has 3 components.

Answer 7

1. cassette
2. intensifying screen
3. film

Question 8

In analog, the _______ is the recording device.

Answer 8

film

Question 9

the _____________________ turn x-rays into light, which in turn makes up the latent image.

Answer 9

intensifying screens

Question 10

Film digitizers are ______ efficient in measuring slight changes in film opacity.

Answer 10

very

Question 11

The ______________________ changes the continuous signal into a discrete signal.

Answer 11

ADC (analog-to-digital converter)

Question 12

The process of assigning numeric values to a signal is _______________.

Answer 12

quantization

Question 13

The number of gray levels in a bit depends on its ____________.

Answer 13

bit depth

Question 14

formula for calculating bit depth

Answer 14

2^x = # of shades of gray

Question 15

bit depth for ADC used in diagnostic imaging is _________

Answer 15

12-32

Question 16

The ability to distinguish objects adjacent to each other is measured with _________________.

Answer 16

line pairs per millimeter

Question 17

higher resolution = individual lines are ____________

Answer 17

separate and distinct

Question 18

How is pixel size is measured?

Answer 18

from side to side of a single pixel

Question 19

How is pixel pitch measured?

Answer 19

from the center of one pixel to the center of an adjacent pixel

Question 20

A typical matrix size for a digital radiograph is _______ x _______ with a bit depth of ____.

Answer 20

3000 x 3000; bit depth of 12

Question 21

A typical matrix size for CT is _____ x _____ with a bit depth of ___.

Answer 21

512 x 512; bit depth of 16

Question 22

2 types of Photostimulable Phosphor plate systems

Answer 22

cassette-less and cassette-based

Question 23

2 types of Flat-Panel Receptors

Answer 23

scintillator based and nonscintillator based

Question 24

Define scintillation (in radiography) and its process

Answer 24

the ability of a material to absorb x-ray energy and produce light; the light is then converted to electrons which create an image

Question 25

3 important parameters used to assess performance of receptors

Answer 25

1. absorption efficiency 2. conversion efficiency 3. detective quantum efficiency (DQE)

Question 26

What does Absorption Efficiency measure?

Answer 26

the percent of energy that strikes a receptor that is actually absorbed

Question 27

What does Conversion Efficiency measure?

Answer 27

the percent of energy absorbed by the receptor that is converted to usable output

Question 28

What is Detective Quantum Efficiency?

Answer 28

DQE is a product of absorption and conversion efficiencies

Question 29

What are the two types of phosphor types for PSP?

Answer 29

1. Turbid (randomly distributed) | 2. Needle (columnar)

Question 30

Needles have less __________ ___________ when compared to columnar. This helps improve ________ ________.

Answer 30

1. light divergence | 2. spatial resolution

Question 31

How long can a latent image remain on a PSP detector?

Answer 31

several hours (roughly 8)

Question 32

PSP latent image can lose ___% of its energy in ___ hours.

Answer 32

25% in 8 hours

Question 33

What holds the electrons elevated in the higher energy state?

Answer 33

conductive band

Question 34

Where do the electrons go while in the resting state?

Answer 34

valence band

Question 35

T/F: The reader's laser light releases all electrons from the F-Trap.

Answer 35

False, some are left behind

Question 36

As the plate travels thru the reader, how is the laser light set up?

Answer 36

it is pointed towards an optic scanner

Question 37

Newer plate readers are line-scan devices which have ______ _______ in a row.

Answer 37

several lasers

Question 38

The newest type of PSP reader is the ___________.

Answer 38

dual-sided

Question 39

Step-by-step process of signal conversion (starting with light emitted from electrons in F-trap)

Answer 39

1. photodetector captures light from PSP plate 2. converts light intensities to electronic signal 3. signal sent to ADC 4. signal undergoes sampling and quantization

Question 40

Photoconductive material used for (1) scintillator-based and (2) non-scintillator-based

Answer 40

1. Amorphous Silicon (aSi) | 2. Amorphous Selenium (aSe)

Question 41

TFT

Answer 41

Thin-Film Transistors; complex circuit device that collects electrons

Question 42

DELs

Answer 42

detector elements of TFT array; a DEL collects electrons that represent the exposure level

Question 43

Fill Factor

Answer 43

used to assess the quality of the FPD; a ratio of the radiation-sensitive area to the non-. 80% Fill Factor means 80% of the detector area is devoted to sensing radiation

Question 44

Fill Factor affects a detector's ______ and _______.

Answer 44

1. spacial resolution | 2. signal-to-noise ratio

Question 45

Noise affects the observer's ability to perceive ______ ______ within an image.

Answer 45

structural details

Question 46

Indirect TFT systems are cassette based. The cassette's scintillator system is made of _________ or ________.

Answer 46

Cesium Iodide or Gadolinium OxiSolfate

Question 47

T/F: CCD requires a scintillator.

Answer 47

true; can be CsI or GdOS

Question 48

3 Advantages of CCD receptors

Answer 48

1. wide range of exposure settings 2. respond to lower light levels from scintillator 3. produces images quickly and instantly refreshes for the next image (good for fluoro)

Question 49

4 steps for CCD image capture

Answer 49

1. scintillator converts x-rays to light 2. light photons reflect off mirror to focusing lens which get directed to CCD 3. CCD converts light signal to electrical signal 4. electrical signal is sent to ADC

Question 50

In a CMOS detector, the light from the scintillator is directed to the CMOS by a ______________.

Answer 50

fiber-optic cable

Question 51

If a detector has a higher spatial frequency, it represent a _________ number of viewable objects on an image

Answer 51

larger

Question 52

Spatial Resolution is measured in _________ per _____

Answer 52

Line Pairs per mm

Question 53

The _________ determines the line pairs per mm we can see.

Answer 53

size of the pixels

Question 54

Better recorded detail (resulting from higher sampling frequency) is ideal for __________ exams.

Answer 54

extremity

Question 55

For ____________ detector, the size of the detector determines spatial resolution.

Answer 55

flat-panel detector

Question 56

1. DEL size of 200 microns = spatial resolution of _____ | 2. 100 microns =

Answer 56

1. 2.5 Lp/mm | 2. 5 Lp/mm

Question 57

T/F: PSP w/200 micron pixels = FPD w/DEL of 200 however, PSP w/100 does not equal FPD w/100

Answer 57

true

Question 58

Nyquist Frequency/Theorem

Answer 58

determines level of spatial resolution for IR

Question 59

Analog receptors produce acceptable images between ___% underexposed to ___% overexposed.

Answer 59

30% under, 50% over

Question 60

Digital receptors produce acceptable images between ___% underexposed to ___% overexposed.

Answer 60

50% under, 100% over

Question 61

The only visual cue a tech has to indicate underexposure is _____ _____.

Answer 61

quantum noise (50%+ underexposed)

Question 62

For a digital image overexposed, ________ ________ is decreased.

Answer 62

image contrast (100%+ overexposed)