DR p1

Question 1

define elongation

Answer 1

type of distortion where anatomical parts appear bigger than norma

Question 2

define foreshortening

Answer 2

type of distortion where anatomical parts appear smaller than normal

Question 3

what aspect of RT does distortion impact

Answer 3

treatment planning

aren’t able to plan accurately

Question 4

image produced is dependent on 3 main things

Answer 4

pt factors - thickess, composition, pathology
exposure factors - kVp, mAs, distance
imagine system characteristics - high voltage gen, filtration, focal spot size

Question 5

digital vs analog

Answer 5

digital - 0s and 1s

analog - stream of info

Question 6

in the initial stages of digital detectors are signals analog or digital? what happens to them?

Answer 6

analog -packets of electronic current

they are converted by a ADC (analog to digital converter) during image readout

Question 7

the digital image is composed of tiny cells of numerical data in a _____ of ____ and ____

Answer 7

matrix
columns
rows

Question 8

each cell in a matrix is called a ____. they are the smallest elements of a digital image

Answer 8

pixel/picture element

Question 9

greater the number of pixels, the higher the _____

Answer 9

spatial resolution

Question 10

an image is described by how many ______ it contains

Answer 10

pixels

Question 11

what limits the spatial resolution?

Answer 11

pixel size

Question 12

can pixels represent multiple shades of grey?

Answer 12

no only one

Question 13

What is spatial resolution best at measuring

Answer 13

recorded detail

Question 14

what is each pixel assigned

Answer 14

a numerical value that corresponds to a shade of grey somewhere between white and black

Question 15

what is a voxel?

Answer 15

volume element (of the pixel)

Question 16

define dynamic range

Answer 16

range of grey scale values that can be assigned to each pixel

Question 17

does digital imagine have more or less spatial resolution than screen film

Answer 17

less spatial resolution

Question 18

what is special about the monitors displaying digital radiographic images

Answer 18

they have liquid crystal displays

Question 19

when an electric current passes through the liquid crystal display what happens

Answer 19

causes the molecules to change shape/direction

either letting light pass through or not (if necessary)

Question 20

what type of light do passive screens use

Answer 20

fluorescent light

Question 21

what type of light do active screens use

Answer 21

LED - light emitting diode

fyi - these are brighter, have superior contrast resolution, and better viewing angles then fluorescent

Question 22

define photometry

Answer 22

science of response of the human eye to visible light

Question 23

what are the 2 laws of photometry

define each

Answer 23

ISL - luminous intensity decreases in proportion to the inverse square of the distance from the source
Cosine law - maximum luminous intensity occurs when a monitor is viewed straight, luminous intensity and contrast decrease when viewing from an angle

Question 24

define DICOM

Answer 24

digital imaging and communication in medicine
protocol/standard to produce, manipulate, exchange, and store imaging data
used so that no data is lost through its transfer
data is viewed consistently

Question 25

what is GSDF

Answer 25

grey scale display function | allows for display of DICOM compatible device with consistent gray scale and appearance

Question 26

what are the 5 objectives of DICOM

Answer 26

``` RT images RT plan RTSS - pt anatomy RT dose RT treatment record ```

Question 27

define PACS

Answer 27

picture archiving and communication systems | universal system for DR images to be stored and transffered

Question 28

what are the 4 components of PACS

Answer 28

image acquisition display system network storage

Question 29

what does PACS improve

Answer 29

image interpretation, processing, viewing, storage and recall

Question 30

what are the 4 stages of digital radiography

Answer 30

image acquisition image processing image display image storage

Question 31

what are the 2 main classes of imaging systems

Answer 31

indirect and direct radiography

Question 32

define indirect radiography (CR)

Answer 32

phosphors react with xrays and store energy for a vrief time until processed

Question 33

define direct radiography

Answer 33

sensors detect radiation leaving the pt and send data to a computer in digital format

Question 34

what does PSP stand for what are other names it goes by what does it do

Answer 34

photostimulable phosphor detector systems aka storage phosphors or imaging plates PSP screen traps energy from xrays that can be read out later

Question 35

PSP + Cassette =

Answer 35

imaging plate

Question 36

CR cassettes and imaging plates also have integrated _____

Answer 36

grids

Question 37

in CR what happens to electrons

Answer 37

electrons are trapped in a higher energy metastable state inside the slate they then become stable in the reader

Question 38

what happens when the electron becomes stable in the reader

Answer 38

light is given off | this light is the signal that creates the images

Question 39

which is able to produce more shades of grey screen film or CR

Answer 39

CR (16000 while SF is only 32)

Question 40

computed radiography a) CONVERTS AN ANALOG SIGNAL TO DIGITAL b) CONVERTS A DIGITAL SIGNAL TO ANALOG c) HAS A PURE DIGITAL SIGNAL d) HAS A PURE ANALOG SIGNAL

Answer 40

a

Question 41

The image receptor used in CR is: a) Flat panel receptor b) Film c) Digital d) PSP screen

Answer 41

d

Question 42

Spatial resolution (in CR) is determined by: a. Distance b. kVp c. Number of pixels d. High voltage generator

Answer 42

c

Question 43

spatial resolution a. Is higher in screen-film radiography than digital b. Is limited by digital file size c. Allows us to see fine details d. All of the above

Answer 43

d

Question 44

Which of the following is not a part of PACS: a. A computer for image display b. An mRI computer c. A PET scan d. Hospitals mainframe

Answer 44

c