LRA-221 Review

Question 1

conventional radiography is also known as -

Answer 1

fil screen / intensifying screen

Question 2

CR or computed radiography is also known as -

Answer 2

PSP (photostimulable phosphor)

Question 3

When acquiring an image using DR (Direct radiography), we need to use-

Answer 3

phosphor on a phosphor plate

Question 4

what type of phosphor is used in PSP (photostimulable phosphor) or phosphor plate?

Answer 4

barium fluorohalide

Question 5

define photoconductor

Answer 5

• are materials that absorb x-rays, resulting in an electrical charge
• a substance that allows an electrical current to move more easily through it after light shines on it

Question 6

define scintillator

Answer 6

• phosphors that produce light when absorbing x-rays

Question 7

define exposure latitude

Answer 7

• the range of exposures that can be recorded as useful densities on a radiographic film for interpretation
• ## Latitude refers to the range of exposure diagnostic image values the image detector is able to produce

Question 8

define look-up table (LUT)

Answer 8

• look-up table (LUT) is a histogram of the luminance values derived during image acquisition.
• The LUT is used as a reference to evaluate the raw information and correct the luminance values
• This is a mapping function in which all pixels (each with its own specific gray value) are changed to a new gray value

Question 9

sensitivity speck

Answer 9

• absorbs ejected electrons
• a place in silver halide crystal where latent image is formed, can also trap electrons
• When the X-rays strike the intensifying screen, light is produced
• The light photons and X-ray photons interact with the silver halide grains in the film emulsion, and an electron is ejected from the halide.
• The ejected electron is attracted to the sensitivity speck.

Question 10

define PAC

Answer 10

• picture archiving and communication
• where images are stored/archived
• network group of computers, servers, and archives that can be used to manage digital images

Question 11

define DICOM

Answer 11

• standards that allow imaging modalities and PACS to communicate in the same “language”
• made it possible for different manufacturers to communicate
• different departments can communicate with each other
• can send off images to different departments
• associated w/ PACS

Question 12

define Matrix

Answer 12

• a square arrangement of numbers (pixel values) in columns and rows and in digital imaging, the numbers correspond to discrete pixel values.

Question 13

define pixels

Answer 13

• picture element
• is the smallest element in a digital image
• contains the smallest divisible component of a digital image

Question 14

define exposure index

Answer 14

the amount of exposure received by the image receptor (IR), not by the patient

Question 15

define deviation index

Answer 15

• the difference between the actual exposure (KIND) and the target exposure (KTGT)
• help the technologist determine whether the image has been underexposed or overexposed
• If the DI is negative, the image has been underexposed.
• If the DI is positive, the image has been overexposed.

Question 16

define contrast resolution

Answer 16

• the ability of the digital system to display subtle changes in the shade of gray.
• digital imaging is directly related to the bit depth of the pixels in the image.

Question 17

define spatial resolution

Answer 17

The ability of the imaging system to demonstrate small details of an object

Question 18

define dynamic range

Answer 18

the ability to respond to varying levels of exposure more tissue densities on the digital image are seen, giving the appearance of more detail

Question 19

define histogram

Answer 19

• a graph representing the range of exposure values recorded by the IR
• representation of the numerical data

Question 20

define rescaling

Answer 20

images are produced with uniform brightness and contrast, regardless of the amount of exposure used to acquire the image

Question 21

define edge enhancement

Answer 21

occurs when fewer pixels in the neighborhood are included in the signal average.

Question 22

define masking

Answer 22

Suppressing frequencies, also known as masking, can result in the loss of small details

Question 23

define low pass filtering

Answer 23

• also known as smoothing
• smoothing occurs by averaging each pixel’s frequency with surrounding pixel values to remove high-frequency noise.
• result is a reduction of noise and contrast
• Low-pass filtering is useful for viewing small structures such as fine bone tissues.

Question 24

define high pass filtering

Answer 24

• When the frequencies of areas of interest are known, those frequencies can be amplified and other frequencies suppressed
• increases contrast and edge enhancement
• useful for enhancing large structures such as organs and soft tissues, but it can be noisy

Question 25

define FPD (flat panel detector)

Answer 25

• systems use an X-ray absorber material coupled to a thin-film transistor (TFT), complementary metal oxide semiconductor (CMOS), or charge-coupled device (CCD) to form the image.
• indirect capture and direct capture

Question 26

define CR (conventional radiographic dynamic range)

Answer 26

• the number of recording densities
• more tissue densities on the digital radiograph are seen, giving the appearance of more detail

Question 27

define spatial resolution

Answer 27

• the amount of detail present in any image

Question 28

define raster

Answer 28

zig zag motion

Question 29

define latent image

Answer 29

image that is not visible due to the image not being processed

Question 30

analog is the same as -

Answer 30

conventional (film screen radiograph)

Question 31

If the CR is stored in a cassette too long, what happens to the image?

Answer 31

• it disappears
• the longer the electrons are stored, the more energy the electrons lose
• if energy is lost, the low energy electrons will not be stimulated enough to escape the active layer, and information will be lost

Question 32

true or false: computed radiography is very similar to conventional radiography?

Answer 32

• true
• they both use cassettes to capture the image (latent image)

Question 33

what is the difference between computed and conventional radiography?

Answer 33

computed:
- digitizes an image
- needs to be processed
- is digitized in the reader

Question 34

is a PSP system, how do we release the latent image?

Answer 34

• use a laser

Question 35

for conventional radiography, what impacts magnification?

Answer 35

• OID (object to image distance)`

Question 36

for direct radiography, what impact magnification?

Answer 36

• OID
• tech is able to adjust it by either zooming in or zooming out