Textbook - Chapter 3 + 4

Question 1

what is interpolation?

Answer 1

mathematical method of creating missing data

Question 2

what are the 4 principal components of a computer?

Answer 2

input, output, central processing unit and memory

Question 3

what are examples of input devices?

Answer 3

keyboard, mouse, touch-sensitive plasma screen, and CT detector mechanism

Question 4

what are examples of output devices?

Answer 4

monitor, laser camera, printer and archiving equipment

Question 5

what is the cpu?

Answer 5

the part of the system that interprets the computer program instructions and sequence tasks

Question 6

what are the three principle types of solid-state memory?

Answer 6

1. rom
2. ram
3. worm

Question 7

which type of solid-state memories are part of the system’s primary memory?

Answer 7

1. rom
2. ram

Question 8

what are rom used for?

Answer 8

• imprinted at the factory
• stores frequently used instructions to start the system

Question 9

what are ram used for?

Answer 9

• has instructions that are frequently changed

Question 10

image reconstruction

Answer 10

use of raw data to create an image

Question 11

attenuation profile

Answer 11

system accounting for the attenuation properties of each ray sum and correlating it with the position of the ray

Question 12

ray

Answer 12

path the x-ray beam takes from tube to detector

Question 13

ray sum

Answer 13

detector senses each arriving ray and measure how much of the beam has been attenuated

Question 14

views

Answer 14

compete set of ray sums

Question 15

back projection

Answer 15

compilation of information from all the attenuation profiles to create an image

Question 16

what are some drawbacks to back projection?

Answer 16

it produces a streak artifact in a star pattern

Question 17

how do you minimize streak artifacts?

Answer 17

filters

Question 18

filters are applied to only ______ data.

Answer 18

raw

Question 19

SFOV

Answer 19

determines the area that the raw data is acquired

Question 20

out-of-field artifacts

Answer 20

when parts of the patient is outside the SFOV causing inaccuracies in the images

Question 21

DFOV

Answer 21

section of data selected to be displayed on the image

Question 22

too large DFOV = image to be _______

Answer 22

small

Question 23

small images due to too large of a DFOV will result in?

Answer 23

• more data in each pixel = decrease in spatial resolution

Question 24

CT display monitor

Answer 24

used to display patient information, scan protocol data, provides many graphic aids to assist in image interpretation

Question 25

DAC

Answer 25

digital to analog converters

Question 26

what do DACs do?

Answer 26

change the digital signal from computer memory back to analog so the image can be displayed on the monitor

Question 27

multiformat cameras

Answer 27

transfers images displayed on monitors to film

Question 28

laser cameras

Answer 28

bypasses putting the image onto the display monitor and transfers it directly to the film

Question 29

window width

Answer 29

determines the quantity of HUs represented as shades of gray on a specific image

Question 30

if the value is higher than the selected range of the window width, what colour will the object be?

Answer 30

white

Question 31

if the value is lower than the selected range of the window width, what colour will the object be?

Answer 31

black

Question 32

window level

Answer 32

selection of HUs that are displayed on the image

Question 33

what should the window level be set at?

Answer 33

a point where the value of the average attenuation number is similar to that of the tissue of interest

Question 34

why is it good practice to widen the window width if a patient is obese or have metallic artifacts?

Question 34

what does a wider window width do?

Answer 34

- increases anatomic diversity - decreases image contrast

Question 35

what size of window width is good for metallic artifacts and obese patients?

Answer 35

wider window widths

Question 36

what size of window width is good for tissues of similar densities like the brain?

Answer 36

lower/narrow window widths

Question 37

what does a narrower window width do?

Answer 37

provides greater density discrimination and contrast

Question 38

dual window setting

Answer 38

when two images of different window widths are superimposed on each other to create a single image