Unit 4: Image Brightness/ABC/Mag. and Fluoro + Pt Exposure and AEC

Question 1

what is flux gain?

Answer 1

a ratio of the number of light photons produced at the OP screen to the number of x-rays absorbed by the IP screen

Question 2

what is the formula for flux gain?

Answer 2

numberof output light photons/number of input x-ray photons

Question 3

what is minification gain?

Answer 3

the ratio of the square of the IP screen diameter to the square of the OP screen diameter

Question 4

What is the formula for minification gain?

Answer 4

(Di/Do)^2

Question 5

OP screen diameter is usually:

IP screen diameter varies from:

Answer 5

1 inch (2.5 cm)

9-25 or 30 cm

Question 6

what determines how much brighter an image will be at the OP screen?

Answer 6

minification gain

Question 7

what is brightness gain?

Answer 7

the ability of an II tube to increase the illumination of an image

Question 8

brightness gain =

Answer 8

minification gain x flux gain

Question 9

the brightness gain of most II tubes is:

Answer 9

5000 - 30,000

Question 10

brightness gain is now called _________________ and is measured in _______________.

Answer 10

Conversion Factor

candela per squared meter (cd/m^2)

Question 11

What is Automatic Brightness Control (ABC)?

Answer 11

brightness controlled by and altered by the machine varying the kVp, mA, or both

Question 12

ABC is designed to compensate for changes in what?

Answer 12

tissue density

Question 13

what is the purpose of ABC?

Answer 13

to maintain image brightness on the display monitor

Question 14

For a fluoro system equipped with ABC mechanism and where the x-ray tube is fixes below the table, moving the image intensifier away from the pt will:

Answer 14

increase pt dose

Question 15

The function of an ABC mechanism of an image intensified fluoro system is to:

Answer 15

maintain a fixed dose rate to the image intensifier

Question 16

the greater the voltage supplied to the electrostatic lenses, the greater the ____________ and closer the ______ ______ moves toward the IP screen. This causes ______________.

Answer 16

acceleration; focal point; magnification

Question 17

image magnification during fluoro is controlled by:

Answer 17

varying the voltage on the electrostatic lenses

Question 18

Which of the following will occur if voltage to the electrostatic lenses increase?

Answer 18

magnification

Question 19

viewing the fluoroscopic image in magnification mode increases:

Answer 19

mA
spatial resolution
pt dose

Question 20

what determines the location of the focal point and the FOV?

Answer 20

IP screen diameter

Question 21

what are advantages of fluoro mag mode?

Answer 21

better spatial resolution
less image noise
less vignetting

Question 22

what are disadvantages of fluoro mag mode?

Answer 22

increased pt dose
reduced FOV

Question 23

what is the weakest link in the fluoro imaging chain?

Answer 23

monitor

Question 24

what increases during mag?

Answer 24

MTF

Question 25

image blur caused by moving the tube rapidly during a fluoro exam is due to:

Answer 25

camera tube lag

Question 26

collimation, intermittent exposure, removal of grid, LIH, dose spreading, beam hardening, pulsed exposure, and cumulative timer are all:

Answer 26

dose reduction techniques in fluoro

Question 27

last image hold is a:

Answer 27

dose-saving feature

Question 28

what is dose spread?

Answer 28

method that spreads the max dose over a broader area of the pt’s skin

Question 29

some reduction of max skin dose can be achieved by rotating the fluoroscope about a ____________ within the anatomy of interest.

Answer 29

centimeter

Question 30

during dose spread, the angle is changed to:

Answer 30

expose different tissue

Question 31

increasing kVp will create a:

Answer 31

harder beam

Question 32

maintaining the highest kVp that will provide acceptable image contrast leads to:

Answer 32

lower skin dose

Question 33

beam energy primarily depends on the _____ selected and the amount of _________ in the beam

Answer 33

kVp; filtration

Question 34

for beam hardening, you need to:

Answer 34

increase kVp and lower mA

Question 35

filtration reduces:

Answer 35

skin dose

Question 36

how much did an addition of 0.1-0.3 mm of copper reduce skin dose?

Answer 36

30-50%

Question 37

size distortion is primarily caused by _____ during fluoro.

Answer 37

OID

Question 38

to have the lowest dose to the pt, have the IR:

Answer 38

right on top of the pt

Question 39

What is a consequence of using “low dose” during fluoroscopy?

Answer 39

quantum mottle

Question 40

during fluoro, which will produce the greatest amount of scatter?

Answer 40

patient

Question 41

in the non-mobile fluoro unit, the x-ray tube moves with the:

Answer 41

image intensifier

Question 42

The back-up timer is typically set at

Answer 42

5 mins

Question 43

before continuation of fluoro what should be done if the timer goes off?

Answer 43

timer should be reset

Question 44

AEC stands for:

Answer 44

automatic exposure control

Question 45

modern equipment uses ionization chambers introduced by _________________ in _____

Answer 45

Russell H. Morgan; 1942

Question 46

Where are AEC detectors located?

Answer 46

in between the pt and IR

Question 47

what is crucial when it comes to AECs and ionization chambers?

Answer 47

positioning

Question 48

plastic inserts for collimators are only accurate at:

Answer 48

the intended SID

Question 49

collimation should be avoided when located:

Answer 49

close to activated chambers

Question 50

Collimating within the field of an AEC receptor will result in?

Answer 50

overexposure

Question 51

inadequate collimation may result in:

Answer 51

light image

Question 52

what is the max exposure per US Public Law?

Answer 52

mAs

Question 53

modern minimum reaction time to terminate exposure in AEC:

Answer 53

.001 seconds

Question 54

for density controls: 0 = -1 = -2 = +1 = +2 =

Answer 54

normal 25% decrease in exposure 50% decrease in exposure 25% increase in exposure 50% increase in exposure

Question 55

poor positioning skills result in increased ___________ when using AEC?

Answer 55

repeat rate

Question 56

What does “APR” stand for?

Answer 56

anatomically programmed radiography

Question 57

What is “APR”?

Answer 57

system that allows radiographer to select a button that represents anatomic area with exposure factors for that area

Question 58

Having the outer cells on during a lateral chest will result in?

Answer 58

underexposure

Question 59

Having only the center cell of the AEC activated for a PA chest will result in?

Answer 59

overexposure

Question 60

the safety features of a fluoro unit do not include what?

Answer 60

high grid ratio