Ch 13

Question 1

System used to consistently control the amount of radiation reaching the image receptor by terminating the length of exposure

Answer 1

AEC

Question 2

what determines the exposure time

Answer 2

AEC

Question 3

When does AEC terminate

Answer 3

when’s predetermined amount of radiation has been detected

Question 4

two types of AEC

Answer 4

pho timers and ionization chambers

Question 5

refers to the use of an AEC device that uses photomultiplier tubes or photodiodes , and aren’t common today

Answer 5

photo timers

Question 6

hollow cell that contains air and is connected to the timer circuit via electrical wires.

Answer 6

ionization chamber

Question 7

why are ionization chamber aec devices considered to be entrance type devices ?

Answer 7

because they are positioned in front of the image receptor

Question 8

AEC devices that measure the amount of radiation transmitted

Answer 8

detectors/ chambers/ cells

Question 9

what used a fluorescent screen

Answer 9

photimers

Question 10

what used a fluorescent screen and a device that converted the light to electricity

Answer 10

phototimers

Question 11

electronic device that converts visible light energy into electrical energy

Answer 11

photomultiplier tube

Question 12

where are phototimer aec devices placed

Answer 12

behind the image receptor

Question 13

how do photimers work?

Answer 13

radiation reaches fluorescent light paddles producing visible light and PM tubes convert the light into electricity which trips the timer and exposure is terminated

Question 14

how do ionization chamber aec work

Answer 14

radiation interacts either detectors and the air inside becomes ionized creating an electrical charge. the charge travels along the timer circuit and the timer is tripped, terminating exposure

Question 15

which is less accurate
photo timers or ionization chambers

Answer 15

ionization chambers

Question 16

what does AEC control

Answer 16

quantity of radiation reaching the image receptor

Question 17

refers to the shortest exposure time that a system can produce

Answer 17

minimum response time

Question 18

what is the minimum response time for modern AEC systems

Answer 18

1 ms

Question 19

refers to the maximum amount of time the x ray exposure continues when using an AEC system

Answer 19

backup time

Question 20

acts as a safety mechanism when AEC fails

Answer 20

back up timer

Question 21

back up timer should be set at what percentage of the expected exposure time

Answer 21

150%-200%

Question 22

what are the density control button numbers?

Answer 22

-2, -1, 1, 2, and 3

Question 23

why shouldn’t toddlers be used for AEC

Answer 23

because they’re probably too small to even cover the detectors

Question 24

Refers to a radiographic system that allows the radiographer to select a particular button on the control panel that represents an anatomic area for which a preprogram set of exposure factors are displayed and can be selected

Answer 24

Anatomically program technique

Question 25

what’s an example of ANATOMIC programming

Answer 25

the difference in technique for an abdomen compared to a chest

Question 26

why is AEC calibration important

Answer 26

to ensure consistent and appropriate exposures to the receptor are being produced

Question 27

reproducibility for changes in exposure

Answer 27

5%

Question 28

reproducibility for pixel brightness levels

Answer 28

30%

Question 29

preestablish guidelines used by the radiographer to set standardized, manual, or AEC exposure factors for each type of radiographic examination

Answer 29

exposure technique chart

Question 30

Devices that measure part thickness

Answer 30

Calipers

Question 31

Based on the concept that KVP can be increased as the anatomic part size increases

Answer 31

variable kVp fixed mAs

Question 32

baseline kVp for variable kVp fixed mAs is increased by ___for every 1 cm increase in part thickness

Answer 32

2

Question 33

VARIABLE KVP FIXED MÁS
increase from 10 CM to 18 at 63 kVp
what would new kVp be

Answer 33

79
63+2 eight times

Question 34

VARIABLE MAS FIXED KVP
for every _________ cm change in thickness the mas should be adjusted by a factor of 2

Answer 34

4-5 cm

Question 35

is fixed kvp or variable kvp better

Answer 35

fixed kvp

Question 36

what happens when you do not collimate when using AEC

Answer 36

more scatter reaches AEC termination exposure early

Question 37

pediatric patient consideration

Answer 37

may not be able to cover detectors so manual technique with a shorter exposure time should be used

Question 38

geriatric patient considerations

Answer 38

may need decreased technique and short exposure time

Question 39

bariatric considerations

Answer 39

may need increase in technique, use of grid to control contrast

Question 40

does fiberglass require a change in technique

Answer 40

NO

Question 41

do plaster casts require an increase in technique

Answer 41

YES

Question 42

Diseases or conditions that decrease the absorption characteristics of the part, making that part less difficult to penetrate

Answer 42

Destructive diseases

Question 43

Diseases or conditions that increase the absorption characteristics of the part, making that part more difficult to penetrate

Answer 43

Additive diseases

Question 44

if the patient has an additive disease, what do we do with the KVP?

Answer 44

increase

Question 45

Examples of positive contrast agents

Answer 45

Barium and iodine

Question 46

Examples of negative contrast agent

Answer 46

air

Question 47

Do positive contrast agents produce more or less brightness

Answer 47

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