physics 1 review/ ch. 26-27

Question 1

all factors affect radiographic quality except:

Answer 1

• OID
• focal spot size
• motion
• angle

Question 2

all factors affect spatial resolution except:

Answer 2

• mAs/kVp
• beam restriction
• anode heel effect

Question 3

what factors affect contrast:

Answer 3

• kVp
• OID
• beam restriction
• patient factors

Question 4

what factors affect distortion:

Answer 4

• OID/SID
• Patient factors

Question 5

As filtration increases, kvp ___ and mAs ___

Answer 5

increases; decreases

Question 6

what 2 things does beam restriction do

Answer 6

• reduce patient dose
• improve contrast

Question 7

described as the variation of intensity towards the anode compared to the cathode and the thickest part of anatomy should be on the cathode end

Answer 7

anode heel effect

Question 8

an increase in spatial resolution is directly proportional to a ____ in OID

Answer 8

decrease

Question 9

where is the actual focal spot

Answer 9

on the anode

Question 10

smaller anode angle gives better resolution by ___ the effective focal spot

Answer 10

decreasing

Question 11

misalignment of the tube, part or receptor can affect…

Answer 11

spatial resolution

Question 12

distortion depends on

Answer 12

object thickness, position and shape

Question 13

insufficient techniques cause ___ on the image

Answer 13

mottle

Question 14

what is in the high voltage circuit

Answer 14

step-up transformer and mA meter

Question 15

ripple of the three-phase 6 pulse

Answer 15

13-14%

Question 16

ripple of three-phase 12 pulse

Answer 16

4%

Question 17

primary function of the transformers

Answer 17

adjust voltage

Question 18

what is the last step of the circuit

Answer 18

rectifier

Question 19

what are the external components of the x ray tube

Answer 19

• protective housing
• glass enclosure

Question 20

internal components of the tube

Answer 20

cathode and anode

Question 21

what is anode made up

Answer 21

tungsten with renium

Question 22

requirements of x-ray production

Answer 22

• source of electrons
• way to accelerate electrons
• way to decelerate electrons

Question 23

by standardizing routine projections the probability of errors is

Answer 23

reduced and the cause for errors is narrowed

Question 24

what are the three general areas in which standardization should be sought

Answer 24

• projections
• exposure factors
• image processing

Question 25

what is the most conducive approach for digital imaging

Answer 25

variable kVp

Question 26

approach in which only one variable is changed from projection to projection

Answer 26

fixed kVp

Question 27

3 goals of the fixed kVp are

Answer 27

- assure sufficient penetration - keep image contrast consistent - simplify and standardize for accuracy

Question 28

approach in which both kVp and mAs are adjusted

Answer 28

variable kVp

Question 29

thin patients require a ___ in mAs

Answer 29

decrease

Question 30

as kVp increases, patient dose...

Answer 30

decreases

Question 31

the minimum kVp is the lowest kVp that still provides some degree of penetration

Answer 31

optimum kVp

Question 32

for every 15% change of kVp, adjust the mAs by a factor of

Answer 32

2

Question 33

what the minimum amount to change the mAs for a noticeable difference

Answer 33

35%

Question 34

approach in which a proper technique can be derived from a technique of another body part

Answer 34

proportional anatomy approach

Question 35

advantages of using technique charts

Answer 35

reduce exposure errors and patient exposure

Question 36

what is the 4 cm rule

Answer 36

double technique for an increase of 4 cm and half for a reduction of 4 cm

Question 37

3 advantages of AEC

Answer 37

- achieve more consistent exposures - reduce repeats - decrease radiation exposure

Question 38

earlier AEC's were employed using a ____, while modern AEC's use ___

Answer 38

fluorescent screen; gas ion chamber

Question 39

what kind of patients absorb more radiation

Answer 39

larger pts

Question 40

what does a thyraton include

Answer 40

- cathode filament - anode plate - one or more grids

Question 41

when does a "short" occur

Answer 41

when a sufficient number of ions and electrons are present

Question 42

AEC only controls what 2 things

Answer 42

exposure time and total mAs

Question 43

if the kVp is insufficient, what kind of exposure time is needed

Answer 43

longer

Question 44

the minimum amount of time it takes for the electric circuit to detect and react to radiation

Answer 44

minimum response time

Question 45

what are 2 reasons for using the back up mAs

Answer 45

- to prevent excessive heat overload of the anode - to prevent excessive radiation exposure to the patient

Question 46

the back up time should never be set to more than

Answer 46

2 times the expected exposure time

Question 47

the maximum length of time x-ray exposures continue when using AEC

Answer 47

preset automatic back up mAs

Question 48

increases or decreases the preset sensitivity of the thyratron by specific percentages

Answer 48

intensity control

Question 49

what is one of the most common causes for resetting the intensity control

Answer 49

inaccurate positioning

Question 50

what is the solution