finals L7

Question 1

most important patient protection characteristic og a radiographic imaging system

Answer 1

filtration

Question 2

state statutes require that general purpose of radiographic units have a minimum total filtration of ___

Answer 2

2.5 mm Al

Question 3

filtration is measured through ___ of the xray beam

Answer 3

half value layer HVL

Question 4

filtration frequency

Answer 4

annually or anytime a change has occurred in the xray tube or tube housing

Question 5

Most systems today are equipped with _____ collimators

Answer 5

positive beam-limiting (PBL)

Question 6

• x-ray field must coincide with the
  light field of the variable-aperture
  light-localizing collimator.
• these fields are misaligned, the intended anatomy will be missed and unintended anatomy irradiated.

Answer 6

collimation

Question 7

(collimation) Distance and centering indicators must be accurate to within ___ of the source-to-image receptor distance (SID).

Answer 7

2% and 1%

Question 8

(collimation) distance indicator can be checked simply with a ___
location of the focal spot is usually marked on the ___

Answer 8

tape measure
x-ray tube housing.

Question 9

• determines the spatial resolution of a radiographic imaging system.

Answer 9

focal spot size

Question 10

3 tools are used for measurement of a focal-spot size:

Answer 10

pinhole camera
star pattern
slit camera

Question 11

difficult to use and requires excessive exposure time.

Answer 11

pinhole camera

Question 12

easy to use but has significant limitations for FS sizes less than 0.3 mm

Answer 12

star pattern

Question 13

standard for measurement of effective FS size

Answer 13

slit camera

Question 14

focal spot size frequency

Answer 14

annually or whenever an xray tube is replaced

Question 15

alternative to focal spot size measurement is the use of ____ to determine limiting spatial frequency

Answer 15

line pair test tool

Question 16

kvp calibration frequency

Answer 16

annually or whenever high-voltage generator components have changed significantly

Question 17

measured kVp should be within ___ of the indicated kVp.

Answer 17

10%

Question 18

variation in kVp of approximately __ is necessary to affect image optical density and radiographic contrast.

Answer 18

4%

Question 19

• operator selectable on most radiographic consoles.
• particularly responsible for patient radiation dose and image optical density.

Answer 19

exposure time

Question 20

exposure time accuracy frequency

Answer 20

annually or more frequently if a component of the console has undergone major repairs

Question 21

Accuracy of __ is acceptable for exposure times of 10 ms or less.

Answer 21

20%

Question 22

Automatic exposure control (AEC) must also be evaluated. It is done by exposing an IR through various thicknesses of ____

Answer 22

aluminum or acrylic

Question 23

I(exposure time) nsertion of a ___ allows one to adequately assess the functioning of the backup timer.

Answer 23

lead filter

Question 24

If the phototimer fails, the backup timer should terminate the exposure at ___, whichever occurs first

Answer 24

6s or 600 mAs

Question 25

- ability of a radiographic unit to produce a constant radiation output for various combinations of mA and exposure time - determined by a precision radiation dosimeter that measures radiation intensity at various combinations of mA and exposure time.

Answer 25

exposure linearity

Question 26

(exposure linearity) radiation output for adjacent mA stations should be within

Answer 26

10%

Question 27

exposure linearity frequency

Answer 27

annually or after significant change or repair of operating console

Question 28

method of assessing exposure linearity is valid or not valid if the exposure timer is inaccurate

Answer 28

not valid

Question 29

(exposure linearity) the mGy /mAs value should be within ___ between adjacent mA stations.

Answer 29

10%

Question 30

Two methods are used to evaluate exposure reproducibility:

Answer 30

- One makes a series of at least three exposures at the same technique factors, having changed technique controls between each exposure. - If the result is not reproducible, this is usually the result of error in the kVp control.

Question 31

filtration tolerance

Answer 31

> 2.5 mm Al

Question 31

exposure reproducibility - Mathematical formulas can be used to determine reproducibility in both instances. - These formulas basically require that output radiation intensity should not vary by ___

Answer 31

more than plus or minus 5%.

Question 32

Two methods are used to evaluate exposure reproducibility:

Answer 32

One can select a combination of technique factors and hold them constant for a series of 10 exposures.

Question 32

collimation frequency

Answer 32

semiannually

Question 33

collimation tolerance

Answer 33

+2% SID

Question 33

focal spot size tolerance

Answer 33

+50%

Question 33

calibration of kvp tolerance

Answer 33

+10%

Question 34

exposure time accuracy tolerance

Answer 34

+5% > 10 ms + 20% < 10ms

Question 34

exposure linearity tolerance

Answer 34

+10%

Question 35

exposure reproducibility tolerance

Answer 35

+5%