Ch 5 The X-Ray Imaging System

Question 1

fluoroscopic couches tilt ___ to the foot side and ___ to the head side

Answer 1

90; 30

Question 2

3 parts of the x-ray system:

Answer 2

x-ray tube, operating console & high-voltage generator

Question 3

radiation quantity:

Answer 3

the number of x-rays or intensity of the x-ray beam, mGya or mGya/mAs

Question 4

radiation quality:

Answer 4

penetrability of the beam, kVp or half-value layer (HVL)

Question 5

most x-ray imaging systems operate on ___ of power

Answer 5

220V

Question 6

voltage can vary by as much as ___

Answer 6

5%

Question 7

line compensator:

Answer 7

measures the voltage provided to the x-ray imagining system and adjusts that voltage to 220V

Question 8

the power supplied to the x-ray system is first delivered to the _____

Answer 8

autotransformer

Question 9

*the autotransformer has a ____ and is designed to ___

Answer 9

single winding and is designed to deliver precise voltage to the filament circuit

Question 10

in the autotransformer the voltage it receives (primary) and the voltage is provides (secondary) are:

Answer 10

directly proportional to the number of turns in the transformer

Question 11

minor kilovolt peak:

Answer 11

“fine tunes” the selected technique

Question 12

*kVp determines the:

Answer 12

quality of the x-ray beam

Question 13

pre-reading kVp meter:

Answer 13

allows the voltage to be monitored before an exposure

Question 14

*thermionic emission:

Answer 14

the release of electrons from a heated filament

Question 15

x-ray tube current if controlled through:

Answer 15

filament circuit

Question 16

in a falling load generator exposure; the result is:

Answer 16

begins at the maximum mA and the mA drops as the anode heats, the result is minimum exposure time

Question 17

*mAs aka _____

Answer 17

electrostatic charge (C)

Question 18

guard timer will:

Answer 18

terminate an exposure after a prescribed time, usually 6s

Question 19

in synchronous timers the minimum exposure time is ___

Answer 19

1/60s

Question 20

*most exposure timers are:

Answer 20

electronic and are controlled by a microprocessor & are accurate to milli seconds (.001s)

Question 21

*mAs timers are used on:

Answer 21

falling load and capacitor discharge imaging systems

Question 22

AEC:

Answer 22

automatic exposure control, measures the quantity of radiation that reaches the IR and terminates the exposure when it receives the required radiation

Question 23

*high-voltage generator has 3 primary parts:

Answer 23

high-voltage transformer, filament transformer & rectifiers

Question 24

turns ratio is the:

Answer 24

number of secondary windings to the number of primary windings

Question 25

voltage is ____ proportinal to the number of turns

Answer 25

directly

Question 26

current is ____ proportional to the number of turns

Answer 26

indirectly

Question 27

the turns ratio of high-voltage transformers are:

Answer 27

500:1 or 1,000:1

Question 28

*transformers will only operate on ___

Answer 28

AC

Question 29

the only difference between primary and secondary wavelengths is ____

Answer 29

amplitude

Question 30

primary voltage is ___ secondary voltage is ___ primary current is ___ secondary current is ____

Answer 30

V kV A mA

Question 31

a common wall plug is ___ Hz and ___ changing direction ____

Answer 31

60 Hz and AC changing direction 120 times a second

Question 32

an x-ray tube is ____

Answer 32

DC

Question 33

*rectification is:

Answer 33

the process of converting AC to DC

Question 34

a rectifier is:

Answer 34

a electronic device that allows current flow in only one direction

Question 35

*voltage rectification is required:

Answer 35

to ensure that electrons flow from x-ray tube cathode to anode only

Question 36

rectification is accomplished with _____

Answer 36

diodes

Question 37

a diode contains:

Answer 37

two electrodes

Question 38

n-type semiconductors have:

Answer 38

loosely bound electrons that are relatively free to move

Question 39

p-type semiconductors have:

Answer 39

spaces or "holes" where there are no electrons

Question 40

half-wave rectification is ______; the result is ______; uses ___ diodes

Answer 40

the inverse voltage is removed from the supply of the x-ray tube by rectification; the result is a series of positive pulses separated by gaps; only half the AC waveform appears in the output; has 0, 1, or 2 diodes

Question 41

during the positive portion of AC waveform ______; during negative portion of AC waveform ______

Answer 41

the rectifier allows electric current to pass; the rectifier does not conduct (no current)

Question 42

full-wave rectification is ______; the output voltage is ____; exposure time is _____

Answer 42

the negative half of the AC waveform is reversed so the anode is always positive, current is shown during both the positive and negative phases; output voltage is positive with no gaps; exposure times halved

Question 43

single-phase power results in:

Answer 43

a pulsating beam

Question 44

three-phase power has:

Answer 44

multiple waveforms superimposed on each other resulting in a waveform that maintains nearly a constant high voltage

Question 45

three-phase power has __ pulses per ____ sec

Answer 45

6; 1/60

Question 46

*with 3 phase power the voltage applied across the x-ray tube is:

Answer 46

nearly constant, never dropping to 0 during exposure

Question 47

SCR's:

Answer 47

silicon-controlled rectifiers

Question 48

*full wave rectification or high-frequency voltage generation is used in:

Answer 48

almost all stationary x-ray imaging systems

Question 49

*during capacitor discharge the voltage:

Answer 49

falls approximately 1kV/mAs

Question 50

single-phase power has ___ voltage ripple

Answer 50

100%, voltage varies from 0 to the maximum value

Question 51

3 phase 6 pulse power has ___ voltage ripple

Answer 51

14%, the voltage never falls below 86% of the maximum value

Question 52

3 phase 12 pulse power has ___ voltage ripple

Answer 52

4%, the voltage supplied never falls below 96% the maximum value

Question 53

high-frequency power generators have ___ voltage ripple

Answer 53

1%, they have greater radiation quality and quantity

Question 54

*less voltage ripple results in:

Answer 54

greater radiation quality and quantity

Question 55

x-rays are performed with:

Answer 55

3 phase power

Question 56

fluoroscopy is performed with:

Answer 56

single-phase power

Question 57

transformers and high-voltage generators power is measured in ___

Answer 57

kilo watts (kW)

Question 58

high-voltage generators provide power to the x-ray tube in 3 ways:

Answer 58

single-phase power, 3 phase power & high-frequency power

Question 59

X-ray systems usually operate on voltages of ______ and currents of ______

Answer 59

25-150kVp, 100-1200mA

Question 60

when using the fluoro table for fluoro not for x-ray:

Answer 60

move the bucky to the foot of the table

Question 61

3 phase generators are found:

Answer 61

on the wall

Question 62

photodiodes are:

Answer 62

below the IR, shuts off based on density

Question 63

ionization chambers are:

Answer 63

above the IR

Question 64

the back up timer is always:

Answer 64

1.5 times longer than the needed exposure time

Question 65

electrons travel from ____ to ____ in the tube

Answer 65

cathode to anode

Question 66

peak x ____ = average voltage

Answer 66

peak x .707 = average voltage (keV)

Question 67

average x ____ = peak voltage

Answer 67

average x 1.41 = peak voltage (kVp)

Question 68

the autotransformer is found:

Answer 68

in the control console

Question 69

the control console is aka:

Answer 69

primary circuit

Question 70

high-voltage section is aka:

Answer 70

secondary circuit

Question 71

going from the primary to the secondary circuit there is a ____ in voltage because there is a _____ in current

Answer 71

step down, step up