Physics Chapter 5

Front 1

what are the three main components of an xray imaging system

Back 1

xray tube, operating console, high voltage generator

Front 2

refers to the number of xrays or the intensity of the xray beam

Back 2

radiation quantity

Front 3

what is radiation quantity usually expressed in, measurement

Back 3

mAs, milliampere.....milligray

Front 4

refers to the penetrability of the xray beam

Back 4

radiation quality

Front 5

how is radiation quality expressed

Back 5

kVp, kilovolt

Front 6

what does the operating system provide controls for

Back 6

KVP, mA, and exposure time

Front 7

measures the voltage provided to the xray imaging system and adjust the voltage to precisely 220 V

Back 7

line compensator

Front 8

has a single winding and is designed to supply a precise voltage to the filament circuit and to the high voltage circuit of the xray imaging system

Back 8

autotransformer

Front 9

change the amount of voltage either increase or decrease it

Back 9

transformer

Front 10

what is xray tube current that crosses from cathode to anode measured in

Back 10

milliamperes, mA

Front 11

how is the number of electron emitted from the filament determined

Back 11

the temperature of the filament

Front 12

where does the filament emit it's electrons

Back 12

on the cathode

Front 13

the cathode is ______
the anode is _______

Back 13

negative, positive

Front 14

as filament current _____, the filament becomes _____, and _____ electrons are released by _______ ______

Back 14

increases, hotter, more, thermionic emission

Front 15

what is the normal current that filaments usually operate at

Back 15

3- 6 A

Front 16

where is the filament located

Back 16

on the cathode

Front 17

what force will emitted electrons be attracted to

Back 17

positive force

Front 18

the release of electrons from a heated filament

Back 18

thermionic emission

Front 19

as the kVp is raised, the anode becomes more attractive to the electrons that would not have enough energy to leave the filament area, these electrons also join the electron stream which effectively increases the mA with kVp what effect is this

Back 19

space charge effect

Front 20

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

Back 20

falling load generator

Front 21

voltage from the autotransformer goes to the filament circuit through the

Back 21

mA selector

Front 22

the filament transformer is what type of transformer

Back 22

step down

Front 23

the voltage reaching the filament at the cathode is _____ than what the incoming was

Back 23

less

Front 24

are voltage and current inversely related

Back 24

yes ( current to the filament increases)

Front 25

the number of xrays used during exposure is determined by

Back 25

tube current, amount of time current is activated, tube current (mA) × time (s/ms) = mAs

Front 26

what will all the xray timers do automatically once the time selected has been achieved

Back 26

stop the exposure

Front 27

what type of timer is not set by the tech, activate should timer circuit fail, prevent an extended exposure

Back 27

back up or guard timer

Front 28

what will break the flow of current to the rest of the system and is separate from the other circuits

Back 28

timer circuit

Front 29

operates at precisely 60 revolutions per second on a 60 Hz system, cannot use these for serial exposure, as the time must be reset between exposures

Back 29

synchronous timer

Front 30

exposure times available will be increments of 1/60 such as 1/30, 1/20

Back 30

synchronous timers

Front 31

most accurate and complex, accurate down to 1ms allows serial imaging, suitable for interventional angiography

Back 31

electronic timers

Front 32

monitors the product of mA and exposure time and terminates exposure when the desired mAs value is attained

Back 32

mAs timer

Front 33

designed to provide the highest safe tube current for the shortest exposure for any mAs selected

Back 33

mAs timer

Front 34

measure the amount of radiation reaching the IR,

Back 34

automatic exposure control

Front 35

the three small ionization chambers placed between patient and IR

Back 35

automatic exposure control

Front 36

when desired charge is reached what terminates the exposure

Back 36

automatic exposure control

Front 37

if AEC fails what timer will terminate exposure once that time has been reached

Back 37

back up timer

Front 38

to achieve kilovoltage in the autotransformer what type of transformer is used

Back 38

step up transformer

Front 39

what are the 3 parts to the high voltage generator

Back 39

high voltage transformer, rectifiers, filament transformer

Front 40

to get the kilovolts needed for the high voltage transformers how many more turns does the secondary coil have than the primary

Back 40

5-10× more

Front 41

current comes from the step up transformer as what type of current

Back 41

alternating current

Front 42

xray tubes require what type of current so that the stream of electrons going from the cathode to the anode is constant in one direction

Back 42

direct current

Front 43

what converts alternating current flow to a direct current type flow

Back 43

rectifiers

Front 44

what is the process of converting AC to DC

Back 44

rectification

Front 45

what is produced by the acceleration of electrons from the cathode to the anode and can not be produced by electrons flowing in the reverse direction

Back 45

xrays

Front 46

current that passes through the xray tube, exists only during the positive half of the cycle when the anode is positive and the cathode is negative, current between cathode and anode would exist only half the time

Back 46

unrectified voltage

Front 47

removed the negative or reverse flow of electrons, no voltage at all periodically 1/20s, end up with 60 xray pulses each second

Back 47

half wave rectification

Front 48

using half the incoming voltage, wasting half the voltage, takes twice as long to make the exposure

Back 48

half wave rectification

Front 49

allows entire incoming power to be used, uses multiple diodes, half the diodes work when electron flow is positive, half doides work when electron flow is negative

Back 49

full wave rectification

Front 50

converts full wave rectified power of 60 Hz to a much higher frequency 500-25000 Hz, then on to high voltage

Back 50

high frequency generator

Front 51

produce a nearly constant potential voltage waveform, improving image quality at a lower patient radiation dose

Back 51

high frequency generator

Front 52

accumulates and stores a specified quantity of electrical charge, energy stored in silicon controlled rectifiers, enough charge is stored so kilovolts can be discharged upon exposure

Back 52

capacitor discharge generator

Front 53

t f as capacitor discharges and loses energy, kilovoltage falls so xray output falls

Back 53

true

Front 54

starts exposure at highest amperage allowed, exposure time is reduced (mA x time= mAs), tube current at max, a lot of heat produced

Back 54

falling load generator

Front 55

tech can pick mAs but not mA

Back 55

falling load generator

Front 56

describes/quantifies the quality of an energy waveform going to the xray tube

Back 56

voltage ripple

Front 57

single phase power has a ____ voltage ripple

Back 57

100%

Front 58

three phase 6 pulse power has a _____ voltage ripple

Back 58

14%

Front 59

three phase 12 pulse power has a ____ voltage ripple

Back 59

4%

Front 60

high frequency has a voltage ripple of

Back 60

1%

Front 61

affects beam quality and quantity

Back 61

voltage ripple

Front 62

penetrability improves

Back 62

quality

Front 63

intensity improves

Back 63

quantity