principle of radiography chapter 5

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1

incoming line current

all xray equipment operates from an incoming line of 210-220 volt

2

the main x ray circuit

must boost the voltage to the range necessary to produce x rays and to permit the radiographer to adjust the amperage, voltage and length of exposure.

3

the main switch

are usually enclosed in an electrical power box

4

the exposure switch

is simple connection that permit current to flow through the circuit. also activates the rotating anode of the x ray tube. The anode must be turning at a sufficiently high speed to avoid melting of the target by the high kilovoltage exposure.

5

to aviod possibility of error

all xray unit that utilize rotating anode have circuitry that prevent an exposure until the anode is turning at the corret speed.

6

what type od power does an xray generator supply?

AC electrical power

7

How can a changing magnetic field produce a current?

by motion between a magnetic and a coil

8

what type of coil does a single phase generator use?

a single coil (solenoid)

9

what are single phase generator characterized by?

a production of a single wave that is sinusoidal varying voltage and circuit

10

what happen to the induce current as the voltage fluctuates through each cycle in a single phase generator?

is also fluctuates

11

when are xray produced in a single phase generator?

only during the positive half of the rotation. nothing is produced during the negative half

12

at what frequency is AC generated in a single phase generator?

60 cycles/sec. or 60 Hz

13

what is the ripple of the waveform of a single phase generator?

100%

14

what is the least efficient way to produce x ray?

single phase generator

15

what is the average energy for a single phase generator

70 KVp

16

how does half wave single-phase generator operate?

it suppresses the negative half of the cycle to where it doesn't go below the 0 line, but nothing is being produced

17

half wave single-phase

100% ripple
1-2 diode
60 Hz per second

18

how much cycle is available of x ray production on a HALF WAVE single-phase generator?

only one half of the cycle is available for x ray production

19

when are x ray produced for the full wave single phase generator?

produce xray during both half of the AC cycle

20

Full wave single phase

-It convert the negative wave to positive
-100%
-4 diode
-60 Hz per 120's second
Use pulsating DC current

21

what can you do with a full wave single phase generator that you can't do with a half wave?

use a higher mA and KVp and shorter exposure time

22

what do 3 phase generator produce?

full wave rectification the voltage never drop to zero

23

three- phase, six pulse

-13-25% ripple (it means that the voltage in the xray tube never falls below
75-87% of the KVP setting on the console).

-6 diode
-360 HZ
-use AC current
-35% higher average photon energy

24

what % more of x ray can be produced with a 3 phase generator vs. a single phase full wave generator?

12-16% more xray

25

what is better for a 3 phase generator vs. a single generator

require less mAs that the single phase , high rating for mA and KVp ( can set technique higher) and exposure time are a short as 1 msec. to has more efficient x ray production

26

what is the disadvantage of three phase generator vs. a single phase generator

contrast is less with the 3 phase generator because of the increase of KVp

27

how does 3 phase 6 pulse generator produce its pulse per cycle?

produce 3 pulse every half cycle which is 6 pulse/ Hz, 360 /second. one pulse every 1/360 sec. getting faster and faster that the single phase

28

3 phase 12 pulse generator

-4% ripple
-96% capacity
-12 diode
-use current supply in AC

29

what is the newest development generator?

high frequency generator

30

what does the high frequency generator use for voltage?

voltage with frequency higher that 60 AC cycle

31

what does the high frequency generator ripple?

1% ripple
99%capacity

32

what are the advantage of high frequency generator?

-compact unit
-less than 2% voltage ripple
-greater mR/MAs output
-shorter exposure time (less chance of motion)
-lower patient dose (25% less)
-longer tube life

33

what are falling load generator designed to produce?

designed to produce exposure in shorter posible time by setting the x ray tube begging at the highest mA setting and then allowing to fall during exposure ( without exceeding the heat loading capacity of the tube)

34

what were falling load generators development primary for?

primary for use with AEC device (where there are not predetermined exposure time)

35

What do falling load generator provide as far as mA and time?

the highest mA setting at the shortest time posible

36

what cause the shortened tube life in the falling load generator?

use high mA and KV

37

power

the unit of power is watt : V x A =W formula applies to 3 phase generator

38

formula for single phase generator

V x A x 0.7 = W

39

high frequency generator

use AC and DC power convert to change the incoming line voltage frequency from 60 Hz to the 6,000 Hz range. Work with a range of 500 to 25.000 Hz

40

how does a capacitor discharged mobil unit work?

feed standard incoming line voltage to primary coil of high voltage transformer ; voltage across electrodo drop during exposure

41

what is use to start and stop exposure for a capacitor discharge mobile unit

a grid controlled tube is usually used to act as a switch to start and stop exposure

42

automatic exposure control (AEC)

provide correct exposure regardless of patient size, control the time of the exposure.
components: 3 ion chambers placed between the patient and the imagen receptor.
it turn off the x ray bean when the proper exposure is reached

43

an autotransformer function as a

KVp and mAs selector

44

ripple measures

variation between maximina and minimum voltage

means how low the wave go

45

the only radiation of any clinical values is:

the only radiation of any clinical values is:
-The radiation that is absorbed in the detector
-is able to converted to a radiographic imagen for interpretation

46

where is the exposure switch located?

primary side of the step up transformer

47

where is the mA meter located?

in the secondary side of the step up transformer

48

what is the typical amperage and voltage sent to the filament circuit?

3-6 A
12 V

49

the transformer that has a single winding that acts as both the primary and secondary winding is called?

autotransformer

50

a transformer with more turns in its primary winding that in the secondary would be expect to ?

decrease the voltage an increase the A Amperage ( step down transformer)

51

which of the following circumstance would cause the backup timer to activate during the operation of an AEC unit?

a tabletop exam is being performer with the chest board select

52

angiography unit

special unit 150 KVp

53

capacitor discharge unit

provide an rms voltage significantly lower that the peak voltage

54

battery operated movie unit

batteries supply nonpulsating direct current to a rotary converter, which provides current similar to 3 phase even greater frequency. compared to capacitor discharge machine this unit have the obvious advantage of 3 phase exposure constantly, higher rms voltage and no leakage.

55

falling load generator

must be used with AECs. it begin exposure at the highest possible mA and then allowing to fall during exposure. it can short the X-ray tube life considerable.it leave the kvp under radiographer control.

56

AEC

do not control any factor except time `

57

full capacity

is how height the wave go