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Flashcards in Rad Review Jerry's Questions Deck (45)
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1

The formula for determining the heat units for a 3-phase, 6-pulse x0ray generator is?

kV x time x mA x 1.35

2

The voltmeter, which reads the kVp selected, is located where in the radiographic circuit?

Between the autotransformer and step-up transformer

3

How many rectifiers are required for a full-wave, 3-phase, 12-pulse x-ray generator?

Twelve

4

During fluoroscopy, what is the range of mA used in the x-ray tube?

0.5-5 mA

5

An exposure is taken with a spinning top on a single-phase, fully rectified x-ray generator at an exposure time of 1/30 sec. If the timer circuit is working properly, the radiograph should yield?

4 dots

6

Why is it important for the x-ray tube to have a vacuum inside it?

This allows electrons to flow without any impedance

7

A tube chart is used to

Provide a safe range of exposure factors that may be utilized

8

Calculate the amount of heat units for the following single-phase, fully rectified unit
70 kVp; large focal spot; 8:1 portable grid; 20 mAs; 0.10 sec; 72" SID

1400 HU

9

Which of the following methods are used to regulate the amount of thermionic emission that occurs at the filament?

Variable resistor

10

Calculate the total resistance for the following circuit if the resisitors are connected in parallel.
5 ohms, 5 ohms, 20 ohms, 30 ohms

2.07 ohms

11

Calculate power for the following series circuit:
20 amps, 3 resistores of 5 ohms, 3 ohms, and 6 ohms

5600 Watts

12

How long does it take for the completion of one sine wave representing 60 hertz of current?

1/60 seconds

13

According to the low of conservation of energy, voltage and amperage have which type of relationship across a transformer?

Inversely proportional to each other

14

In the image intensifier, the anode serves to

Accelerate the electrons across the tube

15

What component in the image intensifier allows images to be magnified?

Electrostatic focusing lens

16

An x-ray tube has a heat storage capacity of 500,000 HU. How many rapid sequence exposures can be made at the following factors, before exceeding the capacity?
200 mA, 80 kVp, 0.4 sec, 30"SID

78

17

The inverse square law relationship between intensity and distance from a source is based upon

Divergence

18

Photomulitplers, thyratrons, and ionization chambers are devices used in

Automatic exposure devices

19

The size of an object is 7". The SID is 40". The OID is 9". What is the resultant size of the image?

9.03"

20

When electrons approach the positive electrostatic field of the target, they are abruptly decelerated and lose energy. This energy is converted to

Bremsstrahlung radiation

21

In the usual diagnositc kV range, insofar as energy absorption from the beam is concerned, which type of interaction between radiation and matter predominates?

Photoelectric effect

22

In the x-ray circuit, the current flowing between the rectifier and the tube is

Pulsating DC

23

In the exposure from an x-ray tube is 400 mR at a distance of 36 inches, what will the new exposure be at 50 inches using the same technique?

207 mR

24

Which of the following statements is/are correct regarding the anode?
I. It is the positive pole
II. The electron cloud forms here
III. It may be stationary or rotating

I and III

25

Minification gain occurs when

Electrons from the photocathode converge on the output screen

26

A radiographic unit that requires an oscilloscope to detect voltage waveform irregularities would be

A 3-phase, 12-pulse unit

27

The thickness of the tomographic section is determined by

Exposure angle

28

The compton effect is characterized by

Part transfer of energy upon collision

29

Gamma and x-radiation are the same in every way except

both do not have the same origin

30

A radioactive source has a half-life of 7 hours. How many hours are required to reduce a 84-millicurie/hr. dose to a level of 5.25 milicuries/hr?

28 hours

31

The basic reqard of the air-gap technique, improved contrast, relies on the following principle

Due to increased OID, the angle of the scatter will miss the film

32

The M shell orbit in atomic formation is able to contain a maximum of

18 electrons

33

X-rays produced from the movement of electrons from an outer shell to an inner shell is termed

Characteristic radiation

34

The incident photon gives up all its energy to cause excitation; a new photon of the same energy is given off in a random direction

Unmodified scatter

35

Produces an ion pair

Photoelectric effect and compton scatter

36

Is responsible for true absorption

Photoelectric effect

37

Is responsible for scattered radiation causing fogged film

Compton scatter

38

Causes ionization in tissue

Photoelectric effect and compton scatter

39

Concerned with only in therapy ranges of 1.02 or greater

Photodisintergration

40

Incident photon with KeV greater than but close to the binding energy of outer shell electrons. Atomic number is high to increase probability.

Photoelectric effect

41

Incident photon with KeV considerably greater than the binding energy of outer shell electrons

Compton scatter

42

Results in true secondary radiation and energues characteristic of the binding energies of the shells involved

Photoelectric effect

43

What is the efficiency of x-ray production, using a tungsten anode, at 90 kVp?

0.675%

44

Faraday's Law is also referred to as the

Law of Electromagnetic Induction

45

During a fluoroscopic procedure, the radiologist selects a smaller field-of-view, resulting in a magnified image on the TV monitor. How does this affect the amount of radiation that the patient receives?

It increases the amount of radiation the patient receives