Unit 1

Question 1

Parts of a cathode assembly

Answer 1

Filament, Focusing cup, wiring

Question 2

Filament characteristics

Answer 2

coil of thoriated tungsten; high melting point; difficult to vaporize; smaller coils produce best detail

Question 3

Thermonic Emission

Answer 3

heating of the filament causes electrons to be released

Question 4

How to extend tube life

Answer 4

depress exposure switches in one motion, decrease rotor time; excessive rotoring causes tube arching (vaporized tungsten)

Question 5

Components to rotating anode assembly

Answer 5

anode, stator, rotor

Question 6

characteristics of anode targets

Answer 6

high atomic number (enhances production of photons); high melting point; heat conducting ability;

Question 7

Anode layering

Answer 7

backed with molybdenum and graphite to assist with heat loading

Question 8

Target Area

Answer 8

portion of anode that electron stream contacts; point where x-ray photons created

Question 9

Actual focal spot

Answer 9

physical area of the focal track that is impacted by electrons

Question 10

effective focal spot

Answer 10

area of the focal spot that is projected out of the tube

Question 11

Line-focus principle

Answer 11

effective focal spot is controlled by the size of the actual focal spot and anode target angle; when target angle is less than 45 degrees the effective focal spot is smaller than the actual focal spot

Question 12

Anode heel effect

Answer 12

radiation intensity is greater on the cathode side because some rays are absorbed by the anode heel

Question 13

Off focus radiation

Answer 13

composed of photons that were not produced at the focal spot; scatter electrons hit other structures in the tube

Question 14

Stator

Answer 14

induction motor electromagnets send currents to the rotor to turn the anode; located outside the vacuum

Question 15

Rotor

Answer 15

hollow copper cylinder attache to the anode disk; currents from the stator cause it to turn

Question 16

Envelope

Answer 16

constructed around the anode and cathode and sealed tight to maintain vacuum; x-ray beams exit the tube through the window; vacuum allows electrons to flow from cathode to anode without encountering atoms in air

Question 17

Protective housing

Answer 17

controls leakage and scatter radiation; made of lead; isolates high voltages; provides means to cool the tube

Question 18

mA

Answer 18

how many electrons are crossing the tube

Question 19

mAs

Answer 19

how many electrons are crossing the tube per second

Question 20

Reciprocity law

Answer 20

Density exposure should remain unchanged as long as the intensity and duration of the x-ray (mAs) exposure remains unchanged.

Question 21

mAs formula

Answer 21

mAs= mA x seconds

Question 22

kVp

Answer 22

speed of electrons; high kVp = higher x-ray penetrability and quantity

Question 23

15% rule

Answer 23

And increase of kVp by 15% will cause a doubling in exposure, the same effect as doubling the mA or doubling exposure time

Question 24

Distance and x-ray emission

Answer 24

As SID increases, beam intensity decreases

Question 25

Inverse square law

Answer 25

I1/I2 = (D2)^2/(D1)^2

Question 26

Exposure Maintenance Formula

Answer 26

mAs1/mAs2 = (D1)^2/(D2)^2

Question 27

Density/ IR exposure

Answer 27

makes detail visible; degree of blackening

Question 28

Typical optical density range

Answer 28

.25-2.5

Question 29

mAs controlling density

Answer 29

longer exposures increase density; need at least a 30% change in mAs to make a visible change in density

Question 30

kVp controlling density

Answer 30

small changes make a large difference; higher kVp increases scatter radiation

Question 31

Focal spot controlling density

Answer 31

does not effect density

Question 32

Anode heel effect with density

Answer 32

Density is greater at cathode side of beam

Question 33

SID effecting density

Answer 33

greater SID = less density

Question 34

Beam restriction effecting density

Answer 34

more restriction decreases density

Question 35

anatomical part effecting density

Answer 35

tissue thickness; tissue type; radiopaque (absorbs photons) or radiolucent

Question 36

Grids affecting density

Answer 36

grid absorbs scatter which decreases density

Question 37

Contrast

Answer 37

difference between adjacent densities

Question 38

dynamic range

Answer 38

range of brightness of the display monitor light emission

Question 39

High contrast

Answer 39

black and white; low kVp

Question 40

Low contrast

Answer 40

many shades of gray; high kVp

Question 41

film contrast

Answer 41

range of densities that the film is capable of recording

Question 42

Subject Contrast

Answer 42

range of differences in intensity of x-ray beam; dependent on kVp, type of irradiated material, amount of irradiated material

Question 43

kVp with contrast

Answer 43

higher kVp=more penetration, more scatter, lower contrast

Question 44

amount of irradiated material and contrast

Answer 44

increase in thickness and field size increases scatter = low contrast

Question 45

type of irradiated material and contrast

Answer 45

materials with high atomic numbers (lead & iodine) absorb x-rays more than low atomic numbers (hydrogen & carbon); large atomic number difference = high contrast

Question 46

focal spot size with contrast

Answer 46

no effect

Question 47

anode heel effect with contrast

Answer 47

little to no effect

Question 48

beam restriction with contrast

Answer 48

restricting the beam reduces amount of photons available and increases contrast

Question 49

SID with contrast

Answer 49

increase of distance increases contrast

Question 50

OID with contrast

Answer 50

air gap causes scatter to avoid IR and increases contrast

Question 51

Filtration with contrast

Answer 51

increases average photon energy which causes more scatter and decreases contrast

Question 52

Grids with contrast

Answer 52

Grids reduce scatter which improves contrast