X-ray

Question 1

principles for x-ray

Answer 1

beam of high energy electrons
interact with a target material
interact with patient tissue, some pass through
interact with image to produce grey scale

Question 2

why is bone very absorbant

Answer 2

due to its high density and atomic no.

Question 3

white parts of image

Answer 3

more energy absorbed

Question 4

what is xray energy measured in

Answer 4

kVp

peak kilovolts

Question 5

what is the role of aluminum filter

Answer 5

absorb low energy photons

Question 6

what is the effects of a higher kVp

Answer 6

lower contrast - more grey

Question 7

what is the effect of a lower kVp

Answer 7

high contrast

Question 8

what is the amount of xrays measured in

Answer 8

mAs

milli amps x second

Question 9

what is the relationship between density and absorption

Answer 9

linear

if you double density of tissue, you double absorption and scattering

Question 10

role of image receptor

Answer 10

convert xrays energy to image

Question 11

different types of receptor

Answer 11

film screen - chemical reaction
computed - sacnning laser
direct-direct - computing

Question 12

how does direct - direct radiography work

Answer 12

as xrays pass through crystals, release electrons, they ionise and form current which is collected at the capacitor.
thin film tranistor is switched so the current is released

Question 13

what should you look at to get a good image

Answer 13

amount of collimnation
centering - where the middle ray will be
limit diverging beam

Question 14

generator

Answer 14

creates high voltage
made up of coils
primary and secondray (has more coils =higher current)
alternating current, changes direction of a magnetic field, generates voltage

Question 15

order of electromagnetic spectrum

Answer 15

radio 
microwaves 
infared 
ultra violet 
xrays 
gamma (highest)

Question 16

useful characteristics of xrays

Answer 16

penetrate matter
interact with matter
can cause certain materials to fluoresce
can cause certain materials to produce electric charge

Question 17

how are xrays generated

Answer 17

cathode produces electrons
filaments are heated, removing electrons
creates a high potenial difference between cathode and anode
electrons accelerate to anode

Question 18

why is the glass tube in oil

Answer 18

heat disserpation

electrical insulation

Question 19

properties of anode

Answer 19

good conductor
good heat disapator
made of tungston

Question 20

electricity

Answer 20

flow of electrons in a material and the rate of flow of electrons is a meaure of the electrical current

Question 21

potential force

Answer 21

is the ‘driving force’ which moves the electrons along a conductor, has an effect on kinetic energy, measured in kVp

Question 22

electric current

Answer 22

amount of current, determines the amount of thermionic emission, measured in milliampes mA

Question 23

3 ways which electrons collide with target

Answer 23

1. interaction between them and outer electrons in the atom (no heat or xray)
2. interaction between them and the nuclei of the atom (heat and xray)
3. interaction between them and individual electron in the inner orbits (heat and xray)

Question 24

how much energy is produced as heat in xray production

Answer 24

95-99%

Question 25

quality of xray beam

Answer 25

measure of its penetraing power

Question 26

quanity of xray beam

Answer 26

measure of the number of photons in the beam

Question 27

why is funneling of xray important

Answer 27

saftey only hits part of the body you want less radiation exposure

Question 28

newtons law of conservation of energy

Answer 28

energy neither created nor desroyed, only changed in form

Question 29

why is tungsten used

Answer 29

heat stable good electrical conductor has alot of electrons - positive protons in nucleus

Question 30

why do we have rotating andoes

Answer 30

heat diserpation preserves the anode more high energy eletrons

Question 31

andoe angle

Answer 31

makes source of xray as close to point source as possible | small angle = closer to point source = more effective source

Question 32

role of filtration

Answer 32

enriches beam with high energy photons by absorbing lower energy xrays higher average energy - greater penetration - reduce skin dose

Question 33

ionisation chamber

Answer 33

gas filled a propotion of incident photons cause ioniastion which is collected at the charged anode of the chambre measure dose area product in cG

Question 34

generators

Answer 34

cathode needs low voltage so mulitple circuits high voltage tranformer voltage rectifier

Question 35

what does voltage rectifier do

Answer 35

converts oscilaiting voltage to constant voltage

Question 36

intensity across the beam

Answer 36

varies because electrons travel into deeper layers of the anode, deeper they go = lower intensity increase as angle is reduced, side closest to andoe is lower

Question 37

fine focus filament

Answer 37

smaller used when geometric focus limit image quality energy focused on smaller area reduce tube loading to prevent damage

Question 38

when is the fine focus filament used

Answer 38

high detail low patient attenutaion extremities

Question 39

broad focus filament

Answer 39

image limited by patient attentuation increased heat dissipation permits higher tube loading

Question 40

when is broad focus filament used

Answer 40

less detail required high patient attenuation chest, abdomen, l.spine