x-ray

Question 1

What does the white or radiopaque shadows represent on an image

Answer 1

dense structures which have stopped the x-ray beam

Question 2

What does the black or radiolucent shadows represent

Answer 2

Areas where the x-ray beam has passed through and not been stopped

Question 3

What does the grey shadows represent

Answer 3

areas where the x-ray beam has been stopped to a varying degree

Question 4

4 factors that quality of radiographic image rely on

Answer 4

contrast, image geometry (position of film + tube), characteristics of x-ray beam, image sharpness and resolution

Question 5

Examples of intra-oral images

Answer 5

periapical, bitewing, occlusal

Question 6

Examples of extra-oral images

Answer 6

oblique lateral, various skull, panoramic

Question 7

The cathode is …….. and consists of a heated ……. of tungsten that provides the source of …..

Answer 7

negative, filament, electrons

Question 8

The anode which is …. consists of a …….. (small piece of tungsten) set into the angled face of a large …. …….. to allow efficient removal of ……

Answer 8

positive, target, copper block, heat

Question 9

What does the focusing device do

Answer 9

stream of electrons at the focal spot on the target

Question 10

A ……….. flows from the …… to the ……. to measure the quantity of ……. being accelerated

Answer 10

current (milliamperage mA), cathode, anode, electrons

Question 11

How is heat removed

Answer 11

by copper block and surrounding oil

Question 12

The high-speed electrons bombarding the target are involved in 2 main types of collision with tungsten atoms:

Answer 12

heat producing collisions

x-ray producing collisions

Question 13

What effects are dental professions primarily concerned about?

Answer 13

somatic stochastic effects

example is cancer induction which can occur with ANY amount of radiation

Question 14

What is made at the end of the anode

Answer 14

made of metal tungsten set into a block of copper

Question 15

What are stray photons responsible for

Answer 15

X-ray tube head leaking slightly during exposure, must never hold X-ray tube as may irradiate hand

Question 16

percentage of energy which is converted to heat and x-rays

Answer 16

heat 99%

x-rays 1%

Question 17

As the deflection increases the …..

Answer 17

bigger photon increased

Question 18

Why are not all x-ray photons the same

Answer 18

because the produce different deflections

Question 19

What does low and high energy photons do

Answer 19

low - penetrating power, will stop in patients soft tissues and absorb
high - pass through patient and hit the film

Question 20

What type of energy photons are more dangerous to the patient and what are more diagnostically useful

Answer 20

low energy - more dangerous

high energy - more diagnostically useful

Question 21

What is the energy of the incoming electrons determined by

Answer 21

size of the voltage applied - the bigger the voltage the greater energy given to the electrons

Question 22

How are they removed from the beam so they do not hit the patient?

Answer 22

passing the beam through a sheet of aluminium which absorbs and filters out the lowest energy photons

Question 23

What is the effect of the aluminium filter

Answer 23

to absorb the lowest energy most harmful photons - lack penetrating power means cannot pass through aluminium, as a result the beam which is used on patients does not contain many harmful photons

Question 24

What are the advantages of being able to control the kV

Answer 24

allows control the eventual contrast differences between the black and white on the resultant film

Question 25

What happens as Kv is increased

Answer 25

penetrating power of photons is increased, less absorption, dose is less to patient BETTER advantage to use HIGHER kV for the patient

Question 26

What happens if kV is low

Answer 26

photons have less energy, more absorption in the patient, so dose is higher to the patient, more of a NEGATIVE effect