Radiography Physics, Health & Safety

Question 1

what is kV, mA, X-ray, y-particle, B-particle and a-particle stand for

Answer 1

kV- kilovoltage

mA- milliamperes

x-ray: photon of electromagnetic radiation released from electron shell

y-particle: photon of electromagnetic radiation released from radioactive nucleus

B-particle: electron or positron released by decay of radioactive nucleus

alpha particle: 2 protons and 2 neutrons released by decay of radioactive nucleus

Question 2

what is the difference between stochastic and non-stochastic

Answer 2

stochastic is based on chance

non-stochastic is dose dependent

Question 3

what is the somatic, mutagenic and carcinogenic considerations associated with radiography

Answer 3

1. somatic: effects over a lifetime
2. mutagenic: offspring effects
3. carcinogenic: lots of evidence of this

Question 4

what are the factors needed to produce x-rays

Answer 4

1. electricity (AC) –> power, voltage, current, frequency
2. 2 circuits –> produce electrons (mA) and accelerate electrons (kV)

Question 5

what are the interactions with tissue

Answer 5

1. transmitted
2. photoelectric effect (absorbed –> depends on atomic number)
3. compton effect (depends on density of tissue –> scatter)

Question 6

what are the effect of different tissues

Answer 6

1. lead = brilliant white
2. bone = white
3. soft tissue = soft grey
4. fat = dark grey
5. air = black

Question 7

what is scatter

Answer 7

the secondary beam

collimation

patient blocks

Question 8

how do you reduce scatter

Answer 8

kV as low as possible

collimation

using gride (increases mAs needed, machine may not be powerful enough)

radiation protection (distance, shielding)

Question 9

what is the inverse square law

Answer 9

double the distance you are away from the radiation the quarter dose you recieve

Question 10

what are grids

Answer 10

grids absorb some of x-ray beam

Question 11

what must be done when using grids

Answer 11

mAs must be increased to compensate

multiply by grid factor

ex. grid factor of 2 = mAs must be doubled

Question 12

what are the benefits of grids

Answer 12

increased image quality (reduced blurring due to scatter)

increased mAs required

Question 13

what is computed radiography

Answer 13

photons excite a phosphor to store an image –> into processor cassette opened –> laser excites phosphor –> light given off an detected –> presented on screen

Question 14

what is direct digital radiography

Answer 14

sensor detects photons

converted into voltages

fed to LCD screen

flexible, fragile, expensive

Question 15

what must there be in the x ray room

Answer 15

1. controlled area
2. local rules
3. access control (locked door, warning light)

* large animal –> need to plan

Question 16

which tissues have high radiosensitivity

Answer 16

gonads

intestinal mucosa

bone marrow

lymphoid

breasts

epithelial (oral cavity, bladder)

thyroid

Question 17

what tissues have moderate tissue radiosensitivity

Answer 17

lens of eye

growing bone

Question 18

what tissues have lower tissue radiosensitivity

Answer 18

mature cartilage/bone

lungs

salivary glands

kidneys

liver

pancreas

adrenal

muscle

CNS

Question 19

what needs to be used for operator protection

Answer 19

gowns

gloves/sleeves

thyroid shields

glasses

monitoring