Intro

Question 1

Which side of the X-ray tube do X-rays come out of?

Answer 1

Anode

Question 2

How are X-rays created within the X-ray tube?

Answer 2

the cathode creates a lot of free electrons, when they hit the anode they become X-ray photons

Question 3

What % of electrons become X-rays?

Answer 3

1-2% the rest turns into heat

Question 4

X-rays move isotropically, what does this mean?

Answer 4

They move in every direction

Question 5

What is primary radiation (PR)?

Answer 5

All the radiation between the source and the patient
Incident radiation or useful beam

Question 6

What is Remnant Radiation?

Answer 6

Radiation which leaves the patient and is going to hit the image receptor
RR=PR-(Absorbed+Scattered)

Question 7

What is secondary radiation?

Answer 7

radiation coming from a place other than the source or target

Question 8

What is scattered radiation?

Answer 8

primary radiation which has been deflected or changed direction

Question 9

What is CR?

Answer 9

Central ray - not to be confused with computed radiography
centre of the Xray beam

Question 10

What is FS/T/S?

Answer 10

Focal spot, target or source - where the X-rays originate

Question 11

What is SID?

Answer 11

Source to image receptor distance

Question 12

What is SGD?

Answer 12

Source grid distance

Question 13

What is SOD?

Answer 13

Source to object distance - the primary beam
also known as TOD (target to object distance), AOD (anode to object distance), and FOD (focal to object distance)

Question 14

What is OID?

Answer 14

object to image receptor distance
also known as OFD - object film distance

Question 15

What is mA?

Answer 15

milliamperes
- quantity or intensity
- one ampere is defined as the current that flows with electric charge of one Coulomb per second
- values of mA influence amount of radiation
- rate of radiation production

Question 16

What is s?

Answer 16

value of time selected
- controls the duration of the exposure

Question 17

What is mAs?

Answer 17

Milliampere seconds
- total quantity of radiation used for a particular exposure

Question 18

What is kVp?

Answer 18

kilovolts peak (quality of radiation)
- determines penetrating ability of the radiation

Question 19

What will happen to the wavelength of the X-ray photons if kVp is increased?

Answer 19

The wavelength will decrease, but the photon will have increased energy

Question 20

What is attenuation?

Answer 20

any process that decreases/reduces the intensity of the beam

Question 21

What factors affect attenuation?

Answer 21

Thickness, atomic number and physical density

Question 22

Why does increased atomic number affect attenuation?

Answer 22

increased amount of outer shell electrons

Question 23

What is the atomic number of bone, muscle and water?

Answer 23

bone - 13.8
muscle - 7.4
water - 5.9

Question 24

What are the physical densities of bone, soft tissue and air?

Answer 24

bone - 1.8 g/cm3
soft tissue - 1.0 g/cm3
air - 0.001 g/cm3

Question 25

How does kVp affect absorption?

Answer 25

by increasing the kVp you are giving the X-ray photons more energy and a shorter wavelength this decreases absorption

Question 26

Does mAs affect absorption?

Answer 26

no

Question 27

What is high contrast?

Answer 27

lots of dark shades and brighter shades, few shades of grey Brightness differences between structures is large

Question 28

What is low contrast?

Answer 28

many shades of grey, brightness differences between structures are small

Question 29

What is mA?

Answer 29

current (I)

Question 30

What is mAs?

Answer 30

total amount of e flow over entire exposure

Question 31

What is reciprocity?

Answer 31

variety of mA and time settings that could produce the same mAs

Question 32

What are the advantages to reciprocity?

Answer 32

- control motion - focal spot size - breathing techniques

Question 33

Why would you want to use a smaller focal spot?

Answer 33

better spacial resolution - crisper edges

Question 34

What is the small focal spot limit by?

Answer 34

mA NOT mAs

Question 35

What is the inverse square law?

Answer 35

I1/I2=d2^2/d1^2

Question 36

What is the intensity maintenance law?

Answer 36

also known as the square law mAs2/mAs1=d2^2/d1^2

Question 37

What is subject contrast?

Answer 37

a measurement of intensity of the remnant beam caused by differential absorption

Question 38

What does image contrast depend on?

Answer 38

subject contrast, scatter radiation, algorithms, processing, post processing

Question 39

kVp and intensity formula?

Answer 39

I1/I2 = (kVp1/kVp2)^2

Question 40

kVp, mAs and intensity?

Answer 40

I.e. solving for I2 I2 = I1 x (kVp1/kVp2)^2 x (mAs1/mAs2)

Question 41

What are grids?

Answer 41

Devices that reduce the amount of scattered radiation reaching the image receptor

Question 42

What factors affect scatter?

Answer 42

kVp, field size, thickness, composition of irradiated material

Question 43

How is a basic grid constructed?

Answer 43

strips of lead interspaced with radiolucent material

Question 44

What is the grid ratio?

Answer 44

GR=h/D D is the width of the interspace material h is the height of the grid

Question 45

If you increase the grid ratio, what happens to the amount of scatter reaching the IR?

Answer 45

decreases

Question 46

Different frequencies effect on grid?

Answer 46

higher frequency, thinner Pb strips, less visible lower frequency, thicker Pb strips, more visible

Question 47

What is contrast improvement factor?

Answer 47

K = image contrast with grid/image contrast without grid 1.5-2.5 depends on kVp, patient thickness and field size

Question 48

What are the Bucky Factors?

Answer 48

How much of an increase in technique is needed compared to non-grid No Grid - 1 5:1 - 2 6:1 - 3 8:1 - 4 12:1 - 5 16:1 - 6

Question 49

Who invented moving grids?

Answer 49

Dr. Hollis E Potter in 1920 moves to blur out grid lines

Question 50

What kind of movement do moving grids do?

Answer 50

either reciprocating (side to side 2-3cm) or oscillating (circular)

Question 51

Will the movement of the grid cause more grid cut-off?

Answer 51

a little bit

Question 52

What are the 4 types of grid errors?

Answer 52

off center off level - angle mismatch off focus - out of proper SID upside down

Question 53

What is the air gap technique?

Answer 53

alternative to using a grid increasing OID - scatter misses IR 1 foot of SID per inch of OID

Question 54

Magnification Factor

Answer 54

MF = SID/SOD MF = Image size/object Size object size= Image size/MF