x-ray imaging SI units Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is a dimension?

A

A dimension is a property that can be measured such as length [L], time [T], or mass [M]. Dimensions are fundamental physical properties that can be measured.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a unit?

A

A unit is a way to assign a number or measurement to that dimension. Units provide agreed systems of measurement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Give an example of a dimension?

A

Length is a dimension, but it is measured in units of meters (m) in the metric system. The length could also be measured using another agreed system such as the Imperial System, in which case the units would be feet (ft).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the main system of units today?

A

The main system of units in use today:
The International System of Units
Referred to as SI Units from Le Systeme International d’Unites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

SI Base Units

A

Quantity Name Symbol Dimension Symbol

Length- Meter-m-L

Mass-Kilogram-kg-M

Time-Second-s-T

Electric current-Ampere-a-I

Temperature-Kelvin-k-θ

Amount of substance-Mole-mol-N

Luminous intensity-Candela-cd-J

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

SI Base & Derived Units Example (velocity/force)

A

Velocity is defined by the simple equation:
v=d/t
Where d is the distance and t is the time. In SI base units:
distance is expressed in units of metres (m)
time is expressed in units of time (s)
So, the derived units of velocity are m/s. The dimensions of velocity are therefore [L] [T]-1

Force is defined by Newton’s Second Law by the simple equation:
F=ma
Where m is the mass and a is the acceleration. In SI base units:
mass is expressed in units of kilograms (kg)
acceleration is expressed in derived units of m/s2
So, the derived units of force are kg-m/s2 which is given a special unit name called a newton
The dimensions of force are therefore [M] [L] [T]-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

SI units used in radiography

A

Quantity/ SI Unit/ Symbol/ Application

Energy
joule
J
Production of X-rays

Power
watt
W
Output of X-ray generator

Electric current
ampere
A
Quantity of electrons flowing in a electrical circuit

Electrical potential
volt
V
Accelerating force acting on electrons in an X-ray tube

Resistance
ohm
W
Quantity limiting the flow of electrons in an electric circuitGray

gray
Gy
Amount of absorbed radiation doseSievert

sievert
Sv
Biological effect of ionizing radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Common prefixes

A

Name/ Symbol/ Base 10/ English Descriptive Word/ Example Usage

giga
G
10’9
billion
GB – gigabyte, unit of memory storage

mega
M
10’6
million
MHz – megahertz, unit of frequency

kilo
k
10’3
thousand
kV – electrical potential across X-ray tube

centi
c
10’-2
hundredth
cm – centimetres, unit of mesurement

milli
M
10’-3
thousandth
mA – milliamp, unit of electric current

micro
µ
10’-6
millionth
mGy – microgray, unit of absorbed dose

nano
n
10’-9
billionth
nF – nanofarad, unit of capacitance

femto
f
10’-15
quadrillionth
fm – femtometre, unit of distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Simple Formulae Example: Equation of motion: v=u+at

A

v is the final speed in metres/second (m/s)
u is the initial speed in metres/second (m/s)
a is the acceleration in metres/second (m/s2)

To calculate the final speed of an object with initial speed 5 m/s moving with an acceleration of 2 m/s2 for 3 seconds substitute these values into the formula
v=u+at=5+2×3=11 m/s
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Simple Formulae Transposition Example

A

v is the subject of the formula above, but suppose we want a formula where t is the subject.
The basic strategy is to get t on its own by moving terms to the other side of the equals sign.
The general rule that we apply in doing this is “What ever operation is applied to one side of the equation then this must be applied to the other side of the equation”

Subtract u
v-u=u+at-u
v-u=at
Divide by a
(v-u)/a=at/a
Swap sides
t=(v-u)/a

Make u the subject: v^2=u^2+2as

Subtract 2as
v^2-2as=u^2+2as-2as
v^2-2as=u^2

Square root each side and swap sides
u=√(v^2-2as)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Linear Relationships: equation

A

y=mx+b

Here, m represents the gradient of the line and b represents the y-axis intercept

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

exponential relationships: equation

A

y= kb’x

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Mass, volume & Density

A

density=mass/volume

If a material has a mass 3.2 g and a volume of 0.4 cm3 its density is given by:
density=mass/volume= 3.2 g/0.4cm^3 =8 g/cm^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is thermal energy?

A

Thermal energy transfer is the movement of heat energy from one substance to another.

Heat energy always moves from objects with high temperature to objects with low.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is heat energy?

A

A form of energy which flows from a hotter region to a cooler region.

Unit of measure:
Measured in Joule (J)

Property:
Flows from a hot area to a cold.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is Temperature?

A

The degree of hotness and coldness of a body.

Unit of measure:
Kelvin (K) and Celsius (degrees C)

Property:
Increases when heated
Decreases when cooled

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Thermal energy equation

A

∆T=E/km

∆T temperature change (°C)
E energy (J)
m mass (kg)
k specific heat (J/kg°C)

18
Q
  1. Which one of the following is NOT an SI base unit?
    a. second
    b. metre
    c. ampere
    d. kilogram
    e. ounce
A

ounce

19
Q
  1. Which one of the pairs of units & dimensions match?
    a. kilogram & [T]
    b. second & [L]
    c. ampere & [T]
    d. kilogram & [M]
    e. kelvin & [M]
A

kilogram & [M]

20
Q
  1. Which one of the pairs of units have the same dimension
    a. second & metre
    b. kilogram & second
    c. ampere & candela
    d. kilogram & foot
    e. second & hour
A

second & hour

21
Q
  1. Which one of the following gives the correct dimensions for speed
    a. [L] -1 [T]
    b. [L] [T]-1
    c. [M] [T]
    d. [M] -1 [T]
    e. [L] [M]
A

[L] [T]-1

22
Q
  1. Which one of the following is a derived SI unit
    a. kilogram
    b. second
    c. volt
    d. metre
    e. mole
A

volt

23
Q
  1. An electrical current of 0.5 A is equal to which one of the following
    a. 5 mA
    b. 50 mA
    c. 500 mA
    d. 5000 mA
    e. 50, 000 mA
A

c. 500 mA

24
Q
  1. A voltage of 75 kV is equal to which one of the following
    a. 7.5 V
    b. 750 V
    c. 7500 V
    d. 75, 000 V
    e. 750, 000 V
A

75, 000 V

25
Q
  1. A voltage of 500 V is equal to which one of the following
    a. 50 kV
    b. 5 kV
    c. 0.5 kV
    d. 0.05 kV
    e. 0.005 kV
A

0.5 kV

26
Q
  1. An electrical resistor has a value of 1 MΩ which is equal to
    a. 1 × 10’9 Ω
    b. 1 × 10’6 Ω
    c. 1 × 10’3 Ω
    d. 1 × 10’2 Ω
    e. 1 × 10’12 Ω
A

1 × 10’6 Ω

27
Q
  1. An entrance surface dose of 1 mGy is equal to which one of the following
    a. 10 µGy
    b. 100 µGy
    c. 1000 µGy
    d. 10,000 µGy
    e. 10,00 µGy
A

1000 µGy

28
Q
  1. An entrance surface dose of 500 µGy is equal to which one of the following. (1 mGy= 1000 µGy)
    a. 0.05 mGy
    b. 0.5 mGy
    c. 5 mGy
    d. 50 mGy
    e. 5000 mGy
A

0.5 mGy

29
Q
  1. An electrical current of 0.0016 A can be expressed in standard form by which one of the following
    a. 1.6 × 103 A
    b. 1.6 × 10-3 A
    c. 16 × 104 A
    d. 0.16 × 10-2 A
    e. 160 × 10-6 A
A

1.6 × 10-3 A

30
Q
  1. An entrance surface dose is measured as 2.3 × 10-3 Gy. Which one of the following expresses this measurement correctly?
    a. 2.3 Gy
    b. 23 Gy
    c. 23 mGy
    d. 2.3 mGy
    e. 230 mGy
A

d. 2.3 mGy

31
Q
  1. An X-ray tube current is displayed as 52 mA. Which one of the following expresses this measurement correctly in standard form?
    a. 52 x 10’-3 A
    b. 5.2 x 10’-3 A
    c. 52 x 10’-4 A
    d. 5.2 x 10’-6 A
    e. 5200 x 10’-6 A
A

52 x 10’-3 A

32
Q

The power dissipated by a resistor is given by the equation P=I^2 R, where P is the power expressed in units of watts, I is the current expressed in units of amps, and R is the resistance expressed in units of ohms. If the formula is rearranged to make I the subject, then which one of the following formulae is correct:
I=(R/P)^2
I=(P/R)^2
I=√(P/R)
I=(PR)^2
I=(PR)^(1/2)

A

I=√(P/R)

33
Q

If the intensity of an X-ray beam at a distance of d1 from the X-ray source is defined as I_1, then the intensity I_2 at some other distance d_2 from the X-ray source can be calculated using the formula for the inverse square law
I_2=I_1 (d_1/d_2 )^2
If this formula was rearranged to make d_2 the subject which of the following formulae is correct
d2=d1 √I2/I1
d2=d1 √I1/I2
d2=I1 √d1/I2
d2=I2 (I1/d1 )^2
d2=d1 (I1/I2 )^2

A

d2=d1 √I1/I2

34
Q
  1. Before melting, most metals in solid form tend to _______ when heated. Select the correct answer.
    a. Contract
    b. Expand
    c. Evaporate
    d. Dissolve
    e. Sublimate
A

b. Expand

35
Q
  1. Which one of the following gives the correct volume for a cube measuring 0.5 cm × 0.5 cm × 0.5 cm.
    a. 0.125 cm2
    b. 0.25 cm3
    c. 0.125 cm3
    d. 1.25 cm3
    e. 0.125 cm-3
A

0.125 cm3

36
Q
  1. Which one of the following gives the correct dimensions for mass density
    a. [L] -1 [T]
    b. [M] [L]-3
    c. [L] [M]2
    d. [M] [L]-2
    e. [T] [M]
A

[M] [L]-3

37
Q
  1. A substance has a mass of 100 g and a volume of 50 cm3. Select the correct density from the following
    a. 2 g/cm2
    b. 0.5 g/cm3
    c. 2 g/cm3
    d. 5000 g/cm3
    e. 20 g/cm2
A

2 g/cm3

38
Q
  1. A large bath of water and a teacup full of water are heated. The initial temperature of the water in each vessel is 20°C and the final temperature of the water is 70°C. Which one of the following statements is true
    a. The water in the bath feels hotter than the water in the teacup when you place your hand in each vessel.
    b. The water in the bath stored the same thermal energy than the water in the teacup and therefore the temperature is the same.
    c. The water in the bath absorbed less thermal energy to achieve the same temperature as the water in the teacup.
    d. The water in the teacup absorbed more thermal energy to achieve the same temperature.
    e. The water in the bath stored more thermal energy than the water in the teacup.
A

The water in the bath stored more thermal energy than the water in the teacup.

39
Q
  1. You burn your hand on a metal pan handle which was heating food on a gas stove. What was likely to be the primary heat transfer mechanism responsible for the handle heating up.
    a. Convection.
    b. Conduction.
    c. Radiation.
    d. Electrical induction
    e. Electrical conduction
A

b. Conduction.

40
Q
A